Fridge Draining T@B Battery During Transit

[Deleted User]

Hi, I have a mystery issue.  It "seems" that the fridge is draining alot on my T@B battery during transit.  I have confirmed that I have power at the 7pin connector on my tow vehicle but it would "seem" that the power isnt getting back to my T@B batteries. For example my batteries went from 100% when I left camp down to 90% after an hour andca half long trip with fridge on the 4th bar of power on the fridge.   Is the fridge just draining that much battery even though I'm getting power from my tow vehicle? 10% in about an hour and a half trip homes seems like alot.  I turned off the battery kill switch when I got home as a routine part of my "arrive home" checklist.  I also use the Curt Echo wireless brake controller that plugs first into the 7pin and then the camper plugs into the back of the brake controller, so there could be a problem there maybe but I dont know how to check that. I just cant think if what to check next.  Help is needed and appreciated! 

pthomas745

How big is your battery?  What are you measuring it with?  Was the battery "rested" when you see the 90% number?  A battery that is not rested will always read lower than the actual state of charge. 

[Deleted User]

I have two 6volt AGM batteries only 1-1/2 years old I dont know actual specs but I think around 220amp hours. Is a 2019 T@B 400.   I have a victron battery monitor and it was 90% today with battery switch in off position so it had to happen on 50mile trip home. It was 100% when I left campground (I looked because I found it drained down when I arrived at camp) i returned from my trip Sunday so battery was rested.  I mean I checked it once a month during the winter and it never went below like 98%. I plugged it up to the house power each month to jerp them charged.

Sharon_is_SAM

Relative to other trips, was it very hot out?  When you hook up to the TV with the alternator on, and the battery switch off, Frig on, what is the voltage being generated from the TV?

N7SHG_Ham

Three way or two way fridge? Three way fridge on battery will probably drain battery faster than it can be charged.

The issue with the vehicle charge line is it may not provide that many amps to start with (more of a trickle charge) and then you loose some power just getting from tow vehicle charging system to tab 400 battery in back of trailer. Undersized wire doesn't help either.

If it is two way fridge, that is pretty energy efficient, I can run that on the factory solar indefinitely with some 🌞

[Deleted User]

I always travel with the battery switch on. Is that maybe where I'm making a mistake? I've never checked to see what voltage I'm getting from TV. 

It's a 3 way fridge. I bet that's it, its draining too fast. I've only noticed it my last two trips but it could have been doing it all along and I just never noticed.  It has been in the 90s too for my last two trips so maybe it was just the perfect storm to drain the battery. I think too, I used to travel with it on the 3rd bar of cold, and I think I did have it on 4 this time. 

I think you might have figured it out. Thanks!!

Sharon_is_SAM

@TabbyShack, towing while the frig is on 12 v uses 11-13 amps/hr and there is no ability to control the frig temperature.   Many TVs can’t handle that and it deplete’s the TaB battery.  You must always leave the battery switch on while towing.  Not only to charge your battery, but to operate the break away brakes in the event of a disconnect.  

[Deleted User]

I always tow with the battery switch on fir the fridge, but I didnt realize it was also powering the emergency brakes.  I think next trip I will put fridge on a lower setting 3 power bars instead if 4 to see how the battery fares. 

Thanks! I guess nothing is broken!!

lkc001

I never use the battery setting on my fridge.  At camp it's either on propane or electric.  I also never tow with the fridge on.  I get the fridge good & cold at home at least 24 hours before then put a 1/2 gallon of frozen water & a few frozen water bottles along with frozen or cold food & pack the fridge shortly before traveling.  With the fridge already cold & frozen jug it stays plenty cold for many hours--when reaching camp start the fridge right away on  electric or propane-- works every time.

pthomas745

How many usable amp hours of battery do you have?  If it is 110 usable amp hours, and your fridge uses (lets say) 12 amps per hour:  You drove an hour and a half, (theoretically 18 amp hours from the fridge) and your battery shows 90 percent.  10 percent of your usable amp hours would be 11 amps.  (Your fridge used 18 amps and your car added 7 amps.)  Sounds normal to me. (Maybe!, unless I'm missing something!)

