Off-Grid Engineering Dual Battery System Q&A

I just installed this Odyssey AGM Group 65 in my 2017 with the Off Grid Engineering dual kit and it fit without issue. I wanted the expanded AH capacity to run my fridge... it's only 6lbs heavier than the recommended group 35 battery on the OGE site.

 

That's amazing you got that bad boy to fit! Nice job.

 

P.S. So I have their recommended Full Throttle Group 35 that has 64 AH, and I can see having as many AH much as you can. I've noticed that on hot days power consumption on my fridge (42L Snomaster) is higher of course as the fridge is not venting to the outside so it's just continually sucking in the Tacoma's interior hot air. Currently I'm on vacation, no plans to drive today, and it's going to be 96 degrees outside. With my Tacoma sitting in the sun, I have the fridge plugged into an outside outlet at a rented cabin.

I'll note that I also have a dual battery setup in a Jeep TJ (using the National Luna isolator), and "I think" that my Jeep's alternator charges the auxiliary battery faster than the Tacoma does? I'm wondering if I should have stepped up to the DC to DC alternative over the split charger? My fridge has different settings where it will turn itself off, and I have it set at the lowest at 10 volts, but I have yet to test how long that will take? At home I'm always parking in a cool garage overnight and driving daily, so the auxiliary battery is getting charged daily. I think when I get back home, I'm going to do a controlled test to see how long the fridge remains running on the Full Throttle (being full, set at 34 degrees, Tacoma setting outside in the sun).

P.S. EDIT: I also want to run a test how quickly the auxiliary battery recharges (and does it really recharge up to 100%?) from being flat.

ANYWAY! Having ice cold beverages (water, soda, beer), sandwiches, cheese sticks, even ice cream, along a road trip with no ice required is a game changer! One benefit is I have already noticed is that I'm just not eating fast food on trips. I'll never go back to a cooler.

 

Installed the OGE dual setup with REDARC last week. Put about 300 miles on the truck after the install, everything is working perfectly and the batteries are very secure with the new trays. I had the trays and tie downs powder coated locally.

Kept the factory starting battery for now.


Added a FT750-35 for the aux battery.


Wired up nicely.


Very happy with the Off-Grid Engineering and REDARC products!

 

I am interested in the split dual-battery system for a Gen 3 Tacoma but have a few questions:

1. I already have a Redarc BCDC which I believe is better than just the BlueSea ML-ACR because it will upcharge the batteries allowing them to properly charge which from my understanding the stock alternator won’t do. Is this true?
2. I like the benefit of being able to switch or link batteries from in-cab. Would there be an issue with adding the BlueSea ML-ACR with the Redarc BCDC?

Thanks!!

 

That is my understanding that the Redarc BCDC is the optimal choice. However from casually checking my auxiliary battery with the BlueSea, it seems that the auxiliary is nearly if not fully charged and charges quick enough. Someday I should actually test charge and discharge rate?

No, I don't think that you could do both at the same time. This is just a thought, I guess if you had a switch that when switched, it disconnects the wiring from the Redarc to the auxiliary to connect the starter battery to the auxiliary. Of course that could blow up your Tacoma if it didn't work right?!

 

i'd be of the opinion that its one or the other. I was going to set up a c-tek unit, but already had the Blu-seas ML-ACR. but it seemed not combinable. I still use the ML-ACR in the engine bay, but also use a VE Orion DC/DC for a lithium in the bed. thats three batteries. i use VE products to do what I thought C-Tek might do.
Blu-Seas works great. by itself.

 

I found this which suggests otherwise...thoughts??

 

That looks like a quality setup. Initially, may be slight easier then using the

$465 RedArc BCDC1225D REDARC 25A in-Vehicle DC to DC Charger with MPPT — Dual Input for Solar & Alternator Charging, Green Power Priority - 12 or 24V Battery Charger Suitable with AGM, Gel, Lithium LiFePO4 Batteries

RedArc BCDC1225D that Off-Grid Engineering sells with their DC to DC kit. Plus, by the diagram you shared, it shows it has a switch like what you want.

 

Thats my thought I will just need a single battery tie-down with the ML-ACR plate.

