# Thread: Is it possible to run a portable ARB fridge/freezer on lithium cells?

1. ## Is it possible to run a portable ARB fridge/freezer on lithium cells?

Newbie here. I am known among my friends as a flashlight junkie but what they don't know is that the real experts are on these forums. Almost everything I know has been learned searching these forums over the past few years. As it happens, my first question has nothing to do with flashlights:

I am trying to figure out an economilcal way to power my portable ARB fridge/freezer (http://store.arbusa.com/Fridges-C11.aspx) with lithium batteries. It runs off of a car's cigarette lighter socket at a fairly low current, so it might be possible. Some background info might be helpful. When the compressor comes on, it draws an initial 5.36 amps and then settles down to a constant 4.86 amps within about 30 seconds. Because the compressor is off much more than it is on, it will run about a day drawing 20 amp hours from the battery. It also has serveral built in protection circuits. One will shut the unit down, and trigger an error light, in an under current situation. This most often happens when plugged into a low current cigarette lighter. It also happened when I put three 3000mAh 18650 batteries in series and tried to power the fridge. Another protection turns off the fridge when the battery hits either 10.1, 11.4, or 11.8 volts. This function is set by the user.

I searched the forums and leaned that there are high current 18650 cells that can handle up to a 10a current. But I am not sure that would be needed because I am thinking I would like to build a battery pack that could run the fridge for at least a day. As I understand it, when you hook the batteries together is parallel, you pretty much add the amp hours together assuming all the cells are the same. So, as an example, if I used 3000mAh cells in goups of three (series, 12.6v), I would then need eight of these units to make a 24 amp hour battery pack. But would that solve my undercurrent situation? This is where I am getting to the limit of my understanding of all of this. I know there are people here who know, but I have no clue.

My mind is kind of stuck on the 18650 cells because that is what I am familiar with. But I don't know if that is the best way to go or if there is even a way to do this without getting into serious bucks. I do know that a lithium deep cycle RV battery is out of my price range because they generally cost over \$1000. Ideally, I would like to keep costs under \$300. Any ideas you have will be greatly appreaciated. I've done an extensive net search and, apparently, no one has tried something like this with these fridges. Assuming there is a way to do it, the benefits are pretty obvious in terms of weight savings and the fact that lithium batteries can be safely discharged further than lead acid/AGM batteries. I'm also thinking there might be a way to charge them faster, but that may not be true. You guys would know.

2. ## Re: Is it possible to run a portable ARB fridge/freezer on lithium cells?

Some more info: I had what I thought was a good idea this morning and now I have no clue as to what is going on. I remembered that the lithium power packs for my 12 volt drill had what looked to be 18650s in them. I took one apart and it did. They are Sanyo UR18650SA's rated at 1300mAh and max. discharge current of 15 amps (http://www.keeppower.com.cn/?MainID=4&ID=95&Language=en). I have two battery packs and so I tied them together in parallel and connected them to a 12v socket with 6 inch lengths of 14 awg wire. I also tied in my multimeter so that I could see if voltage drop might be triggering the error code. Starting voltage was 12.43 which, by coincidence, was almost exactly where the deep cycle lead acid battery was when I unplugged the fridge from it. So I plugged the fridge into the lithium setup. The voltage on the meter did not change and the error light came on within two seconds. I then did it again about 10 times just in case there was some quirk with the meter (e.g., if it was sampling voltage every two seconds or something like that). Same results. Any idea what the fridge is picking up on that is triggering the error code? Could it be reading resistance through some sort of shunt before trying to turn the system on? If so, I would think this setup would pass the test unless the bar is set much higher than it needs to be. The manufacturer recommends a 15a fuse and so, if the batteries really are capable of 15a discharge, I would think this system should at least be close. Then again, the reason I am asking here is because my electrical knowledge is very limited. Any thoughts or ideas would be greatly appreciated.

3. ## Re: Is it possible to run a portable ARB fridge/freezer on lithium cells?

Look into LiFePO4 batteries. they are the safest lithium chemistry, have greater energy density than NiMh though less than Li-ion.
Also the better manufacturers can make them with very large charging and discharging capabilities -you can get replacement car batteries made from them which function as both starting batteries And deeper than deep cycle batteries.

a
lso, the lifepo4 chemistry self heats when under too much load, so basically your deep winter frozen lifepo4 car battery will be a nice warm, full power delivering battery after the first or second time the ignition is blipped.

4. ## Re: Is it possible to run a portable ARB fridge/freezer on lithium cells?

Originally Posted by eh4
Also, the lifepo4 chemistry self heats when under too much load, so basically your deep winter frozen lifepo4 car battery will be a nice warm, full power delivering battery after the first or second time the ignition is blipped.
That batteries going to self heat OK, did you see the two bare uninsulated ends of the cable on the battery pack flapping around?

Norm

EDIT:

5. ## Re: Is it possible to run a portable ARB fridge/freezer on lithium cells?

lol! no I need to rewatch that!

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