Self-discharge is a chemical process ofbatteries and accumulators in which batteries slowly discharge without any consumption current flowing. In primary cells, i.e. batteries, self-discharge occurs much more slowly than in secondary cells, i.e. rechargeable batteries.
The process of self-discharge is temperature-dependent and increases as the temperature rises. For this reason, batteries should be stored as cool as possible. In addition, self-discharge depends on the battery type.
This effect is particularly strong with NiMH batteries, where the self-discharge can be around 25% per month and even higher. This has led to developments with a much lower self-discharge, Low Self Discharge( LSD). The lower self-discharge is achieved by lower internal resistances, which result in a more stable voltage.
The self-discharge of LSD NiMH batteries is about 15% per month, which is comparable to that of NiCd batteries. The self-discharge of gel batteries and lead-fleece batteries is lower, at about 2% to 6% per month.
Since self-discharge in batteries has a direct impact on batterylife, care must be taken to minimize self-discharge in some applications, such as use in pacemakers. For example, there are lithium batteries that have an extremely low self-discharge rate of only 1% per year.