What Size Charge Controller Do I Need For A 100W Solar Panel
If you know how to install a 100-watt solar panel. then you know that a charge controller is a crucial part of your solar array, but just how big should it be, exactly?
When it comes to figuring out what size charge controller you need for a 100-watt solar panel, there are many rough estimates that people use to guess the size that will be needed.
But, these estimates vary quite widely, and just guessing the size of the charge controller because it’s a 100-watt solar panel is a bit risky for your solar system.
To make sure you are accurate, prevent any damage to your batteries, and make sure you are getting the most out of your solar array, it is best to calculate the size and type of the charge controller needed for a 100-watt solar panel specifically for the system you are planning to use.
By doing so, you will get a more accurate answer, and prevent damage and save money in the long run.
What Is A Charge Controller And Do You Always Need One?
First of all, for those of you who were told that you need to get a charge controller but actually have no idea what it is or does, let’s do a recap on what exactly the role of a charge controller is.
To put it simply, a charge controller is a device that helps to prevent batteries that are connected to solar panels from overcharging.
A solar charge controller regulates the voltage and current going to the batteries from the solar panels. It makes sure that the batteries are not overcharged during the day, and it also ensures that the power from the batteries doesn’t run back to the solar panels overnight and leave them drained in the morning.
Batteries usually have a capacity of about 12 volts, and if the voltage coming from the solar panel is more than that, it will likely end up overcharging and causing damage to the battery.
To answer the question of whether you always need one, the answer is not always, but in the majority of cases, you do.
A simple way to tell if you need one is if your solar panel produces 2 or fewer watts for every 50 amp-hours, then it is not necessary.
Even though it is something that you don’t always have to have, we would suggest investing in one anyway to rather be safer and save more electricity.
Different Types Of Charge Controllers
There are two different types of charge controllers that you can get. The one that you end up choosing will depend on your 100-watt solar panel specifications. as well as the makeup of your solar system and the needs that it has.
The two different types are a Pulse Width Modulation (PWM) charge controller and a Maximum Power Point Tracking (MPPT) charge controller.
The main difference between the two is that the PWM is a lot more simple than the MPPT, and can, unfortunately, lead to a substantial loss of solar energy.
MPPT charge controllers are usually used in larger solar systems. PWM controllers are normally sufficient for 100-watt solar panels, but if you know how to connect 2 100-watt solar panels in series, and choose to do so, then an MPPT controller will most probably be needed.
How To Determine What Charge Controller You Will Need
Now that you have come to terms with what exactly charge controllers are, and what type you will need, I’m sure you are still wondering “ what size charge controller do I need for a 100-watt solar panel? ”
It is important to have a correctly sized charge controller. If your charge controller is too small, then the amount that the batteries can be charged, as well as their power output, will be limited and will result in loss of energy and won’t allow your solar system to work with peak performance.
For this reason, your charge controller either needs to be spot on with its size, or slightly bigger than what is required to get the maximum performance out of your system.
As much as the size is important, it is also crucial to make sure you don’t go for the cheapest, poorest quality charge controller.
Although you may think it is something you can skimp on when you see the cheap ones that are available on the market, rather don’t.
If you do, it can end up damaging the batteries of your solar array and can lead to failure of the batteries, as well as the entire system as a result, leaving you in the dark.
Estimates Of Charge Controller Sizes for 100-Watt Solar Panels
There are several suggestions given for the size of charge controllers needed according to the size of the solar panels they will be connected to.
Some say for a 100-watt solar panel your charge controller should be 10 amps, others say 7.5 amps for every 100 watts, and some sources suggest that you should calculate the total watts of your solar panels, and divide that amount by 14.4 if your system is 12V, by 28.8 if it is 24V, and by 58.8 if your system is 48V.
With the huge discrepancies between these suggestions, it is not worth the risk of just randomly choosing one to follow and hoping for the best.
Instead, we would recommend that you calculate the size of the charge controller needed specific to your 100-watt solar panel array.
