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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Solar Charge Controller Settings
A solar charge controller has various settings that need to be altered for it to function properly, such as voltage ampere settings. Today you will get to know about solar charge controller settings along with solar charge controller voltage settings.
Solar Charge Controller
The amount of power generated from the solar panel travels to the inverter batteries. This power needs to be maintained and regulated. A solar charge controller is used for this purpose. It sends short energy pulses to the battery. The average output produced by an MPPT solar charge controller can be 42 volts. You will require additional batteries to produce higher voltages. Here is the catch: to prevent your batteries from damage, you need to choose the right solar charge controller.
Solar Charge Controller Settings
Just installing a charge controller won’t solve all your problems. There are different settings that need to be checked and manually adjusted. Different types of batteries like Lithium Iron Phosphate (LIPO), lithium, iron phosphate, lead-acid, and Absorbent Glass Mat (AGM) batteries have different settings. However, there are only two types of charge controllers.
MPPT controller or maximum power-point tracking controller
PWM controller or pulse width modulation controller
Before starting to set up the solar charge controller, you need to understand its functioning of it. Here are the points that you need to keep a note of while installing and setting up the solar charge controller.
Once the battery is fully charged, the battery will not hold more solar energy in comparison to the chemical content.
- If the battery is charged high, it can result in the development of heat and gas inside the battery.
- Electrolytes inside the battery began to expand. This further led to the development of bubbles.
- This chemical process leads to the generation of hydrogen gas, which is explosive.
- An overcharged battery will decrease the capacity and increase the aging process of the battery.
The Parameters:
Battery Floating Charging Voltage
The voltage at which a battery is maintained once it is fully charged is known as the battery floating charging voltage. This voltage maintains the capacity of the battery by self-discharging it. The typical voltage for a 12V system is 13.7V and for a 24 V system, it is 27.4V. 58.4V is the voltage for a 48V system.
Battery Over-Discharging Protection Voltage
It is also known as under voltage cutoff voltage and its value should also be in accordance with the battery type. In solar charge controller settings, the voltage value range for a 12V system is 10.8V to 11.4V. For a 24V system, it is 21.6V to 22.8V, and 43.2V to 45.6V for a 48 V system. So, the typical values are 11.1 V, 22.2 V, and 44.4 V.
Battery Overcharging Protection Voltage
This voltage value should be set as per the battery type. This voltage is also termed a fully charged cutoff voltage or over-voltage cutoff voltage. This voltage value for a 12-volt system ranges between 14.1 V and 14.5 V. For a 24-volt system, it is 28.2V to 29V and for a 48V system, it is 56.4V to 58V. So overall, the typical value for the voltage is 14.4V, 28.8V, and 57.6V.
Charge Controller Capacity
It is the maximum number of amperes that your solar charge controller can handle. It is the parameter on the basis of which a solar charge controller is rated. It can be 10A, 20A, 30A, 40A, 50A, 60A, 80A, or 100A.
Maximum Charging Current
It is the maximum output current of the solar panels or solar arrays. It is the output that you receive from the batteries.
System Voltage
It is also known as the Rated Operational Voltage of your solar power system which refers to the battery bank voltage (direct current operational voltage). Usually, the value is 12V, 24V, or 48V. However, a medium-scale or a large-scale charge controller system has voltage values of 110V and 220V.
Solar Charge Controller Voltage Settings
These are the most critical settings that need to be done carefully for the better functioning of the solar charge controller. A solar charge controller is capable of handling a variety of battery voltages ranging from 12 volts to 72 volts. As per the basic solar charge controller settings, it is capable of accommodating a maximum input voltage of 12 volts or 24 volts.
You need to set the voltage and current parameters before you start using the charge controller. This can be done by adjusting the voltage settings. Here is the list mentioning the most critical voltage settings for the solar charge controller.
