Fridge Draining T@B Battery During Transit

Denny16

Yes absorption fridges require very little 12VDC power when running on propane, and they work OK on AC.  But in hot ambient temperature situations, they can only cool 30-35 degrees be,ow the ambient temp, same when running in DC only, which takes even more amps, than a compressor fridge.  Running on propane, the only other limiting factor is the amount of propane you have, and a 20lbs tank should last a week.

A DC compressor fridge runs in AC/DC, and whilst on DC takes about 24-30 amp hrs a day in average conditions.  It can keep its contents at a more consistent temp, well at or below 40F, and only comes up to 43-45 under very hot ambient temp conditions, way cooler than a propane fridge in the same conditions.  A good solar and at least 60-100 AmpHrs. of available battery power will keep you going for a long weekend, and solar the battery can
 recover its charge during the day, so linger stays are possible.  Yes you need a way to keep charging the battery, solar or generator to go longer than 3 days.

I do not like the lack of temp control, and the fire risk of using a propane fridge.  For me a AC/DC or DC compressor fridge is my preference.  But each user needs to decide what fits best for their situation.  So it is nice to have a choice. 
cheers

johnfconway

On the plus side in our part of the southwest is reliable sun. Thus far we only boondock and that's not likely to change. Every USFS road map we look at is festooned with dispersed camping site "dots". Did learn on last week's trip to bring telescoping pole with microfiber head to clean road dust from solar panel.

When 3-way is jettisoned this winter, have no fear of running shy of DC power. Would not want to be in predominantly hot, humid and gray sky climate. If I did, would likely still go 12V/compressor and bring generator along.

ChanW

We usually tow with the three way off. We make sure we have a container or two of ice to keep in there though.

I tried charging from both the TV and the solar while we drove. The Victron seems to be programmed to shut down if there's an outside source of power. I had to disconnect the seven-pin charge line (pulled the fuse in the TV) to get the solar to maintain charging. Otherwise it would shut down.

I think I've read lately though, that Victron has reprogrammed their controller to better handle two sources. Not sure. Makes sense though!

AirBoss said:

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. 

TNOutback

I suspect, @AirBoss, you are getting a decent charge from your ‘04 Dino-killer with a fixed voltage alternator.  Whether it is enough to keep a 3-way running on 12V from draining your batts on a long trip, I don’t know.  I would say you could disconnect from your solar charge controller and give it a test.  If the refrigerator is consuming 11-12 amps/hr., and your TV charging voltage is ~14V-ish, maybe it balances out?

Growing up, my parents had a Coachmen travel trailer, and I spent 12 years with my own Outback TT, and neither could tow with the 3-way refrigerator on 12V as it would drain our battery.  I attempted it after switching to dual 6V Trojan batteries, but it struggled to maintain safe temperatures in the summer, and would eat up a significant amount of battery life before we even arrived at a boondocking campsite. We could get by with it off while in route, but only if our destination was no more than a couple of hours away and everything in the refrigerator was precooled before we started.  We ended up buying a lot of ice and packing coolers to carry our food, and admittedly, on long trips sometimes I towed on propane, or just resigned ourselves to food shopping after arriving at our destination.  At the end of the day, using 12V as your power supply for heating an absorption refrigerator is just a very inefficient use of battery power.

They are great for long-term boondocking, but it’s the in-between home and your destination that I always struggled with.

ScottG

AirBoss said:

...
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?  
...

I've towed nearly nine hours on a couple occasions. Heat was not extreme and we had packed the fridge with containers of ice (and probably meat that was still frozen). Everything was fine--the box alone makes a pretty good cooler.

ChanW

Yeah, ours too. But with it switched off for long drives, we did have to be sure there was at least one container of ice in there while on the road, to keep it from getting too warm, and turning the cheese to mush (nothing worse than mushy warm cheese with wine)

ScottG said:

AirBoss said:

...
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?  
...

I've towed nearly nine hours on a couple occasions. Heat was not extreme and we had packed the fridge with containers of ice (and probably meat that was still frozen). Everything was fine--the box alone makes a pretty good cooler.

johnfconway

What's driving decision making in our case is hours over 41 degrees on consecutive days on three trips from end of May through end of September. Honestly I might have ignored all of this if I hadn't done a 5 year "encore career" managing the county food pantries. Had to re-certify food safety training each year to comply with state-level foodbank's policy. 41 degrees is the upper limit. Above that restaurants get closed down for lack of compliance and/or monitoring. Like most things biological it's probability based. I would be bummed if the resources did not exist to change over and make this unequivocally safe. Having to find space in the freezer to pre-freeze water containers so my refrigerator has crutches reminds me a lot of the prepping for tent camping that was supposed to be in rear view mirror!

druthazer

@TabbyShack.   I, Bob, had same problem with my new to me  2017 tab 320 this june.   Because the old & tired float battery voltage dropped very low, it drew more current and popped the little 15a fuze.   I wanted to use the 3 wsy fridge on longer road trips and to boondock as well so I put in 2 standard deep cycle (75 ah)  batteries in parallel from Batteries Plus and installed 2 X 100w flexible solar panels with controller from Renogy on the tab roof with special 3M  dual sidedTape..   Cost me a little over $600 and everything works really well so far.  We have taken about 4 trips since all installed and everything is great including 7 day trip to Great Smokey Mtns with 3 night boondocking.   
Highly recommended...mod that I did myself without drilling any holes in the roof or shell.  Dual battery conversion rack fits fine and works well.  See my posts and photos on solar panel threads. 
I haven't tried the "lights on trick"  but always have running lights.... would be very interested to hear more about lights on.  I tow with a 2017 toyota highlander AWD.      PS I kept 3 way absorption fridge to use with gas when not on shore power; works great.           Bob & Dianne - Richmond, VA

Tampakayaker

druthazer said:

@TabbyShack.   
I haven't tried the "lights on trick"  but always have running lights.... would be very interested to hear more about lights on.  I tow with a 2017 toyota highlander AWD.                 Bob & Dianne - Richmond, VA

There has been conflicting information about the lights on trick.

It seems that on a lot of older trucks (maybe SUVs also) by turning on your headlights the alternator would put out a higher voltage/amperage, which helped charging your camper battery.

But, some people have mentioned that with all the newer energy/fuel saving features on newer vehicles that is no longer the case.