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Collection: Solar Charge Controllers: How to choose
Solar charge controllers, or solar charge regulators, manage the current between your solar panels, battery bank and load. They are essential to protect your batteries from overcharging or draining, while maintaining a constant voltage for your load. Most "12 volt" panels generate 16 to 20 volts: in the absence of regulation the batteries will be damaged from overcharging (most 12V batteries need around 14 to 14.5 volts to fully charge).
PWM solar charge controllers
PWM solar charge controllers (pulse width modulation) are affordable and well suited to small applications (gate control, fans, small LED lights), often found in small amperage (10A to 60A).
When installing a PWM solar charge controller, always connect the system in the exact order: battery first, then load, then solar panel. Disconnect the system in the exact reverse order: solar panel, load, then battery.
MPP charge controllers
MPPT controllers (maximum power point tracking), while expensive, tend to be preferred for high power systems with constant load because of their high efficiency (large pumps or heating resistors, large battery banks). They work very well in regions with cloudy weather.
How to choose between MPPT and PWM regulators
PWM are very popular in South Africa because our weather (sunny) doesn't justify a controller that can adjust to low-light conditions. It is much more economical to use a 20% bigger solar panel with a PWM controller than a more expensive MPPT regulator with a slightly smaller panel.
PWM solar controllers have an average efficiency of 80 to 85%, whereas MPPT ones reach up to 97%. This makes a real difference if the electric load of your system is constant and high, and if you are restricted in the size & number of solar panels you can use (limited roof space).
If your system is powering a gate motor, LED security light or remote camera, an inexpensive PWM 10A or 30A solar charge controller is always sufficient.
Which solar charge controller is right for you
When choosing a solar charge controller, pay attention to the type of batteries it is compatible with. Lithium-ion and Lithium Iron Phosphate (LiFePO4 or LFP) batteries for instance often require specific controllers, as their battery charge patterns are very different from lead-acid batteries.
Make sure you use solar panels that match your battery voltage. When using a solar charge controller that can feed batteries of different voltages (12/24V or 12/24/48V), read the specifications and check what is the maximum PV input voltage for your battery (example: 23V max solar input for 12V batteries, 46V for 24V etc). The maximum voltage of your solar panel is usually described as "Open Circuit Voltage" or "Voc" in the specs of the panel.
Comparison and tests between PWM and MPPT controllers: video by @WillProwse, US Youtuber