- Absorption Duration: (Adaptive/Fixed)
- Absorption Voltage: 14.60 volts
- Automatic Equalization: (Disabled / Equalize every X Days) Disabled
- Equalization Current Percentage: 25%
- Equalization Duration: 4 hours
- Equalization stop mode: (Fixed Time / Automatic on Voltage) Fixed time
- Equalization Voltage: 14.40 volts
- Float Voltage: 13.50 volts
- Low-Temperature Cutoff (optional): Disabled
- Maximum Absorption Time: 6 hours to 3 minutes (max) per 100Ah battery capacity
- Maximum Absorption Rate: 30 minutes per 100Ah battery capacity
- Manual Equalization: Select start now
- Maximum Equalization Duration: 3-4 hours
- Re-Bulk Voltage offset: 0.1 volts
- Tail Current: 2.0A
- Temperature Compensation (mV/°C): 27.7 volts / 40° Celsius-25° Celsius
Note: Settings can be changed manually on the controller or from the PC Software. Follow the instructions of the manufacturer for the best results.
Steps in Solar Charge Controller Settings
While you set up your new solar charge controller, you should begin with properly wiring the controller to the battery bank and solar panels properly. Once the wiring is properly done and the controller detects the power, its screen will light up. Other steps are as follows:
Enter the settings menu by holding the menu button for a few seconds.
Charge current PV to Battery will be displayed
Battery Type Selection can be done by pressing the menu button for a long time.
The battery voltage will be auto-detected by the controller.
According to the user manual, set the setting for absorption charge voltage, low voltage cutoff value, float charge voltage, and low voltage recovery value.
If the system has an option for setting up the discharge value for DC, then set it as per the user manual.
Once the setting is done, the charge controller will instantly start the charging process.
PWM Solar Charge Controller User Manual
The user manual of a PWM or a pulse width modulation solar charge controller contains information regarding the following:
LCD Display or Key
A solar charge controller has a digital display that displays a number of things on the panel through abbreviations or signs and symbols. Here is the list of those things and what they mean.
- A panel with a small sun shining indicates the solar panel charge.
- An arrow near the panel when it is bold black means the system is on Aqualation or buck when the arrow is flicking it means it is on float mode.
- A square filled with horizontal bars indicates battery.
- Near the battery sign, there is an arrow indicating the output.
- A bulb sign indicates the load
- V% indicates the voltage
- AH is for ampere hours
- A square-shaped box indicates a menu. It is used for switching between different displays. You can enter or exit the setting by pressing it for a long time.
- An up arrow is used to increase the value
- A down arrow showing a decrease in the value
LCD Display or Setting
To browse different interfaces in the solar charge controller settings, press the menu button. The LCD or key display discussed in point 1 is the main display. Next displays in order when you press the menu are:
- FloatVoltage – The screen shows LIT, voltage, and the battery
- Discharge Reconnect – Shows LIT, voltage, battery, output (arrow), and load (bulb)
- Under voltage Protection – Displays LIT, voltage, empty battery symbol, and load (bulb)
- Work Mode – It displays hours (H), output (arrow), and load (bulb). OH, means dawn to dusk, 24H means load output is for 24 hours, and 1-23H means the load is on after sunset and closed after sunrise hours.
- Battery Type – LIT and the battery box with horizontal bars, determine the amount of battery charged and the type of battery. LIT is for lithium. After this, you are again on the main display.
Important: To switch On or Off the load manually on the main display, press the down key.
Product Features
- 3-stage PWM charge management
- A built-in industrial microcontroller with adjustable parameters
- A pulse width modulation solar charge controller has the following features:
- Battery Switching functions between lithium and lead battery. The lithium battery is the default setting and switches it to the battery type interface by holding it for 3 seconds.
- Dual metal–oxide–semiconductor field-effect transistor (MOSFET) Reverse current protection with low heating dissipation
- In-built protection for short-circuit open circuits, overload, and reverse
Safety Instructions
Every electrical appliance comes with a list of safety instructions that are prepared according to the appliance. A PWM controller has the following safety instructions mentioned in its user manual.
