Saturday, November 21, 2009

Lead Acid Batteries

I spent two days this week learning about Lead acid batteries. One particularly interesting fact I learned is that Lead dissolves in water but not acid. This has some odd consequences.

When a battery is charged it consists of Lead sheets in acid. When you discharge the battery the acid reacts with the lead leaving behind just water. This is a big problem, in a reasonably short time the plates will have dissolved enough to be useless. The battery cannot be recovered.

So, if your car battery dies because you left your lights on, it might be alright for a day or two, but leave it for a month and you have one very dead battery. Even a week would be pushing your luck... Also this means that batteries must be stored while charged. For long term storage they need to be recharged every couple of months. Otherwise they slowly lose the acid needed to keep the Lead out of solution.

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