The AR Drone uses a Lithium Polymer battery cell that is actually an excellent choice for system like the AR Drone. Lithium Polymers have a high discharge rate and a high energy storage/weight ratio. The downside is that they can cause you all kinds of grief if you don’t take care of them properly.
The charger that comes with the AR Drone is a good balance between cost, safety, and performance. A good charger will generally run you close to $95 and can charge the AR Drone batteries in about 15 minutes versus the 1.5 hours the included charger takes. The reason the included charger takes so long is that it does not charge at a high current rate. This helps to keep the batteries as cool as possible when charging.
Battery Maintenance and Charging Tips
Do Not Charge Immediately After Flight
This is very important as the batteries will be quite warm after an extended flight and putting them directly on the charger can create a potentially hazardous situation. If lithium batteries get too hot, they can catch fire. Make sure you let them cool down before charging by letting them sit. A good rule of thumb is to let them set for twice as long as you ran them. So if you just did an 8 minute flight, let them sit for at least 16 minutes.
Do Not Fly Immediately After Charging
Similar to the above, you want to keep the batteries from getting too hot and yanking them off the charger and slapping them into your AR Drone is not a good idea. Let them rest for 10-15 minutes after pulling them from the charger.
Inspect Batteries Before Every Flight/Charge
If you see any damage to the batteries, do not use them…period. Any damage to the cells will drastically increase the odds of the cells failing, and when I say failing, I mean bursting into flames and burning your house down. Take these batteries seriously. Keep a fire extinguisher or a pail of sand handy when charging.
With proper care and maintenance, your batteries should last a good long time and keep you flying as much as possible. Just keep in mind a few simple tips to ensure that you take care of them and they will take care of you.
You will find more general information on LiPo batteries in this article link.