Drain Batteries

Batteries Canon Rebel XS: drain before charging?

I bought a Canon Eos Rebel XSi during the holidays and it came bundled with two batteries (Battery Pack LP-E5). My question is: These batteries are the type that I need to drain completely before recharging or should I just fully charge them, no matter what level they are in power before photographic output?

Their total bill each time they are lithium-Ion Batteries, they do not suffer from the effects of memory loss and the lithium-ion can actually lose their lives if you let them drain all the way often.

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