If you have 220 usable amp hours, and wound up at 90 percent, your fridge used up 22 amp hours in that hour and a half, which would indicate your car isn't providing much of a charge at all.

[Deleted User]

Thanks IKC001 for the suggestions. I do always use some ice packs, but I've not been turning the fridge on the day before. I will certainly start doing that.  

I've heard it's not safe to travel with the fridge on propane. Any truth to that?

For the usual short trip home, I will just put fridge on a much lower power setting. I've been putting it in level 4 out if 5 so since fridge, but since contents are very cold, I'm sure I can put on level 1 or even off and do fine. 

I wonder what people do on long trips? 

[Deleted User]

Pthomas, I'm sure I have at least 220 amps. I can't see the batteries. They are housed in a plastic case, but I know I saw it written on papers somewhere. 

I'm still going to research is the wireless brake controller might be blocking or reducing the power coming from the TV. Since it plugs directly into the TV 7pin and then the camper plugs into the back if that. It was a brand new product last year so maybe this is an issue no one realized at first. 

VictoriaP

TabbyShack said:

I've heard it's not safe to travel with the fridge on propane. Any truth to that?

It is not legal to drive with propane on in some places, due to the potential fire hazard, and you must also remember to turn it off before entering gas stations due to the risk of flame from the burner + gas fumes. To me it’s neither worth the risk nor the hassle of looking up where along my route it is or is not specifically prohibited. 

Many people still do it regardless.

[Deleted User]

I agree! Not worth the risk! I will not be doing that! I will be using  frozen bottles of water!

Thanks!

pthomas745

@TabbyShack if you have 220ah's of batteries, that means you have 110 "usable" amp hours.   In that case, the first part of my paragraph applies.  It would seem your battery is providing some charge to your trailer, just not enough to keep up with the fridge.  Your vehicle does a better job than mine does!

[Deleted User]

Thanks! That's right because you cant drain below 50%...and I wouldnt even knowingly go that low.  I'm going to go out tomorrow to use my volt meter on the 12volt lead on the 7pin on the TV and then.....once the intense heat wave eases, I'm going to back the TV around back and hook to trailer and see what readings I get on the Victron battery monitor. thanks for your help, and others, I'm relieved that nothing is malfunctioning. 

RollingBnB

some of the Newer tow vehicles will lower the alternator output when the battery is charged. You can override that by turning on the headlights. My tv will run at 12.8 lights off, 14.3 lights on.

GibW

Like RollingBnB said... We have to turn our headlights on to “trick” the alternator into providing enough output. 

[Deleted User]

Oh wow, I will try that! 

ChanW

As @Sharon_is_SAM mentioned, on the 3-way in 12v mode, there is no way to control the fridge temp.
The 3-way fridge bypasses the internal thermostat in 12v mode. The fridge is either ON or OFF, so setting it to "1" or "5" doesn't matter. It's always on.
As others have said,  chances are it's simply that your TV charging system can't keep up with that high amperage demand.
Our Tacoma 'kicks down' to a trickle charge shortly after starting, no matter if we have the headlights on, have a large gauge charging wire, or kick it two or three times. It's just thinking it's smart, and probably meeting fuel mileage requirements.

[Deleted User]

good to know. I assumed I was being able to control the fridge settings while towing.  As others suggested, I just started plugging in the camper the night before with fridge on and then putting already cold/frozen items in there to keep the fridge cold....along with some ice packs.  

Ron

I believe that I have posted this before.  Look up the Redarc 12volt to 12 volt charger. It takes the variable voltage from you tow vehicle and raises it through a 3 step charging profile to charge and maintain your trailer battery.  I ran a second independent charge wire to it from my Jeep.  This may or may not be necessary for everyone.  I also disconnected the Jeep power to the 7 way plug to avoid a feed back loop.  

johnfconway

Based on what owners have said (and some measured) in another post, I get a sense that 3-way fridges may suffer from unit to unit variation as well as generally being a very bad idea if most camping trips are 82 degrees and higher for several hours during the day. Not really sure why a dealer in a place like Phoenix or similar would even have a trailer with one in the lot. But they do. Absorption refrigeration was invented in 1858. Danfoss sealed compressor arrived around 1998. We're temporarily stuck with a 3-way because I didn't do my homework. Hoping that others looking at T@Bs seriously consider saying no to this old, old technology.

