What is a solar charge controller and why are they important?
As the name suggests, a solar charge controller is a component of a solar panel system that controls the charging of a battery bank. Solar charge controllers ensure the batteries are charged at the proper rate and to the proper level. Without a charge controller, batteries can be damaged by incoming power, and could also leak power back to the solar panels when the sun isn’t shining.
Solar charge controllers have a simple job, but it’s important to learn about the two main types, how they work, and how to pair them with solar panels and batteries. Armed with that knowledge, you’ll be one step closer to building an off-grid solar system!
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Key takeaways
- Solar charge controllers allow batteries to safely charge and discharge using the output of solar panels.
- A charge controller is needed any time a battery will be connected to the direct current (DC) output of solar panels; most often in small off-grid systems.
- The two kinds of charge controllers are pulse-width modulation (PWM) and maximum power point tracking (MPPT).
- PWM charge controllers are less expensive, but less efficient, and are best suited for small off-grid systems with a few solar panels and batteries.
- MPPT charge controllers are more expensive and more efficient, and are good for larger off-grid systems that can power a small home or cabin.
- The top off-grid charge controllers are made by brands like Victron, EPEVER, and Renogy, but non-brand-name charge controllers can be just fine if you know what to look for.
Who needs a solar charge controller?
A charge controller is necessary any time a battery bank will be connected to the direct current (DC) output of solar panels. In most cases, this means a small off-grid setup like solar panels on an RV or cabin. If you’re looking for information on how to use solar and batteries off the grid, you’re in the right place!
There are also charge controllers aimed at providing battery backup for an existing grid-tied solar system that is on the roof of a home or business. This application requires a high-voltage charge controller and usually involves rewiring the system to direct a portion of the solar output through the charge controller.
How does a solar charge controller work?
Fair warning before we get started: we’re about to discuss voltage, amperage, and wattage. If you need a refresher on how these things work together, check out our article on watts, kilowatts, and kilowatt-hours.
A solar charge controller is connected between solar panels and batteries to ensure power from the panels reaches the battery safely and effectively. The battery feeds into an inverter that changes the DC power into AC to run appliances (aka loads).
How a charge controller works within an off-grid solar system.
The four main functions of a solar charge controller are:
- Accept incoming power from solar panels
- Control the amount of power sent to the battery
- Monitor the voltage of the battery to prevent overcharging
- Allow power to flow only from the solar panels to the batteries
As a battery charges, its voltage increases, up to a limit. The battery can be damaged if an additional charge is applied past this limit. Therefore, the ability of a battery to provide or accept power can be measured by its voltage. For example, a typical 12-volt AGM lead-acid battery will show a voltage of 11.8 volts at 10% charged to 12.9 volts at 100% charge.
The main function of a solar charge controller is to ensure the amount of power that is sent to the battery is enough to charge it, but not so much that it increases the battery voltage above a safe level. It does this by reading the voltage of the battery and calculating how much additional energy is required to fully charge the battery.
Another important function of the charge controller is to prevent current from traveling back into the solar panels. When the sun isn’t shining, the solar panels aren’t producing any voltage. Because electricity flows from high voltage to low voltage, the power in the battery would flow into the solar panels if there was nothing in place to stop it. This could potentially cause damage. The charge controller has a diode that allows power to flow in one direction, preventing electricity from feeding back into the panels.
How solar power gets from panels to batteries
As we mentioned above, power flows from high voltage to low. So, to add energy to the battery, the output voltage of a solar panel must always be a little higher than the voltage of the battery it’s charging. Thankfully, solar panels are designed to put out more voltage than a battery needs at any given time.
Here’s an example: Say you have a single 100-watt solar panel and a 12-volt battery. Remember from above that a 12-volt battery is actually able to charge up to about 12.9 volts. 12 volts is what is called its “nominal voltage,” while the actual voltage of the battery depends on how charged it is. It might sink to 11.8 volts at low charge, and 12.9 volts when full.
The 100-watt solar panel can put out a maximum of 18 volts, which is a little too high for the battery to accept safely. Leaving it connected to the battery too long could result in a dangerous situation, eventually causing pressure to build up inside the battery and vent out the side as chemical steam.
You need a charge controller in between the solar panel and the battery to limit the voltage available to the battery. But it’s not just about the voltage. it also has to withstand a certain amount of current (amperage) flowing through it. That’s where the amperage rating of the charge controller comes in.
Charge controller amperage rating
The number of amps of current a charge controller can handle is called its “rating.” Exceeding the amperage rating can cause damage to the wiring within the charge controller. Let’s consider a charge controller rated to handle 30 amps of current. The single 100- watt solar panel described above puts out 5.5 amps of current at 18 volts. That amperage is much lower than the charge controller’s maximum of 30 amps, so the charge controller can easily handle the output of the singular solar panel.
In fact, it could handle the output of multiple solar panels wired in parallel (which increases current output). But there’s an important rule about charge controller ratings to consider: always make sure your charge controller is rated to handle 25% more amps than your solar panels are supposed to put out. That’s because solar panels can exceed their rated current output under especially bright sun, and you don’t want to fry your charge controller on the rare occasion when that happens.
Keeping that rule in mind, the 30-amp charge controller in our example could accept a nominal output of up to 24 amps. You could wire as many as four of those 5.5-amp solar panels in parallel to create a solar array capable of putting out 22 amps, staying under the charge controller’s rating plus the 25% cushion. If you think you might expand the size of your solar array in the future, get a charge controller rated for 50% more amps than your immediate needs.
Matching voltages
Another consideration when choosing a charge controller is the voltage of the battery bank you want to charge. Wiring batteries in series increases the voltage they can deliver and accept. For example, two 12-volt batteries wired in series will operate at 24 nominal volts. There are charge controllers on the market that can pair with battery banks of 12, 24, 36, and 48 volts. You need to make sure the charge controller you purchase can pair with the voltage of the battery bank.
Battery charging stages
There are three stages of charging a battery: bulk, absorption, and float. They correspond to how full the battery is.
- Bulk: When a battery charge is low, the charge controller can safely push a lot of energy to it, and the battery fills up with charge very quickly.
- Absorption: as the battery nears its full charge (around 90%), the charge controller reduces its current output, and the battery charges more slowly until it’s full.
- Float: when the battery is full, the charge controller lowers its output voltage just a bit to maintain the full charge.
Think of it like pouring water from a pitcher into a cup with a very slow leak: when the cup is empty, you start pouring and quickly increase the amount of water being poured until the cup is nearly full. Then you reduce the flow until the cup is full. In order to keep the cup full despite the leak, you pour just a trickle to keep it topped off.
The bulk/absorption/float process was developed for lead-acid deep cycle batteries. Some newer lithium batteries allow for higher current up until they’re quite full, meaning a charge controller paired with a lithium battery can be set to shorten or eliminate the absorption stage.
Types of charge controller
There are two main ways to control the flow of power to a battery, and they correspond to the two types of charge controller: pulse-width modulation (PWM) and maximum power point tracking (MPPT).
Pulse-width modulation (PWM)
Pulse-width modulation is the simplest and cheapest automatic way to control the flow of power between solar panels and a battery. There are PWM charge controllers on the market for between about 15 to 40.
A PWM charge controller ensures the battery never charges to more than its maximum voltage by switching the power flow on and off hundreds of times per second (i.e. sending “pulses” of power) to reduce the average voltage coming from the solar panels. The width of the pulses reduces the average output voltage.