This way it will be much more accurate and beneficial to your system and can end up saving you money and frustration.
Factors To Consider Before Determining The Size Of The Charge Controller
Before you can determine what size charge controller you will need, you will have to determine what the size and structure of your solar array are going to need to be.
Although this may seem overwhelming, don’t panic just yet, we are going to break down the process of figuring out the sizing of your solar array step by step.
The Load Of Appliances That Need To Be Powered
First, you are going to need to estimate how much load and appliances you are going to be running, as well as for how long.
This can be done by calculating the amperes or the watts that each appliance uses. These details should be stated at the back of each appliance.
By using the above, and estimating how long you will need each appliance for, you can work out the amp hours required for each appliance.
Add the individual amp-hours together, and see how many amps you are going to require per hour, as well as for how many hours they need to be supplied.
Battery Type And Size
You will also need to determine what type of battery you’d like to use. lithium or lead-acid. as this will affect the size of the battery that you will need to meet the demands of your load.
After you have chosen the type, you will be able to determine the size, and the number of, batteries needed to keep your appliances running.
Amount Of Solar Panels Needed
You will need to figure out how many solar panels you need, especially if you are planning on using 100-watt solar panels. Ideally, your solar panels should be big enough to fully charge your chosen battery on a sunny day, but also provide enough energy if it is overcast.
For this reason, you might want to consider more than one 100-watt solar panel, depending on the size of the battery you have chosen.
Since there are so many changing and unpredictable variables to consider, nature being one of them, it may be wise to get too many solar panels rather than too little.
Calculating The Size Of The Charge Controller Needed For A 100-Watt Solar Panel
Since you have worked out all of the above, you can now figure out what size charge controller you will need for your specific 100-watt solar panel array.
To do the calculation, we suggest using the formula power = voltage x current.
Since we know the power, and the voltage, we need to work out the current. This can be done by rearranging the formula to current = power/voltage.
In our case, 100/12 = 8.33 amps. So, if you have one 100-watt solar panel, a 10 amp charge controller would be necessary, as it is safer to round up.
If we had 3 100-watt solar panels, the equation would be 300/12 = 25 amp, so we would suggest getting a 30 amp charge controller.
So, even though the rough estimates of the size of the charge controller for a 100-watt solar panel may be close enough to our calculations, it is safer for you to work out the size as we did, and not just guess.
This may be more tedious to do but can possibly save you a lot of money and troubles in the long run.
If you are still struggling with the process of figuring out exactly how big your solar array needs to be, before you can even attempt calculating the size of the charge controller, we would suggest consulting a professional.
They can guide you as to how big the solar array should be, which will allow you to then work out the size of the charge controller that you will need.
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Battery Charge Controller
For many people, building their own solar panel system and living off-grid is becoming a reality instead of a dream. Connecting the solar panels directly to a single battery or bank of batteries for charging may work, but is not a good idea. What’s needed is a battery charge controller to safely charge and discharge your deep cycle battery for a longer lifespan.
A standard 12 volt solar panel which can be used to recharge a battery, could actually be putting out nearly 20 volts at full sun, much more voltage than the battery needs. This difference in voltage between the required 12 volts need for the battery and actual 20 volts being generated by the solar panel translates into a greater current flow into the battery.
This results in too much unregulated solar generated current overcharging the battery which could cause the electrolyte solution within the batteries to overheat and evaporate off, resulting in a much shortened battery life and ultimately, complete battery failure.
Then the quality of the charging current will directly affect the life of any connected deep cycle battery, so it is extremely important to protect batteries of a solar charging system from being overcharged, or even undercharged, and we can do just that using a battery charge regulation device called a Battery Charge Controller.
A battery charge controller, also known as a battery voltage regulator, is an electronic device used in off-grid systems and grid-tie systems with battery backup. The charge controller regulates the constantly changing output voltage and current from a solar panel due the angle of the sun and matches it too the needs of the batteries being charged.
