[ProDigit]

Not sure. Farad rating goes together with the rated voltage.
The higher the cap can handle voltage, the lower the farad rating.
I believe the 2-3 Farad cap I have, handles up to ~1000W of energy for 1 second,or at 13 v helps out the battery with about 76Amps. That's quite a bit!
It's also not meant to start the car with, but merely a helper to the battery. It proves a starter with greater initial energy, and charges up again after the starting process is done, and the alternator takes over.
The cap is also larger than any motorcycle battery.
About 4 of these fit in a large size car battery.
I'm sure the 400Farad ratings are a bit off, as a similar cap of 400 farad would be the size of an entire motorcycle.