your swith can take many hundredes of volts, just not current.

think of current as water in a pipe, you can only force so much water down a small pipe. the leads on flight packs are quite thin and cant take that ammount of current. the plug is even worse.
on 1.5amps the leads start to warm up, thats why i stay at one amp. the switch dosnt take the current anyway because the charge lead is soldered directly to the batt lead.
btw.. heres what happens when you dont adjust your charging amps from car racing the night before and charge at 5amps