400 amps will destroy these batteries instantly.

At what voltage does the generator create 400 amps? I have never seen a portable generator capable of 400 amps, this is huge current. Unless its 400 amps at only 12V, which is not going to help in electric car, since you need much higher voltage.

These batteries are not very good for EV since they are not deep cycle and will not last long and will provide very little range. It all depends on your expectations from this conversion.

Let me know if you need any help with EV conversion...