Lithium-Ion (Li-Ion) 1100 mAh 7.4 V Black BP-511's are lithium-ion batteries, and as such can be recharged safely at any charge state without significantly reducing the effective life.Some batteries (like those in the 1D) must be periodically discharged completely to maintain battery life. This is not necessary for the BP-511.The storage capacity of lithium-ion battery packs decreases gradually with use. Typically, the BP-511 can handle about 300-400 full discharge/recharge cycles without a noticeable loss of capacity. After that, performance, as measured in the number of shots per charge, decreases quickly and the battery pack becomes unusable.The battery level displays in EOS DSLRs that use BP-511's change their readouts in 4 steps (full, half empty, blinking, nothing) based on specific voltage levels, which explains why limited shooting can produce a dramatic change in read-out.Lithium-ion battery packs, like most other secondary (i.e., rechargeable) batteries, very typically "recov