WTD - Info on rechargable batteries and the the charger itself!

    I have just been given a verbal good hiding for not using rechargable batteries, had a quick scoot on the net for the batteries and a charger. However, to be honest, I have no idea what I am looking for. Theres NIMH, NAMH, He man. Show Horn.

    I dont get it!

    Just looking for AA and AAA.

    If anyone knows of whats best to look for or knows of a good deal, I would be forever in your debt!!



    nimh or nicad are good the higher the capacity the longer the battery last when charged. best to use rechargable for high drain equipment eg digital camera etc.

    Original Poster

    Cheers guys!

    Batteries nowadays generally don't need conditioning as it's done in the factory. If you feel you want to though just to make sure, it won't harm it. Conditioning a battery is simply a process called Deep Cylcing. Which is basically:
    Charge to full capacity. Discharge to zero (won't happen if you're using a motor, you need a solid state discharger for this). Repeat twice to three times.

    All batteries give off heat while charging. The chemical and ionic change is exothermic. This is only noticeable when fast charging. Batteries are endothermic while idle and while under drain loads. This means they require heat. This is why batteries don't perform as well in cold conditions as they do in warm conditions. This is also why you can leave dead batteries beside a fireplace and they'll actually charge up again.

    Memory effect is somewhat of a mythical figure in batteries. It does exist but only in Lead Acid (SLA) batteries. Nickel Cadmium (NiCd) batteries have a charge memory but this can be "wiped" by deep cycling once. It rarely occurs in good quality NiCd's anymore unless proper maintenance isn't taken out on it once in a while. Nickel Metal Hydride (NiMH) don't suffer from charge memory at all.

    NiCd's hate fast charging. If you have NiCd's, trickle charge them where possible. NiCd's don't mind being overcharged on trickle chargers though, it act's like a "maintenance charge" keeping them topped up.
    NiMH's, conversely hate being trickle charged. It generally destroys them over time. NiMH's became popular because they can go to such high capacities and still be fast charged. They do heat up on fast charge though and unless you keep them ventilated (I often put a fan in front of them) and cool then you could be subject to a reaction called thermal runaway.

    Thermal runaway is when a battery gets so hot during charge, that it begins to self-perpetuate the charge current, even when disconnected. It is essentially charging itself. It will continue to do this until it is either cooled down or simply explodes. It's rare with a good charger, but it happens.

    Some advice from my own experience:

    Don't bother with NiCads. They have low capacity, awful memory effects and wear out quickly.

    NiMH batteries are what you should be looking for. Stick to buying branded batteries rather than generic no-name ones - I use Energiser AAA and Fujifilm AA and both have worked well for me.

    Make sure your charger is "smart" (i.e. microprocessor controlled). Smart chargers are capable of measuring the charge level and will charge each battery for the correct amount of time to achieve the maximum capacity. This will help to preserve the life of the batteries and ensure maximum usage time. Don't buy cheap "dumb" chargers that use a fixed timer or have to be switched off manually, as these will inevitably over or under-charge the batteries.
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