Lipo Batterys and charging

I had a lot of questions about Lipo batteries when I first started.  I heard a lot of horror stories about fires and explosions if not charged correctly.   So far, I have yet to destroy a battery or have any problems.  I follow a few simple rules and I dont leave batteries charge unattended.  Below are a few key points to helping you understand LiPo batteries.  DISCLAIMER: The information below is all information I found in the internet.  Do your homework and proceed at your own risk!

Understanding the specs of the battery

A battery will have a series of numbers on it describing it's specs such as "2200 mha, 2S, 40C".  What does it all mean!  There are 3 (sometimes 4) key things to look for.

2200 mha = The total capacity of the battery.  This has 2200 mha of potential power when charged.
2S = This is 2 battery cells wired in Series.  (some larger batteries may have a "P" in them for "Parallel" or even a combination of both!)
40C = This battery can safely discharge at up to 40X it's capacity per hour.  40 * 2200mha = 88,000 mha/h or 88 AMPS!!  That's a lot of juice!  The higher the C rating, the faster it can deliver power.

You may also see another "C" rating for Charging.  Most batteries should not be charged at more then 3C.  We will talk more about that in a minute.

I dont see Voltage listed?  Isn't that important?   YES!  It is important.  Nearly all Lipo batteries have a voltage of 3.7v per cell that climbs to 4.2v per cell when fully charged.  To find the voltage, multiply the total cells in Series (2S in the example above)   The pack in the example above would be 2 (as in 2S) x 3.7v = 7.2v  up to (2 x 4.2v) = 8.4v

Why does the battery have 2 connectors? - 1 connector is used to connect to the speed control.  This puts all the power through 1 connector.  The other connector is called the "Balance" connector.  This has a wire running to each cell individually so that each cell can be monitored and charged individually.

How do I charge a Lipo Battery?  

A lipo battery requires a special LiPo battery charger.  The Lipo battery charger has a port for the balance plug as well as the main power plug.  Most charges will let you set a the number of cells, and charge rate.  

How if works - The charger will charge each cell individually and top them off at 4.2v each.  This is because the cell chemistry is much more sensitive and we can easily damage cells if we over charge them.  If you have 1 bad cell, the charger will stop when it recognizes that cell will not take a charge.  If it was not charging each cell individually, it would not know that.  It might charge several cells to 100%, however, because of the 1 bad cell, the charger thinks the pack has not reached it's full charge voltage and keeps charging until the good cells over charge and catch on fire!