Magnum Gold RV24-140 battery; Indel B 31L fridge

[Crabapple]

My trailer has the above marine deep cycle battery, which is also labeled 140 Min Res.
The battery was new last year, has not had a lot of use. I also have the small 31L IndelB fridge, these are similar to ARB etc.
Question is, how long should this battery when fully charged keep the fridge working if I didn't run anything else in the trailer? I have trip planned where I will lay over for 3 nights/2 days without driving, think it would last that long? Day time temps probably 70 ish, cool nights. Parked in partial or full shade.

[Crabapple]

DOH!! Just realized I can easliy test this out at home before I leave! Anyone care to guesstimate in advance?

[bdosborn]

My Waeco uses 0.5 amp-hrs in 70F weather with the interior temperature set to 40F. 3 days = 36 amp hours. Your battery is probably around 75 amp-hr capacity so you're right at the upper limit of your battery capacity. As always YMMV and higher outside or interior temperatures has a big effect on energy usage.

Bruce

[desertmoose]

Well... based on the 60 quart Engel we just picked up and a group 24 deep cycle battery... I'd say it won't make it.

We went camping last weekend and tried it out. Filled it about half full of frozen bottles of ice, and a tub of ice cream.
Was comfortable during the day (high 70's?) and nice and cool at night. We kept the non-vented portion of the freezer covered with an old sleeping bag.
Precooled it the day before at home on 120 AC. Had the freezer plugged into the truck power outlet for the drive to camp. Everything was frozen when we hit camp Friday night and hooked it up to the standalone battery. Set the control to "3" to see how it did.

The ice cream was getting to be soft serve by Saturday night, so set the control to "5", which is the max. We swapped some partially melted ice bottles into the freezer and put solid frozen ones into the separate ice chest. Also had to swap to a different battery. The first one was down to just under 12V.

The freezer ran overnight on the second battery. The ice cream was rock hard when we got home. I didn't check the voltage on the second battery when I unhooked it and plugged the freezer into the truck power outlet for the ride home though.

So, this oversize box ran a battery down in one day at the "3" setting. We were dreaming about a 35 quart one, but when this thing came up on Craigslist for about a third of new, we grabbed it. Way bigger than we need as a freezer though.

Not as good as we hoped, but this was a worst case. Partially full. Nevada camping in August, and running it as a freezer instead of a refrigerator.

So, we had already planned on getting solar panels for our other trailer, a 30' toyhauler. The furnace in that thing drains the batteries overnight in cold weather. Crappy design for a furnace in my opinion. Have had to run the generator for hours during the evening to charge the battery to make it through the night.

Now that we have the portable freezer, I'm planning on making the solar panels/ controller swappable from the toyhauler to the rack on the truck. Use them to keep ahead of the freezer while tear camping, and to keep from running the generator while camping in the big trailer. I have two 140 watt panels on order. Hopefully one will be enough for the tear application, but if required, I have enough room on the truck rack for both panels.

Time will tell.... (was fun to have ice cream while tear camping though...)

Sam

[bdosborn]

Yup, running the fridge as a freezer is brutal on the battery. Especially if you're refreezing things. Sooooo, you get long battery life or ice cream. Pick one but you can't have both.


Bruce

[Crabapple]

So this test went reasonably well. Fridge was a constant 5C (41F) for 48 hrs off this battery. Daytime temps were ~75F and nights ~60F. Trailer is parked in shade for about half the day. When I checked it at 60 hrs the fridge had shut down (it has safety to prevent discharging the battery too much) and temp on display had climbed to 8C (46F) so it must have shut off closer to the 60 hrs than to 48. All I had inside was a single half full 500 ml water bottle, the water was still nicely cold. The fridge was closed throughout, I but think this is offset somewhat by not having a lot of contents to help keep things cool too. So I think I could do 2 days/3nights with the fridge running off the battery, provided I didn't use it for anything else and wasn't into it needlessly. Running the car for 15 minutes here and there to recharge a bit would make a difference too, I think? Maybe enough to recharge a cell phone and or camera battery too?

[GuitarPhotog]

1. you should not drain a battery below 50% if you expect to keep using it for a while

2. 5C is barely food safe (41F), 8C is not food safe

That's all folks

<Chas>

[bdosborn]

I'd check the specs on the fridge for the battery disconnect voltage. Mine disconnects at 11.5V, which is a discharge level that is hard on batteries, especially marine type. Most battery manufacturers recommend 12V as the lowest discharge voltage. I added a low voltage battery disconnect that will disconnect at12V because of the fridge. Also, I think the highest recommended temperature for food storage is 40F.

FWIW,
Bruce

[Crabapple]

I set it at 3C on our Bay of Fundy trip with this fridge and everything in the bottom was frozen. The temperature is stratified throughout so the digital readout doesn't tell the whole story, the interior tends to be colder for sure at the bottom. Also it's used mostly for dairy, etc...no raw meat.

[highdesertranger]

so the important number for batteries is amp/hours(ah) and the number for you refer is ah consumption. if you keep taking your batt below 50% of its ah rating you will not have a long lived batt. will die long before its time. once you take your batt down to 50% or less you must recharge it immediately. if you don't the next time you stop even for a couple of hours your batt is going to be dead. whatever food that is in your refer is going to be bad. also relying off your alternator to recharge your deep cycle is not a good option. if you run your batt down to the 50% range it will take 10 hours plus of driving to get it back to close to 100%. this is straight through driving not 5 hours one day and 5 hours the next day. now the good news the ah rating of your refer can be cut buy 1/3 under most conditions. so if your refer says it draws 6 amps or 6ah, it will under all but the hottest circumstances only draw 2 amps per hour. it only runs for 20 minutes per hour. I find this a good average to go by. however over 24 hours this adds up to 48ah. if you have a 100ah battery it must be recharged. you are at your 50%. this is where a solar panel comes in or if can you plug in to charge at your lay over. one of these two options are a must imho. highdesertranger

[Crabapple]

thanks...good to know. I was worrying more about over charging the battery by leaving it plugged into shore power all the time while home?