Denny16

Yes John, it is time to toss Absorption fridges out the door.  No need not to use a more efficient Danfoss type compressor fridge.  I would not buy an RV with a Absorption fridge, even if the dealer had to switch one out as part of the deal.
cheers

4ncar

Yes, the absorption type fridge is not as efficient as a compressor style; I have both. That said, I do not have any operating issues with my Norcold, other then the occasional over frosting of items too close to the fins. I just rotate items. As to the battery drain on 12v, yes this can happen. It is however, a function of the TV’s ability to charge. My truck(Colorado duramax) has no issues. I monitor while in motion with the BT app of my BMV 712. FYI.

ScottG

I think tossing out the absorption fridges can be a matter of some debate. There have been some recent discussions here about the power demands of compressor (2-way) fridges compared to absorption (3-way) fridges running on propane. 

It seems the prevailing thought was that successful extended dry camping with a compressor fridge (regardless of how efficient) would likely require a beefed up battery and/or a more predictably reliable charging system.

Verna

My 2014 T@B S Max had the 3-way absorption fridge and it did well. I mostly used it for propane, electric when available, but never on 12V. 

I think if you perform periodic maintenance plus cleaning of the components, it should last for many years to come. The absorption fridges have been the standard for years and they should last for years to come. 

 

The compression fridges also work well, but beefed up batteries and possibly good solar panels will overcome the earlier challenges of higher battery draw. 

TNOutback

Most modern tow vehicles have “smart” alternators that limit the alternator’s output as a way to improve fuel economy.  As such, you will never get more than a “trickle” charge from your tow vehicle unless, as @Ron mentioned above, you install a separate 12V to 12V charging circuit to plug into your camper.  Two-way compressor refrigerators use only 15-20% of what a 3-way refrigerator uses on 12V, so they are less of a burden on your batteries while on 12V.

gulfarea

Do a search on how many fires have been caused by gas refrigerators in rv's. I had one with a recall on a Winnebago and when I pulled it out to replace it with a residential I found burnt wood cleates around the upper vent area. Jut not for me when 2 way ones work so well . Art

johnfconway

ScottG said:

I think tossing out the absorption fridges can be a matter of some debate. There have been some recent discussions here about the power demands of compressor (2-way) fridges compared to absorption (3-way) fridges running on propane. 

Yes, absolutely. Each trailer owner needs to look at where and when they camp. Then measure performance of the fridge under predominating conditions. In our case I can get it to the dispersed camping area around 38 degrees. Within 3 hours it's up to 51 degrees on propane. Peaks at 53 degrees. At best it will get down to 41 degrees overnight. Then back to 53 degrees in a couple of hours. When it's hot out, even with decent night cooling, our unit cannot keep up. 30 to 35 degree differential from ambient in warm to hot conditions is not unusual. If our unit is an aberration (doubt it), we're sure as heck are not going to file warranty claim to get another one. Been around too long at this point to be taken out by cold-loving bacteria tainting our food because of a conditionally useless $1100 refrigerator.

AirBoss

I'd be curious to know the ratio of charging contribution of a 3-way fridge while towing with fridge on Battery. How much of the "charging" of the twin 6Volt AGM batteries is generated from the TV and how much is generated from the Victron? Sure there's a way to test...just haven't gone there yet.

Anyone experiment with shutting off the 3-way (no Battery...and NEVER gas) while towing for 5-6 hours? Did the fridge suffer significantly, even though it was never opened while being towed?  

Know there are some that loath the 3-way units and I appreciate the difference of opinion. That said, I like having options.