Roll up solar panels - fridge power

[TangoBlue]

Any of the panels you mention will *help*.

If you are only gone a few hours, and assuming your starting battery is in good shape and fully charged when you leave, you will be fine. I used to leave my fridge run all night off the starting battery -- but I never let it sit for more than 10 - 12 hours before restarting the Jeep, and of course the ambient temperature was lower at night than during the day, and the fridge had a low voltage cut off on it. On some trips, we even ran the fridge off of one of the cheap battery jump-start packs plugged into the cigarette lighter when using a car w/o a outlet that stays hot with the key turned off.

It helps to load the fridge with as much water as you can, and make sure it is cooled off to your set temperature before you park the truck and head out for the day.

That's been my experience too. I have my ARB mounted in the back of my truck and I'm either on the move or parked. I often go similar time lengths without impact to the battery. At night, I turn it off and have consistently noted a 4 to 10 degree increase so it maintains temperature very well. Bottom line... I think you'll be fine with a single battery with your described application. Give it a while and re-evaluate your needs after a few months of experience. I'll also share with you that dual batteries are in my near future.

 

[chris snell]

The ARB fridge draws 0.87 amps/hr at 12V. If my math is correct, this is 10.44W of power draw. That's very low, about the same as running two superbright LEDs. With a good battery like a DieHard Platinum PM-1 or Odyssey PC2150, you should be fine.

 

[Martyn]

The ARB fridge draws 0.87 amps/hr at 12V. If my math is correct, this is 10.44W of power draw. That's very low, about the same as running two superbright LEDs. With a good battery like a DieHard Platinum PM-1 or Odyssey PC2150, you should be fine.

Chris

Fridges are difficult items to calculate their power draw for multiple reasons:
The compressor is kicking on and off
There is an initial power surge when the compressor comes on
The compressor cycle varies with ambient temperature
Varies with how full the fridge is packed
Varies with how many times the fridge is opened
Varies when it's in direct sunlight

The last three on the list can mean the difference between running the fridge for 3 days of a group 31 or 5 days.

The only way to determine average power drawer is to run the fridge hooked up to something like a Doc Wattson Meter

When we do long term testing we hook the fridge up for 3 months and take daily recordings. For example the Engel 45 has an average power draw of 1.2 amps per hour, 24 a day, or 28.8 amps per day. The actual power drawer on surge is 2.2 amps, regular compressor running is 0.9 amps, and between cycles 0 amps.

Relating this to solar panels, the 60 watt foldable solar panels we use provide 3.6 amps of power per hour. If we make the assumption that we get 8 hours of full sun that will give us 28.8 amps of power to store in the battery. Which conveniently is the amount of power the fridge uses in 24 hours (love the way that works out).

Any power we get beyond that full 8 hours of full sun can be used to power our LED lights, charge cell phones etc.

 

[RHINO]

this topic is interesting to me. at what point does the battery stop storing power? i know it depends on the battery but you mention 28.8 @ 8hrs of sun. if you had more sun at what point would the battery be full and store no more?

for my own curiosity, and for the sake of a separate base camp away from the vehicle, would it be a good case to have a second battery but not hook up to the vehicles charge circuit and instead have a switch so you would run off the rig while driving and flip over to complete solar "off grid" so to speak when parked?

and while were on the subject how do amp hours relate? is it as simple as running for 50 hrs if you draw one amp per hour on a 50 amp hour battery for example?

i can run wires like a champ but there is so much about electricity i dont understand.

 

[TangoBlue]

Excellent points Martyn; I suspect your testing would stress the hinges of the fridge more than power consumption... the number of times the fridge was opened to extract a cold adult beverage will effect power consumption for sure!

That's will mean a lot of solar panels... :beer:

 

[Martyn]

Excellent points Martyn; I suspect your testing would stress the hinges of the fridge more than power consumption... the number of times the fridge was opened to extract a cold adult beverage will effect power consumption for sure!

That's will mean a lot of solar panels... :beer:

So long as you replace a cold beer from the fridge with a warm beer to be cooled you stay ahead of the game. If you remove the cold beer and don't replace it then all you do is cool air which escapes when you open the fridge.

On the subject of when will the battery store no more, it's the job of the controller to sense power in from the panel as well as the charge of the battery. It works as a gatekeeper. If the battery needs charging it lets power through. If the battery is fully charged it stops the flow of power to the battery.

 

[TangoBlue]

So long as you replace a cold beer from the fridge with a warm beer to be cooled you stay ahead of the game. If you remove the cold beer and don't replace it then all you do is cool air which escapes when you open the fridge.

LOL! Practical science in action. Always ahead of the game Martyn!

 

[chris snell]

Martyn,

The point I was trying to make is that the average overnight camper doesn't need to worry about a solar panel. If you're stopping the truck in the afternoon and starting up again the next day, you're going to be fine without a panel. That's not to say that a panel is not a good piece of emergency kit to have if you are travelling alone.