- Do not connect another charging source with the charge controller. The controller is suitable only for regulating solar modules.
- For the controller to recognize the battery type, ensure the battery has enough voltage before you begin the installation process.
- Install the controller on a well-ventilated and flat surface. While running, the controller will be heated.
- This controller is suitable for lithium batteries. All kinds of lead batteries (open, AGM, and gel) are also compatible with it.
- To minimize loss, keep the battery cable as short as possible.
System Connection
In solar charge controller settings, it contains instructions related to the connection. It tells you which port you need to connect to which wire.
- Connect the battery to the charge regulator (plus and minus)
- Connect the consumer to the charge regulator (plus and minus)
- Connect the photovoltaic module to the charge regulator (plus and minus)
Technical Parameter
This section contains all the information regarding the voltage, amperes, input, output, size, weight, etc. of the PWM solar charge controller.
- Batt voltage – 12 volts / 24 volts auto adapt.
- Charge current – 10A (KYZ 10), 20A (KYZ 20), 30A (KYZ 30)
- Discharge current – 10A (KYZ 10), 10A (KYZ 20), 10A (KYZ 30)
- Max solar input – less than 41 volts
- Model – (KYZ 10) (KYZ 20) (KYZ 30)
- Operating temperature –.35 ~60° Celsius
- Size or weight – 13370355 millimeters or 140 grams
- Standby current – greater than 10 mA
- USB output – 5 volts / 2 A Max
The technical parameters of lithium and lead batteries under certain parameters are mentioned in the table below.
| Type of Battery | Equalization | Float | Undervoltage Protection | Discharge Reconnect |
| Lithium (LIT) battery | 12.8 volts | 12.0 volts (default, adjustable range 11.5-12.8 volts) | 10.7 volts (defaults, adjustable range 9.0-11.0volts) | 11.6 volts(defaults, adjustable range 11.0-11.7volts) |
| Lead acid battery (bAt) | 14.4 volts | 13.7 Volts (defaults, adjustable range13-15V) | 10.7V (defaults, adjustable range9.0-11.0 Volts) | 11.6 Volts (defaults, adjustable range11.0-11.7V) |
Trouble Shooting
Every electronic appliance faces some problem that can be easily resolved with troubleshooting. The basic problem and its solution are mentioned under the troubleshooting column in the PWMM user manual. Here I have mentioned the problem – probable cause – solution.
- Charge icon not on when sunny – Solar panel is open or reversed – Reconnect
- Load icon off – Battery low – Recharge
- Load icon off – Mode setting wrong – Set again
- Load icon slow flashing – Overload – Reduce load watt
- Load icon slow flashing – Short circuit protection – Auto-reconnect
- Power off – Battery too low reverse – Check battery or connection
Solar Charge Controller 24V Settings
After the solar charge controller settings for a 12V system, the 24V system is the most common charge controller used in residential solar power systems. The basic settings for this are mentioned in the user manual of your charge controller. However, here are a few basic settings that are for a 24V system.
- Battery Floating Charging Voltage is 27.4V
- Battery Over-discharging Protection Voltage is 21.6V to 22.8V
- Battery Overcharging Protection Voltage is 28.2V to 29V
- Solar charge controller settings for AGM battery
The solar charge controller setting for an AGM or Absorbent Glass Mat battery is also for 12 volts, 24 volts, or 48 volts. The maximum charge current should be at 50A maximum per 100Ah battery capacity. The absorption voltage should be 14.60 volts and the float voltage at 13.50 volts. Equalization voltage at 14.40 volts and bulk voltage offset at 0.10 volts. Absorption duration should be adaptive, and duration should be between 6 hours to 30 minutes per 100Ah battery capacity. The current percentage for equalization is at 25% and its duration at 4 hours max.