Here’s an image to illustrate how the pulses work:
For example, if the charge controller accepts 18 volts from the solar panel, it might adjust the pulses so they’re on 82% of the time, and off 18% of the time. This would reduce the average voltage by 18%, down to about 14.8 volts, which can be used to charge a half-full AGM battery. As the battery gets close to a full charge, a PWM charge controller shortens the pulses even further, down to around 77% of the time, or 13.8 volts, to prevent the battery from overcharging.
Unfortunately, the excess energy produced by solar panels is wasted to reduce the output voltage. In our example, the charge controller would average around 80% efficiency. This means it’s very important to make sure the output voltage of the solar panels is not too much higher than the voltage of your battery bank with a PWM charge controller to minimize wasted energy. If your solar array outputs a much higher voltage, the PWM charge controller will cut that voltage down to what the battery can accept, and waste the rest.
Something like 80% efficiency is fine for small off-grid applications like a few solar panels hooked up to a couple of batteries, especially at the low cost of a PWM charge controller. For larger systems with much higher output, it is generally preferable to use the other kind of charge controller technology known as maximum power point tracking, or MPPT.
Maximum power point tracking (MPPT)
An MPPT solar charge controller operates by converting the incoming power from solar panels to match the theoretical highest-efficiency output at the right input voltage for the battery. The charge controller does this by calculating the point at which the maximum current can flow at a voltage the battery can accept, then converting the solar panel output to that mixture of voltage and current.
The major advantages of MPPT charge controllers are greater efficiency and compatibility with higher voltage solar arrays. This means that you can charge a 12V battery bank with a larger solar array wired in series, as long as you stay within the limits of the controller’s amperage rating. You can calculate this limit by taking the total wattage of the solar array and dividing it by the voltage of the battery bank to get the maximum possible output in amps.
Let’s use the same example numbers as before. The solar panel is putting out 100 watts, or about 5.5 amps into 18 volts. The MPPT charge controller converts the output to 14.8 volts but loses about 5% of the power in the conversion process. So the MPPT controller’s output current is about 6.4 amps, times the 14.8 volts, or 95 watts.
Theoretically, in an hour of full sun, the MPPT charge controller will have delivered 95 amp-hours of energy to the batteries, compared to the PWM charge controller’s energy output of about 80 amp-hours. In practice, it isn’t quite that simple, as solar pro Will Prowse discovered in this video:
Common features and settings on a charge controller
The basic features of the simplest PWM charge controller include the ability to set the type of battery and battery bank voltage, and lights indicating the phase of charging (bulk, absorption, and float). advanced PWM and MPPT models come with a small LCD display for programming and data display, a heat sensor port to monitor battery temperature, and a communications port to connect the charge controller to an external display or computer. The most advanced charge controllers offer Bluetooth connectivity and an app for customizing settings.
Recommended prodcuts
There are tons of fine charge controllers available on the market. Search any solar supply or online marketplace like Amazon and you’re bound to turn up dozens of results.
The cheapest PWM charge controllers can be had for around 15, and are often rebranded versions of the same design. These lack many features but are relatively reliable for how inexpensive they are. expensive PWM charge controllers built with better quality materials can be had for under 50, while full-featured MPPT charge controllers are priced anywhere from 100 to 200.
Below are a few of our recommended charge controllers at different price points for a medium-sized off-grid setup.
Renogy Wanderer 30A 12V PWM
The Renogy Wanderer 30A PWM charge controller is a solid choice for a smaller off-grid setup. It can handle up to 30A of current at 12V, so it’s not meant for a large system.
It doesn’t have a screen, but it does pair with the three main kinds of lead-acid batteries as well as lithium ones. It has a connector port for an optional temperature sensor and includes an RS232 port that can be used to program the charge controller or even to add Renogy’s BT-1 Bluetooth module for connecting to the Renogy app on your smartphone.
The Wanderer can be had for about 40 from Amazon or Renogy direct.
EPEVER Tracer BN 30A 12V/24V MPPT
The EPEVER Tracer BN MPPT 30A charge controller is not the cheapest MPPT charge controller on the market, but it’s a very good one. With a die-cast aluminum body, sturdy connectors, and a DC output to power loads like DC appliances or LED lights, the Tracer BN is a robust piece of equipment perfect for handling solar charging of lead-acid batteries in 12- and 24-volt banks. It can accept an incoming power output of up to 2,340 watts of solar panels (that’s equal to three parallel strings of four 60-cell solar panels wired in series). The Tracer can be programmed to charge lithium batteries, but it doesn’t come with a preset charging profile for them.
This EPEVER Tracer BN kit at Amazon includes a temperature sensor, mounting hardware, and a separate screen for programming and monitoring the health and state of charge of your battery system. Price at the time of publishing was 179.99.
Victron Energy SmartSolar 30A 100V MPPT
Victron is one of the most trusted solar brands in the world, and its technology is now becoming more widely available in the United States. This 30A, 100V charge controller is known as one of the best on market. Just like the EPEVER controller, it works with 12- or 24-volt battery banks but allows for slightly lower voltage solar input. To stay under this charger’s rating, you could run as many as three parallel strings of three 60-cell solar panels in series to achieve an output of 90 volts at around 20 amps (1,800 watts of solar output).
It’s made with quality components, calculates maximum power point quickly and with high efficiency, and is very easy to use. The SmartSolar line of charge controllers all come with Bluetooth connectivity on board and can connect to the VictronConnect app on Android, iOS, macOS, and Windows for easy programming. Perhaps most importantly, you get a 5-year limited warranty that protects you against defects in materials and workmanship.
The SmartSolar 30A is the most expensive product on our list at around 225 on Amazon, but reading the reviews from its users, you can see why the expense might be worth it.
Solar charge controllers: are they right for you?
All the information above should give you a good basis of knowledge about how solar charge controllers work and how to pair them with solar panels and batteries, but there’s no substitute for practical, hands-on experience! If you have a few bucks to spend, you can set up a pretty simple off-grid solar “generator” using a single solar panel, a charge controller, a battery, and a cheap inverter. Choosing a charge controller that’s oversized for a small application gives you a chance to increase the size of the solar array and battery bank as you gain experience or find new ways to use the stored solar energy.
Now go out there and start making solar and batteries work for you!
Best MPPT Charge Controllers
Just so you know, this page contains affiliate links. If you make a purchase after clicking on one, at no extra cost to you I may earn a small commission.
I spent weeks testing 5 of the best MPPT solar charge controllers on the market.
I built a custom testing setup and tested their ease of use, build quality, and power output. I also researched their specs and spent time using their mobile apps to monitor my system and create custom charging profiles.
Based on all that, here are my reviews and recommendations.
Quick Recommendations: Best MPPT Solar Charge Controllers
Here’s the TLDR version of my rankings:
- Top Pick:Victron SmartSolar MPPT 100/30
- Budget Pick:Renogy Rover 40A
- Honorable Mention:EPEver Tracer 4215BN
- Renogy Rover Elite 40A
- EPEver Tracer 4210AN
Or keep reading for my full MPPT charge controller reviews.
Note: Most of the charge controllers I tested offer models with different charge current ratings, max PV voltages, and/or compatible battery voltages. So if you see one on this list you like, but it isn’t compatible with your system, just search for the other available models and you’ll probably find one that is.
