Quick Answer
When the solar array voltage exceeds battery bank voltage, the solar charge controller prevents overcharging by diverting excess energy to a dump load or a load shed, protecting the battery bank from damage.
Excess Energy Handling
When the solar array voltage exceeds the battery bank voltage, the charge controller must handle the excess energy. A well-designed solar charge controller can divert this excess energy to a dump load, such as a heating element or a resistive load, which safely dissipates the excess energy. The dump load’s resistance should be calculated to match the solar array’s voltage and current to avoid overheating or electrical shock.
Charge Controller Sizing Considerations
To ensure proper handling of excess energy, the charge controller must be sized correctly. The charge controller’s maximum input voltage rating should be at least 25% higher than the maximum solar array voltage to account for voltage spikes and temperature variations. For example, a solar array with a maximum voltage of 60V would require a charge controller with a maximum input voltage rating of at least 75V (60V x 1.25).
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