Doug - Thanks for letting out some of the secrets of out of envelope performance. Would you have any guess of batt capacity used typically?
The 2 tractors I converted just use normal deep cycle batteries you can buy anywhere, they are 110amp/hrs and 125amp/hrs. I was more interested in range or run time without spending a ton of $
These guys who race or compete have way better battery packs, if there using lead acid they use the AGM type battery because it delivers more amps than the same size of wet flooded batteries can. When you compete you want as much power, amps for a short period of time and the AGM battery does that, it also charges up faster than conventional wet cells.
I'm not a battery expert but this is what I've being able to find out on the net.