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KS Mobile's Battery Doctor is a really easy to use and helpful battery analyzer tool that doesn't require a degree in electrical engineering or computer science to be useful. What I particularly like about it is that it gives tips on what apps and components to turn off to get the most from your battery. Its battery charging utility is also very handy.
While I've found its battery life estimates to be a little optimistic, I can forget it that for its helpfulness, simple interface, and price: Free.