What Does a Charge Controller Do?
A solar charge controller keeps a battery bank from overcharging and turns off solar panels at night to block current from reversing from the batteries to the panels, an important function since electrons can flow both ways. Learn more about how charge controllers work and how they add to battery life.
Solar charge controllers were created with two distinct and important purposes:
1. They keep a battery bank from overcharging
2. They turn off the solar panels at night to block current from reversing from the batteries to the panels, a significant function since electrons can flow both ways.
In practical terms, charge controllers are important because if you hook a solar array directly to a battery without the overcharge protection they provide, you’ll boil the battery dry and ruin it.
How Charge Controllers add to Battery Life?
Early charge controllers contained a simple relay that opened at a pre-set high voltage and closed at a pre-set lower voltage, allowing 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.
Nowadays, almost any charger can get a battery to 80% (Bulk) charge. The trick is charging the next 20% (Absorb). In the bulk mode there are variable voltages and all the available (Constant) current (Amps). When a pre-programed voltage setting is reached, the charger passes off to the Absorb mode (and timer).
The Absorb Mode and Timer uses constant voltage and variable (tapering down) current (amps) for a predetermined period of time (Absorb time). This is the most important mode as this is the one that gets the batteries to full charge. Batteries must, for the health of the battery, come to a full charge at least every ten days.
Many charge Controllers cannot be programed, rendering them useless for battery health and long life. Many people think the Charge Controller has some intelligence that senses the batteries and take care of the Absorb Time. The reality is the Charge Controller manufacturer has no idea of how many watts of solar you have and what batteries you bought. It is a mathematical computation and must be programed into the controller.
Everyone wants a less expensive Charge Controller but in the end, you might save a few bucks on the controller and spend a small fortune replacing batteries. Think about the future of your system, and your wallet!
Next, check out our Charge Controller sizing post, "How Big of a Charge Controller do I need?"
If you still have questions, call us and we can help! 888-826-0939