The charge controller does this by controlling the flow of electrical power from the charging source to the battery at a relatively constant and controlled value.
Thus maintaining the battery at its highest possible state of charge while protecting it from being overcharged by the source and from becoming over-discharged by the connected load. Since batteries like a steady charge within a relatively narrow range, the fluctuations in output voltage and current must be tightly controlled.
Solar Battery Charge Controller
Then the most important functions of battery charge controllers used in an alternative energy system are:
- Prevents Battery Over-charging: This is too limit the energy supplied to the battery by the charging device when the battery becomes fully charged.
- Prevents Battery Over-discharging: Automatically disconnect the battery from its electrical loads when the battery reaches a low state of charge.
- Provides Load Control Functions: Automatically connect and disconnect the electrical load at a specified time, for example operating a lighting load from sunset to sunrise.
Solar panels produce direct or DC current, meaning the solar electricity generated by the photovoltaic panels flows in only one direction only. So in order to charge a battery, a solar panel must be at a higher voltage than the battery being charged. In other words, the voltage of the panel must be greater than the opposing voltage of the battery under charge, in order to produce a positive current flow into the battery.
When using alternative energy sources such as solar panels, wind turbines and even hydro generators, you will get fluctuations in output power. A charge controller is normally placed between the charging device and the battery bank and monitors the incoming voltage from these charging devices regulating the amount of DC electricity flowing from the power source to the batteries, a DC motor, or a DC pump.
The charge controller turns-off the circuit current when the batteries are fully charged and their terminal voltage is above a certain value, usually about 14.2 Volts for a 12 volt battery. This protects the batteries from damage because it doesn’t allow them to become over-charged which would lower the life of expensive batteries. To ensure proper charging of the battery, the regulator maintains knowledge of the state of charge (SoC) of the battery. This state of charge is estimated based on the actual voltage of the battery.
During periods of below average insolation and/or during periods of excessive electrical load usage, the energy produced by the photovoltaic panel may not be sufficient enough to keep the battery fully recharged.
When the batteries terminal voltage starts to drop below a certain value, usually about 11.5 Volts, the controller closes the circuit to allow current from the charging device to recharge the battery bank again.
In most cases a charge controller is an essential requirement in any stand-alone PV system and should be sized according to the voltages and currents expected during normal operation. Understanding your batteries and their charging requirements is also a must for any battery based solar system.
Any battery charge controller must be compatible with both the voltage of the battery bank and the rated amperage of the charging device system. But it must also be sized to handle expected peak or surge conditions from the generating source or required by the electrical loads that may be connected to the controller.
There are some very sophisticated charge controllers available today. Advanced charge controllers use pulse-width modulation, or PWM. Pulse width modulation is a process that ensures efficient charging and long battery life. However, the more advanced and expensive controllers use maximum power point tracking, or MPPT.
Maximum power point tracking maximizes the charging amps into the battery by lowering the output voltage allowing them to easily adapt to different battery and solar panel combinations such as 24v, 36v, 48v, etc. These controllers use DC-DC converters to match the voltage and use digital circuitry to measure actual parameters many times a second to adjust the output current accordingly. Most MPPT solar panel controllers come with digital displays and built-in computer interfaces for better monitoring and control.
Choosing the Right Solar Charge Controller
We have seen that the primary function of a Battery Charge Controller is to regulate the power passing from the generating device, be it a solar panel or wind turbine to the batteries. They assist in properly maintaining the solar power system batteries by preventing them from being overcharged or undercharged, thus offering long life to batteries.
The solar current being regulated by a battery charge controller not only charges batteries but can also be passed to inverters for converting the direct DC current to alternating AC current to supply the utility grid.
For many people who want to live “off grid”, a charge controller is a valuable piece of equipment as part of a solar panel or wind turbine power system. You will find numerous charge controllers manufactures online, but choosing the right one can sometimes be quite confusing and to add to your worries they are not cheap either, so finding a good quality solar charge regulator really matters.
