I've had my 86 Cat 27 for about 9 months now. It's on the hard
now and I removed the batteries to the basement. Two Group 34 AGM
new in '09. One battery
is holding 12.6v. The other can't seem to get up much past 6.75v. I have a very good and new dual battery charger
on the boat. At home I have a single
6 amp charger
with a 8 amp boost. When I plug
in the single
and try to boost it it immediately switches to Float. Even if I leave it plugged in overnight it won't get over 6.75 volts. Is this battery FUBR? During the season I normally had the shore power
plugged in and the dual charger on. Everything was normally off but I left one of the batteries 'On' to run the auto bilge pump
. So maybe, If in rained a great deal, The pump might run a few minutes and switch off. I usually trie to switch between batteries on which would be left on.
I've read enough about batteries to know that one is suppose to replace both batteries, not just one. And not to mix types. Two AGM
batteries would be very expensive and really frustrating knowing that one battery is just fine. So, the question is, are these 'rules' all that iron clad? Does anyone have any experience replacing just one? Mixing types? Also, is there a way to bring back the low battery?