Refrigerator on battery

I have a REALLY dumb question, but I do need an answer. Pardon my ignorance, please. The discussion heretofore said I could leave my 2004 2720SL hooked to electricity with the unit closed before leaving on my trip the next morning. Here's the dumb part: what do I leave my refrigerator set on: electricity or battery, both with the fan on I know. If it's left on electricity setting, then when I unplug from the house current, I have no refrigerator cooling. Or do I put it on battery setting, and the electricity keeps the TM battery charged via the converter.

I should have asked this earlier, but it didn't occur to me until we were loading the refrigerator for our trip tomorrow morning.

Sue, set it on 12V (battery). The converter will take care of the battery and the refer. Hope this helps.

Happytrails

I just spent over an hour looking for a post I had read about an external power disconnect switch for the refrigerator. Maybe I was having a senior moment and what I had actually read a few days ago was the battery disconnect switch.

Here is what I want to accomplish.:

Load the TM the night before, including the fridge, leaving the fridge on 12 volt and the external fridge fan on also. Then close the TM and plug in the shore cable. I have a 2005 so there is no problem plugging it in.

Next morning, unplug the shore cable and tow trailer to work, where it will sit closed for 8-9 hours. This is enough time for the fridge on 12v to seriously drain the battery. I can unplug the TV to protect the TV battery. At the end of the day I plug the TM to TV and off we go. This will allow the TV to operate the fridge and charge the TM battery while on the road.

I need an external switch to disble 12v to the fridge/fan. There are two reasonable choices:

1. Have an external disconnect switch for the fridge and fan.
2. Have an external disconnect switch to disconnect the battery completely.

Is there anything in the TM that should have powered to it all the time? I can't think of anything. That being the case then a battery disconnect switch will solve my problem.

The alternative is that at work I level the TM and open it up to run on propane all day and then switch to 12v and close it down at the end of the day.

Popbeavers,
Based on what you stated you want to accomplish, disconnecting from your TV accomplishes the disconnect from TV battery while using the TM battery to power the fridge. No other battery disconnect is necessary, unless you want to prevent the fridge from running down the TM battery during the 8-9 hours you are at work.

Two other suggestions:
1. Install a battery isolator on your TV so that the TV battery is isolated electronically from the TM, but still charges the TM battery while you are towing.

2. Pre-cool the fridge (using shore power) at least 24 hours before you load it. The food should be able to stay properly cool for 12 hours without any power to the fridge. However, that still leaves you with the problem of keeping the fridge powered sufficiently until you reach your destination.

Suggest you (1) install an external battery disconnect so you can "turn off" power to the TM accessories, and (2) pre-cool the fridge at least 24 hours before loading it.

We are formerly from San Jose, and my TM used to be parked in the Foothill College parking lot all day when we planned to leave on a trip after work. I never concerned myself with the fridge issues, because I left it running on 12VDC while I was working. It didn't run the battery down, and our food was properly cool when we arrived at our destination, usually within 2-3 hours after I left my office.

[RockyMtnRay]

Originally Posted by PopBeavers

I just spent over an hour looking for a post I had read about an external power disconnect switch for the refrigerator. Maybe I was having a senior moment and what I had actually read a few days ago was the battery disconnect switch.

Here is what I want to accomplish.:

Load the TM the night before, including the fridge, leaving the fridge on 12 volt and the external fridge fan on also. Then close the TM and plug in the shore cable. I have a 2005 so there is no problem plugging it in.

Next morning, unplug the shore cable and tow trailer to work, where it will sit closed for 8-9 hours. This is enough time for the fridge on 12v to seriously drain the battery. I can unplug the TV to protect the TV battery. At the end of the day I plug the TM to TV and off we go. This will allow the TV to operate the fridge and charge the TM battery while on the road.

Nearly all dealers will equip TMs with a Grp 27 RV/Marine battery...which is basically a boat engine starting battery with some (not much) deep cycle capability. It is NOT a true deep cycle battery. Most of the Grp 27 batteries are nominally rated at 115 Amp hours...when new and properly charged. However, that's at about a 5 amp rate of drain. At the 12 amp drain rate that's typical with the TM refer and refer fan running, they're really about 80 amp hour batteries and you can/should only drain them to 30%....that means about 55 amp hours available or about 5 hours of refrigerator operation before the battery drops below 30% of charge.

Because these are NOT deep cycle batteries, taking the battery below 30% of charge causes irreversible damage to the plates (which gets worse the deeper the discharge)...the result is each such discharge causes a definite (5 to 10%) loss of total charge capacity. After about a dozen such deep discharges, your battery's capacity is reduced to maybe only 50 amp hours.

