2 1/2 yr old 12v battery that has had good maintenance. Took rig to the shop for some routine maintenance on other systems. Battery read 12.8 . Today (5 days later) battery read 9.8v. I've read on several posts about damage to batteries by over discharge and I wonder if the battery is ruined. Hooked it up to a good three stage charger to see if it would charge. Would damage show immediately (not charge?) or would it just not stay charged very long? Have a 3-4 week trip planned soon with the probability of several nights without hook-ups.

Damage will probabky not be immediately noticed. I would just charge it and use it until you notice it not holding a charge as it should. Coukd be years from now.

Only time will tell if the battery is damaged beyond practical use. Charge it, check fluid levels if applicable and test it in the driveway before the trip. Be prepared to replace enroute if it doesnt last a night or two boondocking.

Check the Specific Gravity of all the cells after charging.

Every time you discharge a battery, even a little bit, it is "damaged" in the form of reduced capacity. Deeper discharges or longer periods without recharging result in more capacity loss. Eventually the capacity is reduced so much you feel the need to replace the battery. That day will come a little earlier than if the battery hadn't been discharged so deeply, but you may never even notice the difference.

Some chargers will not charge a very depleted battery. There is a threshold voltage that must be present for the charger to be operational. We don't know which charger you have. Using jumper cables from a running vehicle will increase the voltage so that any charger will charge the battery. Did the battery become discharged because of the typical parasitic draws present in most travel trailers? A disconnect switch will keep that from happening. If I was in your situation, I'd replace the battery with a quality deep cycle battery and install a disconnect switch (or remove a cable if pressed for time). Having to replace a battery while on the road can be problematic.

Battery damage | Good Sam Community

16 Replies

wa8yxm
Explorer III
Aug 09, 2017
DEEP CYCLE batteries like the GC-2 (six volt) likely will recover

MARINE/deep cycle.. MAY but the odds are way lower..

Suggestion.. Charge it back up and see what happens,
GoPackGo
Explorer
Aug 09, 2017
FYI - I just bought a Grp 27DC battery at Walmart - $81. Made by Johnson Controls I believe.
pianotuna
Nomad III
Aug 09, 2017
Charge it.
Equalize it.
Use it.
Take along some money on the trip for an emergency replacement.
Carry jumper cables to get you through "one night" if need be.
ScottG
Nomad
Aug 09, 2017
I suspect your battery has shorted internally. They can do this at any age.
If so, you will not be able to charge it.
RJsfishin
Explorer
Aug 09, 2017
Charge it,....you won't notice the slight degradation it has suffered,... it will be fine.
time2roll
Nomad
Aug 09, 2017
I always say there is a lot of wear and tear getting service performed.
Always some issue when I get stuff serviced.

Done is done. Charge it up and see how it works. Doubt the shop is going to hand you a new battery.
j-d
Explorer II
Aug 09, 2017
red31 wrote:
take it autozone or similar and let them charge/test it.

Not a bad idea, but let's clarify if this is a "deep cycle" battery as used in Coach/House part of a motorhome, or in a Trailer/Fifth Wheel. If it's a deep cycle, its rating'll be in Amp Hours. If it's a Chassis/Starting battery, rating'll be in Cold Cranking Amps. A deep cycle won't do well in a CCA load test.
I remember a chain auto parts store that seemed to condemn every battery they tested...
jkwilson
Explorer III
Aug 09, 2017
red31 wrote:
take it autozone or similar and let them charge/test it.

Unfortunately, a load test tells you very little about the performance of a deep-cycle battery. If it fails, the battery is probably bad, but a deep-cycle can pass a load test and still not have the guts to last as long as you need it to.
red31
Explorer
Aug 09, 2017
take it autozone or similar and let them charge/test it.
MNtundraRet
Navigator
Aug 09, 2017
If you did not have the single battery on "disconnect" when you left it for service, it could easily discharge that far in only 5 days. That battery is 2.5 years old now.

I don't think the service location did anything to damage your battery. Recharging the battery after 5 days would bring it back close to it's capacity for a 2.5 year old 12v battery. If your trailer is close to home leave the battery connected for 5 days after recharging and see how far it drops.