Solar Panel Solar Charge Controllers Explained

Posted June 09, 2020

In this article, we explain two different types of charge controllers to pair with your solar array and connect to RELiON lithium batteries.

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Can Solar Panels Charge Lithium Batteries?

Lithium batteries and solar panels make a great power source for an off-grid home or RV, but they need one more component to work: a solar charge controller.

What is a solar charge controller?

The charge controller protects the battery during charging and also prevents the battery from sending current into the solar panels overnight. It is the gatekeeper between a solar array and a battery. it protects the battery during charging and also prevents the battery from sending current into the solar panels overnight when the battery’s voltage is higher than the solar array’s.

Types Of Solar Panel Charge Controllers

  1. Pulse With Modulation Controller (PWM Controller)
  2. Maximum Power Point Tracking Controller (MPPT Controller)

There are two kinds of charge controllers, and both can connect your solar array to a RELiON battery. The first is a pulse width modulation controller. A PWM is like an on/off switch that connects and disconnects the solar array from the battery.

Based on the battery’s voltage, the charge controller allows bursts of current to pass from the solar array to the battery. The lower the voltage in the battery, the longer the bursts. The higher the voltage, the shorter the bursts. This is what we mean by pulse width modulation - the amplitude of the pulse remains the same, but the duration varies.

The other common type of solar charger is a maximum power point tracking controller. The MPPT monitors the voltage on both sides: the solar array as well as the battery. When the voltage of the array is higher than the voltage of the battery, the MPPT steps down the input voltage. This topology allows the controller to efficiently operate at a higher solar array voltage. . Higher array voltage means lower current while delivering the same amount of power. This translates to smaller and less expensive wiring and switch your gear between the solar array and battery bank.

An MPPT controller is always calculating and delivering the greatest amount of power it can safely send between the solar array and the battery: that’s the maximum power point. This maximum power point will vary depending on sun angle, changes in ambient cell temperature, and cloud cover. As a result, an MPPT charge controller operates more efficiently and lets you harvest more energy over time. This can translate into faster and more efficient battery charging over time. An MPPT controller sees the most benefit when operating during colder times of the year but still provides the advantage of higher voltage array wiring regardless of temperature.

Pulse width modulation controllers are less expensive and are appropriate when you have relatively small, simple set-ups like an RV or boat. If you’re somewhere with a lot of sunlight and you don’t draw too much from your battery, a pulse width modulator could be the right choice.

If you have a larger or more complex system with a greater physical distance between the battery bank and array, or you are using your system in a location with variable weather, a maximum power point tracking controller is a better option.

Before buying a charge controller, take the time to sketch out how much power you can generate from your solar panels, what sort of activities you will be powering, and the conditions where you’ll need this power. That will help guide you to the right purchase. And if you’re still not sure, contact us and we’ll be happy to work with you.

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