Top Pick: Victron SmartSolar MPPT 100/30
| Rated charge current: | 30A | Max. PV open circuit voltage (Voc): | 100V |
| Battery voltage: | 12/24V | Battery types: | LiFePO4, sealed (AGM), gel, flooded, custom |
| Max. PV input power: | 440W @ 12V, 880W @ 24V | Max. wire size: | 6 AWG (16 mm2) |
| Bluetooth monitoring: | Yes (built-in) | Temperature sensor: | Yes (built-in) |
Pros: Easy to use, built-in Bluetooth, robust mobile app, custom charging profiles
Cons: Expensive, mediocre wire terminals, no screen
Best for: Those looking for the best MPPT charge controller who don’t mind paying top dollar; advanced users who want the most features and customizability
Review
For the sake of everyone’s wallets, I almost hoped the Victron wouldn’t be my favorite. But it was.
Out of the box, I found the Victron to have the most features and be the easiest to use. It’s about as “plug and play” as it gets.
Bluetooth is built in to all the models in the Victron SmartSolar MPPT product line. Once the Victron is installed, you can use the free VictronConnect mobile app to monitor and customize your system.
The Victron was the only MPPT I tested with Bluetooth built in. All the other charge controllers in this review make you buy a 30-40 Bluetooth module for that feature. That helps justify the Victron’s price a bit.
The VictronConnect app has a lot of features. It can be a little overwhelming at first. But, once you learn your way around it, it can be quite powerful. You can use one of the many battery presets or, for advanced users, easily create and save custom charging profiles.
And that’s just the tip of the iceberg. Victron makes all sorts of accessories — sensors and shunts and the like — that can pair with the app as well and communicate with your controller to customize and optimize your system. It’s a solar nerd’s playground.
I also performed a power output test and the Victron placed first — by a hair. I wouldn’t put too much stock in these results because of the variables I couldn’t control (e.g. panel temperature, fluctuations in solar irradiance), but it was nice to see a first place finish from a top-of-the-line MPPT.
The Victron’s wire terminals are passable, but nothing to write home about. The screws felt high quality, but the terminals themselves were shallow and a little too close together for my taste.
Otherwise, the build quality of the Victron felt solid. The case and heat sink seem durable. It was also the smallest and lightest controller I tested, if that’s an important factor in your system.
I tested the bestselling Victron SmartSolar MPPT model on Amazon at the time of my research, which happened to be the 100/30 model (100V PV voltage limit, 30A charge current rating).
But Victron has a huge product lineup and sells SmartSolar controllers with a wide range of PV voltages (75-250V) and current ratings (10-100A). So if the model I’ve tested is too much or too little for your purposes, you can upgrade or downgrade accordingly.
Budget Pick: Renogy Rover 40A
| Rated charge current: | 40A | Max. PV open circuit voltage (Voc): | 100V |
| Battery voltage: | 12/24V | Battery types: | LiFePO4, sealed (AGM), gel, flooded, custom |
| Max. PV input power: | 520W @ 12V, 1040W @ 24V | Max. wire size: | 8 AWG (10 mm2) |
| Bluetooth monitoring: | Yes (requires additional purchase) | Temperature sensor: | Yes (included) |
Pros: Great value, easy to use, good mobile app (must buy Renogy BT-1 Bluetooth Module to use), custom charging profiles
Cons: Not compatible with Renogy Battery Voltage Sensor
Best for: Those looking for the best bang for their buck
Review
I’ve had the Renogy Rover 40A for over 6 months, and I’ve become quite familiar with it during that time.
It’s well-priced and easy to use. It’s compatible with all the most common types of solar batteries, plus has the option to create custom charging profiles.
Renogy has a mobile app called Renogy DC Home. To use it with the Rover 40A, you’ll have to buy the Renogy BT-1 Bluetooth Module.
The Renogy app is good, but I found it a little less feature-rich than Victron’s. For many users it will have everything you need. I suspect advanced users may want a little more customization, though.
The Rover’s wire terminals were good but not great. The terminals felt roomier than the listed max wire size, but the screws were a little loose and hard to tighten at times.
The screen on the Rover 40A displays nearly every system spec I could hope for. It’s also easy to use it to select your battery type, edit load settings, and create custom charging profiles.
In my power output test, the Rover tied for last with the EPEver Tracer 4210AN. They both output a max of 142 watts compared to the 146 watts of the Victron which placed first. I think the difference of 4 watts is negligible.
The Rover 40A doesn’t have a port for connecting a battery voltage sensor, which I don’t love. You have to upgrade to the Rover 60A or Rover 100A for that feature. Battery voltage sensors help charge controllers adjust their charging voltage to account for voltage drop, which is helpful in certain systems.
Overall, the Rover 40A is a good MPPT charge controller for the money. It has all the features and battery presets you need to set up your system quickly and easily. And for more advanced users, you can create custom charging profiles and buy the BT-1 Bluetooth Module for remote monitoring.
Honorable Mention: EPEver Tracer 4215BN
| Rated charge current: | 40A | Max. PV open circuit voltage (Voc): | 150V |
| Battery voltage: | 12/24V | Battery types: | Sealed (AGM), gel, flooded, custom |
| Max. PV input power: | 520W @ 12V, 1040W @ 24V | Max. wire size: | 4 AWG (25 mm2) |
| Bluetooth monitoring: | Yes (requires additional purchase) | Temperature sensor: | Yes (included) |
Pros: Excellent build quality, my favorite wire terminals, 150V PV voltage limit
Cons: Must make custom charging profile if using with lithium batteries, Bluetooth monitoring is harder to set up
Best for: Those looking for a charge controller with great build quality; users with lead acid batteries; users with lithium batteries who don’t mind creating custom charging profiles
Review
From a hardware perspective, the Tracer 4215BN — sometimes called the Tracer BN or Tracer BN Series — was my favorite charge controller.
It’s big and heavy and virtually one entire heat sink. The wire terminals were easily my favorite. They felt like tanks. And they’re the biggest in this review – capable of handling up to 4 AWG wire. If you like to overgauge your wires, this is one to consider.
However, the hardware in a charge controller isn’t the full story. Charge controllers also have a software component. When that’s lacking, it makes the controller harder to use.
I didn’t test the EPEver app, but from reviews I’ve read it’s a little clunky. The included MT50 screen is great, though. It’s easy to view all your system specs and select your battery type. If you’re using lead acid batteries, the Tracer BN is about as plug and play as any other MPPT.
But it has no preset for LiFePO4 batteries. You’ll have to create your own custom charging profile if using lithium. It isn’t that hard to do, but it’s certainly not as easy as selecting your battery type from a menu.
These usability hurdles are small, but more noticeable than on the other controllers in this review. If you’re comfortable with technical product manuals, they shouldn’t be difficult to overcome. And, once you do, you’ll have a great controller that feels like it could last a lifetime.
As a final heads up, the Tracer BN’s days might be numbered. While doing research for this article, I tried to find this controller on EPEver’s website, but couldn’t.
From years of product testing, I’ve come to see these removals as the first sign of a product’s discontinuation. For now it’s still available on Amazon, but time will tell.
Renogy Rover Elite 40A
| Rated charge current: | 40A | Max. PV open circuit voltage (Voc): | 100V |
| Battery voltage: | 12/24V | Battery types: | LiFePO4, sealed (AGM), gel, flooded |
| Max. PV input power: | 520W @ 12V, 1040W @ 24V | Max. wire size: | 6 AWG (16 mm2) |
| Bluetooth monitoring: | Yes (requires additional purchase) | Temperature sensor: | Yes (included) |
Pros: Cheapest MPPT tested, good mobile app (must buy Renogy BT-2 Bluetooth Module to use)
Cons: No custom charging profiles
Best for: Those who want a cheap MPPT and only plan to use preset battery charging profiles
Review
Based on its name, I wouldn’t fault you for assuming the Renogy Rover Elite is a more advanced version of the Renogy Rover. I know I certainly did.