 

[goodtimes]

There is another option, a little more expensive than the prices you have listed for the solar panels, but a lot more versatile . . .


National Luna Portable Power Pack

It's pretty much a dual battery system in a box. When you don't need it, just unplug it, pull it out, and store it in the garage. Added benefit is that with the purchase of an extra cable (or building one from locally available materials), you can move it between multiple vehicles.

 

[Martyn]

Martyn,

The point I was trying to make is that the average overnight camper doesn't need to worry about a solar panel. If you're stopping the truck in the afternoon and starting up again the next day, you're going to be fine without a panel. That's not to say that a panel is not a good piece of emergency kit to have if you are travelling alone.

I agree with you completely. Not everyone needs a solar panel

The variable is know what shape you battery a fridge can cause havoc with an already weak battery. If I was running my fridge off a single starter battery I would install a low voltage cut off to make sure i could still start the vehicle.

The NL Power Pack is a great way to provide portable power for a fridge, as well as back up for the starting battery.

 

[RHINO]

i have two such cuttoffs, one built in the fridge and one built in the rig, both from the factory. and they work, i have had the fridge shut down with a blinking light (low power) and the rig starts right up.

 

[Cabrito]

Thought I'd post up what I just experienced today.

Pulled the truck in the garage on Sunday evening. Emptied the fridge but left two 1 gallon water bottles in it.

I FORGOT TO TURN IT OFF!!! (that was Sunday just before dark)

Fast forward to this morning Wed. Got in the truck and guess what? It started!!! It was a little sluggish but it did fire right up.

Some specifications:
Old ARB MT35 with a Two Zone on top (Two Zone is empty) Fridge had two gallons of water in it.
Battery is a Interstate MT-85 with over five years on it.
Fridge was not opened once during since Sunday evening to Wed morning.

Not sure what the point is, but thought I'd share my real world experience.

 

[ddog45]

I just purchased a norcold tek 2 fridge today off of craigslist. My current setup consists of a deep cycle battery in the adventure trailer and dual yellow top batteries in the jeep. I fear that I have made camping very complicated. If I keep the fridge full of beer, food and water at all times and keep it in the shade do I really need to worry about draining my batteries to the point that the jeep wont run? When we are in moab we leave the trailer unhooked from the jeep for 2-3 days at a time. Should I put another battery in the trailer for trips such as this?

 

[wrcsixeight]

Ddog45, we would need the specs of your battery to determine if you need another. Specifically make, A/h rating, and age.

I have a Norcold front loading fridge, which is less efficient than a chest type.

I use about 20 to 24 amp hours per 24 hours to power this fridge in 75 degree ambient temps. It claims to draw 2.7 amps when it is running. After 3 years it draws closer to 2.5 amps.

Your TEK 2, I believe, draws 3.0 amps, but depending on the Ambient temps, how much is in it, It should run less than 20 minutes out of an hour if left full and unopened, figure 1 amp per hour.

If you have a healthy fully charged 100 amp hour battery and the fridge is the only load on the battery and all the food/beer within it is already cold, you can run it for 50 hours, before the battery reaches that 50% threshold. These numbers are general.

If Your battery says RV/Marine/trolling/deep cycle, it is not a true deep cycle, but a dual purpose battery. They are not as tolerant of deep discharges as a true deep cycle battery. If this type of battery is not brand new, and has not been kept fully charged and recharged quickly after each use, it will not have anything close to it's original capacity.

The Ambient temps of the trailer will play a big part in efficiency of the unit.

Keep it low, on the shady side, and make sure the vents have no obstructions. Use at least 10 awg cable from the battery.

Before you leave home, make sure the battery is fully charged. You cannot rely on the alternator to do so.

I will guess that yes, you will need another battery in the trailer, or solar, for 3 full days unattended ice cold beer on your return.

Once the battery voltage drops to a certain level, the fridge will perform badly, if at all, and you might hurt the fridge, and will significantly reduce the capacity of the battery by doing so.

 

[dzzz]

I just purchased a norcold tek 2 fridge today off of craigslist. My current setup consists of a deep cycle battery in the adventure trailer and dual yellow top batteries in the jeep. I fear that I have made camping very complicated. If I keep the fridge full of beer, food and water at all times and keep it in the shade do I really need to worry about draining my batteries to the point that the jeep wont run? When we are in moab we leave the trailer unhooked from the jeep for 2-3 days at a time. Should I put another battery in the trailer for trips such as this?

I see a solar panel in your future......
I agree with the previous posters who said if you drive a lot a solar panel may not be necessary. But three days on one battery is a stretch.
There are small 30-40w rigid panels for under $200. Add a $50 controller. End up at about $220 plus shipping.
At this point the old ice chest is probably looking pretty good........