The original and main purposes of solar charge controllers are to protect your battery bank from being overcharged and to turn off the solar panels at night to block current from reversing from the batteries to the panels (electrons can flow both ways). If you hook a solar array directly to a battery with no overcharge protection, you’ll boil the battery dry and ruin it.
The first charge controllers contained a simple relay that opened at a pre-set high voltage, and closed at a pre-set lower voltage to allow the panels to resume charging the battery. Battery life was of no apparent concern as there was no way to properly fully charge a battery bank.
Almost any charger can get a battery to 80% (Bulk) charge. The trick is the next 20% (Absorb). In the bulk mode we have variable voltage and all the available (Constant) current (Amps) when we reach a pre-programed voltage setting the charger pass off to the Absorb Mode (And Timer) this mode uses constant voltage and variable current for a predetermined period of time (Absorb Time)
If this calculation has been done based on the available solar watts and the amp hour capacity of the battery, the absorb time can be determined. This setting will then be programmed into the charge controller (by you or your installer).
The factory default voltage and absorb time settings are useless (unless you’re trying to kill your batteries) because there is no way that the folks over at the factory could know how much solar you bought or what size battery bank you have. Sound too complex? Well no fear, we’ll do the math for you when you buy a charge controller.
Call Toll Free 888-826-0939 for more information on Charge Controllers