But you’d be wrong. It’s actually a cheaper version. (Whose idea was that?)
The Rover Elite was close to being one of my recommended picks. It has a lot going for it: It’s the cheapest MPPT I tested. It’s compatible with all the main types of solar batteries. And, if you buy the Renogy BT-2 Bluetooth Module, you can connect the Rover Elite to the Renogy app to monitor your system from your phone.
Based on that, I think it’s a good budget option for DIY solar beginners, or users who just plan on using the battery presets.
But if you want to create custom charging profiles, know that the Rover Elite doesn’t have that option. I know from plenty of reader emails and Комментарии и мнения владельцев that advanced users like to customize their charging setpoints.
Unlike it’s more expensive cousin, the Rover Elite does have a battery voltage sensor port. You can buy a Renogy Battery Voltage Sensor and connect it to the Rover Elite to improve the controller’s battery voltage reading.
I’ve tested a handful of Renogy products over the years, and I always seem to come to the same conclusion: they’re good quality for the price. The Rover Elite is the same. Overall, it’s a good cheap MPPT.
EPEver Tracer 4210AN
| Rated charge current: | 40A | Max. PV open circuit voltage (Voc): | 100V |
| Battery voltage: | 12/24V | Battery types: | LiFePO4, sealed (AGM), gel, flooded, LiNiCoMnO2, custom |
| Max. PV input power: | 520W @ 12V, 1040W @ 24V | Max. wire size: | 6 AWG (16 mm2) |
| Bluetooth monitoring: | Yes (requires additional purchase) | Temperature sensor: | Yes (included) |
Pros: Fast power point tracking, custom charging profiles
Cons: Not the easiest to use, mediocre wire terminals
Review
The Tracer 4210AN — sometimes called the Tracer AN or Tracer AN Series — is a solid controller.
But, when pitted side by side against the others, it didn’t stand out to me in any way. I’m not sure what type of user I’d recommend it for.
I think it’s a good value for the money, but not as good as the Renogy Rover. The build quality is solid but not outstanding. I think the wire terminals are subpar.
On startup, it did track the maximum power point the fastest of any controller tested (in about 9 seconds on average, compared to the 57 seconds of its sibling, the Tracer 4215BN, which placed last). That’s something, I suppose.
It has a good screen and, on Amazon at least, the 40 amp model comes with the MT50 display included.
But I do want to underscore that this is a well-made unit. It works well, is solidly built, and even has the lowest power consumption of those tested. EPEver claims ≤12mA (it doesn’t say at what voltage), which is less than the 30mA (at 12V) of the Victron, the next closest.
If this controller is on sale, or you just prefer the EPEver brand, I’d say go for it. If it was the only MPPT I owned, I expect I’d end up being perfectly happy with it.
How to Choose the Best MPPT Charge Controller for Your Needs
Rated Charge Current
Also called: rated battery current, battery charge current or rated output current
The rated charge current is the maximum amount of current (in amps) that the charge controller can charge the battery at. It’s such an important number that it’s often included in the product name (e.g. Renogy Rover 40A — “40A” is the rated charge current).
30A-40A: Many popular MPPTs (including all the ones I tested) fall in this range. They can usually handle between 400-500 watts of solar at 12 volts and 800-1000 watts of solar at 24 volts. They’re best used with lithium batteries of 80Ah or greater and lead acid batteries of 130Ah or greater.
40A: MPPTs with charge current ratings greater than 40 amps are designed for large solar systems. They can usually handle greater than or equal to 600 watts of solar at 12 volts and 1200 watts at 24 volts. Some may also be compatible with 36V and 48V batteries and capable of handling even greater PV power inputs at these voltages.
Note: Charge controllers with load terminals may also list a rated discharge current (aka rated load current). This is how much current the controller can output through its load terminals.
Maximum PV Voltage
Also called: maximum PV open circuit voltage, maximum input voltage
Use our solar panel voltage calculator to calculate the maximum open circuit voltage of your solar array. Then, pick a charge controller with a maximum PV voltage greater than this number.
100V-150V: This is the most popular PV voltage range for MPPT charge controllers. Models in this range can usually handle 3-6 12V solar panels wired in series.
150V: MPPTs in this range are designed for large solar arrays. They can usually handle 7 or more 12V solar panels wired in series.
Note: Estimating the max voltage of your solar array is not as simple as multiplying open circuit voltage by the number of solar panels wired in series. This is because solar panel voltage increases as temperature drops. To get an accurate estimate, you’ll have to correct for temperature.
Battery Voltage
Also called: system voltage, nominal battery voltage
This number refers to the nominal battery voltage the controller is compatible with. You may see the word “auto” next to the battery voltage — e.g. “12/24V Auto.” This means the charge controller automatically detects whether you’re using a 12V or 24V battery bank.
12/24V: Many popular MPPT models are compatible with 12 and 24 volt batteries. Indeed, these are the compatible battery voltages of all the models I tested for this review.
12/24/48V: There are higher-end MPPTs compatible with 12, 24 and 48 volt batteries. These are usually MPPTs with higher charge current ratings.
12/24/36/48V: Some brands sell models that are also compatible with 36 volt batteries.
Note: Some charge controllers also list a max battery voltage in their spec sheet. As you’d expect, you don’t want your battery voltage to exceed this number.
Compatible Battery Types
Make sure the charge controller you’re getting is compatible with your type of battery.
Here are the most common types of solar batteries:
- LiFePO4 (Also referred to as lithium iron phosphate, LFP, or simply “lithium”)
- Gel
- AGM/Sealed lead acid
- Flooded lead acid
If a controller is compatible with a type of battery, it essentially means it has a preset charging profile for that battery chemistry that you can select when you set up the controller.
Custom charging profiles: Many MPPT controllers also offer the ability for you to create custom or “user” charging profiles. These let you select all the voltage setpoints — such as absorption voltage and float voltage — so you can tailor it for your specific battery.
In essence, custom profiles make the controller compatible with all main types of solar batteries. Many advanced users also like to adjust these numbers to try to maximize their battery lifespan.
Maximum PV Input Power
“PV” refers to solar panels, so this number is the max solar array wattage you can connect to the controller.
You’ll notice that the controller has different max PV input power ratings for different voltages. This is because watts is based on both volts and amps (W = V A).
If you’re having trouble figuring out what charge current rating you need, you can also refer to this number for guidance.
Bluetooth Monitoring
Being able to monitor and control your solar system from an app on your phone is great convenience. Don’t underestimate how nice it can be! MPPT controllers fall into three different buckets here:
Built-in: Some controllers have Bluetooth built in, meaning you don’t need to buy anything in order to start monitoring your system from your phone. Of the controllers I tested, only the Victron SmartSolar came with Bluetooth built in.
Additional purchase required: A lot of controllers require an additional purchase before you can use Bluetooth monitoring. You have to buy a Bluetooth module that connects to the controller. These typically cost 30-40. The remaining 4 controllers I tested fall into this bucket.
No Bluetooth: Some MPPT charge controllers come with no Bluetooth capabilities at all. The only way to monitor your system with these is through the screen or LED lights on the controller.
Wire Terminals
Look for good wire terminals with quality screws. Cheap charge controllers skimp on their wire terminals and you’ll notice right away. They’re easier to strip and you can’t tighten the screws down as much. They may be quicker to loosen over time.
