Battery 12.1v to 11.5 Overnight?

[jonnie3]

My brand-new batteries went from 12.1 V to 11.5 V overnight. The only thing running was the refrigerator in propane mode and the propane leak detector. Is this normal for brand-new batteries? The temperature outside today is 98°. Would that have something to do with it?

[uncle_bob]

Hi

Either your batteries are badly damaged or you have some other loads running on the battery. Without knowing which AS you have, it's a bit tough to guess what else might be powered up. If you have a three way fridge, the propane getting an air bubble might switch it to 12V. Temperature wise, the battery voltage should go up overnight as the battery cools.

One thing to think about: If the 12.1V was while the battery was charging (maybe off the solar) and the 11.5V was after things had settled overnight ... this is pretty normal. The battery would have been well below 50% charge when you started the process. You need to wait about a half hour to an hour after you are done charging to get a "good" voltage reading.

Bob

[jonnie3]

Thank you for your reply Bob. The batteries were recently installed at Jackson Center, so I don't think the batteries would be badly damaged. The 12.1 V reading was after the trailer had been sitting for about a month with the battery disconnect in the store position. When I returned to the trailer today is when I got the 11.5 V reading. My trailer is a 2015 25 ft flying cloud.

[Al and Missy]

12.1 volts, with no significant loads, is indicative of 50% charge level for lead acid batteries. For best life, they should not be allowed to discharge below this level. 11.5 is indicative of 90% discharge. Continued discharge to this level will significantly shorten battery life.

I don't know what fridge you have, but if it has a humidity control switch, it should be off. That powers heat strips around the door to control condensation. They burn significant power, about half an amp.

With 98 degree outside and no AC, the fridge may have been running a lot. The gas valve draws about 0.25 amps. Figure another 0.25 for the control board.

All of that totalled up is about 1 amp. You don't say what batteries you have, or how long you were gone from the trailer, but assuming 2 group 24s you have about 160 amp hours total, and you burned somewhere around 40% of that, or 64 amp hours. Unless you were gone 3 days or so between those readings, you have some loads you don't know about or bad batteries.

Al

[uncle_bob]

Hi

Depending on what AS you have, you could have anywhere from 60 AH of battery to 250 AH. That's a lot of range. You only want to go to 50% of these numbers so the real "useful" capacity would be 30 to 125 AH. As mentioned above you went past the normal limits on your batteries.

Toss in on top of that - some models come with inverters and some do not. If your model comes with an inverter, talking about it being on or off is a useful discussion. If you don't have an inverter .. not worth talking about.

No matter what model you have, things like age and condition of batteries matter. A 12 year old battery is likely not a first class battery. If you have a 2018 on it's first trip out, there are different things to dig into than on a 1966.

Lots of variables, lots of different directions to go with this.

Bob

[wulfraat]

Originally Posted by jonnie3

Thank you for your reply Bob. The batteries were recently installed at Jackson Center, so I don't think the batteries would be badly damaged. The 12.1 V reading was after the trailer had been sitting for about a month with the battery disconnect in the store position. When I returned to the trailer today is when I got the 11.5 V reading. My trailer is a 2015 25 ft flying cloud.

This issue has been covered at pretty good length on the forum

Even in the store position both the propane leak detector and inverter (which bypass the use/store switch and are directly connected to the batteries) place a low level draw on the batteries. They will kill the batteries in 30-45 days as you've observed.

The only way to eliminate draw on the batteries while in storage (assuming you don't keep your trailer plugged in) is to physically disconnect the batteries from the system. You can do this manually by removing both negative ground leads on the battery posts (one for main 12v trailer power - automotive clamp - and one for the inverter - ring terminal) or you can install a mechanical marine grade disconnect switch as many have done.

See attached photo of an typical disconnect switch to isolate the batteries from the trailer. And here is a link to a recent thread on this topic:

23fd Battery disconnect switch install
http://www.airforums.com/forums/showthread.php?t=168120

At this stage your batteries have been "bounced" past 50% discharge and the (cheap) stock group 24 interstate batteries don't like that / will likely not hold a full charge again. Yes, bouncing them just once can permanently affect their ability to store energy.

Charge them up and let them sit (disconnected from the trailer) for at least 24 hours then check the voltage and report back.

Airstream replaced my batteries under warrantee just 2 weeks after I bought the trailer. They sat on the dealer lot for a while and of course were bounced due to background draws. They would only hold 12.5 volts after a proper charge. They would then draw down to 12.1 in no time.

The new ones hold 12.8v and voltage decline is much more consistent with amp hour usage.

[jonnie3]

I appreciate all of the replies. Just to clarify, the batteries sat for one month in the store position. Yesterday I switched it over to the "use" position to run the fridge overnight in order to get it down to temp for today. So the battery went from 12.1 to 11.5 overnight with the switch in "use". I may be wrong but dont I need the switch to be in "use" even when the fridge is running on propane? Hopefully my batteries will charge up during my six hour trip tomorrow, then plugging into 30 amp

[thiel]

Originally Posted by jonnie3

I appreciate all of the replies. Just to clarify, the batteries sat for one month in the store position. Yesterday I switched it over to the "use" position to run the fridge overnight in order to get it down to temp for today. So the battery went from 12.1 to 11.5 overnight with the switch in "use". I may be wrong but dont I need the switch to be in "use" even when the fridge is running on propane? Hopefully my batteries will charge up during my six hour trip tomorrow, then plugging into 30 amp

As far as I know, you need to be in USE to run the fridge on propane since there is a small 12v draw needed to make it work.

[wulfraat]

Originally Posted by thiel

As far as I know, you need to be in USE to run the fridge on propane since there is a small 12v draw needed to make it work.

Correct, you need the inside switch to be in the "use" position for the fridge to work if not on shore power.

[uncle_bob]

Hi

Simple answer: You need some way to trickle charge your batteries when they are in storage.

Bob

[gypsydad]

I posted earlier on another thread about this. I had this issue with a "new" 2012 AS few years back. Found bad cells from the AS dealer. 2 weeks ago, same thing happened to a friend who just picked his new 2017 23' from AS dealer. 12.5 to 11.3 overnight with only fridge on. Turned out to be bad Interstates, which they replaced without any hassle. You should have the cells checked so you know status for sure, but that's what it sounds like. If under 1 year old, (even new from Jackson Center) Interstate will likely replace at No Charge. It's a hassle to get AS dealer involved...they just have too many things going on to put you at top of their service priority list, unfortunately. Interstate guys told me they have "service routes" which include checking the batteries at all their customers, like Costco and RV dealers....they routinely replace the batteries after 6 months if still sitting on the shelf. Most RV dealers have batteries installed in units...they sit on the lot, and although the dealers are supposed to check out, including checking the cells for fluid, they take the lazy way out and typically just check the meter after connected. Sucks.