Charging LiPo batteries

1) Charging LiPo batteries at over 1C ...

a) Is not recommended. Charging over 1C is perfectly acceptable if used in conjunction with a balancer, this is 100% necessary. For example, EVOLITE and EVOLITE V2 cells can be charged at 2C, EVO25 at 2.5C and EVO30 at 3C.

b) Shortens the life-span of the cell. NO, from extensive testing we have found very little or no reduction in life. There are other more important factors about cycle life than how fast you charge them.

Please note, fast charging must be done with a balancer. When charging at higher rates slight differences in IR means voltages will rise at different rates, therefore requiring balancing. Only when the charge switches to constant voltage, will proper balancing take place due to the lower charge currents. Also, balancers discharge at a constant current, so it will take longer to balance a pack. Think of each cell as a bucket of water, the hole in the bottom is the balancer. If you fill the bucket up faster, it will take longer for it all to "balance"...see?

2) Li-Po batteries require a "break-in" process this is a slightly more grey area. Older packs used to need so, yes, but with modern cell matching which the bigger brands all include in their manufacturing process, it isn't so much the case. However, the first cycle of the pack IS NOT the best cycle. It takes about 3 cycles to get the best performance out of the pack, and it will stay at this level for many more cycles. We have noted this happens with all discharge rates from ultra high currents to low currents.

3) Li-Po batteries should not be discharged beyond about 80% of their capacity. Like all battery types, the less you use them, to a degree, the better. Yes, cycle life does increase the less you use the battery. Taking 100% of the capacity (or more) out of a battery is not healthy and is the number one reason for reduced cycle life.

4) Li-Po batteries should not be charged right after flying never had an issue. Most of the time lipo's come out of the helicopter/plank fairly cool and nowhere near a dangerous level so putting them on charge strait away wont hurt them. Unlike nickel based cells, lipo's don't get warm during a charge, so they cool down in the charge. Of course this may affect balance, but from experience of using charging and discharging packs every single day, its not too much of an issue. Like most things, use your common sense, if its roasting hot, don't put it on charge, if its warm/col, no problems!

The MOST IMPORTANT THINGS TO REMEMBER with lipo's is of course to use a little BRAIN POWER, stick to some basic rules and read the extensive instructions included with all packs. The main basic rules for extended life are:

DO NOT charge over 4.25v per cell

DO NOT discharge below 3v per cell UNDER LOAD. Landing with a pack of 10.5v (3s) is perfectly normal, under load this could still have hit 9v

ALWAYS use a balancer when you can. The more cells you have in a pack the more likely it is to go out of balance. High current apps like helicopters need balancing every single charge, where as a RX pack wont need it so much as really, max of 5A wont be much to a pack capable of 50A

DO NOT flatten a battery! No need to extend flight times to a max until you are forced to auto it in. Time your flights until you have to land, then set a timer for a minute less. An easy, simple way to increase lifetime.

Source: http://helifreak.com/showpost.php?p=591341&postcount=6

Also Note:

The result of over discharge: Over discharging will result in chemical changes within the cell that cannot be reversed by the following charge and this reduces the capacity of the cells. Cells should not be discharged below an on-load voltage of about 2.5V to 3.0V although if the period is kept very short it may be acceptable.

If the voltage is allowed to remain low for some time as a result of self discharge, then metallic copper may be formed within the cell. this copper could result in a partial or total short circuit rendering the cell useless. If the cell does not permanently short, then it would be possible to recharge it but this should not be done as copper will still be within the cell and a short circuit could occur at any time. I assume this is the reason why lithium chargers will not allow a charge to commence if the voltage is below the minimum specified, the cell or battery being safe whilst it has a low state of charge. A cell in this condition is likely to have lost a lot of capacity so throw it away to ensure safety.

Manufacturers rate the lithium based battery at an 80% depth of discharge. Repeated full (100%) discharges would lower the specified cycle count. It is therefore recommended to charge lithium more often rather than letting it discharge down too low. Periodic full discharges are not needed because lithium is not affected by memory.

Source: http://www.bladebusters.com/batteryguide.html