Some people also like to over-gauge their wires. Thicker wires help minimize voltage drop and make it easy to expand your system later on. If that’s you, you’ll want to pay attention to max wire size.
Power Consumption
Charge controllers consume a modest amount of power, which will be listed on the specs sheet. In most DIY solar systems, the power consumption isn’t enough to make a material difference.
However, power consumption can come into consideration if your solar panels will go for long stretches without receiving sunlight. For instance, one reader from Scandinavia wrote to me about how charge controller power consumption factored into his buying decision because the solar panels on his off-grid cabin were covered in snow for most of the winter. He didn’t want the charge controller to consume so much power that it fully drained his batteries.
In these situations, look for a controller with low power consumption. Most charge controllers have lower power consumption at lower system voltages, so you may want to keep your battery bank at 12 volts. PWM charge controllers tend to consume less power than MPPTs, so you may want to also consider a PWM model.
Temperature Compensation
If you’re using lead acid batteries and they’ll be experiencing wide temperature swings, you should look for a charge controller that adjusts its voltage setpoints based on temperature — a featured called temperature compensation. Lithium batteries don’t need temperature compensation.
To have this feature, the controller needs to have a temperature sensor. The sensor will either be a built-in internal sensor, or an external sensor included in the box or available as an additional purchase.
If it’s an external sensor, You plug it into the temperature sensor port on the controller and then tape the probe to the battery.
Operating Temperature Range
Pay attention to operating temperature range if your charge controller will be experiencing wide temperature swings — such as if it’s located in a boat, RV, or campervan without AC. The higher-end models are typically able to handle wider temperature ranges.
MPPT vs PWM Charge Controllers
MPPT charge controllers are more expensive, but more efficient. Most are around 95% efficient.
PWM charge controllers are cheaper, but less efficient. They are around 75-80% efficient.
What’s more, MPPT controllers often have higher charge current ratings, such as 30 amps or more. This means you can connect more solar panels to them. (The MPPT models included in this test, for instance, can handle solar arrays of 400-1000 watts depending on system voltage.) They also have higher PV voltage limits, so you can connect more panels in series which can save you money on wiring.
PWM charge controllers usually have lower charge current ratings, such as 10-30 amps, making them best suited for solar arrays of 400 watts or less. They often only have high enough PV voltage limits for 1-2 12V solar panels in series. If you’re using lots of solar panels with a PWM, you’ll probably have to wire them in parallel which can increase wiring costs.
The Bottom Line
I liked all of the MPPT charge controllers I tested for this review. I’d be happy to have any of them in my system. Alas, the job of a reviewer is to rank the options from best for worst.
After testing 5 MPPTs side by side and comparing their spec sheets, I think the Victron SmartSolar MPPT is the best MPPT charge controller on the market. I thought it had the best build quality and was the easiest to set up and use.
The Renogy Rover 40A has the best bang for your buck. It’s a well-made model that can be paired with Renogy’s mobile app if you also buy the BT-1 Bluetooth Module.
Lastly, the EPEver Tracer 4215BN is built like a tank and has the best wire terminals of any charge controller I’ve ever used. It’s not compatible with lithium batteries out of the box, but you can use the included MT50 screen to create a custom charging profile.
As a reminder, all the charge controllers I tested offer models with different charge current and PV voltage limits. If you like the Victron, for instance, but need a higher current rating, consider the Victron SmartSolar MPPT 100/50. It has a 50 amp current rating, compared to the 30 amp rating of the model I tested.
A small ask: If you found my MPPT charge controller reviews helpful and are planning to buy one, please consider buying through one of my affiliate links below. I’ll get a small commission (at no extra cost to you) which will help fund more reviews like this one. Thank you!
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What is a solar charge controller?
A solar charge controller, also known as a solar regulator, is basically a solar battery charger connected between the solar panels and battery. Its job is to regulate the battery charging process and ensure the battery is charged correctly, or more importantly, not over-charged. DC-coupled solar charge controllers have been around for decades and are used in almost all small-scale off-grid solar power systems.
Modern solar charge controllers have advanced features to ensure the battery system is charged precisely and efficiently, plus features like DC load output used for lighting. Generally, most smaller 12V-24V charge controllers up to 30A have DC load terminals and are used for caravans, RVs and small buildings. On the other hand, most larger, more advanced 60A MPPT solar charge controllers do not have load output terminals and are specifically designed for large off-grid power systems with solar arrays and powerful off-grid inverter-chargers.
Solar charge controllers are rated according to the maximum input voltage (V) and maximum charge current (A). As explained in more detail below, these two ratings determine how many solar panels can be connected to the charge controller. Solar panels are generally connected together in series, known as a string of panels. The more panels connected in series, the higher the string voltage.
- Current Amp (A) rating = Maximum charging current.
- Voltage (V) rating = Maximum voltage (Voc) of the solar panel or string of panels.
MPPT Vs PWM solar charge controllers
There are two main types of solar charge controllers, PWM and MPPT, with the latter being the primary FOCUS of this article due to the increased charging efficiency, improved performance and other advantages explained below.
PWM solar charge controllers
Simple PWM, or ‘pulse width modulation’ solar charge controllers, have a direct connection from the solar array to the battery and use a basic ‘Rapid switch’ to modulate or control the battery charging. The switch (transistor) opens until the battery reaches the absorption charge voltage. Then the switch starts to open and close rapidly (hundreds of times per second) to modulate the current and maintain a constant battery voltage. This works ok, but the problem is the solar panel voltage is pulled down to match the battery voltage. This, in turn, pulls the panel voltage away from its optimum operating voltage (Vmp) and reduces the panel power output and operating efficiency.
PWM solar charge controllers are a great low-cost option for small 12V systems when one or two solar panels are used, such as simple applications like solar lighting, camping and basic things like USB/phone chargers. However, if more than one panel is needed, they will need to be connected in parallel, not in series (unless the panels are very low voltage and the battery is a higher voltage).
MPPT solar charge controllers
MPPT stands for Maximum Power Point Tracker; these are far more advanced than PWM charge controllers and enable the solar panel to operate at its maximum power point, or more precisely, the optimum voltage and current for maximum power output. Using this clever technology, MPPT solar charge controllers can be up to 30% more efficient, depending on the battery and operating voltage (Vmp) of the solar panel. The reasons for the increased efficiency and how to correctly size an MPPT charge controller are explained in detail below.
As a general guide, MPPT charge controllers should be used on all higher power systems using two or more solar panels in series, or whenever the panel operating voltage (Vmp) is 8V or higher than the battery voltage. see full explanation below.
What is an MPPT or maximum power point tracker?
A maximum power point tracker, or MPPT, is basically an efficient DC-to-DC converter used to maximise the power output of a solar system. The first MPPT was invented by a small Australian company called AERL way back in 1985, and this technology is now used in virtually all grid-connect solar inverters and all MPPT solar charge controllers.
The functioning principle of an MPPT solar charge controller is relatively simple. due to the varying amount of sunlight (irradiance) landing on a solar panel throughout the day, the panel voltage and current continuously vary. In order to generate the most power, an MPPT sweeps through the panel voltage to find the sweet spot or the best combination of voltage and current to produce the maximum power. The MPPT continually tracks and adjusts the PV voltage to generate the most power, no matter what time of day or weather conditions. Using this clever technology, the operating efficiency greatly increases, and the energy generated can be up to 30% more compared to a PWM charge controller.
