We have one 12v battery in a travel trailer. After driving for 5-6 hours on Friday, we boondocked in Texas. 40s at night, 50s during the day. We only used 1 led light in the evening and the water pump a few times. The fridge is on all the time (battery/propane). Yesterday Saturday, in the morning when we used the water pump, it kept rattling away as if it didn't have enough power. Fridge and lights worked.We plugged in the portable 100w solar panel. The charge controller read 9.7v! After a few hours of solar charging, it went up to 12.2v but by the time the sun set, it showed 11.57v even though nothing but the fridge was on in the camper.This morning (Sunday), when we plugged in the solar, it read 9.7v. Water pump kept rattling away after we washed our hands and the led lights were dimmer with the pump on.Some facts:- flooded battery dated 2013- type marine (it shows cranking amps on the label)- fluid level is okIs the battery dead / beyond repair? How come the fridge and lights still work?Based on my limited knowledge, a battery shouldn't be below 12.3v ... Based on the past experiences, one night of light usage after driving, the battery should still be around 12.6v...

its time for a new battery. anything under 12.8 is not good and its 5years old. buy a deep cycle marine battery even a wal mart will do a good job, I,ve got two wal marts in my MH that are six years old and still going.

midnightsadie wrote:its time for a new battery. anything under 12.8 is not good and its 5years old.A fully charged flooded battery with no load on it should read in the 12.72 volt range, under load voltage will obviously drop, and the greater the load the greater the voltage drop. One can easily see voltage drop into the high 11s under heavy load but once that load is removed voltage will bounce back. Ideally you don't want to draw a flooded deep cycle battery down any more than ~ 50%, meaning it's unloaded voltage should drop no lower than ~ 12 to 12.1 volts. From the OP's description it would seem his battery is due for replacement.

jornvango wrote:We have one 12v battery in a travel trailer. After driving for 5-6 hours on Friday, we boondocked in Texas. 40s at night, 50s during the day. We only used 1 led light in the evening and the water pump a few times. The fridge is on all the time (battery/propane). Yesterday Saturday, in the morning when we used the water pump, it kept rattling away as if it didn't have enough power. Fridge and lights worked.We plugged in the portable 100w solar panel. The charge controller read 9.7v! After a few hours of solar charging, it went up to 12.2v but by the time the sun set, it showed 11.57v even though nothing but the fridge was on in the camper.This morning (Sunday), when we plugged in the solar, it read 9.7v. Water pump kept rattling away after we washed our hands and the led lights were dimmer with the pump on.Some facts:- flooded battery dated 2013- type marine (it shows cranking amps on the label)- fluid level is okIs the battery dead / beyond repair? How come the fridge and lights still work?Based on my limited knowledge, a battery shouldn't be below 12.3v ... Based on the past experiences, one night of light usage after driving, the battery should still be around 12.6v...If it read cranking amps it's not a deep cycle and not meant for storage usage as would be encountered with solar or other charging methods.

As just mentioned, those dual battery (starting/storage) are not true deep cycles. If this battery is only for storage purposes, buy a true deep cycle. True deep cycles will not include anything about cranking amps as they are not designed to crank anything.

Do an energy survey and then get adequate batteries, solar panels and a controller according to the survey. One battery and a “part time” solar panel won’t cut it. Mount solar panels on the roof and they will charge all day. Just one led light, a little water pump use and fridge isn’t fun.

Battery down to 9.7v ?? | Good Sam Community

Harvey51
Explorer
Jan 08, 2019
The voltage on a battery is overly optimistic after charging. Wait a few hours after any charging to measure voltage and use the 12V side of life voltage chart that says 12.0 is 50%, 12.6 is 100%. As an example, my batteries have been disconnected since September and still read over 12.6 V.
If you want to more accurately and conveniently see the state of charge, get a battery monitor that counts amp hours in and out.

If you choose to buy regular batteries instead of AGM which don’t like low temperatures, I recommend the Costco ones that say Deep Cycle on the side. Mine are 6 years old and still excellent. This time I’ve kept them over 80% charge with solar and engine charging. Never plugged in or used a generator.
Sam_Spade
Explorer
Dec 26, 2018
jornvango wrote:
now it's showing 12.4V. (all in a matter of 2-3 minutes after unplugging and putting some load on the battery)

I'll be on the lookout for a replacement.

Probably the right thing to do but it could also mean that you have a constant high current load on the 12 V system.

Might want to disconnect the batteries to see what they measure with NO load.
Sam_Spade
Explorer
Dec 26, 2018
marcsbigfoot20b27 wrote:

I have 3 in series, no maintenance.

I don't think so.
3 12 Volt batteries in series would be 36 volts.
Even 3 6 V ones would be 18 volts.
SoundGuy
Explorer
Dec 26, 2018
marcsbigfoot20b27 wrote:
Sams club, group 31 AGM East Penn/Dekka (branded Duracell) grey case, made in USA.
I have 3 in series, no maintenance.

Surely you mean 3 in parallel. 3 G31s in series would be 36 volts. :E

Installed the same battery in our Freedom Express - no complaints. Here in Canada they're distributed by East Penn to RV Care dealers under the branded name Traveler's Choice.
2oldman
Explorer II
Dec 25, 2018
jornvango wrote:
When I unplug, the battery shows 12.9V as you would expect.
Check it again after 10 minutes. Too bad Santa didn't get you a new battery.
time2roll
Nomad
Dec 25, 2018
Be careful continuing to use a bad battery. Easy to overheat, get low on electrolyte and and have a minor explosion.
jornvango
Explorer II
Dec 25, 2018
Merry Christmas!

We've been at an RV park and plugged in. The battery correctly shows 13.5V while plugged in. When I unplug, the battery shows 12.9V as you would expect.
Then I run the water pump, lights, etc. and in a matter of minutes it went down to 11.9V and now it's showing 12.4V. (all in a matter of 2-3 minutes after unplugging and putting some load on the battery)

I'll be on the lookout for a replacement.
marcsbigfoot20b
Explorer
Dec 25, 2018
Sams club, group 31 AGM East Penn/Dekka (branded Duracell) grey case, made in USA.
I have 3 in series, no maintenance.
Sam_Spade
Explorer
Dec 25, 2018
opnspaces wrote:
Batteries have 2 volts per cell.

Not correct.

A conventional wet cell battery has 2.1 volts per cell, for a total of 12.6.
An AGM has about 12.15 per cell.

The part after the decimal point is IMPORTANT since one that reads just 12.0 is more than half discharged.
opnspaces
Navigator II
Dec 25, 2018
jornvango wrote:
We just arrived at our next destination after driving for 6 hours. Battery level shows 9V

Looks like we need to look for a place to order a replacement on the road.

You have a bad battery. Batteries have 2 volts per cell. A 12 volt battery that mysteriously drops to 10 or 9 volts has a dead cell. You'll need to replace it, If you want a true 6 volt you'll have to buy two to get the needed 12 volts. Costco and Sams Club carry them for about $85 each, I don't think you'll be able to find a true deep cycle 12 volt at a Walmart or auto parts store.

But, what do you use the battery for? If you are constantly off the grid then a true deep cycle would be a good idea. But if you almost always have an electrical hookup, then almost any cheap starting battery from Walmart should work fine.

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