Charge Controller

The main function of a charge controller or regulator is to fully charge a battery without permitting overcharge while preventing reverse current flow at night.

It saves you money! The best part is that it can (and should) be used in either a grid tie or off grid application. If a non-self-regulating solar array is connected to lead acid batteries with no overcharge protection, battery life will be compromised.

Your solar panels and deep cycle batteries will last much longer. A simple charge controller contains a transistor that shunt the PV charging circuit, terminating the charge at a pre-set high voltage and, once a pre-set reconnect is reached, opens the shunt, allowing charging to resume.

A more sophisticated charge controller utilize pulse width modulation (PWM) or maximum power point tracking (MPPT) to assure the battery is being fully charged. The first 70% to 80 of battery capacity is easily replaced, but the last 20% to 30% requires more attention and therefore more complexity. How to size a charge controller.

Charge controllers are rated and sized by the array current and system voltage. Most common are 12, 24, and 48-volt controllers. Amperage ratings run from 1 amp to 60 amps, voltages from 6-60 volts. For example, if one module in your 12-volt system produces 7.45 amps and two modules are utilized, your system will produce 14.9 amps of current at 12 volts. Because of light reflection and the edge of cloud effect, sporadically increased current levels are not uncommon.

For this reason we increase the controller amperage by a minimum of 25% bringing our minimum controller amperage to 18.6. Looking through the products we find a 20-amp charge controller, as close a match as possible. In most cases because the cost is not that high, in relation to your entire renewable energy system, for that reason we always recommend a slightly larger model.

There is no problem going with a 30-amp or larger charge controller, other than the additional cost. If you think the system may increase in size, additional amperage capacity at this time should be considered. We have worked with several models and makes and have found that most of them are super quality, from Morningstar, Sunsaver, Schneider Electric (formerly Xantrex), we have tested them all and are of equal quality.

Finding the right solar charge controller is very important for the longevity of your system, without it your battery life will be severely compromised.