PWM Vs MPPT Example
In the example below, a common 60 cell (24V) solar panel with an operating voltage of 32V (Vmp) is connected to a 12V battery bank using both a PWM and an MPPT charge controller. Using the PWM controller, the panel voltage must drop to match the battery voltage and so the power output is reduced dramatically. With an MPPT charge controller, the panel can operate at its maximum power point and in turn can generate much more power.
Best MPPT solar charge controllers
See our detailed review of the best mid-level MPPT solar charge controllers used for small scale off-grid systems up to 40A. click on the summary table below. Also see our review of the most powerful, high-performance MPPT solar charge controllers used for professional large-scale off-grid systems here.
Battery Voltage options
Unlike battery inverters, most MPPT solar charge controllers can be used with a range of different battery voltages. For example, most smaller 10A to 30A charge controllers can be used to charge either a 12V or 24V battery, while most larger capacity, or higher input voltage charge controllers, are designed to be used on 24V or 48V battery systems. A select few, such as the Victron 150V range, can even be used on all battery voltages from 12V to 48V. There are also several high voltage solar charge controllers, such as those from AERL and IMARK which can be used on 120V battery banks.
Besides the current (A) rating, the maximum solar array size that can be connected to a solar charge controller is also limited by the battery voltage. As highlighted in the following diagram, using a 24V battery enables much more solar power to be connected to a 20A solar charge controller compared to a 12V battery.
Based on Ohm’s law and the power equation, higher battery voltages enable more solar panels to be connected. This is due to the simple formula. Power = Voltage x Current (P=VI). For example 20A x 12.5V = 250W, while 20A x 25V = 500W. Therefore, using a 20A controller with a higher 24V volt battery, as opposed to a 12V battery, will allow double the amount of solar to be connected.
- 20A MPPT with a 12V battery = 260W max Solar recommended
- 20A MPPT with a 24V battery = 520W max Solar recommended
- 20A MPPT with a 48V battery = 1040W max Solar recommended
Note, oversizing the solar array is allowed by some manufacturers to ensure an MPPT solar charge controller operates at the maximum output charge current, provided the maximum input voltage and current are not exceeded! See more in the oversizing solar section below.
Solar panel Voltage Explained
All solar panels have two voltage ratings which are determined under standard test conditions (STC) based on a cell temperature of 25°C. The first is the maximum power voltage (Vmp) which is the operating voltage of the panel. The Vmp will drop significantly at high temperatures and will vary slightly depending on the amount of sunlight. In order for the MPPT to function correctly, the panel operating voltage (Vmp) must always be several volts higher than the battery charge voltage under all conditions, including high temperatures. see more information about voltage drop and temperature below.
The second is the open-circuit voltage (Voc) which is always higher than the Vmp. The Voc is reached when the panel is in an open-circuit condition, such as when a system is switched off, or when a battery is fully charged, and no more power is needed. The Voc also decreases at higher temperatures, but, more importantly, increases at lower temperatures.
Battery Voltage Vs Panel Voltage
For an MPPT charge controller to work correctly under all conditions, the solar panel operating voltage (Vmp), or string voltage (if the panels are connected in series) should be at least 5V to 8V higher than the battery charge (absorption) voltage. For example, most 12V batteries have an absorption voltage of 14 to 15V, so the Vmp should be a minimum of 20V to 23V, taking into account the voltage drop in higher temperatures. Note, on average, the real-world panel operating voltage is around 3V lower than the optimum panel voltage (Vmp). The String Voltage Calculator will help you quickly determine the solar string voltage by using the historical temperature data for your location.
12V Batteries
In the case of 12V batteries, the panel voltage drop due to high temperature is generally not a problem since even smaller (12V) solar panels have a Vmp in the 20V to 22V range, which is much higher than the typical 12V battery charge (absorption) voltage of 14V. Also, common 60-cell (24V) solar panels are not a problem as they operate in the 30V to 40V range, which is much higher.
24V Batteries
In the case of 24V batteries, there is no issue when a string of 2 or more panels is connected in series, but there is a problem when only one solar panel is connected. Most common (24V) 60-cell solar panels have a Vmp of 32V to 36V. While this is higher than the battery charging voltage of around 28V, the problem occurs on a very hot day when the panel temperature increases and the panel Vmp can drop by up to 6V. This large voltage drop can result in the solar voltage dropping below the battery charge voltage, thus preventing it from fully charging. A way to get around this when using only one panel is to use a larger, higher voltage 72-cell or 96-cell panel.
48V Batteries
When charging 48V batteries, the system will need a string of at least 2 panels in series but will perform much better with 3 or more panels in series, depending on the maximum voltage of the charge controller. Since most 48V solar charge controllers have a max voltage (Voc) of 150V, this generally allows a string of 3 panels to be connected in series. The higher voltage 250V charge controllers can have strings of 5 or more panels which is much more efficient on larger solar arrays as it reduces the number of strings in parallel and, in turn, lowers the current.
Note: Multiple panels connected in series can produce dangerous levels of voltage and must be installed by a qualified electrical professional and meet all local standards and regulations.
Solar panel voltage Vs Temperature
The power output of a solar panel can vary significantly depending on the temperature and weather conditions. A solar panel’s power rating (W) is measured under Standard Test Conditions (STC) at a cell temperature of 25°C and an irradiance level of 1000W/m2. However, during sunny weather, solar panels slowly heat up, and the internal cell temperature will generally increase by at least 25°C above the ambient air temperature; this results in increased internal resistance and a reduced voltage (Vmp). The amount of voltage drop is calculated using the voltage temperature co-efficient listed on the solar panel datasheet. Use this Solar Voltage Calculator to determine string voltages at various temperatures.
Both the Vmp and Voc of a solar panel will decrease during hot sunny weather as the cell temperature increases. During very hot days, with little wind to disperse heat, the panel temperature can rise as high as 80°C when mounted on a dark-coloured rooftop. On the other hand, in cold weather, the operating voltage of the solar panel can increase significantly, up to 5V or even higher in freezing temperatures. Voltage rise must be taken into account as it could result in the Voc of the solar array going above the maximum voltage limit of the solar charge controller and damaging the unit.
Panel Voltage Vs Cell Temperature graph notes:
- STC = Standard test conditions. 25°C (77°F)
- NOCT = Nominal operating cell temperature. 45°C (113°F)
- (^) High cell temp = Typical cell temperature during hot summer weather. 65°C (149°F)
- (#) Maximum operating temp = Maximum panel operating temperature during extremely high temperatures mounted on a dark rooftop. 85°C (185°F)
Voltage increase in cold weather
Example: A Victron 100/50 MPPT solar charge controller has a maximum solar open-circuit voltage (Voc) of 100V and a maximum charging current of 50 Amps. If you use 2 x 300W solar panels with 46 Voc in series, you have a total of 92V. This seems ok, as it is below the 100V maximum. However, the panel voltage will increase beyond the listed Voc at STC in cold conditions below 25°C cell temperature. The voltage increase is calculated using the solar panel’s voltage temperature coefficient, typically 0.3% for every degree below STC (25°C). As a rough guide, for temperatures down to.10°C, you can generally add 5V to the panel Voc which equates to a Voc of 51V. In this case, you would have a combined Voc of 102V. This is now greater than the max 100V Victron 100/50 input voltage limit and could damage the MPPT and void your warranty.
Solution: There are two ways to get around this issue:
- Select a different MPPT solar charge controller with a higher input voltage rating, such as the Victron 150/45 with a 150V input voltage limit.
- Connect the panels in parallel instead of in series. The maximum voltage will now be 46V 5V = 51 Voc. Note this will only work if you use a 12V or 24V battery system; it’s unsuitable for a 48V system as the voltage is too low. Also note, in parallel the solar input current will double, so the solar cable should be rated accordingly.
