@MN Driver, Thanks for the tips. I think I might be ok with the non-isolated part. At least now I know thanks to you.
My battery bank is going to be 72V @ 40AH. I don't know if I really care about quick charges. I probably will actually try not to do that if I can to prolong the pack's lifespan (slower charging helps right?)
According to this site (just a quick google search): http://www.csgnetwork.com/batterychgcalc.html
I can do a charge at 13A in about 4 hours. Maybe say 6 hours if I assume the website is being optimistic. That's fine for me I think. If it takes anything more than 1-2 hours, I might as well just wait another 4-10 hours if it will get me a cheaper charger.
Is that logic valid/rational?