It’s best not to go for those low quality cheaper ones, as they may actually harm the battery life and increase your overall expense in the long run. For a little peace of mind then why not Click Here and check out some of the better battery charge controllers available from Amazon and learn more about the different types of solar charge controllers available as part of your solar power system helping you to save money and the environment.
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Комментарии и мнения владельцев already about “ Battery Charge Controller ”
Hi. Im considering a combination of wind and solar power generation for my boat kept on mooring. I think a combination would be good as Scotland not blessed with lots of sun and my mooring is a bit sheltered with harbour wall. Can i plug output from 2amp wind turbine into a Renogy mppt regulator (20 amp), would it manage the power to my batteries in same way as with a solar panel?
MPPT controllers have been used for photovoltaic (solar) power for a long time, but can also be used for wind turbines. In real life the wind speed is not constant, but changes continuously, thus the ideal rotor RPM for maximum torque will also change. What is important to remember is that there is an optimum RPM for each wind speed, and that is where we want to run the wind turbine to achieve MPPT. However, to work properly the controller needs an MPPT power curve that is specific for the wind turbine that you want to hook up to the controller. So check the MPPT’s manual if you can connect it to a wind turbine. If not, then it is not advisable since unlike PV, a wind turbine can output much higher open circuit input voltages (Voc) when it is not loaded up or your batteries are full.
I have a 730 W, 76 V solar panels system charging 24 V battery set up using a Morning Star MPPT charge controller in an OFF GRID set up. Which is the best suited APC or LUMINOUS UPS/Inverter that is solar compatible that can be used.
Hello, I have read your site with interest. We have a large dwelling with a business operating from it. Our standing load without all onsite is around 4KW This is a combination of servers and IT equipment, freezers, fridges etc. When all onsite with heating lighting TV’s etc. this can reach 10KW our energy costs are spiralling out of control. We have a large paddock approx 50m from the nearest 240V electrical connection into the site wiring that is in a barn. We are looking at taking a step into solar. Our initial aim is to simply power the office load using purely solar Generated energy whenever it is operating and obviously use the grid for any shortfall. We know the property will consume all of the power generated. We had a couple of thoughts. 1) Simple system. Setup an array that can generate approx 3KW and connect it to a Solar inverter and simply connect that into the property wiring system as an input. Whatever it produces should be consumed first before we need to get energy from the grid. Is this assumption correct assuming we have a local load at or exceeding the solar-generated capacity? 2) As an expansion of 1) above. We would look to build a larger array and connect that to a battery bank (this looks like the black magic area) that has enough capacity to provide a stable supply to an inverter that would then be connected as before into the property wiring systems that would provide a variable load of between 4 and 10KW we have seen peaks of 12KW on our monitor that is clamped onto the incoming 100A 240V Grid connection. How would we size the array and battery system and corresponding Invertor etc. Are higher voltage panels better than lower voltage panels? Are higher string voltages better than lower voltages from a power conversion point of view. e.g. is it more efficient to convert from 48V to 240V rather than 12 or 24V to 240V If I have a string of 24V 1000Ah made up of a series connected 2 x parallel 12V strings of 5 x 12V 200Ah batteries giving me 24V 1000Ah of capacity or in theory 24KWh what size inverter would I need to provide power into the property and would my system use the power I have before going to the grid? I am sure some of these questions are a bit basic but we are very DIY-orientated people and want to build this ourselves. Any help in understanding this would be great. I am sure there is much left out of my note. Like cable sizing etc. Logically I think we know what we think is happening, but, that doesn’t make it so! Like will we consume all we have before taking anything from the grid? I apologise for any typos or grammer. Cheers Tony
