How is everyone powering their portable fridges?

vision-quest

Observer
12 volt fridges use about 25 amps in a 24 hour period when set to 40 degrees. I measured this on my edgestar fp430 with a dc wattmeter, most 12 volt fridges use the danfoss compressor so they will have similar power use.

A 100 ah battery will only last you 2 days before you have to charge it, the reason is because you dont want to drain below 50 percent which will decrease the life of the battery.

From my own experience using a 75 ah agm battery, it wouldnt run the fridge more than a day without it being charged. Connected to my 120 watt panel and good weather, I could run the fridge 24/7 for months at a time.

Interesting, I didn't know the limit was 50%. I'm assuming that's the same with devices such as the Goal Zero Yeti etc? Good to hear about your panel. Do you have it permanently mounted on the roof? I'd love to do that but I have a CVT rooftop tent on there right now and thus no room to really put one.
 

CaliMobber

Adventurer
Answers seem to jump all over, skip the non sense, this is a fact.

My 4runner with a arb fridge and 2 yellow tops in 80-90deg days set at 36F with a 80w solar panel on the roof has been sitting since...sunday night. so thats 4 days of use and I checked the battery hours after the sunset and it was 12.7. which is full as can be. So I can tell you 80w solar in mild days can go indefinitely.

Like others have said it has a low voltage cut off but it really doesnt take to much solar to keep an ARB running 24/7.
 

4x4junkie

Explorer
Do you need a transformer or anything like that between the panel and fridge? Or are the panels usually plug and play?

You need what is called a Charge Controller. It installs between the panel and your battery to regulate the energy coming in from the panel so that it doesn't overcharge the battery.


Interesting, I didn't know the limit was 50%. I'm assuming that's the same with devices such as the Goal Zero Yeti etc?

It's true for anything that uses a lead-acid type battery.
It's not a hard-fast limit, but a gradual lessening of the number of charge-discharge cycles a battery will provide. Discharging it to 50% you might get 700 cycles out of it, whereas discharged to 10% you might get 300 cycles. It also depends on how much you use your battery too... If you're cycling it almost daily (such as if you're living full-time out of your vehicle), then depth of discharge will matter a lot more than if you only use it for a week at a time several times a year. In the latter case I wouldn't worry much about depth of discharge, the battery is more likely to go flat due to age than from being cycled too deeply too much.
 

1Louder

Explorer
Interesting, I didn't know the limit was 50%. I'm assuming that's the same with devices such as the Goal Zero Yeti etc? Good to hear about your panel. Do you have it permanently mounted on the roof? I'd love to do that but I have a CVT rooftop tent on there right now and thus no room to really put one.

Anything with a traditional deep cycle battery it's true. That why the new (now very expensive) lithium ion batteries are so much better. You can drain them to zero. This is no different than with older battery technology in laptops, phones, etc. Companies like Tesla are pushing for larger and better batteries. In the end we will all benefit. So yes in theory if you have a 100ah battery you really have 50ah to play with when doing longevity calculations prior to charging.

If I were you I would close your RTT when you are gone for day and just set a panel on top of that when gone. I would not leave my RTT deployed. The weather can be too un-predictable. I have seen a properly staked RTT flip closed due to high winds.
 

vision-quest

Observer
Anything with a traditional deep cycle battery it's true. That why the new (now very expensive) lithium ion batteries are so much better. You can drain them to zero. This is no different than with older battery technology in laptops, phones, etc. Companies like Tesla are pushing for larger and better batteries. In the end we will all benefit. So yes in theory if you have a 100ah battery you really have 50ah to play with when doing longevity calculations prior to charging.

If I were you I would close your RTT when you are gone for day and just set a panel on top of that when gone. I would not leave my RTT deployed. The weather can be too un-predictable. I have seen a properly staked RTT flip closed due to high winds.

Appreciate that. Is there a way to put some kind of "permanent" fixture on top of the bag for the CVT tent? Obviously the bag could in theory be removed but I'm hoping that's unlikely. Also, how would the solar panel attach to whatever device it's being used with? I'm assuming there's some kind of cabling and I'm having a hard time working out how that would work with a solar panel that is being moved on and off the roof. With a permanently fixed one you would drill a hole in the roof.
 

CaliMobber

Adventurer
Was going respond with same. 12.7 is not close to full. Specs are specific to the batteries. On my trailer using lifeline agm, full batteries with no charging going on are about 13.3.

Not to shoot you guys down but mine never sits at 13v anymore. even with no fridge in the car and days of charging. a few hours after sunset mine settles at 12.7/8 volts. Maybe it has to do with them being like 6+ years old, but I dont see 13v anymore. I monitor my batteries like crazy. All batteries don't settle on the same volts either. might have something to do with the morning star charge controller.

12.7 not even close to full? thats just silly, of course they are close( maybe not fully topped but they are close). optima even says at 13.1v don't charge more than 1amp. im sure the fridge has pulled a little juice out by that time as well.


in the end my fridge runs indefinitely off an 80w panel, or at least as long as its sunny and not too hot out.
 
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Ducky's Dad

Explorer
Not to shoot you guys down but mine never sits at 13v anymore. ...

12.7 not even close to full? thats just silly, of course they are close( maybe not fully topped but they are close). optima even says at 13.1v don't charge more than 1amp.
Not to shoot down your confidence, but this is from the Optima website. The top lines are for the starting batteries (Red and Blue), so if you had a Red, 12.7 would be on the money. The second set of data is for the deep cycle (Yellow and Blue DC). Since you have a Yellow, you need to be between 13.0-13.2 OCV to be at full charge. The age of your battery and past charging practices are probably factors in its ability to take a full charge, but the fact is that it is not at 100% state of charge at 12.7 OCV, even if that is the most that your particular battery will take.
Open circuit voltage (OCV) and storage:

OCV: 34 / 34R / 34/78 / 34M / 75/25 / 78 / 35 / 25 (about 12.6-12.8 volts for a new, fully charged battery)

D34 / D34/78 / D27M / D31M / D27F / D75/25 / D35 / D31T / D31A / D51 / D51R / DS46B24R / D34M (about 13.0-13.2 volts for a new, fully charged battery)
http://www.optimabatteries.com/en-us/support/battery-care/maintenance-and-storage/

Regarding the 1 amp max charge at 13.1 OCV, that is their spec for a float or maintenance charge at 13.2-13.8V input.
During maintenance, the voltage should be regulated between 13.2 and 13.8 volts, 1 amp maximum.

I did not find a "state of charge" graph or table on the Optima website, but here is one from the Odyssey website. Different battery, different specs, but both are AGM deep cycle, so approximately correct. Note that an Odyssey is fully charged at 12.84 OCV vs the 13.1 for your Optima, so interpret accordingly. The Odyssey graph shows that a battery that is down about 0.4V from a full charge is resting at about 65% of the energy that it should be storing. So not anywhere near a full charge.

Odyssey state of charge graph.jpg
http://www.odysseybattery.com/documents/US-ODY-TM-002_1214.pdf
 

Bbasso

Expedition Leader
I've got a lot more answer than you're looking for but my solar system is two 100wt, PWM cc, 310ah battery bank.
With that, my fridge (Engel 45) hasn't been off since early October... and I still have lots of stuff using power.

But it's space and weight, something to consider.
 

bearman512

Adventurer
Not to burst anyone's bubble but in the RV world 12.8 is the steady state after the battery rests for 2-3 hours for AGM and wet cell is 12.6 for 100% charge. You should never check the battery state immediately after charging.
12v-voltage-chart-676.jpg
 

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