The Different Solar Charge Controllers in Solar Energy Systems.

This solar charge controller is a very vital part of a renewable solar energy system. Though, in my experience, I have noticed many new guys bypass it as something not that useful to be spending money on it.

What is a solar charge controller?

It is a solar charge regular designed to optimise the charging of batteries by regulating the current and voltage coming from the solar panel.

It is connected between the batteries and the solar panel/panels.

^{Source: A simplified diagram of a solar system showing the solar charge controller}

This diagram is an oversimplified than what is obtainable in a real-life connection; there are circuit breakers between the battery and the charge controller and between the solar panel and charge controller.

Real-life connection looks like this image of a charge controller showing the connection of a circuit breaker and surger arrestor before the batteries (image credit: me)

As I mentioned earlier in my article The Battery Care in Renewable Energy: The Use of Multi-stage Battery Charging System, there is need to charge the batteries properly to avoid getting their lifespan reduced.

To do that in a solar setup a suitable charge controller is used.

Principle of operation

How a solar charge controller works is dependent on the type of controller. There are two types of solar charge controller, there is

1. Pulse Width Modulator (PWM) controllers and;
2. Maximum Power Point Tracking (MPPT) Solar Charge Controllers.

PWM Controllers

The pulse width modulation transfers pulses of electricity to the battery at varying intervals. As each pulse ends, the controller switches off and measures the battery charge capacity and then depending on the charge level adjusts the output values to be the same. It behaves like an intelligent switch between the solar panels and batteries through turning on and off thus controlling the current and voltage that goes to the battery.

This method ensures that voltage from the solar panel arrays would always be pulled down to near that of the battery's voltage.

For example, if you are using a low-cost PWM solar charge controller on a 24V battery bank and 250W solar panel.

During charging, the 250w solar panel is connected to the battery.

Let's assume you have an 8A 250w solar panel connected to a 24V battery bank through a low-cost PWM charger. During charging, we would have the following power.

P= IV
P= 24 x 8 = 192W

This system effectively loses 52W (250-192)W

This loss even gets worse during cloudy days.

So you should give it a thought the next time you are offered a PWM charge controller very much cheaper than MPPT by that dishonest salesman who assures you they are the same. That is a lie.

The PWM charge controller is a low-cost solution for small systems only when solar cell temperature is moderate to high (between 45°C and 75°C). To fully utilise the potential of the MPPT controller, the solar panel array voltage should be noticeably higher than the battery voltage.

MPPT Charge Controller

This controller is a more sophisticated system that comes at a higher cost too. A typical PWM to MPPT charge controller's price is usually in the ratio of 1:2 or something close or more.

The MPPT charge controller is most recommended for large solar panel arrays where the harvested input voltage is considerably higher than the battery voltage. It transforms this "excess" voltage into current and thus charges the battery faster.

Take a look at this MPPT solar charge controller made by Fangpusun that my friend uses.

^{MPPT solar charge controller in action (Image taken by me)}

Measured quantity	Input	Output)
Voltage (V)	100.0	26.8
Current (A)	6.3	21.2
Wattage (W)		570

If you could see the displayed parameters, (apologies for the poor picture quality). You would notice these.

Notice that the input voltage coming in from solar panel is 100V This is far higher than the battery voltage (26.8V), this is a 24Volt DC system. But the MPPT converts this excess voltage to current (21.2A) making the batteries charge faster.

The MPPT can adjust its input voltage to harvest the maximum power coming in from the solar array and converting it to appropriate voltage and current to optimally charge the system batteries.

If there is any questions, correction or recommendation, please drop it in the comment section. Thank you for reading.

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