Note: Assuming you are using a 12V battery and 2 x 300W panels, the MPPT charger controller output current will be roughly: 600W / 12V = 50A max. So you should use a 50A MPPT solar charge controller.
Guide only. Use the new String Voltage Calculator to determine panel voltages accurately.
Basic guide
The charge controller Amp (A) rating should be 10 to 20% of the battery Amp/hour (Ah) rating. For example, a 100Ah 12V lead-acid battery will need a 10A to 20A solar charge controller. A 150W to 200W solar panel will be able to generate the 10A charge current needed for a 100Ah battery to reach the adsorption charge voltage provided it is orientated correctly and not shaded. Note: Always refer to the battery manufacturer’s specifications.
Advanced Guide to off-grid solar systems
Before selecting an MPPT solar charge controller and purchasing panels, batteries or inverters, you should understand the basics of sizing an off-grid solar power system. The general steps are as follows:
- Estimate the loads. how much energy you use per day in Ah or Wh
- Battery capacity. determine the battery size needed in Ah or Wh
- Solar size. determine how many solar panel/s you need to charge the battery (W)
- Choose the MPPT Solar Charge Controller/s to suit the system (A)
- Choose an appropriately sized inverter to suit the load.
Estimate the loads
The first step is to determine what loads or appliances you will be running and for how long? This is calculated by. the power rating of the appliance (W) multiplied by the average runtime (hr). Alternatively, use the average current draw (A) multiplied by average runtime (hr).
- Energy required in Watt hours (Wh) = Power (W) x Time (hrs)
- Energy required in Amp hours (Ah) = Amps (A) x Time (hrs)
Once this is calculated for each appliance or device, then the total energy requirement per day can be determined as shown in the attached load table.
Sizing the Battery
The total load in Ah or Wh load is used to size the battery. Lead-acid batteries are sized in Ah while lithium batteries are sized in either Wh or Ah. The allowable daily depth of discharge (DOD) is very different for lead-acid and lithium, see more details about lead-acid Vs lithium batteries. In general, lead-acid batteries should not be discharged below 70% SoC (State of Charge) on a daily basis, while Lithium (LFP) batteries can be discharged down to 20% SoC on a daily basis. Note: Lead-acid (AGM or GEL) batteries can be deeply discharged, but this will severely reduce the life of the battery if done regularly.
For example: If you have a 30Ah daily load, you will need a minimum 100Ah lead-acid battery or a 40Ah lithium battery. However, taking into account poor weather, you will generally require at least two days of autonomy. so this equates to a 200Ah lead-acid battery or an 80Ah lithium. Depending on your application, location, and time of year, you may even require 3 or 4 days of autonomy.
Sizing the Solar
The solar size (W) should be large enough to fully charge the battery on a typical sunny day in your location. There are many variables to consider including panel orientation, time of year shading issues. This is actually quite complex, but one way to simplify things it to roughly work out how many watts are required to produce 20% of the battery capacity in Amps. Oversizing the solar array is also allowed by some manufacturers to help overcome some of the losses. Note that you can use our free solar design calculator to help estimate the solar generation for different solar panel tilt angles and orientations.
Solar sizing Example: Based on the 20% rule, A 12V, 200Ah battery will need up to 40Amps of charge. If we are using a common 250W solar panel, then we can do a basic voltage and current conversion:
Using the equation (P/V = I) then 250W / 12V battery = 20.8A
In this case, to achieve a 40A charge we would need at least 2 x 250W panels. Remember there are several loss factors to take into account so slightly oversizing the solar is a common practice. See more about oversizing solar below.
Solar Charge controller Sizing (A)
The MPPT solar charge controller size should be roughly matched to the solar size. A simple way to work this out is using the power formula:
Power (W) = Voltage x Current or (P = VI)
If we know the total solar power in watts (W) and the battery voltage (V), then to work out the maximum current (I) in Amps we re-arrange this to work out the current. so we use the rearranged formula:
Current (A) = Power (W) / Voltage or (I = P/V)
For example: if we have 2 x 200W solar panels and a 12V battery, then the maximum current = 400W/12V = 33Amps. In this example, we could use either a 30A or 35A MPPT solar charge controller.
Selecting a battery inverter
Battery inverters are available in a wide range of sizes determined by the inverter’s continuous power rating measured in kW (or kVA). importantly, inverters are designed to operate with only one battery voltage which is typically 12V, 24V or 48V. Note that you cannot use a 24V inverter with a lower 12V or higher 48V battery system. Pro-tip, it’s more efficient to use a higher battery voltage.
Besides the battery voltage, the next key criteria for selecting a battery inverter are the average continuous AC load (demand) and short-duration peak loads. Due to temperature de-rating in hot environments, the inverter should be sized slightly higher than the load or power demand of the appliances it will be powering. Whether the loads are inductive or resistive is also very important and must be taken into account. Resistive loads such as electric kettles or toasters are very simple to power, while inductive loads like water pumps and compressors put more stress on the inverter. In regards to peak loads, most battery inverters can handle surge loads up to 2 x the continuous rating.
Inverter sizing example:
- Average continuous loads = 120W (fridge) 40W (lights) TV (150W) = 310W
- High or surge loads = 2200W (electric kettle) toaster (800W) = 3000W Considering the above loads, a 2400W inverter (with 4800 peak output) would be adequate for the smaller continuous loads and easily power the short-duration peak loads.
ATTENTION SOLAR DESIGNERS. Learn more about selecting off-grid inverters and sizing solar systems in our advanced technical off-grid system design guide.
MPPT Solar Oversizing
Due to the various losses in a solar system, it is common practice to oversize the solar array to enable the system to generate more power during bad weather and under various conditions, such as high temperatures where power derating can occur. The main loss factors include. poor weather (low irradiation), dust and dirt, shading, poor orientation, and cell temperature de-rating. Learn more about solar panel efficiency and cell temperature de-rating here. These loss factors combined can reduce power output significantly. For example, a 300W solar panel will generally produce 240W to 270W on a hot summer day due to the high-temperature power de-rating. Depending on your location, reduced performance will also occur in winter due to low solar irradiance. For these reasons, oversizing the solar array beyond the manufacturers ‘recommended or nominal value’ will help generate more power in unfavourable conditions.
Oversizing by 150% (Nominal rating x 1.5) is possible on many professional MPPT solar charge controllers and will not damage the unit. However, many cheaper MPPT charge controllers are not designed to operate at full power for a prolonged amount of time, as this can damage the controller. Therefore, it is essential to check whether the manufacturer allows oversizing. Morningstar and Victron Energy allow oversizing well beyond the nominal values listed on the datasheets as long as you don’t exceed the input voltage and current limits. Victron MPPT controllers have been successfully used with 200% solar oversizing without any issues. However, the higher the oversizing, the longer the controller will operate at full power and the more heat it will generate. Without adequate ventilation, excess heat may result in the controller overheating and derating power or, in a worst-case scenario, complete shutdown or even permanent damage. Therefore always ensure adequate clearance around the controller according to the manufacturer’s specifications, and add fan-forced ventilation if required.
Warning. you must NEVER exceed the maximum INPUT voltage (Voc) or maximum input current rating of the solar charge controller!
