“WHY DO I NEED A SOLAR CHARGE CONTROLLER? I ALREADY HAVE PANELS”
SOLAR PANELS are designed to produce power from the sun. Every solar panel has many cells, each producing about 0.5 volts when exposed to sunlight. These cells are added together in a series of parallel and series connections to produce workable power most often used to charge batteries.
In a nutshell, this power needs to be controlled in order that it does not damage the batteries by overcharging them and destroying the battery cells in the process.
The BATTERY is a charge and discharge energy storage device: Much like a fuel tank in a car. Fill the tank, drive slow and steady on the accelerator, and your car will drive for many kilometres. Drive it hard and heavy on the accelerator, the tank will run dry much faster with far fewer kilometres. Batteries are no different. They will need to be recharged efficiently enough to be full when they are needed.
Here’s how we introduce the SOLAR PANELS to the BATTERY:
The SOLAR CHARGE CONTROLLER is the essential link between the two. It controls the solar charge voltage so it does not exceed the safe battery recharge voltage; it also controls the level of charge on the battery and cuts the power delivered to a very small trickle to keep the battery fully charged and ready.
The PWM charge controller is the cheapest controller but is limited in what it does. It mimics the battery voltage and thus if the battery is at 10.5 volts, it will put a 10.5 volt charge at full SOLAR PANEL current into the battery. This is a slow charge, and any extra voltage is blocked and thus wasted. “It is not very efficient, but it does the job, right?” If you say so, I suppose. Batteries often are not full for when they are needed- the sun sets before they are full.
The MPPT controller constantly tracks the maximum power output from the panels, remembers the ACTUAL full battery voltage and applies this power at this voltage. The charge is very much faster and far more efficient. But that’s not all it does. It also uses the excess voltage to make a few MORE amps to speed up the charge if needed. It can also be set to recondition the battery cells to gain optimum service life from them. This controller is far more expensive than the PWM charger, sure, but it saves a huge amount of time and battery life!