12V mystery

[narcodog]

Here's one I cannot figure out. I have two AGM group 31 battery's that are about four years old. They stay plugged in when at home and I have a 2020 Trimetric monitor which I monitor often whether on the road or here at home to see if there is any change.
Now the mystery, last week I drove eleven hours with a stop over night after seven hours. The monitor was reading 12.6v when I hit the road. I arrived at my destination and spent the night where I was going to be parked for three nights. Wed. night I used LED lights, pump a little and the fridge was on 12v. Thursday morning the reading was 12.5 and the monitor stated I was at 99%. At noon I came back to the rig and the volts were at 12.5 and 95%. At 5pm I returned and my reading was 11.2v. Now nothing was on, no lights, no pump no furnace just the fridge and CO/LP detector.

I ran the genset for three hours knowing it was not going to recharge the batterys in that amount of time. At 0500 I got up and the fridge was flashing and the batterys were dead again, which was expected.

I hit the main switch and used my third battery a group 27 which is on a separate circuit. That battery lasted through Friday and Saturday.

On Saturday night I was at a State Park and plugged in. The batteries took the charge and I kept them charging until Sunday evening. I hit the main switch because I wanted to see if they would now hold the charge, and they did straight through Tuesday morning when I hit the road. Drove two days home and did not plug in until Thursday, again to see if the would hold the charge, and they did.

So, here what do you 12v guru's think might have happened as this has never occurred in the 13 years that I have had the rig.

[Grit_dog]

The fridge in our old 03 and 05 switches automatically. Nice becasue, seems no matter what I do, if I hit about 80mph or there's nasty winds while driving freeway speeds, it goes out about 1/2 the time. DC kicks in, but it'll only run the fridge in hot weather about 8 hours before killing fully charged batteries.

[ticki2]

NRALIFR wrote:

ticki2 wrote:
...... Some 3 way fridges will automatically switch to 12v DC if running on gas and it blows out or runs out . Check the settings on fridge . It could also be a faulty board . 12v to run controls is small . 12v to run heating element is huge.

Are you sure about that? The three 3-way fridges I’ve had would not go to DC mode automatically. It always had to be a manual selection. I only have my current fridge to refer to, and it’s almost 20 yrs old. I have to manually set it to DC mode when we hit the road, otherwise it tries to run in LP mode. But, if that’s correct it would certainly account for the battery drain.

Another thing that might have happened (I’ve done this myself a few times) is leaving the wall thermostat switched to “Heat” mode, and the furnace turned on while we were away.

:):)

That is why I said some . A Few years ago I helped a friend replace his fridge with a Dometic 2652 . It had manual and auto settings . In auto it worked as I described . In manual it worked as you said . Good point on the thermostat , I have had that happen to me also .If the thermostat is not shut off ,some with separate switch,the furnace fan will just keep running even when gas is off .

[NRALIFR]

ticki2 wrote:
...... Some 3 way fridges will automatically switch to 12v DC if running on gas and it blows out or runs out . Check the settings on fridge . It could also be a faulty board . 12v to run controls is small . 12v to run heating element is huge.

Are you sure about that? The three 3-way fridges I’ve had would not go to DC mode automatically. It always had to be a manual selection. I only have my current fridge to refer to, and it’s almost 20 yrs old. I have to manually set it to DC mode when we hit the road, otherwise it tries to run in LP mode. But, if that’s correct it would certainly account for the battery drain.

Another thing that might have happened (I’ve done this myself a few times) is leaving the wall thermostat switched to “Heat” mode, and the furnace turned on while we were away.

:):)

[ticki2]

narcodog wrote:

Grit dog wrote:
OP said fridge was on 12V at first then did not say thereafter.
Agree, I don't see a fridge running on DC power for a day or 2 on 2 batteries very well.
IF the OP meant that he switched the fridge to LP gas and THEN the batteries went dead, could be wind or something else caused the LP fridge to blow out, it switched back to DC power and sucked the batteries down.

I don't believe his fridge runs for days at a time on DC power and 2 car batteries.

I guess I was not clear on the operation on the fridge. It was on LP which uses 12v to operate it.
I have never run my fridge on 12v alone and never will. Just sayin.

Some 3 way fridges will automatically switch to 12v DC if running on gas and it blows out or runs out . Check the settings on fridge . It could also be a faulty board . 12v to run controls is small . 12v to run heating element is huge.

[Wild_Bill_888]

Any chance an inverter was left on and ac came on while you were gone, or it looped back thru the charger?

When the genny was on was it loaded heavily by the charger delivering high current, or loafing?

[3_tons]

Trying to run an ammonia fridge off two batteries is a losing proposition...

[jimh406]

I’d check connections too including the voltage meter.

[pianotuna]

Hi,

Check the ground connections.

[Kayteg1]

In this case, sounds like your batteries are dying.
You are not saying what charger you keep them on at home, but lot of RV chargers are battery killers.
You need one with float circuit to have it hooked up for long periods.

[narcodog]

Grit dog wrote:
OP said fridge was on 12V at first then did not say thereafter.
Agree, I don't see a fridge running on DC power for a day or 2 on 2 batteries very well.
IF the OP meant that he switched the fridge to LP gas and THEN the batteries went dead, could be wind or something else caused the LP fridge to blow out, it switched back to DC power and sucked the batteries down.

I don't believe his fridge runs for days at a time on DC power and 2 car batteries.

I guess I was not clear on the operation on the fridge. It was on LP which uses 12v to operate it.
I have never run my fridge on 12v alone and never will. Just sayin.

[Grit_dog]

OP said fridge was on 12V at first then did not say thereafter.
Agree, I don't see a fridge running on DC power for a day or 2 on 2 batteries very well.
IF the OP meant that he switched the fridge to LP gas and THEN the batteries went dead, could be wind or something else caused the LP fridge to blow out, it switched back to DC power and sucked the batteries down.

I don't believe his fridge runs for days at a time on DC power and 2 car batteries.

[hedge]

A 2-way fridge on propane uses barely any 12v power. I'm thinking the guys above are talking about 3-way fridges running on 12V. That would definitely be a power hog.

[Kayteg1]

When all the gauges have their reading tolerances and battery converts chemistry into electricity, what is hard to control process. ...
I still think electric refrigerator in hot afternoon will take nice chunk of battery power.

[work2much]

If it is a 2 way ammonia fridge you are powering with the batteries that requires a pretty big bank and charging source to run 24/7

2 group 31 batteries should be about 200 AH with only 100AH being usable (without degrading batteries cycle life) BTW 11.2 is basically dead. You never want to discharge that far. You may want to test your batteries for capacity to see how healthy they are.

Our fridge uses about 30 AH DC on electric. Cycling 50/50 is still 360 AH.in a day. Do you know what the fridge draws when the heating element is on? These ammonia fridges are not very efficient on electric.

Since you have been doing the same as the past 13 years without a problem I am stumped on a couple levels, mainly on how you are able to run your fridge on battery all day and overnight.

[Rolling_Condo]

First I would check all connections, from the converter to the batteries.