IMPORTANT. Oversizing solar is only allowed on some MPPT solar charge controllers, such as those from Victron Energy, Morningstar and EPever. Oversizing on other models could void your warranty and result in damage or serious injury to persons or property. always ensure the manufacturer allows oversizing and never exceed the maximum input voltage or current limits.
about Solar Sizing
As previously mentioned, all solar charge controllers are limited by the maximum input voltage (V. Volts) and maximum charge current (A – Amps). The maximum voltage determines how many panels can be attached (in series), and the current rating will determine the maximum charge current and, in turn, what size battery can be charged.
As described in the guide earlier, the solar array should be able to generate close to the charge current of the controller, which should be sized correctly to match the battery. Another example: a 200Ah 12V battery would require a 20A solar charge controller and a 250W solar panel to generate close to 20A. (Using the formula P/V = I, then we have 250W / 12V = 20A).
As shown above, a 20A Victron 100/20 MPPT solar charge controller together with a 12V battery can be charged with a 290W ‘nominal’ solar panel. Due to the losses described previously, it could also be used with a larger ‘oversized’ 300W to 330W panel. The same 20A Victron charge controller used with a 48V battery can be installed with a much larger solar array with a nominal size of 1160W.
Compared to the Victron MPPT charge controller above, the Rover series from Renogy does not allow solar oversizing. The Rover spec sheet states the ‘Max. Solar input power’ as above (not the nominal input power). Oversizing the Rover series will void the warranty. Below is a simple guide to selecting a solar array to match various size batteries using the Rover series MPPT charge controllers.
20A Solar Charge Controller. 50Ah to 150Ah battery
- 20A/100V MPPT. 12V battery = 250W Solar (1 x 260W panels)
- 20A/100V MPPT. 24V battery = 520W Solar (2 x 260W panels)
- 40A/100V MPPT. 12V battery = 520W Solar (2 x 260W panels)
- 40A/100V MPPT. 24V battery = 1040W Solar (4 x 260W panels)
Remember that only selected manufacturers allow the solar array to be oversized, as long as you do not exceed the charge controller’s max voltage or current rating. always refer to manufacturers’ specifications and guidelines.
solar charge controller Price guide
The older, simple PWM, or pulse width modulation, charge controllers are the cheapest type available and cost as little as 40 for a 10A unit. In contrast, the more efficient MPPT charge controllers will cost anywhere from 80 to 2500, depending on the voltage and current (A) rating. All solar charge controllers are sized according to the charge current, which ranges from 10A up to 100A. Cost is directly proportional to the charge current and maximum voltage (Voc), with the higher voltage and current controllers being the most expensive.
A general guide to the cost of different size solar charge controllers:
- PWM 100V Solar controllers up to 20A. 40 to 120
- MPPT 100V Solar controllers up to 20A. 90 to 200
- MPPT 150V Solar controllers up to 40A. 200 to 400
- MPPT 150V Solar controllers up to 60A. 400 to 800
- MPPT 250V Solar controllers up to 80A. 800 to 1200
- MPPT 300V Solar controllers up to 100A. 900 to 1500
- MPPT 600V Solar controllers up to 100A. 1600 to 2800
About the Author
Jason Svarc is a CEC-accredited off-grid solar power system specialist who has been designing and building off-grid power systems since 2010. During this time, he also taught the stand-alone power systems design course at Swinburne University (Tafe). Living in an off-grid home for over 12 years and having designed, installed and monitored dozens of off-grid systems, he has gained vast experience and knowledge of what is required to build reliable, high-performance off-grid solar systems.
Disclaimer
This is to be used as a guide only. Before making any purchases or undertaking any solar/battery related installations or modifications, you must refer to all manufacturer’s specifications and installation manuals. All work must be done by a qualified person.
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Industry StandardSize: 58.7” x 26.8” x 1.4”, 3′ cable with connectors, generate 5.32 amp power, charge 12 volt or 24 volt battery. Industry standard, quick connect cables, work in series or in parallel.
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SPECIFICATIONS
| ATTRIBUTE | VALUE |
| Maximum Power(Pmax): | 200W |
| Maximum Power Voltage(Vmp: | 37.6V |
| Maximum Power Current(Imp): | 5.32A |
| Open Circuit Voltage(Voc): | 45.4V |
| Short Circuit Current(Isc): | 5.83A |
| Maximum System Voltage(Vmax): | 1000VDC |
| Temperature Range: | -40°C ~ 90°C |
| Max Series Fuse Rating: | 15A |
| Weight: | 26.5 lbs |
| Dimensions: | 58.7 x 26.8 x 1.4 in |
BUILT-IN COMPONENTS
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MPPT Solar Charge Controller 12V 24V 48V 60A 3200W
Intelligent maximum power point tracking technology increases efficiency 25%~30% 2. Compatible for PV systems in 12v, 24v or 48v 3. Three-stage charging optimizes battery performance 4. Maximum charging current up to 60a 5. Maximum efficiency up to 98% 6. Battery temperature sensor (BTS) automatically provides temperature compensation 7. Support wide range of lead-acid batteries including wet, AGM, and gel batteries 8. Multi-function LCD displays detailed information
Application
MPPT Solar Charge Controller 12V 24V 48V 60A 3200W is mainly used for solar power station, home solar power system, solar street light control system, mobile solar power system, DC wind solar generating systems.
MPPT Solar Charge Controller 12V 24V 48V 60A 3200W Technical Specifications:
| 60 ~115VDC | ||
| 145VDC | ||
| 50A | ||
| Sealed lead acid, AGM or Gel | ||
| 60A | ||
| 98% | ||
| Three stages: bulk, absorption and floating | ||
| 110% : audible alarm | ||
| Yes | ||
| Yes | ||
| LCD panel indicating solar power, load level, battery voltage/capacity, charging current, and fault conditions | ||
| Three indicators for solar, charging, and load status | ||
| 315 x 165 x 128 | ||
| 4.5 | ||
| IP 31 | ||
| 0 ~ 100% RH (No condensing) | ||
| -20°C to 55°C | ||
| -40°C to 75°C | ||
| 0 ~ 3000 m |
SEO article
Principle of 12v mppt solar charge controller
The 24v mppt solar charge controller can detect the generation voltage of the solar panel in real time, and track the maximum voltage and current (VI), so that the system can charge the battery with the maximum power output. Used in solar photovoltaic system, to coordinate the work of solar panels, batteries, load, is the brain of the photovoltaic system.
To charge the battery, the output voltage of the solar panel must be higher than the current voltage of the battery. If the voltage of the solar battery plate is lower than the battery voltage, the output current will be close to 0. So for the sake of safety, when leaving the factory, the peak voltage of solar panels (Vpp) is about 17V, which is the ambient temperature of 25 degrees C standard setting. When the weather is very hot, the peak voltage Vpp solar panels will be reduced to about 15V, but in the cold weather, the peak voltage can reach 18V.
We compare the difference between the 12v mppt solar charge controller and the conventional solar controller. The traditional solar charging and discharging controller is a bit like a manual gear box, when the engine speed increases, if the gear box can not be increased accordingly in gear, it is bound to affect the speed. But for the solar 24v mppt solar charge controller, the charging parameters are set in the factory, which means 48v mppt solar charge controller can track the maximum power point of the solar panels in real time, to show the maximum efficiency of solar panels. The higher the voltage, you can output more power through the maximum power tracking, so as to improve the efficiency of charging. Theoretically, the use of 12v mppt solar charge controller of the solar power system will improve the efficiency of 50% than the traditional way. However, according to our actual test, due to the environmental impact and various energy losses, the final efficiency can be improved by 20%-30%.
In this sense, 48v mppt solar charge controller, is bound to eventually replace the traditional solar controller.