Solar Charge Controller Settings for Lithium Batteries
Before you begin setting up your lithium batteries, remember that lithium batteries do not require temperature compensation. Also, if you are replacing lead batteries with lithium batteries and the settings are set at Equalized this needs to be changed. To change this, select, EQE (Master equalizer enable/disable) on the charge controller display. This can also be done by selecting OFF the dip switch in other controllers. Some common settings for a multi-stage charge profile need to be set to the following settings:
- Charge voltage – 14.4 volts (3.6 VPC)
- Absorption time – 30 minutes to balance lithium cells
- Float voltage – 13.6 volts
- Resting voltage (default) – 3.4 VPC
Solar Charge Controller Settings for Lead Acid Battery
The lead acid battery is a classic configuration in a solar power system. Once you convert the battery type from lithium/AGM to lead acid battery, the original set parameters for a lead acid battery will be used. These configurations are already installed in the charge controller system. And sometimes, it is just plugging and using the system.
Well, today you learned about the alteration in solar charge controller settings in accordance with the type of batteries your inverter has. Also, solar charge controller voltage settings should be carefully done to get the maximum potential output from the solar charge controller.
Olivia is committed to green energy and works to help ensure our planet’s long-term habitability. She takes part in environmental conservation by recycling and avoiding single-use plastic.
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2 Комментарии и мнения владельцев
Hello, very nice article! Could I have 2 questions: 1.) I have the same type controller. Do you know, why my solar controller is changing battery setup from B03 to B01 by itself? Is it damaged? 2.) Now I miss arrow on display between solar panel and battery. Does it mean, that battery is fully charged? Thank you.
Dear Jaro, Thankyou for reaching out to us. For Query 1: Solar Charge Controller changing battery setup from B03 to B01. We have found that said settings mean as follows: B03 – Battery Over Voltage – This error occurs when Input voltage to battery terminals exceeds 17.5-V B01 – Battery Disconnected – This fault code appears when the Portable solar kit cannot detect a battery bank. The issue you are facing can be due to the following reasons: 1- Automatic Configuration – Some controllers adjust their settings based on the battery type and conditions they detect. Check your controller’s manual to see if it has this feature and disable it, according to instrcutions listed in the manual. 2- Firmware or Software Issue: Glitches in the controller’s firmware or software can cause unexpected behavior. Check for firmware updates or try resetting the controller to its factory settings. If this doesnt work, contact the manufacturer to get the controller checked for damage and for possible repair. For Query 2: Arrow on Display between Solar Panel and Battery It is difficult to determine the exact meaning without knowing your controller’s model. 1- In some cases, the arrow indicates charging. 2- It could also mean the battery is fully charged. 3- Or, there might be an issue the controller requires a reset. Follow steps listed in the manual to do the same. And if the issue is still unresolved, there could be some issues with wiring between the 3 components. Last option is to get the entire system checked by an authorized technician and contact the manufacturer for assistance.
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What Is a Solar Charge Controller, and Do You Need It?
Installing solar panels requires understanding the workings of many components: solar batteries, inverters wiring, conduit bending… If you’re going the DIY route, you could practically work as an electrician once you finish the installation!
The charge controller is one component of a solar power system that confuses many people. A solar charge controller is necessary for most residential PV panel installations. Let’s explore what exactly a solar charge controller does and whether or not you’ll need one for your setup.
What Is a Solar Charge Controller?
A solar charge controller is a device that regulates the energy that travels from the solar panels into the battery. Solar generators convert and store power in a battery, with the electrical capacity recharged by the solar panels. A solar charge controller regulates the electrical current to prevent the battery from electrical surges that can damage it and reduce its lifespan.
A solar charge controller is essential if your PV solar array feeds a battery bank. If you are on a grid-tied system, you probably don’t need a solar charge controller.
How Does a Solar Charge Controller Work?
A solar charge controller regulates the voltage transmitted from the solar panels to the batteries.
Solar panels for a 12V battery system are usually rated for 17V. It may seem counterintuitive, but there is a good reason for it.
Solar panels rarely output their full power rating due to clouds, dirt on the panels, or other environmental factors. So, if they were only rated at 12V, they would always be putting out less power — which a 12V battery cannot accept.
