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ITGlossary · Batteries
Equalising Charge
A controlled charge at a higher than normal voltage that brings all cells of a lead-acid battery to the same state of charge.
Technical level:Advanced
Over time the cells of a lead-acid battery string drift apart: some stay slightly undercharged and begin to sulphate. Equalisation overcharges them slightly for a limited time so they complete their charge, and in flooded batteries the gas bubbles also mix the electrolyte.
It is applied mainly to flooded batteries such as OPzS and to solar systems that rarely reach full charge. On sealed AGM and GEL batteries it is done only if the manufacturer allows it, and on lithium batteries never, since there the BMS balances the cells.
After every equalising charge, check the water level and make sure the room is well ventilated.
Related terms
- State of Charge (SoC)A battery's current charge level as a percentage of its capacity, from 0% (empty) to 100% (fully charged).
- Fast ChargingA charging method that restores battery capacity quickly without damage by controlling current, voltage and temperature.
- Lithium-ion BatteryA rechargeable lithium-ion battery with high energy density, long life and faster charging than lead-acid batteries.
- Eurobat Design Life ClassesA classification of sealed lead-acid batteries by their design life on float charge at 20 °C.
- Flooded Lead-Acid BatteryA battery with liquid electrolyte and vent caps that needs regular checks and topping up with deionised water.
- OPzS / OPzV Tubular BatteryStationary 2 V lead-acid cells with tubular positive plates, flooded (OPzS) or sealed with gel (OPzV), built for a very long life.