bac 8000 pre-charge

Does someone know if a pre-charge resistor is needed for a 450 amp, 72v with bac8000? I'll be using a main power shut off switch. If so, a resistor size would be appreciated. Thanks

A precharge of some sort would be a good idea at 72v, both to avoid damage to the controller and the contactor. Use ohm's law (Voltage = current x resistance) to properly size a resistor. For example, if you want to limit the precharge current to 2 amps, then a ~36 ohm resistor should be used (72v/2amps). Since 72v x 2amps is 144w, you would want a 144w resistor, but because it would only be for a couple seconds of precharging, you could use a lower wattage resistor.

Thank You for the info and the ability to do the math.