Charging Tips for NiMH Batteries

Brand new NiMH batteries would benefit from an initial slow, overnight charge. Basic charging rate would be capacity divided by 10. For example, a 700mAh battery would be charged at a rate of 70mA (i.e. 70 milliamps). This would take around 10 hours to charge a 700mAh battery at 70mA. Doing this "slow" charge "cycles" the battery and conditions the battery to give better performance.

Overnight charging is also "easy" on the battery, giving it a longer lifespan as compared to a battery that is "fast" charged.

For the charger, is is best to buy a peak detection charger designed for NiMH batteries. These chargers detect the peak voltage of the battery during charging, and will automatically stop charging. This protects your battery from being overcharged and damaged.

The charge rate is a compromise. Charging to fast will damage your batteries, while charging too slow is not good enough for impatient people like me.

If you have to fast charge, do not go higher than twice the rated capacity. For example, a 700mAh battery can be fast charged at 1400mA. Charging this battery at 2000mA will most likely damage it.

Tip: A better compromise would be to buy an extra battery pack. That way you can always charge overnight and avoid the need to fast charge.

NiMH Battery Care
Here are some basic guidelines to help prolong the life of your
NiMH batteries.

1. Do not allow the pack to be fully discharged.
2. Do not overcharge.
3. Avoid undercharging. charge to the fully capacity.
4. Do not charge a hot battery.
5. Let the battery cool down naturally (air) rather than placing in ice.
6. Overnight "slow" charging is better than "fast" charging.

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