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ITGlossary · Batteries
Self-discharge
The gradual loss of charge in a battery kept in storage without use, caused by internal chemical reactions.
Technical level:Basic
Every battery slowly loses energy even when it is disconnected. The rate depends on the chemistry and above all on temperature: the warmer the room, the faster it empties. Lithium batteries usually lose less charge than lead-acid batteries.
This matters for spare batteries and for UPS units kept in storage. A lead-acid battery forgotten on a shelf for many months can run down so far that sulphation sets in and it never fully recovers.
Store batteries fully charged in a cool place, and recharge lead-acid batteries about every six months at 20 °C, more often if the room is warm.
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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.
- Cycle LifeThe number of charge and discharge cycles a battery withstands until its capacity falls, usually, to 80% of the original.
- Deep-Cycle BatteryA battery designed to be discharged deeply and recharged again and again without wearing out quickly.
- Fast ChargingA charging method that restores battery capacity quickly without damage by controlling current, voltage and temperature.
- Battery Charging CurrentThe amount of current supplied to charge a battery, regulated by the UPS system.
- Battery Management System (BMS)A system that monitors and manages the performance, health, and charging of batteries.