A 12V battery at rest is around 12.7V, and a charging battery is around 13.6 to 14.4V. So, a solar panel must generate at least this much electrical output.
A solar charge controller takes the electricity from the solar panel — around 16 to 20V — and downregulates it to the voltage the battery currently needs. This amount can range from 10.5V to 14.6V depending on the battery’s current charge, the temperature, and the controller’s charging mode.
Charge controllers ultimately protect against battery damage. Inconsistencies in the electrical output, power surges, and other external factors can overcharge and damage a solar battery.
Types of Solar Charger Controllers
There are two main types of charge controllers: PWM and MPPT. Neither is necessarily “better” than the other — each has advantages depending on climate, array size, and system components.
While MPPT controllers typically cost more than PWM, the difference is negligible considering the total solar installation cost. Always choose a controller because it is the right tool for the job — not because it is cheaper.
PWM Charge Controllers – PWM (Pulse Width Modulation) controllers are generally smaller and less expensive than MPPT controllers. PWM controllers often come standard with small solar systems, such as RV and small cabin setups.
When using a PWM controller, the voltage from the array needs to match the battery voltage. Off-grid solar panels (those rated at 17-18V) are required when using PWM controllers, which sometimes cost more than grid-tied panels (often rated at 37V).
PWM controllers work best in “ideal” conditions — warm, sunny weather. When the weather becomes colder, batteries operate at less efficient rates.
A PWM controller is not able to adjust voltages. Instead, it shuts on and off as the voltage from your solar array inevitably varies — this auto shut-off also results in some loss of power.
MPPT Charge Controllers – MPPT (Maximum Power Point Tracking) controllers are more expensive than PWM, but they are significantly more efficient in many circumstances.
MPPTs draw out the current at a rate based on the panel’s maximum voltage. They can utilize a higher-voltage array with lower-voltage batteries. You can use the mass-produced, lower-cost PV modules standard on residential homes.
An MPPT controller can accept and modulate varying voltages. They harness excess power that a PWM would otherwise waste.
Who Needs a Solar Charge Controller?
All off-grid solar systems require a solar charge controller to regulate the energy moving to and from the batteries.
You won’t usually need a solar charge controller for grid-connected renewable energy systems. The utility company gathers any excess energy produced and utilizes the electricity.
When Should You Use a Solar Charge Controller?
Almost all solar systems that utilize batteries will require a solar charge controller. Tiny solar setups are the only exception — 5-watt trickle chargers and similar devices will not need one.
For example, many golf cart owners will keep their batteries charged over winter with a small panel. This setup does not need a charge controller between the panels and the golf cart batteries.
If you are hooking up a full array of 400W panels, you will need an adequate solar charge controller (likely of the MPPT variety).
Some solar solutions already have a built-in charge controller, such as the EcoFlow Portable Power Stations. The controller, batteries, inverter, power outlets, and everything else are part of the power station — you just need to add the solar panels.
How to Size Charge Controllers Correctly?
Solar charge controllers come in various sizes for arrays of varying voltages and currents. Choosing the wrong one can lead to power loss and inefficiency.
First, you’ll want to check the voltage rating on the charge controller. Most PWM controllers are rated for 12 or 24V, while MPPT controllers can handle 12, 24, 36, and 48V systems. Robust off-grid energy solutions like EcoFlow’s Power Kits come with an MPPT charge controller and 48V battery (or batteries) built-in.
Most charge controllers have an “amps” rating. Smaller PWM controllers may be rated at 10, 20, or 30 amps. MPPT controllers are often rated at higher amps — 80 or 100 amps are common — to accommodate larger PV arrays.
To determine the potential amps that a solar array can output, we need to make a simple calculation:
Let’s say we have an 800-watt array running at 12 volts. We can plug these numbers into our equation:
Amps = 800 watts / 12 volts = 66.67 amps
The system could produce up to 66.67 amps. A charge controller rated below this amount can overload and malfunction. For this example, you would want a charge controller rated at 70 amps.
