Why C-Rate, Not Just Amps, Determines Safe Charging
A LiPo battery's charge rate is conventionally expressed as a "C-rate" — charge current relative to the battery's own capacity, not as a raw amp value alone — because what's a safe charge current genuinely depends on the specific battery's capacity, not on a fixed absolute number. A 1C charge rate means charging at a current numerically equal to the battery's capacity in amp-hours (a 2000mAh battery at 1C charges at 2A); charging faster than the manufacturer's rated maximum C-rate risks overheating, swelling, or in worse cases, a genuine fire hazard specific to lithium battery chemistry.
This is exactly why the same charge current (say, 2A) can be perfectly safe for one battery and dangerously excessive for another — a 4000mAh battery at 2A is only a modest 0.5C rate, while a 1000mAh battery at that same 2A is a much more aggressive 2C rate, well beyond what many standard LiPo cells are rated to handle safely.
Charge time isn't simply capacity divided by current either — actual charge time is typically somewhat longer than the naive calculation suggests, since most LiPo charging profiles taper current down as the battery approaches full charge (the "constant voltage" phase following the initial "constant current" phase), which extends real charge time beyond the linear estimate.