89SP charger/converter info needed. How many converter/chargers needed?

[wl89spman]

My SP has 2 PD9155's(55 amps each).They don't charge batterys high
enough(11-11.5v). If I replace them do I need 2 or can I get one that is 80amps.
Do most coaches have 2 chargers/converters? I have a sw in the shore power door
that is labled HIand LO.I understand that it selects one(LO)or both(hi).Does
everybody have this sw? And where do you leave the sw positioned? How many AMPS
do I need for a charger/conveter?
Thanks for any help
Ed Gardels 89SP
Arlington, Texas