Unfortunately, there are many unapproved and poor chargers on the market.
While they are often nice and cheap, they only partially utilize the rechargeable battery.
A good charger meets the following characteristics:
- Fast charging: For the convenience of NiCd batteries, it is often important for batteries to be full within 1 to 2 hours.
Given the composition of NiMH batteries, fast charging within that time is not recommended, and chargers made specifically for these NiMH cells take at least 3 to 4 hours. - Automatic charging current: It is important that the charger has a built-in check for the correct charging current for the particular battery type.
- Overcharge protection: Good chargers have an automatic timer, or an electronic control for overcharging that causes charging to stop when the battery is fully charged.
Uncontrolled overcharging can cause the battery to become so hot that chemical processes cause the valve to pop open.
Batteries that have become much too hot also break down internally, rendering them useless. - Drip charging: After the charging process, the charger should be able to switch to trickle charging.
If you leave the batteries in the charger for several days (or weeks) after charging, the charger ensures that the battery remains full at all times.
Self-discharge is then compensated by the charger adding extra energy.
