March 4, 2009

TIP: No excuse not to use rechargeable batteries

Alkaline batteries, specifically the AA size, enable all sorts of electronic gadgets. Many modern gadgets, however, go through AA's so quickly that it quickly becomes costly to keep the devices powered up.

The original rechargeable batteries were NiCAD or nickel-cadmium chemistry. They worked, and still have their uses in battery packs for cordless telephones and portable power tools, but as AA's, they are a little limited in today's gadgets. The capacity of these older chemistry batteries just can't keep up with modern demands. in addition, they suffer from a detrimental memory effect which can lead to a permanent reduction in the battery's capacity.

NiMH batteries took care of the memory issues and represented a significant improvement in capacity as measured by the milliampere-hour (mAh) rating. Instead of the sub 1000 mAh ratings for Ni-Cad AA's, ratings in the mid-2000's are common place and go as high as 2900 mAh (please be careful of manufacturer's ratings, some have a tendency to let's just say, round up, this is especially true of cheap no-name batteries).

The NiMH chemistry is not perfect, however. The batteries suffer from significant self-discharge and while they are often claimed to have long lives, they do seem to fall short of the claims if used 'hard' (ie high current draw applications).

Today, there is a second generation of NiMH batteries referred to as "low discharge". As one might presume, this newer chemistry addresses the self-discharge issue that plagues the standard NiMH. Nothing is free in life, however, and at least for now these batteries are of lower capacity than the high end standard NiMH. Most of these newer batteries fall in the 2000-2100 mAh capacity range.

Unfortunately, the industry has not come up with a good marketing term to discriminate between regular and low discharge NiMH batteries. The most common method of separation is the use of the term "pre-charged" somewhere on the low discharge battery package. Because of the low discharge properties, manufacturers are able to ship the batteries already charged and ready to insert into your electronics.

So if you haven't already, give rechargeables a try, there's something for everyone! I recommend high capacity standard NiMH for high current draw applications to maximize battery life. For low current draw applications, the low discharge version is the best choice.

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