SLA's SUCK!
I put the 6v 15AH bat in series with the 48v 14AH pack & didn't go any further. I think these 12v 7ah batt's will be used in my kids toys. I'll just use my NIMH packs for everything. BTW I now have 450mi on the ebike & everything is holding up great
I even had to ride it in the rain
I did water proof every thing as much as I could.