560 Ultra Battery Mystery?

After charging the trailer battery using 120 volt house current, why does the battery, reading 12.2 at the time the power plug is pulled after a three hour charge, then read 10.1 about a hour later? There is no evidence of any fixture in the trailer drawing power. The same reported drop in battery power after charging happens occurs in other instances. The battery is an AGM and is three years old. Any diagnosis or remedies?
Thanks,
Wendell

 

This indicates that at best, your battery is not fully charged, and at worst, the battery is bad. Is the 12.2 volts reading with the power plugged in, or just after disconnecting? A fully charged battery will read 12.7 or 12.8 right after charging, settling down to about 12.5 after a few hours.

Three hours is nowhere near long enough to charge a Camp In battery with the built in charger. If the battery is quite low (10.1 is pretty low) it can take a day or two to fully charge back up.

 

Thanks for the data:
The power reading is when the 120 is connected - it then drops after disconnection.
Your charging time makes sense as this is not a car battery. I'll give it a full two days of charging connection.
Wendell

 

Good luck, post your results. The trailer battery is actually similar capacity to a car battery in a small compact car or large motorcycle. The charger in the trailer is quite small and would take a couple of days to recharge a car battery too. I have several of these save chargers I use to maintain the batteries in collector cars that are not driven regularly.

The voltage reading while charging should be approaching 14 volts. This type of charger does some weird things while charging and fiddles the voltage to get a good charge. And, when it thinks the battery is fully charged it shuts off and so will read essentially the same as when the charger is not connected, monitoring the battery charge level and switching on now and then to top up the charge.

10.1 volts is a pretty deeply discharged battery, you should try not to let it get that low as it may reduce the lifetime of the battery and may not recover completely.

 

To all, thanks for the input:
The battery proved, by a three-day test, to be defective. Now, an Interstate brand "6 pack" battery is installed and a storage maintenance charging program now a commitment. The "6 pack" reference is to the battery construction being six connected cylinders within a surrounding casing. It was recommended by a trusted RV repair shop. I'll report the outcome of a regular electrical charging maintenance program.
Wendell