Will the addition of a large capacitor to the battery pack be a violation of the battery weight rule?
Its not an additional battery but it uses battery power.
On a road course it could be an advantage but not so much on a fast closed track where you are at max throttle for most of the race.

Vic

I would think boost caps would be allowed if they were fully discharged before your battery pack was installed.  It would make the battery rule tougher to inforce but still legal from what I can determine.

I agree. they are legal as long as they are not precharged. I have always felt they would be a great way to "smooth out" in rush to the motor.

We normally keep our batteries in the car and off the car charging up till the time we  role the car to the line.
Would we need to keep it disconnected or switched off during charging?

If the capacitor was installed on the battery side, they would hold a charge till the throttle was engaged. You likely would get a little extra boost off the line then the charge would smooth out and you may or may not even notice them in there. If they were on the motor side, they likely would smooth out the in rush when you hit the throttle hard (possibly might make the car keep going for a few seconds after you let off the throttle too). There already is a fairly large capacitor inside most controllers (notice the large spark when connecting). Depending on the size of capacitors you are installing, remember they can be a little dangerous when you have them charged. Aaron