Not exactly sure what you are asking but I will give it a go.
If you wan to maximize your battery, read this from our FAQ: Maximum Battery Life - BlackBerryFAQ
Always keep the battery topped off when you are near a power source. Life depends on usage so it is difficult to help. However, Lithium batteries do not like to go down past 20% on a regular basis. If that is happening to you, then you might have damaged it and need a replacement. Plus, the BB has been out for a relatively long time so you might need a new battery anyway. They do not last forever.