There are a number of good points raised here, and we will attempt to answer them. Firstly, an inverter fed grid-connected, or grid-tied system is basically a bunch of solar panels (or turbines) connected to a single inverter (or a collection of small inverters) feeding power directly to the utility grid. Generally, PV inverters operate as current sources injecting electric current into the utility grid in-phase with the grid voltage. It is commonly assumed that ALL the power generated by the PV panels (array) is consumed at the point of generation but this is not always the case. Power consumed is both active (real) and reactive. PV panels generate active power only. If your average power consumption is, for example, 10kWh per day, and you generate 12kWh for the 4 hours of full sun that day, then some of the inverters output power maybe autoconsumed and some may flow into the utility grid. Equally 100% inverter current may flow into the grid and you may consume 100% from the grid, just slowing down your energy meter in the process. On average PV panels generate maximum power for 4 to 5 hours of full sun per day as they do not consistently generate power 24 hours per day at their nominal output wattage rating. Oversizing an inverter by having more DC input power than the inverters AC output power, may increase power output in lower light conditions, thus extending the 5 hours. As would solar tracking. Connecting a battery bank would allow for more autonomy but at a cost and an increased array size, as now the array has to charge batteries for 5 hours plus feed the grid. Then the size and type of grid-connected system would ultimately depend on how many hours of autonomy you require and how much you are willing to pay upfront. Higher string voltages are better providing everything stays within tolerance at worst case conditions. As P = VI, a higher voltage (V) means a lower current (I) for a given power (P) and therefore smaller diameter cabling so cheaper. PV panel voltage depends on the wattage (100W or 400W) of the panel. Higher PV wattages means physically bigger panels, which means more m 2 of installation area.
the article states the controller should stop charging a 12V battery at approx 14.2V, what about 6 volt batteries – same?
No of course not. A single 3-cell 6 volt rechargeable battery should have a fully charged terminal voltage of about 6.35 volts. To correctly charge a wet battery, the output voltage of the charging system needs to be slightly higher than the batteries fully charged terminal voltage, to ensure that the charging current flows in the direction from charger to battery. A constant voltage equal to between 2.35 to 2.45 volts per cell is recommended for charging storage batteries. Thus for a 12 volt, 6-cell battery this is between 14.1 and 14.7 volts, so the charge controller should stop charging the battery once this voltage level is reached, or switch to a low current float charge. For a 6 volt, 3-cell battery this voltage level is between 7.05 and 7.35 volts.
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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- 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.
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.
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!
Connect Solar Panel to Charge Controller: 3 Steps (w/ Videos)
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.
In this guide I’ll show you how to connect a solar panel to a charge controller in JUST 3 steps.
To help you out, I’ve made a wiring diagram and step-by-step videos. Follow along and your charge controller will be wired and set up properly in no time.
Note: I’ve sized the materials for my energy needs. You can copy them as-is or adjust as necessary.
Step 1: Connect the Battery to the Charge Controller
Note: These installation instructions should not supersede those in your charge controller’s or battery’s manual. Where these instructions differ from your manual’s, follow your manual!
Check out the wiring diagram to see how to connect a solar panel to a charge controller:
Here’s the important thing to know:
Connect the battery to the charge controller FIRST. Then you connect the solar panel SECOND.
If you do it in the wrong order, you can damage the charge controller. And that just wouldn’t be any fun.
Ok! Let’s connect this battery.
Connect the negative battery cable to the “-” battery terminal on the charge controller. Connect the positive battery cable to the “” battery terminal.
Now connect the battery cables to the battery terminals. Connect negative first, then positive.
Your charge controller should turn on or light up. For instance, mine has a light labeled “BATT” that turns on when the battery is properly connected.
Your battery is now connected!
Step 2: Connect the MC4 Solar Adapter Cables to the Solar Panel
This step takes all of 20 seconds to do.
Locate the MC4 connectors at the ends of your solar panel’s cables. There’ll be a male and a female one. They’ll look like this:
Connect the MC4 inline fuse and positive solar adapter cable to the positive solar panel cable. Connect the negative solar adapter cable to the negative solar cable. Don’t let the exposed wires touch! ⚡
Didn’t I say it’d take all of 20 seconds?
