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ITGlossary · Batteries
Battery Charging Current
The amount of current supplied to charge a battery, regulated by the UPS system.
Technical level:Intermediate
After every discharge, the UPS charger recharges the batteries with a controlled current and then keeps them at a maintenance (float) voltage. The size of this current determines how quickly the UPS is ready again for the next outage.
Small UPS units usually have a charger of a few amps, sufficient for their internal batteries. For lead-acid batteries a typical charging current is around 10% of capacity (0.1C), for example about 10 A for a 100 Ah bank. Too high a current heats the batteries, while too low a current leaves the system exposed for hours.
Practical tip: when adding external batteries for longer runtime, check whether the charger is adequate. Otherwise the recharge time may exceed 24 hours and a stronger or additional charger will be needed.
Related terms
- C-rateThe charge or discharge current expressed as a multiple of battery capacity, e.g. 1C for a 100 Ah battery means 100 A.
- Fast ChargingA charging method that restores battery capacity quickly without damage by controlling current, voltage and temperature.
- State of Charge (SoC)A battery's current charge level as a percentage of its capacity, from 0% (empty) to 100% (fully charged).
- AC ChargingCharging with alternating current, where the vehicle's on-board charger converts it to direct current to fill the battery.
- Charging Power (kW)How much energy flows into the battery per hour, which in AC charging depends on voltage, current and the number of phases.
- DC ChargingFast charging in which the station converts power to direct current and feeds it straight into the battery, typically at 50 to 350 kW.