A charge rate of 1c was pretty much the standard for a long time. For your 2200mah battery this would mean you would charge the battery at 2.2 amps. Silicon Graphene batteries can take charge rates of up to 10c, which for a 2200mah battery would be 22 amps. If your battery isn't of Silicon Graphene construction you can charge at 2c or 4.4 amps without causing any harm.