Lipo batteries are very different type of battery from earlyer types such as Nicads and NimH and require a different approach to charging
LI-po's cells have a nominal voltage of 3.7 volts so giving rise to packs with voltage ranges from
1 cell = 3.7 volts
2 cells in series = 7.4 volts
3 cells in series = 11.1 volts
The S1, S2, S3 and so on refers to the amount of cells in a given pack I.E S2 = 2 cels 7.4volts .
C Rating LiPo cells tend to be given a C or current rating. This is the maximum average recommended discharge current for the cell. I.E A pack that is rated 1900mAh and a 20C rating. would work out at 1.9 amps x 20 to give a maximum output of 38amps So the higher the C rating the higher the constant currant output
One thing that is really important with charging LiPo batteries is to use a charger designed specifically for LiPo batteries, and with most LiPo-specific chargers it's necessary to correctly select the cell count. Though most good chargers are able to do this automaticly now .Chargers Tend to constant current charge to 75% of the cell capacity until the pack voltage reaches 3.6 volts per cell. This charges the pack to about 80% of total capacity. The the charger will switch to a constant voltage charge rate of 3.6 volts per cell to top off the battery. To fully charge an empty pack normaly takes about one and a half hours. Also it is vital to have a ballancer on your charger if you us packs of more than 2cells this makes sure that the cells have the same charge in each cell
If LiPo batteries are improperly charged they can in the right conditions explosive. It is imperative the importance of using a charger specifically designed to charge LiPo batteries, and to be positive that the manual cell count (if the charger has one) is correctly set for the specific battery being charged. If you use a good quality LiPo charger, these batteries are totally safe !!!.
LiPo Do's and Don'ts
Only use a charger that is specifically designed to charge LiPo batteries. Using other types of chargers can cause an extreme fire hazard!
LiPos don't develop memory like Ni-Cds. Just charge without cycling or discharging them.Store LiPos at least partially charged. LiPos will maintain their performance levels over time, even during non-use,.Don't Use any type of charger that is not specifically designed to charge LiPo batteries. Using non-LiPo-specific chargers can cause an extreme fire hazard!Don't Fully discharge your LiPo battery pack.
Most speed controller have a voltage cut off that will prevent over-discharging the battery. Discharging a LiPo beyond it's critical minimum voltage will cause damage and dramatically reduce your battery life .If you have a crash and the battery is damaged, don't put the battery in your car or house immediately after a crash.
It's possible that a chemical reaction can take place in the damaged battery that could cause a fire. Put the battery in a safe place for a least one hour.