I don't have an answer to your question, but welcome to the forum.

I'll take a wag and say that for a car battery, the maximum charging rate won't be much more than the typical car alternator output, maybe 80-100 amps. A typical home garage car battery charger usually puts out 6-10 amps. Pro garage charger, maybe 50 amps.

I'm sure one of the guys who's playing with electric car conversions will have a better answer.