Battery Self discharge rates:
- Bad news: all batteries have what is called a
self discharge rate. - Good news: if you have a rechargeable battery
all you need to do is recharge your battery!
Let me explain in greater detail the concept of battery self discharge.
All batteries will self discharge over a period of time naturally whether the battery is used or not. This means that the battery capacity will go from 100% down to 0% over a time period regardless if the battery is being used or not. Again recharging the battery corrects this naturally occurring reality.
Battery self discharge rate varies based on the chemistry type used and the temperature the battery is at: higher temperatures increase the self-discharge rate. This explains why batteries left inside cars on hot days must be recharged more frequently!
Battery self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery. Battery self-discharges does decrease the overall shelf-life of batteries and causes them to initially have less than a full charge when actually put to use.
Here are average self discharge rates for the following chemistries:
|
NiCd |
NiMH |
Lead Acid |
Li-ion |
Li-ion polymer |
Reusable Alkaline |
|
|
Self-discharge / Month (room temperature) |
20% |
30% |
5% |
10% |
~10% |
0.3% |
The rate at which batteries self discharge depends on the type of battery, state of charge, charging current, ambient temperature and other factors. Lithium based batteries suffer the least amount of self-discharge (around 2–3% discharge per month), while nickel-based batteries are more seriously affected by the self-discharge rate.
To reduce the rate of battery self discharge during storage then store the battery at lower temperatures to reduce the rate of self-discharge and preserves the initial energy stored in the battery.