109 replies to this topic

[Desert Scruff]

I have a CR85 Isotherm refrigerator in a 2016 Fleet and recently have had the voltage drop to 10.5 volts on three occasions. The drop occurred after the fridge had been running almost continuously for 10 hours, using about 25 Ah each session.

I have two AGM batteries less than two years old and all the tests I've done on the batteries show they are in excellent shape. I was scheduled to have a final test done, a stress test, but have to drive 250 miles round trip to the shop.

When the voltage is at 10.5 and I turn the fridge off, the voltage immediately jumps to 12.5. In doing online research I discovered it is not uncommon for the voltage to drop when the fridge compressor runs. I also know this can be caused by the wiring to the fridge being too small.

But assuming FWC did not use too small a gauge wire, does anyone have an idea what is causing the voltage drop and what to do about it?

I have also had to make numerous manual adjustments to the thermostat to keep the fridge from either freezing food or becoming too warm. On another post I saw where a fan inside the fridge will solve that problem.

Thanks for any help you have to offer (and I would rather be talking about a trip than complaining about a problem).

[challinger]

I took delivery of a Hawk in March of 2017 also with the CR85. This April I experienced the exact same thing. I removed the two batteries (Exide) and had them load tested and both failed. I called the phone number on the battery for the warranty and they replaced both of them with no questions asked. I ended up installing two 6 volt batteries and changed out my Zamp charge controller to a Victron. I'm thinking the Zamp overcharged the batteries also setting off the propane alarm regularly. I noticed the alarm would only go off when the batteries were being bulk charged at 14.4 volts. Everything has been working fine since l made those changes.

Carl

[RC Pilot Jim]

Desert,

Did an auto repair shop test the batteries? or did you? 

 

Our AGM model Inimidator by East Penn Mfg. is tested every 6 months by my regular mechanic. Battery is over two years old now (guarantee 2 years). In March it was tested = still over 80% good. Roof solar panel keeps it topped off to 100%. Works well under a load.

[Desert Scruff]

Thanks, Carl, for the input. I get the battery stress test done in a couple of days. It sounds like we are/were dealing with the same thing. I hadn't thought about the Zamp controller overcharging but I have wondered if the converter's "smart" charger was a culprit. If the batteries fail the load test I will take the same path you did to solve the problem. Did you add the fan inside the fridge box? Which Victron controller did you change to? I already have added the Victron battery monitor to track the Ah going out of the batteries.

 

I would go to 6 volt batteries but one corner of the Fleet battery box has an adjoining cabinet projecting into it a few inches at the top and that is enough to prevent accommodating the additional height of one of the two 6 volt batteries. 

 

Jim, thanks, and you can see I'm heading for the final battery test.

[ardvark]

The amp draw as measured at the fridge compressor is what when this happens?

[challinger]

Desert Scruff, I very seldom used the converter so I ruled that out. I did add a fan inside the fridge and monitor the temps with the AcuRite wireless fridge thermometer. I'm satisfied with the results of the fan. I went with the SmartSolar MPPT 100/30.

Ardvark, In my case I was looking at the app on my phone checking the battery stats when all of a sudden the volts started dropping very fast. It took about 30 seconds to go from 12.7 down to 10.5. The amp draw at the time was the normal 3.8 with the fridge running. The amp draw never changed while the volts dropped off. This was at night so no solar and the camper was not plugged into shore power. I got lucky with the timing to witness this.

[Wallowa]

Question:  Why change from 12v to 6v batteries?

 

Thanks...

[Desert Scruff]

With two 6 volt batteries I would get about 200 usable Ah versus 85 usable Ah with the two 12 volt batteries. That's the way I understand it.

 

I should correct myself in the first post in talking about the drop in voltage possibly being caused by too small a gauge wire. Again as I understand it, that voltage drop would be at the fridge and not the battery. The voltage drop to 10.5 I was seeing was at the battery.

[ardvark]

Amp hours of two 6s in series or two 12s in parallel is roughly the same: http://www.batteries...fm?TID=20#ANC20 Historically the advantage of 6s over 12s has been plate thickness although it has been argued more recently that with quality batteries the difference in charging cycles is not greatly different.

 

With an atypical rapid discharge, voltage only tells you something is happening, but not what. In the case of the fridge, how much amperage should it be drawing versus how much is it actually drawing? If everything is good there, then you are looking at maybe batteries that can't handle the load or something else.

[Desert Scruff]

FWC says the amp draw of the fridge averages 2.7 and my monitoring shows that is the range I'm in even at 10.5 volts. 

 

On 6 volt batteries I meant to say, I would gain 15 Ah available over the 12 volt batteries, going from 170 Ah total 12 volt to 200 Ah 6 volt. 

No wonder I need help.