Lead acid batteries have more of a linear discharge rate (btw don't think that just because you have a SLA battery it means that it's a deep cycle) whereas Nicad and Li-ions tend to give almost full power then run down quickly when they reach their limit.

I think the guy is confusing how many watts his motor and controller is for what his batteries are and doesn't have a clue as to the Ah and discharge rating of his batteries.

Been a while since I figured this but if I remember right the "C" rating on a Li-ion is the discharge rate so for example if you have a 2600 mAh 20C pack you can discharge them at 20 times the mAh rating but like I said it's been a few years since I was on top of Li-ion technology.

Also if you have multiple sets of batteries you can go a long time before you have to charge all of them, even up to 4 hours so wonder if he did because that long of a continuous draw on one set, unless it's a massively over sized pack, seems a little tough to believe . lol