If you truly need to be able to run the refer for 8 to 9 hours on battery power, the only viable way is to replace the single Grp 27 battery with a pair of true deep cycle 6 volt Golf Cart batteries. These can be safely discharged to about 20% of capacity many times without any loss of capacity...and the nominal amp hours is about twice that of the single Grp 27. The combination of more available amp hours and abililty to have deeper discharge means about 3 times as much power for extended refer operations.

Keep in mind that although most tow vehicles will recharge the TM battery while enroute with the refer on (some won't), the recharge rate is very low (only about 5 amps). So, if you mostly (or fully) discharge the battery before departure, it's very unlikely your battery will be more than slightly recharged upon arrival at the campground. Not a problem if the campground has electrical hookups, but a very big problem if it doesn't and you are planning several days of boondocking.

I need an external switch to disble 12v to the fridge/fan. There are two reasonable choices:

1. Have an external disconnect switch for the fridge and fan.
2. Have an external disconnect switch to disconnect the battery completely.

Is there anything in the TM that should have powered to it all the time? I can't think of anything. That being the case then a battery disconnect switch will solve my problem.

Shutting off the fridge during the day will work if it (1) was fully precooled, (2) the food you load is fully chilled beforehand, and (3) you do not carry frozen food that shouldn't be refrozen if it thaws because it will melt. Ice cream...or most frozen entrees...lose much of their quality if they thaw and then are refrozen.

The alternative is that at work I level the TM and open it up to run on propane all day and then switch to 12v and close it down at the end of the day.

This is a good alternative if you can do it and don't want to go the dual battery route. It's really the only alternative if you will be camping without electrical hookups and must arrive with a fully charged battery.

Wouldn't it be easier to just place a small block of dry ice in the fridge?

[RockyMtnRay]

Originally Posted by Cobra500

Wouldn't it be easier to just place a small block of dry ice in the fridge?

The problem with dry ice is there is no control whatsoever on how cold it will make the refrigerator. At least for those of use who put lettuce (and other foodstuffs that would be ruined by freezing) in the refrigerator, the interior temperature of the refer compartment must be closely controlled around 40 degrees plus or minus about 5 degrees. Dry Ice has a temperature of -109 degrees...given enough time it could easily drop the temperature of the entire refrigerator well below zero!

Some of us actually routinely travel with frozen food in the freezer compartment (like ice cream) and food that must not freeze in the refrigerator compartment (like lettuce). With the refrigerator's thermostat properly adjusted (and a small fan to circulate air within the refrigerator compartment)...and, of course, a supply of power (either electrical or propane), it's entirely realistic to keep the frozen stuff frozen and the delicate stuff unfrozen, yet fully chilled. But a thermostated source of cooling is absolutely mandatory to do this...and dry ice is not thermostated.

Good points- but, If you are worried about overfreezing, just insulate the dry ice ...or use "regular" ice, blue ice, etc. Back in the days of trailer iceboxes, we used to use multiple layers of newspaper to extend the cooling period of dry ice to several days. The idea here was to temporarily cool food without draining the battery, away from an ac source.

I prefer dry ice because it is is colder (lasts longer) and it does not make everything wet when it melts.

[RockyMtnRay]

Originally Posted by Cobra500

Good points- but, If you are worried about overfreezing, just insulate the dry ice ...or use "regular" ice, blue ice, etc. Back in the days of trailer iceboxes, we used to use multiple layers of newspaper to extend the cooling period of dry ice to several days. The idea here was to temporarily cool food without draining the battery, away from an ac source.

I prefer dry ice because it is is colder (lasts longer) and it does not make everything wet when it melts.

It really boils down to how you view the trailer (travel trailer with all amenities or as a "camper" with some "roughing it").

If you see the trailer as a camper...and the refrigerator as a self-powered ice box or cooler that's solely there to keep food from spoiling, then yes, chilling it with dry, regular or even blue ice is more than sufficient.

Me...I see my TM as a quasi-luxury travel trailer and I expect its refrigerator to be just as good at maintaining tight temperature control for both frozen and delicate foods as I do the residential refrigerator in my home. And I expect the TM refrigerator to be able to have that kind of temperature control without depending on an AC source as over 90% of my camping is done in primitive forest service campgrounds that do not have electrical hookups. IOW, I want my trailer to truly be a Manor by the Trail...even in a remote wilderness.

And because I see my trailer as a luxury travel trailer I tend very strongly toward pretty fancy, almost gourmet fare...from appetizers (frequently some slices of Brie cheese with grapes) to desert (usually something ice cream based). If you look in my pictures here, you'll find shots I took of a nice repast a year or so ago that featured roast asparagus with smoked salmon, accompanied by a nicely chilled Chablis...created when I was about 30 miles from the closest town and at least 10 miles from the closest power outlet.

With those kinds of expensive foodstuffs on board, refrigerator temperature control is critical. And to augment the propane power to get that kind of control, I've added both dual Golf Cart batteries and 170 watts of solar panels.

Keeping food cold with dry/wet/blue ice will simply not meet my needs.