You’ll also want to check that your batteries are compatible with the charge controller. Lithium-ion and lead-acid batteries utilize different technology. Most controllers are designed for one battery type or the other.
Control Set Points vs. Battery Types
Most charge controllers operate at different voltages depending on the current state of the battery. For instance, a PWM controller may charge the battery most of the way, then reduce the voltage for a final trickle charge. The level at which the controller changes voltage is called a control set point.
Different battery types require varying methods of charging. Lithium-ion batteries utilize a three-stage charging system: precharge, constant current, and supplementary.
The precharge stage uses a low current for batteries that are nearly dead. Then, the constant current stage provides a steady supply at full power. Finally, the supplementary stage keeps the lithium battery at maximum charge.
Lead-acid batteries utilize three main charging stages: bulk, absorption, and float. The bulk stage sends maximum power to the batteries until they hit around 80-90% capacity. For the absorption stage, the current begins to drop. Finally, the float stage provides a trickle charge to keep the batteries topped off.
Why Are Displays and Metering Important?
Many solar charge controllers now feature an LCD. The display allows the user to monitor essential system vitals, such as battery charge percentage, current voltage, and time remaining on the battery at the current load. Some basic controllers for smaller systems will omit the LCD screen as the information may be unnecessary.
Other systems like the EcoFlow DELTA 2 have intelligent monitoring and Smart app control. The in-built metering system lets you see the input and output levels of the battery and other critical information, including the battery’s vitals, charge time, and more, all on the smartphone app.
Understanding Control Set Points vs. Temperature
The temperature has a significant effect on battery charging. The energy in batteries flows with more ease while in warm temperatures. The battery has a harder time moving energy around as it gets colder.
Most control set points are set for room temperature operation. Temperature compensation is featured in most charge controllers to adjust the voltage for various temperatures. Some controllers have built-in temperature sensors, while others utilize a remote sensor.
Some charge controllers even allow for custom set points based on temperatures. Battery manufacturers each recommend a different adjustment based on the temperature, so this feature enables the homeowner to dial in their system.
Common Features and Settings on a Charge Controller
Charge controllers for residential applications will almost always have an LCD to convey essential information. Many controllers will allow custom set points to work well with your battery bank and climate.
Most charge controllers have built-in protection against reverse polarity, overload, short-circuiting, and other standard electrical issues.
Advanced technologies integrated into premium controllers will even allow remote monitoring on a smartphone and Bluetooth operation. Software like the EcoFlow Smart app enables you to manage these features from a smartphone.
Conclusion
Building your solar system can be challenging, as it requires you to understand the basics of electricity. However, putting the system together is manageable once you learn the essentials.
A solar charge controller is at the center of your solar system. It bridges the gap between your PV array and your battery bank. Make sure you choose the correct controller to prevent any issues down the line.
All-in-one solutions can be helpful if the electrical jargon is too much for you. The EcoFlow Solar Generators and Power Kits are a great way to switch to solar, with a built-in MPPT controller and Smart app to make metering and regulating your energy use even easier.
Frequently Asked Questions
You always need a solar charge controller if you are installing an off-grid solar system with batteries. Only the smallest panels — such as 1 or 5-watt trickle chargers — can operate without a controller. You do not need a solar charge controller for grid-tied residential systems. Instead, the utility grid regulates the electricity flow and absorbs the excess power.
A 100W panel needs a solar charge controller if it is supplying a battery. Many small solar systems utilize just one 100-watt panel and a single battery. This system would require a charge controller to regulate the current that travels into the battery.
A 7-watt solar panel does not require the use of a charge controller. These panels allow low-voltage trickle charging, which does not need regulation of the electrical flow.
EcoFlow is a portable power and renewable energy solutions company. Since its founding in 2017, EcoFlow has provided peace-of-mind power to customers in over 85 markets through its DELTA and RIVER product lines of portable power stations and eco-friendly accessories.