Solar Charge Controller Basics: Solar modules produce electricity when the sun shines. The charge controller regulates the flow of electricity from the solar modules to the battery bank. When the battery bank is low, the charge controller feeds all the electricity from the array to the batteries. When the batteries reach a state of full charge, the charge controller stops or redirects the supply of electricity to prevent overcharging. Modern charge controllers can have the ability to hold the battery bank in a “float” state of charge if the bank is not being used. At night the charge controller prevents a reverse flow of current from the batteries to the modules. There are three basic types of charge controllers – series, shunt and pulse width-modulated. A series controller, the most basic type, acts as a switch to disconnect and re-connect the solar modules to the battery bank. A shunt type controller redirects the current from the solar modules – either by simply short-circuiting the array or by directing the current to some other load. Pulse width-modulated charge controllers, the most up to date type, maintain the battery bank in a float state of charge. “Float” is the voltage level just below gassing voltage. Keeping the batteries in this state of charge delivers their best possible life without using excessive electrolytic. Charge controllers are generally selected by their size or ability to control a given amount of current, and by their operating voltage.

Maximum Power Point Tracking: Many people have asked about power point tracking and whether it has any real advantages. Maximum Power Point Tracking (MPPT) converts the difference between a solar module rated voltage, (usually 17 volts) and a battery banks charging voltage (up to 14.7 volts) into usable charging current. Often claims are made for up to a 30% increase in charging current. This gain, however, is possible under a very limited set of conditions. The “extra” module voltage is there for a reason: to allow for real world use of the solar module, that is the voltage drop caused by the array wiring and other components, including the charge controller, between the solar array and batteries. Also, high ambient temperatures cause the solar module to drop in voltage further reducing this “extra” voltage. Having said that, there are times when the voltage difference will be high enough to provide extra current to a battery bank utilizing this type of charge controller. Cold weather comes to mind, as well as low battery bank voltage. Under these conditions, it can be possible to get as much as 10% to 30% more current from your solar modules. A more important use for the MPPT charge controllers featured is the ability to use higher voltage arrays to charge lesser voltage battery banks that is a 48 volt array can charge a 24 volt bank (or even a 12V bank). The higher voltage means less current through the array wires and therefore less voltage drop. Longer distances can now be done using smaller wire sizes. This is a very important feature of these particular charge controllers.

PWM Charge Controllers
Voltage: 12V/24V/48V
Current: 6A/10A/20A/40A

Existing Home UPS to Solar Conversion PWM Controllers

MPPT Charge Controllers
Voltage: 12V/ 24V/ 48V/ 72V/ 96V/120V/144V/192V/240V
Current: 40A/60A