Step 3: Connect the Solar Panel to the Charge Controller
Your battery is connected.
Your solar panel wires are ready to go.
Now it’s time to do what you came here to do — connect solar panel to charge controller!
Connect the negative solar cable to the “-” solar terminal on the charge controller. Connect the positive solar cable to the “” solar terminal.
Note: On some charge controllers, the solar terminals are labeled “PV.” This stands for “photovoltaic,” which refers to the method of producing energy using solar panels.
Like before with the battery, the charge controller should light up or somehow indicate that the solar panel is properly connected.
At this point, consult your charge controller’s manual to see if you need to program it at all. You may have to indicate your battery type, voltage, or other details.
Fortunately for me, my controller’s default settings matched my system’s specs, so I didn’t have to change anything.
And that’s it!
Now you know how to connect a solar panel to a charge controller!
Whenever you want to disconnect your solar panel, be sure to do everything in reverse order: disconnect the panel first, THEN disconnect the battery.
Put your solar panel in the sun, and let it charge your battery with free solar energy. Relax and daydream about your next DIY solar power project.
Tip: If you want some ideas on how to add on to this setup, check out my tutorial on making your first solar panel system.
Solar Panel to Charge Controller Wiring FAQ
Why do I need solar adapter cables?
Your solar panel’s cables likely come with pre-attached MC4 connectors. MC4 connectors are great for connecting two solar PV wires together…
…but they can’t connect to a charge controller. So we need solar adapter cables.
Solar adapter cables have an MC4 connector on one end and are stripped at the other. That way, you can connect the MC4 connector to the solar panel cable and then connect the stripped end to the charge controller.
What if my solar panel doesn’t have MC4 connectors?
Buy some solar adapter cables with the connectors that match the ones on your solar panel wires.
If you can’t find any, you might have to make your own by cutting two lengths of solar PV wire, stripping both ends, and crimping on matching connectors.
Why isn’t my charge controller lighting up/turning on when I connect my solar panel?
Your panel probably just needs some sun!
Put it outside in direct sunlight. Your charge controller should light up or somehow indicate that the panel is properly connected and the battery is charging.
If that doesn’t work, check your charge controller’s manual for troubleshooting.
MPPT vs PWM | The two major types of solar charge controllers are:
As shown in the chart below, PWM controllers tend to be smaller and they operate at battery voltage, whereas MPPT controllers use newer technology to operate at the maximum power voltage. This maximizes the amount of power being produced which becomes more significant in colder conditions when the array voltage gets increasingly higher than the battery voltage. MPPT controllers can also operate with much higher voltages and lower array currents which can mean fewer strings in parallel and smaller wire sizes since there is less voltage drop.
PWM controllers need to be used with arrays that are matched with the battery voltage which limits what modules can be used. There are many 60 cell modules with maximum power voltage (Vmp) equal to about 30V, which can be used with MPPT controllers but are simply not suitable with PWM controllers.
To answer the question: Which is better, PWM or MPPT? All things being equal, MPPT is a newer technology that harvests more energy. However, the advantages of MPPT over PWM controllers come at a cost, so sometimes a less expensive PWM controller can be the right choice, especially with smaller systems and in warm climates where the MPPT boost is not as significant.
PWM vs. MPPT Solar Charge Controller Comparison
|Array voltage is “pulled down” to battery voltage
|Convert excess input voltage into amperage
|Generally operate below Vmp
|Operate at Vmp
|Suitable for small module configurations
|Suitable for large module configurations that have a lower cost per watt
|Often chosen for very hot climates which will not yield as much MPPT boost
|Provide more boost than PWM, especially during cold days and/or when the battery voltage is low
Every Morningstar PWM and MPPT solar charge controller is listed on the Morningstar Product Series page. Each listed product is hypertext linked to its product page that includes datasheets, operation manuals, and other helpful information.
