Portable "dual battery" for fridge

[Bumbo]

I felt like making a small battery pack and decided to use an old firewall chassis which i've had in the junk pile.

I was playing around with fitting components and I think it might work out nicely. Still have a to build it up and do a bunch of testing but it looks promising

It should be enough battery to run the fridge 100% duty cycle for 1.5 to 3 hours.

It has the ability to charge off the DC port when the car is running. AC cable is optional. Should be good for running errands, should just about last the whole day.

 

[mrblah]

if you are going to go through the trouble of building that, you might as well build one that can take a bigger battery....same cost, but at a larger footprint.

Look up marine troller boxes, or battery boxes...... you can build it for cheap, and can use whatever automotive battery you want.

When I got mine, i wanted at least 100ish amp hours, because usable hours is usually half that.

 

[nglayton]

I'm impressed 12 AA batteries can run a 12v fridge for any length of time much less 1-2 hours........

 

[sn_85]

I'm impressed 12 AA batteries can run a 12v fridge for any length of time much less 1-2 hours........

Not sure if sarcastic or not but he's probably using 18650 Li-ion batteries.

 

[Bumbo]

Not sure if sarcastic or not but he's probably using 18650 Li-ion batteries.

Yes... these are 18650 cells.

I'm impressed 12 AA batteries can run a 12v fridge for any length of time much less 1-2 hours........

I actually decided to make it 14 total.

7S2P - 7 in series , 2 in parallel.

Give you a 24 volt configuration... which is also very efficient for the fridge.

 

[nglayton]

Not sure if sarcastic or not but he's probably using 18650 Li-ion batteries.

My comment was more about capacity. AA's are just not that big.

I know you can get the voltage, but the run time is surprising.

I thought the fridge would pull more power.

 

[Bumbo]

if you are going to go through the trouble of building that, you might as well build one that can take a bigger battery....same cost, but at a larger footprint.

I would agree, but it's not my only battery project I have in the works... Size and weight was the name of the game here.

Plus I'm just tinkering on the bench... recycling parts I have in my junk drawer to make something useful.

It's small enough I can keep it in or around my fridge, and if a family member wants to use it they can. Plus, there are other things are can use this pack for.

Unlike lead acid, lithium can take more than a 50% depth of discharge. 70-80% is the norm.

 

[Bumbo]

My comment was more about capacity. AA's are just not that big.

I know you can get the voltage, but the run time is surprising.

I thought the fridge would pull more power.

The voltage of each cell is 3.7 volts nominal with a 2200mah capacity, so 7 in series 2 in parallel gets me 25.90 volts with 4.4 amp hours total capacity.

The fridge only uses around 1.5 to 2 amps at 24 volts under normal operation so 1-2 hours isn't a stretch.

It's capable of outputting 20 amps continuous. I am not even coming close to stressing the cells.

 

[J.F. Sebastian]

Was considering a "solar generator" like an Inergy Kodiak but the prices are just too crazy.

Was looking at building a portable battery box at this point with a solar controller, inverter, etc. and then found-out about these. Most likely the route I'm going to go, available locally and the price is right.

Cool idea you came-up with there! My PowerGorilla is already setup to be plug and play in this application but don't know if I want to depend on it to power a fridge for more than a day.

 

[jrandom]

I am not even coming close to stressing the cells.

That is my only concern with DYI battery packs, you obviously know what your doing or you wouldn't be doing it. I follow electric longboard builder groups, and lol yeah I have seen my share of flamed out battery packs. Salvage cells?

 

[fourwd1]

I really like this thread but it would benefit more folks if it was in the General Discussion section instead of 5th Gen section.

 

[Bumbo]

I really like this thread but it would benefit more folks if it was in the General Discussion section instead of 5th Gen section.

Sure, I agree... While this project will eventually end up in a 5th Gen it could be applied to anything.

Perhaps I will make another thread in the 5th Gen section about it in the later stages of the final build once I start actually working with the truck.

 

[Bumbo]

That is my only concern with DYI battery packs, you obviously know what your doing or you wouldn't be doing it. I follow electric longboard builder groups, and lol yeah I have seen my share of flamed out battery packs. Salvage cells?

Yes… these are salvaged cells, but all in VERY good condition. If anything they are all pretty close to new in terms of capacity. Final build will be done using all the same make and model 2900mAh Panasonic 18650s.

My project is actually taking a bit of a different route since I posted this thread… here is a video.



I am doing some pretty extensive testing… here is what we have so far:
ARB50 - 24 hour consumption in 80F ambient = 358 watt hours
That includes the 45 watt hours it took to get from 80F to 23F
Average = 15 watt per hour to run the fridge

Each battery board = 75 watts hours
Each battery board can run the fridge for 5 hours
I plan on using at least 8 for a 40 hour run-time +/-

It's far from complete, but I am just planning the layout, base/box, wiring, charging, and saftey stuff. The final product will be 100% plug and play with the rear outlets on a 5th gen, or any other SUV that has accessory power back there.