Pre Charging an Open Revolt

[carpinteyrorsb]

Hi there,

I have been searching the forum for details and information on pre charging an Open Revolt controller.

My questions are,

1) Do I need to pre charge?
2) Why do I need to pre charge?
3) How do I pre charge? Can I just have a switch and appropriate resistor and wait a few seconds until I know they're charged or do I need something more...complex?

Any advice would be welcomed.

Cheers,

Adam

[LeadFoot]

1) Yes.
2) Because when you turn on the controller the input capacitors look essentially like a short circuit - the peak current to charge the caps will be approximately equal to Pack Voltage / (Battery Pack Resistance + Capacitor Internal Resistance). That will almost certainly be in the 10kA range. This kind of surge current can do all sorts of damage as you might imagine.
3) The controller should handle precharge, not you. That said, the usual way of precharging the input capacitors is to use a relay to bridge the main contactor with a wirewound resistor. The main contactor is closed either when dV/dt drops below a certain rate or after a certain amount of time. I prefer the former method; many people go with the latter method as it is simpler to implement.