Traditional solar regulators featuring PWM (Pulse Width Modulation) charging operate by making a connection directly from the solar array to the battery bank. During bulk charging when there is a continuous connection from the array to the battery bank, the array output voltage is ‘pulled down’ to the battery voltage. The battery voltage adjusts slightly up depending on the amount of current provided by the array and the size and characteristics of the battery.
Morningstar MPPT controllers feature TrakStar technology, designed to quickly and accurately determine the Vmp (maximum power voltage) of the solar array. TrakStar MPPT controllers ‘sweep’ the solar input to determine the voltage at which the array is producing the maximum amount of power. The controller harvests power from the array at this Vmp voltage and converts it down to battery voltage, boosting charging current in the process.
Why Choose PWM Over MPPT
The preceding discussion of PWM vs. MPPT may cause some to wonder why a PWM controller would ever be chosen in favor of an MPPT controller. There are indeed instances where a PWM controller can be a better choice than MPPT and there are factors which will reduce or negate the advantages the MPPT may provide. The most obvious consideration is cost. MPPT controllers tend to cost more than their PWM counterparts. When deciding on a controller, the extra cost of MPPT should be analyzed with respect to the following factors:
Low power (specifically low current) charging applications may have equal or better energy harvest with a PWM controller. PWM controllers will operate at a relatively constant harvesting efficiency regardless of the size of the system (all things being equal, efficiency will be the same whether using a 30W array or a 300W array). MPPT regulators commonly have noticeably reduced harvesting efficiencies (relative to their peak efficiency) when used in low power applications. Efficiency curves for every Morningstar MPPT controller are printed in their corresponding manuals and should be reviewed when making a regulator decision. (Manuals are available for download on the Morningstar website).
The greatest benefit of an MPPT regulator will be observed in colder climates (Vmp is higher). Conversely, in hotter climates Vmp is reduced. A decrease in Vmp will reduce MPPT harvest relative to PWM. Average ambient temperature at the installation site may be high enough to negate any charging advantages the MPPT has over the PWM. It would not be economical to use MPPT in such a situation. Average temperature at the site should be a factor considered when making a regulator choice
Systems in which array power output is significantly larger than the power draw of the system loads would indicate that the batteries will spend most of their time at full or near full charge. Such a system may not benefit from the increased harvesting capability of an MPPT regulator. When the system batteries are full, excess solar energy goes unused. The harvesting advantage of MPPT may be unnecessary in this situation especially if autonomy is not a factor.
Why Choose MPPT Over PWM
Increased Energy Harvest:
MPPT controllers operate array voltages above battery voltage and increase the energy harvest from solar arrays by 5 to 30% compared to PWM controllers, depending on climate conditions.
Array operating voltage and amperage is adjusted throughout the day by the MPPT controller so that the array’s power output (amperage X voltage) is maximized.
Less Module Restrictions:
Since MPPT controllers operate arrays at voltages greater than battery voltage, they can be used with a wider variety of solar modules and array configurations. over, they can support systems with smaller wire sizes.
Support for oversized Arrays
Unlike PWM controllers, MPPT controllers can support oversized arrays that would otherwise exceed the maximum operating power limits of the charge controller. The controller does this by limiting the array current intake during periods of the day when high solar energy is being supplied (usually during the middle of the day).
While energy from the array is capped or shaved off during the middle of the day, the oversized array is able to provide more power during teh early and late part of the day compared to smaller non-oversized array.
Download Our PWM vs MPPT White Paper
Please click here to download the Traditional PWM vs Morningstar’s TrakStar™ MPPT Technology white paper. Morningstar’s MPPT charge controllers use the TrakStar advanced control MPPT algorithm to harvest maximum power from a Solar Array’s peak power point. It is generally accepted that even the most basic MPPT controller will provide an additional 10‐15% of charging capability, when compared to a standard PWM regulator. Besides this extra charge capability, there are several other important differences and advantages between MPPT and PWM technologies that are outlined in this whitepaper.