I generally charge all my batteries at 1C. So for that 2p pack I would run my charger at 5.5A
Almost correct. Here is more of the whole story.
Parallel cells are kind of a special case. If the resistance of each cell is exactly the same you could charge at 1 times the combine capacity. I.E. 2 2200mah cells would charge at 4.4A. However they may have some difference in resistance so one cell may get 2.3 and the other 2.1 causing some degradation.
1C means 1 times the capacity. In the example above the capacity is 5400mah. A 1 C charge rate is thus 5.4 amps.
In reality 5.5 would probably be fine but generally the lower the charge current the more cycles the pack will last.
Some times you can actually determine the make and model number of a cell and find a data sheet. Often the average number of cycles until the pack only has half its original capacity will be listed at different discharge levels and different charge currents. A pack may last 500 cycles at 1C and 800 at .5C.
Also lithium ion or lithium polymer batteries do not charge at constant current through out the charge. Toward the end of the charge cycle it will be far less.
I have a lithium polymer pack that is rated to charge at 5C. The capacity is 2.65 amp hours so 2.65 x 5 = 13.25A. My charger will only put out 10A! However I charge at 5A because its still very quick and I want my pack to last a lot of cycles.
Another example is some 18650 lithium ion cells I had long time ago were 2400mah but only at .8C so 2.4 x .9 = 2.16 at 1C they were 2200mah.
How conservative or aggressive to charge your pack is a personal decision and should be made based on the trade off of charge time vs number of cycles the pack will last. Some times if I forget to charge until just before a ride I will throw my 2.65Ah 5C charge pack on at 10A and let it fast charge.
Its still better to fast charge with in the spec and have it run from full to half charge than to go out partially charged and run from half to empty. Running to empty puts a lot of ware on a pack.
