Frequently Asked Question

CLASSIC - 3-Stage Charging Explained
Last Updated 3 years ago

Three Stage Battery Charging for Lead-Acid type

The BULK stage involves about 80% of the recharge, wherein the charger current is applied up to the available energy, and voltage increases. The properly sized charger will give the battery as much current as it will accept up to charger capacity (25% of battery capacity in amp hours is recommended), and not raise a flooded battery over 125° F, or an AGM or GEL (valve regulated) battery over 100° F.

The ABSORPTION stage (the remaining 10-20%, approximately) has the charger holding the voltage at the charger's absorption voltage (between 14.1 VDC and 14.8 VDC per 12 volt unit, depending on charger set points) and decreasing the current until the battery is fully charged. If the battery won't hold a charge, or the current does not drop after the expected recharge time, the battery may have some permanent sulphation.

The FLOAT stage is where the charge voltage is reduced to between 13.0 VDC and 13.8 VDC per 12 volt unit and held constant, while the current is reduced to less than 1% of battery capacity. This mode can be used to maintain a fully charged battery indefinitely. If the load demand requires current during float the charge controller will switch to "FLOAT MPPT" and ramp up output to maintain the float voltage and power the loads.

At the end of the day our Charge Controllers with go into a "RESTING" mode waiting for the next day to start the cycle all over again. The Classic (TM) has an option called "SKIP DAYS" that can be set to not do a 3-stage charge everyday. If this is set, the Classic will wake up in FLOAT for the number of days set to skip. This is useful for an unoccupied during the week cabin where there are no loads except on the weekends.

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