12v 6A Charge Controller

Charge Controllers

These are absolutely essential for all but the smallest solar power systems. If a solar panel's output is more than a few watts and it was directly connected to the battery, you can easily overcharge it, for when it is full, there is nothing stopping the solar panel from supplying power to the battery. And at night, a battery will discharge through the solar panel (in reverse polarity).

Many charge controllers exist on the market, from small units capable of a few amperes, up to ones that can handle 100 amps. Their features also vary, from simple fixed voltage output (via PWM), through to fully automatic, intelligent micriprocessor controlled charging systems. The higher end controllers include a LCD to display the status and statistics.

Popular small units, such as the 12v 6amp one (shown to the right) also have a "night time switching" capability. As soon as dusk falls, the night load is switched on. This is most suitable for night time lighting applications. They also feature a fixed LVD (low voltage disconnect) to prevent the battery from over-discharge when its voltage drops too low.

12v 30A LCD Charge Controller

More expensive units, such as the SBC-7130, include a three-stage charging regime to ensure the batteries are kept in better shape. A bulk charge is followed by an absorption stage, then it switches over to float charge mode. It also has a 30 amp charging capability, along with an LCD display of battery voltage, PV amps, and the number of amp hours for each of the past three days. A dual-colour LED also provides an indication of the battery state at a glance.

For the above two charge controllers, it is not advisable to connect a power inverter to the 'load' terminals. The inverter's power draw can easily exceed the current rating of the charge controller, leading to blown fuses, or ultimately, failure and fire. Unless otherwise recommended by the manufacturer of the charge controller, inverters must always be directly connected to the batteries.

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