How to Choose a Solar Charge Controller (The EASY Way) – Green Building Elements

By On Mar 31, 2022

Solar charge controllers are an essential part of any off-grid solar panel system as they protect the battery from overcharging. To choose the right solar charge controller for your system, you only need to take care of two things:

voltage
Current capacity (in amperes)

In this simple guide, we’ll explain how to choose a solar charge controller in just two steps and help you get the most out of your machine.

Step 1: Choose the right voltage

Your solar charge controller needs to be compatible with the voltage of your system, so this is the first thing to consider when making your selection. Most systems use one of the following:

But that doesn’t mean you should have a different battery voltage. The voltage at the battery and charge controller of your system must match (1)

While the primary function is to prevent battery overcharging, many other functions can also be used including low voltage load disconnection, load regulation and control, backup power source control, power diversion to and auxiliary load, and system monitoring.

Some solar charge controllers, namely inexpensive PWM controllers, can only be used with one voltage, while more expensive MPPT controllers can pair voltages that do not match.

Step 2: Select the appropriate power capacity

The next thing to consider when choosing a solar charge controller is its current capacity. This means your charge controller must be large and powerful enough to handle the amount of energy your solar panel array is producing.

To calculate the current capacity required, determine how many amps your system typically produces and add 25% to account for transient increases in current levels (2).

When in doubt, it is always better to have a solar charge controller that is too big than too small.

Using a solar charge controller with too few amps (i.e. improperly sizing the charge controller) can result in inefficient energy conversion and overheating, but using a controller larger than you need will have no ill effects.

Other things to look out for when choosing a solar charge controller

As you can see, finding the right solar charge controller for your PV system shouldn’t be too daunting. If you’re still feeling a bit uncomfortable with the process, here’s a great image to clear things up:

I won’t spoil it for you, but once you know the basic specs you’re looking for, you’re practically ready to start shopping. However, before you buy a charge controller, there are a few other things you can consider to find the model that’s best for you.

Multi-voltage function

Solar charge controllers with multi-voltage function allow you to adjust the charge voltage setpoint to make the device more effective. In general, your voltage set point should be directly inverse of your battery temperature to allow it to fully charge without overheating.

In other words, you should increase the setpoint in colder weather and decrease it in warmer months.

charge control

Load control refers to the ability to turn off your battery’s output when the charge controller detects that the battery bank is running low. Most charge controllers have this feature, so it’s usually a question of whether you want a controller with automatic load control or do you prefer manual.

remote access

If you’re willing to pay a little more, you can get a solar charge controller that lets you monitor and control it from anywhere. This is especially useful if you travel frequently and want to keep track of your solar panels and charge controllers (3)

Typical balance of system equipment for a standalone system includes batteries, charge controllers, power conditioning equipment, safety equipment, and gauges and instruments.

Remote access would fall into the instrumentation category, and this would give you even more control over your energy usage.

It’s important to monitor your system’s charge, current, voltage (including open circuit voltage), temperature, and more. So make sure the controller you choose has an easy-to-read display. Many newer models have distinctive LCD displays that are easy to read at a glance.

frequently asked Questions

The main types of solar charge controllers are PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking). Pulse width modulation charge controllers, or PWM charge controllers, were the original charge controllers, simpler in design and less expensive than MPPT charge controllers.

Maximum Power Point Tracking charge controllers or MPPT charge controllers limit their power to ensure batteries are not overcharged, resulting in efficiencies of 90% or more. This makes MPPT charge controllers relatively more expensive but better suited for larger solar panel systems where efficiency is important and in colder, cloudier climates (4).

You can get a good deal on a solar charge controller by taking your time and shopping at places like Green Building Elements.

Decide whether a PWM (Pulse Width Modulation) charge controller or MPPT (Maximum Power Point Tracking) charge controller is best for your solar panels and desired connected devices, then size accordingly to get the best to get out of your money and your machines.

If you’re looking for recommendations, click or tap here to go to our shopping guide, which features all of our top picks of the year.

Technically, you don’t need a warranty on your solar charge controller, but having one doesn’t hurt.

Parts occasionally wear out, so it’s a good idea to have a guarantee on solar devices, especially MPPT and PWM charge controllers, as they can get quite expensive. Most charge controller warranties will protect you for three to five years, but you should always check before you buy.

references

Batteries and charging control in self-sufficient photovoltaic systems. Retrieved from: http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1292-01.pdf
SOLAR CHARGE CONTROLLER DEEP CYCLE BATTERY CHARGE. Retrieved from: https://www.bluepacificsolar.com/charge-controllers.html
Required balance of system equipment for renewable energy systems. Retrieved from: https://www.energy.gov/energysaver/balance-system-equipment-required-renewable-energy-systems
WHAT IS THE DIFFERENCE BETWEEN MPPT AND PWM CHARGE CONTROLLERS? Retrieved from: https://www.renogy.com/blog/what-is-the-difference-between-mppt-and-pwm-charge-controllers/