Solar Charge Controllers - What and Why

Solar charge controllers are required by most solar power systems that involve the use of batteries. They work to regulate the power as it moves from the solar panels to the batteries. A proper charge controller will keep the batteries from being overcharged. The simplest kind of charge controller functions to monitor the battery voltage and opens the circuit to stop the charging process when voltage reaches a certain level. PWM extends battery life even more, as it decreases stress on the battery.

The latest advancement in solar charge controllers is maximum power point tracking, or MPPT. Most solar panels produce more voltage than is needed by the batteries. An MPPT charge controller will also largely eliminate the amount of power loss that a solar power system experiences. Preventing reverse-current flow is another ability which certain modern charge controllers possess.

Why Do I Need Solar Charge Controllers?

It is extremely important to have a solar charge controller to protect your batteries from being overcharged. The output voltage of your solar panels is constantly changing. PV charge controllers come in all shapes and sizes. Easy to install, a PV charge controller is required in almost every solar power systems that utilize batteries. Most solar panel controllers come with either a simple LED or digital displays.

The current passing through the solar charge controller charges the batteries used in various household items. At night or when solar modules aren't generating any power, power can actually flow backwards from the batteries to the solar modules, draining the batteries. The solar charge regulator would ensure that this doesn't happen. If solar energy is not actually passing from the solar panels to the circuit, it disconnects the solar panels from the batteries and stops the reverse flow of current.

Because a charge controller enables you to monitor battery charging, thus avoiding over or under-charging, then if you are planning an on-grid system, you won't need a controller. If you are contemplating on off-grid system using batteries, are planning to use solar and wind power in the same system, or are merely planning a backup power source for outages-which requires batteries-then you will need to choose a good charge controller for your system.

Different Types of Solar Charge Controllers

There are several different basic types of charge controllers, the first being the series cycling controller which is probably the simplest; the series cycling controller prohibits overcharging of your batteries simply by turning your solar panel's current off and on based on the battery voltage. If the battery voltage is to nearly full charge, a mechanical relay on the controller shuts off the charge. When the battery voltage begins to fall and gets low enough, the charge controller kicks back in.

The constant voltage controller goes through bulk charge first, which allows the power to go straight from the solar panels to the batteries until they are charged. The second stage is called the absorption stage which holds the maximum battery voltage by reducing the charge current. Float charge is the third stage and occurs when the battery voltage is reduced once the charge is complete. The constant voltage charge controller avoids excessive evaporation of battery water, thus extending the life of your expensive batteries. If you are using sealed, AGM or gel batteries, the three-stage constant voltage controller would be the best, safest method of charging your system.

Finally, a diversion charge controller never cuts off from the charging source; it charges the batteries to the maximum set voltage, then the diversion control senses the voltage.