How to choose new 8D house batteries.
Existing batteries are 5 yrs old 8D AGM's. after only running my ceiling fan for an hour or two they're discharged down to 12.5V from 13.5. I'm guessing they are nearing the end of their lifespan.How ...
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sh410 wrote:
A fully charged battery at rest 12.6V. The 13.5V you are seeing is a surface charge.
The full charge for a conventional battery at 80 F is 12.65 but for an AGM it typically is 12.8.
YOu can't use that 13.5 "surface charge" number for anything, except maybe to assure yourself that something is charging the battery.
An AGM at 12.5 is about 65-70% charged and might be "on the way out"
if that happened over a short period with a light load.
The other consideration, however, is that 13.5 is just a float voltage for an AGM. If the charging voltage never goes above that they might not be getting fully charged......ever.
You need to check that out before sinking a **** load of money into new batteries.
