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Battery Specs

Sometimes I think they have more ratings than they do electrons! While it can be really confusing at first, all those ratings are actually quite useful when you know what they mean.

Commonly, we as consumers want some kind of easy to compare feature. Batteries pose an interesting twist to that. More so than with many other products, we have to choose what to compare depending on what we are going to use them for.

For example, when choosing a battery for our car, its main job is to start the engine. That requires a lot of current all at once so we need a battery that provide a lot of power really fast. If we are choosing a battery to run a night light at our campsite, however, we need a pretty small current that can run all night. Thus, we need a spec that will guide us as to how long our new battery can provide power.

Everyone one knows water and electricity don't mix, right? Well, I find one of the things that makes electricity hard to understand is the fact that you can't see it. Interestingly enough, electricity behaves a lot like water. So, I like to think of electricity in terms of water - because water can be seen.

All that said, and knowing what the specs are, selecting batteries can still be challenging. Battery producers often advertise ratings that don't really tell us what we need to know. Because the ratings are so often not understood by the consumer, often times the ratings supplied are more of a marketing decision than a technical decision. There are, of course, some cases where ratings are exagerative or even deceptive; and suppliers can get away with that as well because the average consumer doesn't understand the rating well enough to call them on it. Still, knowing the following specs and sticking to an atleast somewhat reputable brand should enable you to select a battery that will work for most any common purpose.

mAh - This specifies how much current a battery can provide and for how long. In English, that basically means how much energy it can hold.

This is the spec that might be important for our nightlight; and in terms of the water analogy, this would be how much water a bucket can hold.

CCA - This specifies how much current a battery can provide instantaneously(sp?).

This is the spec we would want to look at for our new car battery; and for the water analogy, this would be how fast we can pour the water out of the bucket.

MCA - Similiar to CCA, but marine version. Has slightly different voltage levels and minimum performance times at which the battery is tested.

Reserve Capacity - How long a battery can provide power at a current flow specified for the rating. This is very similiar to the mAh rating; but is a different way of testing and expressing it. Typically, it is the number of minutes a battery can provide a 25 amp current.

Since our load is unlikely to match the test current, I find it less helpful but still valid for comparison purposes. In terms of water, this would be how long a steady stream of water can flow out of a leak in the bucket before the bucket is empty.

Voltage - How much pressure the battery provides. Typically, this rating must match the desired use. To much pressure might force the magic smoke out, and too little won't operate our device correctly. Actual measurements will vary some with state of charge.

In terms of water, this would be how much water pressure is on a garden hose. Too little, the sprinkler doesn't spin and too much might burst the hose.

Chemistry - Quite simply, what the battery is made of. I can't think of any other product that can be made of such a variety of materials. I'll list some types for reference, but mainly remember that different types work well for different purposes. Here are a few of those types, and a brief description of each: