Battery Not Charging

Originally posted by Sleepless techntrek is probably correct.  However, I have sometimes salvaged marine batteries that have been very low on water.  Fill the cells with distilled water and put the battery on a charger.  It may come back to life although it may not have the capacity it once had.  It is probably ruined, but it is worth a try.

I always buy the Group 27 deep cycle batteries sold by Walmart for all my marine and RV needs.  Most tire dealers and auto parts stores sell deep cycle batteries, but I buy from Walmart because of their prices.  I am sure others will express other favorite sources of brands, but most of the people in my circles buy from Walmart, too.  Just be sure to purchase

Group 27 rather than the smaller Group 24 size.

Bob

If your battery is fully charged, 11.5 volts may possibly be indicative of a bad cell.   It should be in the 13 -13.5 volt range.  Most auto supply stores, tire stores, etc., will normally test your battery free, just to be safe. 

Bob

Costco's Kirkland brand deep-cycle batteries are also good value for money.

Bill, a true load test is conducted by applying a high wattage drain to the battery.  I use a 1000 watt load tester and within seconds I can tell the condition of the battery.  For example, 13.5 volts may drop as low as 7 or 8 volts.  LED lights and the Fantastic fan don't draw all that many volts to reliably test the battery condition.

During your test, were you connected to shore power?  Assuming you were not, check the voltage at the isolated battery again to see if there was a voltage drop.  I have used "damaged" deep cycle batteries to run my shrimping lights or for other non-critical uses, but I never trust them as a primary house battery in a trailer or a boat.

Bob