How I added a Solar Powered Fridge to my Car

May 9, 2020

I have at various points over the past few years had van envy. That is to say jealousy of people with tricked out sprinter vans with fridges, full beds & kitchens. Having been on my fair share of month-plus long road trips the appeal and utility was not lost on me. That said I was never ready to shell out $40k for one of my own, nor was I interested in becoming a master carpenter and building out my own shell (perhaps someday). Not to mention the fact that I just paid off the loan on my trusty Subaru Forester so it seemed foolish to commit myself financially to another vehicle when the one I had worked so...alright.

One of the items I was most jealous of in tricked out Sprinters was the fridges! Being able to live off the grid with cold beer and bacon seemed to good to pass up. So I didn't. I ended up tricking out my Subaru (or shall we call it a Camparu?) with a solar panel, aux battery & a fridge.

** this post is a work in progress. If you have any questions about what I did feel free to reach out through email or twitter

V0 - Portable fridge

Components

  • Alpicool C15 Portable Refridgerator - $179.00 - This is the cheapest and smallest refridgerator with a compressor I could find. A friend bought one and used it in his car before me so I had reason to believe it would work decently well. At at a price of $200 (give or take) what's there to lose?
  • 35 AH Deep Cycle Golf Cart battery - $63.99 - I didn't want to start with a full car battery in my car so this is what I picked. It's worked quite well although it probably is the weakest link in my system. Upgrading to a 50-100 AH battery would provide more piece of mind when leaving raw meat in the fridge for a day or two while out hiking. After all, who doesn't want a burger at the trailhead after a long hike?
  • 12v Battery Tender (charger) - $24.98 - before getting too crazy I wanted to make sure the initial componets worked well together, so I bought this charger so I could charge up my battery at home and test out my fridge with it.
  • Battery erminal to plug adapter - $6.95 - The fridge comes with a 12v plug (that fits in the sockets you usually find in a car). In order to attach the fridge to my battery I'd need one of these.
  • A couple nuts, washer & bolts to attach the adapter to the battery

With all of these components I had a fridge that I could take on the road with me and run it overnight. You can even leave the fridge plugged in to the car while you drive and move it over to the battery once you park for the evening. Afte a trip or two with this set up it was clear the battery & fridge worked well together so it was time to kick things up a notch. Who wants to remember to unplug the fridge every time you turn the car off anyway!?

V1 - Hook your battery up to the alternator

Components

  • Continous Duty Solenoid - $36.20 - the most important item of this step. It's basically an electric switch that turns on & off based on an input voltage.
  • 4 Gauge Battery Cables - $28+ - this need to be pretty beefy to ensure they can carry all of the power from your alternator. The thinner the cable the more energy loss on the way to your aux battery. If they're TOO small the can catch fire...don't skimp here, go with 4 AWG to be safe. These ones come with terminals already attached but You can also buy in bulk and attach the terminals yourself. The only thing is you'll need a REALLY big crimp to do this. I ended up going to a marine supply shop here in seattle and using a crimp to do it myself.
  • Inline circuit fuse/switches - $18.99 - remember how I said these cables are carrying a lot of power? That means bad stuff can happen if you don't ensure you have a fuse in the system in the case that there is a short circuit.
  • Multimeter - $11.99 - This enables you to find a spare fuse socket to hook up to the solenoid. It needs to have power when the ignition is in the on position & none when you turn the car off.
  • 12 Gauge wire - $20.95 - You'll need some wire to carry the voltage from the fuse box to the solenoid. 100ft is over kill and I didn't love this wire because it was super stiff but it ended up working well enough.
  • Wire stripper - $11.98 - You'll need some way of cutting, stripping and crimping your wire in order to rig this whole thing up.
  • Terminal Crimps - $6.29 - you could just shove a wire into the socket but this is a little bit more...refined way of doing it.
  • Fuses - $10.99 - these are good to have so you don't end up blowing a circuit in your car if you mess something up or if the cable insulation wears out).
  • Electrical Tape - $9.98 - it's good to wrapp all open wire connections so they are insulated.

Got all that!? Phew, that's a lot of little things. Don't worry this next part isn't too complicated. The next step is figuring out where these thing are going to go in your car/engine compartment.

Here are the important things you need to find:

  • spare fuse socket that provides power when the ignition is on. I was hoping to find one that only lit up when the engine was on but all I could find was ones that lit up when the key was turned to the on position (even if the engine was off). This means your aux battery will be pulling power from your main battery whenever you leave your ignition on (even with the engine off). Remember this and don't drain you battery.
  • a place to mount the solenoid, ideally in the engine compartment
  • A way to get power though your firewall (what separate the engine from the inside of the car)

Below you'll see the fuse box circled in red and a rubber plug in the firewall circled in blue.

Please excuse the thikc layer of sludge coating everything inside my engine compartment caption

Mounting the solenoid

This might be one of the more difficult parts of the build. I found this hollow sheet metal tube running along the side of my engine compartment and figured why not drill some holes in it!? Once I'd drilled the holes I had to take out a bunch of bolts that helped attach the front side panel of my car to the sheet metal so I could fit my arm down there and hold the other side of the bolts/nuts to tighten the solenoid in place. I also covered everything in some black duct tape to make it look better?

The lid to the fuse box can easily be removed if you undo the clips on the sides. Inside hopefully you'll find an empty socket. The one I use had 4 holes (you can see it below). Use the multimeter to measure the voltage across two of the terminals until you find one that has no power when the car is off and ~12+ volts when the car is on. Once you've found that you've got your trigger for the solenoid.