CAUTION!……A rheostat cranked to max current (minimum resisatance) is same as a direct short on the battery. Leave it that way for too many seconds and the battery will self-destruct. Watch the wattage rating on the rheostat too, for example, If you have the rheostat set to draw 3 Amps at 7.2 volts, that is 21.6 Watts – the rheostat will get hot in a hurry – it is rated to dissipate that wattage? some are, some aren’t. With it cranked up to a dead short, all that heat is happening inside the battery – bad news.
I may have misunderstood – I assumed you were putting a rheostat directly on the battery with a current meter, and that’s all – if the rheostat you are talking about is in the Merc test instrument, disregard what I just said.
Dave
