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NiMH battery charger

A NiMH battery charger is a practical and useful device which replaces the energy in rechargeable batteries by forcing an electric current through them.

Intelligent NiMH battery chargers have a special negative Delta V feature which means they only charge batteries until a specific voltage has been reached, and then trickle charge them thereafter until disconnected.

These chargers can monitor the voltage and temperature of the battery, plus the time of charging, and will automatically stop charging once a combination of factors indicates that the battery is full. This avoids batteries being damaged through overcharging.

Using a NiMH battery charger

The charge current of a NiMH battery charger will depend on the technology and capacity of the battery which you’re charging, with the current required for recharging a mobile phone battery being completely different – for example – from the current needed to recharge a 12 volt car battery.

In the case of NiMH batteries, the batteries’ voltage gets gradually higher during the charging process until the batteries are fully charged. Thereafter the voltage starts to decrease, thus indicating to the intelligent charger that full charge has been reached. Typically, intelligent NiMH chargers will fast-charge a battery up to about 85% of its full capacity before switching to trickle charge.

Prolonging rechargable battery life

Some scientists maintain that nickel-based rechargable batteries, such as NiMH batteries, should be fully discharged each time before being re-charged; otherwise the batteries will gradually lose their capacity, owing to “memory effect”.

However, this is not entirely accurate…. You can charge nickel alloy cells at any point during their discharge cycle and still avoid the problem of the “memory effect”, provided you run the battery down completely and then recharge it once a month (ie once every 30 charges or so).

When purchasing a battery charger, opt for a versatile model that allows you to recharge various types and sizes of battery, including NiMH batteries and:

• AAA batteries.
• AA batteries.
• NiCD batteries.
• Battery packs.

If properly looked after and used in accordance with manufacturers’ instructions, your NiMH battery charger should give you many years of reliable service, and could save you a lot of money on battery costs. Further savings can be achieved through buying your batteries online.