Jim, these came from 48v golf cars--four T-1275s each. I got two used ones of a set of four where the new buyer of the used golf car requested all new batts.
They also have ones that are 48v but use six 8v batts. ISTR they were trending to the 8v batt way of doing it so not as many used T-1275s at that place as before, but still some.
Can't see how we could use 8v batts except as a 24 or 48 as discussed in the other thread on that. You could use that DC DC converter to make 12v from three 8s, but no idea how to recharge the three 8s. When doing it with four 6s or two 12s you can recharge half at a time with a 12v charger.