Portable Fridge Question

8 would be great, wanted 4 just as extra precaution, could only get my hands on 2 for a reasonable quality/price/without delay. Such is life...

 

This is exactly what I am doing with the fridge I'm getting. My question for you is, how are you keeping the aux battery charged? And what battery did you go with? I need to get an aux battery still.

 

I installed the Off-Grid Engineering dual battery system (the one with the Blue Sea ML-ACR relay) along with 2 brand-new Northstar AGM's--before I found the TW threads that go into great detail about the "smart" alternators in 3rd gen. Tacoma trucks and how their low charging voltage (capped at 14.2v) kills batteries. (Northstar AGM's have a sticker right on top that states a charging voltage requirement of 14.6-14.8v.)

In less than a year, the insufficient voltage coming from the alternator damned near killed the aux battery (it wouldn't take or hold much of a charge, but always read as full) --meaning that it had become severly sulfated. Luckily I was able to resurrect it by running the battery through a series of desulfation charging cycles using my brother-in-law's 30 year old "dumb" charger. The charger ran 18-22v @ 20 amps, for 2-6 hours, followed by a resting period of 24-48 hours in between charging cycles. I stopped further charging when the resting voltage was a consistent 12.9v. It took about 2 weeks (roughly 6 or so charging cycles) to bring it back to life, but today it behaves much like it's new.

There are several workarounds to having this issue in the very first place, and all are well documented here on TW. Search is your friend.

Fast-forward to today: I'm running 4x100 watt solar panels (@12v) on top of my canopy; fused and with both legs running through DC circuit breakers. I added a 3rd Northstar AGM in the bed of the truck, which is tied directly to the aux battery. Now the solar panels keep the aux & 3rd AGM fully charged, and have the capability of charging all 3 batteries when the Blue Sea ML-ACR relay is engaged.

If I had to do it all over again, I would still get the OGE dual battery system--but I would opt for the one that comes with the Redarc DC to DC charger and I'd add a Redarc relay.

Hope that helps. I can add a few photos of my setup, if you like. Let me know. Good luck.

And yes, someone is going to pop-up and say that you can't (or shouldn't) try to desulfate a sealed AGM (or that it won't work or something else silly like that.) Yes you can, but the process is slow and requires maintaining a constant vigil on the voltage, amperage AND temperature--of the battery AND the charger. It also requires a completely manual battery charger; if it has charging modes or profiles it's not a manual charger.