Initial Charging: When you first get your battery you should charge it until your charger or device indicates that it is fully charged. If your device/charger does not indicate whether or not it is fully charged, then check your device/charger manual for charging times. It can take 1-12 hours to fully charge depending on the chemistry of your battery and the type of device and charger. After that it is good to charge it as needed while making sure you do not leave it at a low charge level for long periods. Also, please keep in mind that it can take 2-4 initial full charges/discharges before a new battery begins to provide maximum performance/runtime.

Recharging: Your battery was designed to be charged regularly and should NOT be left at a low charge level for long periods. You should charge it as often as needed to prevent the charge level from getting much below 15% of full.

Charging During Storage: Do not store the battery in the machine for long periods unless being used and charged often. During storage your rechargeable battery will trickle discharge naturally (or slowly lose its current charge) and will trickle discharge (self discharge) much faster when stored in the machine. Long storage periods can permanently diminish the overall life of the battery especially when the battery is left at a low charge level for too long. If you will be storing your battery for a long period of time, be sure NOT to store it at a low charge level. Bring the charge level up to full before storage and then top off the charge level as needed during storage (to prevent it from sitting too long at low charge). It is highly recommended, even during storage, that you charge the battery regularly to prevent the possibility of the battery sitting at low charge for too long (sitting at low charge for too long will cause deep discharge which can permanently damage the cells and render the battery useless). Damage from deep discharge is NOT a defect and therefore it is not covered by warranty. For rechargeable lithium batteries in storage (including lithium ion and lithium polymer), a full recharge might be needed every 3-6 months. For rechargeable nickel batteries in storage (NICD and NIMH), a full recharge might be needed every 1-2 months. Nickel batteries trickle discharge in storage faster than lithium batteries.

More Info:

• Storing battery in the tool or machine? Storing the battery in the tool or machine that the battery was meant to power will accelerate the rate of natural self-discharge of the battery's cells. That means, when stored in the machine, you'll have to charge it much more often in order to prevent deep discharge compared to if the battery was disconnected from the machine during storage. Some batteries are easier to detach/disconnect from the machine than others (a battery in a power tool can be easily disconnected while a battery in a laptop you generally will not disconnect).
• Storing battery in the charger? Storing the battery in (or connected to) the charger will accelerate the rate of natural self-discharge. That means, it will have to charge more often in order to prevent deep discharge compared to if the battery was disconnected from the charger during storage. Some chargers will automatically begin recharging each time it detects the battery's charge getting low enough, while other chargers simply will still show full charge with no further status updates until you remove the battery from the charger and reinsert it in the charger (which means, for those chargers that do not automatically recharge again as the battery is stored on the charger, the battery will reach deep discharge levels and you won't know it until it's too late!). So, it is best to bring the battery to full charge on the charger and then remove it from the charger very shortly after the charger indicates full charge. Then unplug charger from the outlet to also extend the life of the charger.
• Each chemistry has different charging times. NiCad and NIMH batteries require 10-12 hours to fully charge while Lithium Ion batteries can be charged withing 1-4 hours (depending on capacity).
• A portable device should be turned off while charging. This allows the battery to reach the threshold voltage unhindered and reflects the correct saturation current responsible to terminate the charge.
• Charge at a moderate temperature. Do not charge below freezing.
• Lithium-ion does not need to be fully charged every time. This holds true with NiCad or NIMH batteries.
• Chargers use different methods for “ready” indication. The light signal may not always indicate a full charge.
• Discontinue using charger and/or battery if the battery gets excessively warm.
• Before prolonged storage, charge the battery so that it won't trickle to a low charge too quickly.
• Over-discharged batteries can be “boosted” to life again, but not always.
• Deep-discharging batteries is not something you need to do with each charge but only once in a while (example: if you are trying to diagnose the battery's condition or test your device's battery gauge). Fully discharging Lithium Ion, Lithium Polymer, NICD, and NIMH batteries is not recommended on a regular basis.