DIY Green Energy For Homes

Solar Charge Controller

Virtually all solar electric systems that use batteries require a solar charge controller. Sometimes called a regulator, a solar charge controller safeguards the batteries from overcharging or over-discharge.

This it achieves by regulating the power flowing from the solar panels to the batteries. When batteries are over-charged, their life-span will be significantly cut down - as a result of the electrolyte boiling to gas - and at worst, they will get damaged beyond usable form.

How does a solar charge controller work?

The most basic of solar charge controllers censors battery voltage and when it reaches a certain point, it will open the circuit to stop the charge flow. Similarly, the charge controller will disconnect the load when the battery has been discharged below a certain voltage deemed safe ‘cut off’ voltage.

On older controllers, a relay was used to open or close the circuit, which halts or starts charge flow to the batteries. More advanced controllers utilize pulse width modulation (PWM) to gradually lessen the amount of power reaching the batteries as they get closer to full charge.

This way, the batteries get fully charged with minimal stress applied to them, helping to keep them in pristine condition. This type of controller also helps to keep the batteries in a float state (fully charged) for extended periods. although pulse width modulation doesn’t have any mechanical connections to sever, it is a bit complicated.

Some pricey controllers utilize LED displays (and even LCD displays) to show what the current battery state is, the state of current flowing into the battery bank from the panels, and the state of the current being supped out by the loads.

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The most advanced charge controller is known as the maximum power point tracking (MPPT). These charge controllers can convert surplus voltage into amperage, which has many advantages.

The most widely used solar electric systems use 12-volt batteries, similar to ones used in cars - some may use different voltages but similar advantages apply to them as well. Solar panels usually have the capacity to harness much more voltage than is enough to charge the batteries.

In essence, optimal levels of charge voltage can be achieved by converting surplus voltage into amps, and at the same time reducing the charge time of the batteries. Thus, the  solar electric system will operate at optimal levels all the time.

MPPT is also very useful in reducing power losses. High energy losses result from the low voltage in the wires connecting the panels to the charge controllers (high voltages equals less energy lost). When a MPPT controller is used, higher voltages will flow through the wires, where the controller will then convert the excess voltage to more amps, which significantly  minimizes power loss in the wiring. 

Obviously, MPPT controllers cost a lot more than PWM controllers, but the benefits are worth every extra penny. If it is within your budget, you definitely need to buy a MPPT charge controller for your solar electric system.

One more function of charge controllers is to prevent current from flowing backwards. At times when the panels are not absorbing any energy, charge can be drained out of the batteries and flow backwards. A charge controller will duly detect this and disconnect the load.

So, depending on how much power you anticipate to generate, talk to your installer about the benefits of using a solar charge controller.

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