 

Correct they offer a continuous duty solenoid that can link both batteries vis momentary switch

 

I’ve been curious about battery drain with my 42 liter Snomaster fridge, which I’ve been running full-time in my Tacoma since installing this dual battery system last spring, using the Full Throttle Group 35 batteries. I’ll note that most nights I plug the fridge into a garage outlet. On a recent trip, I didn't drive my Tacoma for three days, that sat in the sun, so I did bring an extension cord to plug in the fridge to a cabin's outlet.

For some background, in 2017, I originally bought the Snomaser for a Jeep TJ for two-week camping trips as I was tired of dealing with a cooler and ice. I would usually drive every day so the auxiliary battery in my Jeep was to run the fridge overnight. The fridge otherwise has been a beer fridge for my garage. In my Jeep, I figured that during the summer, the fridge would run at least 24 hours on a Group 34 AGM battery. With several fall camping trips (ie. colder temps), the fridge would run upwards of 48 hours on the auxiliary battery.

So to test power drain in my Tacoma, I started with charging both batteries (connected) overnight with a CTEK charger, and I took readings with a simple volt meter from both batteries as well as the outside and inside (cab) temperatures. Of course, the hotter temp it is inside my Tacoma, the fridge will use more power. Obviously it is (at least) best to leave a window cracked to allow cooler air into the cab, however I left the windows up.

Friday 7:00 am (parked in garage)
Both batteries 13.1v
Fridge set at 34 degrees, had been plugged into a garage outlet, fridge was 95% full.

Drove 15 minutes to work
Friday 7:15 am
Starter: 12.82v
Auxiliary: 12.78v
Temp Outside: 68 degrees
Temp Inside Cab: 72 degrees
Fridge temp: 34 degrees

Friday 12:00 pm
Starter: 12.84v
Auxiliary: 12.72v
Temp Outside: 81 degrees (cloudy morning, sun had just come out)
Temp Inside Cab: 90 degrees
Fridge temp: 34 degrees

Friday 4:10 pm
Starter: 12.75v
Auxiliary: 12.23v
Temp Outside: 85 degrees (sun had been out all afternoon)
Temp Inside Cab: 96 degrees
Fridge temp: 34 degrees

Drove 15 minutes (to garage at home, garage had two hot vehicles)
Friday 4:25 pm
Starter: 12.97v
Auxiliary: 12.71v
Fridge temp: 34 degrees

Friday 8:30 pm (parked in garage)
Starter: 12.67v
Auxiliary: 11.83v
Temp Inside Cab: 85 degrees
Fridge temp: 34 degrees

Saturday 4:30 pm (parked in garage)
Starter: 12.63v
Auxiliary: 11.36v
Temp Inside Cab: 86 degrees
Fridge temp: 34 degrees

Sunday 7:30 am (parked in garage)
Starter: 12.67v
Auxiliary: 11.27v (fridge was beeping that it had turned off)
Fridge temp: 44 degrees

Sunday 4:00 pm
Starter: 12.67v
Auxiliary: 11.27v (fridge was off)
Fridge temp: 60 degrees

Drove 15 minutes
Sunday 4:15 pm
Starter: 12.58v
Auxiliary: 12.04v

Drove 15 minutes
Sunday 4:30 pm
Starter: 12.91v
Auxiliary: 12.43v

What’s all this mean to me?

• The Group 35 with summertime temperatures will run the fridge set at 34 degrees for at least 24 hours.
• The interior cab temperature is an issue with power consumption. Leaving a window cracked or having some kind of outside venting would be ideal to increase the running time.
• Driving 30 minutes is not enough time to charge the auxiliary battery from near zero to a full charge.
• However, driving 15-30 minutes (my commute time) is enough time to recharge the battery for running the 9 hours that I’m at work.

And?

• First of all, I love having a fridge for road trips vs. the old days of having a cooler and it’s been my favorite must have for camping. No more having to add ice and drain a cooler each day. For trips, I find that I eat less fast food as I can take sandwiches and my own drinks. Not to mention having ice cold beer without the ice.
• For trips, I keep the fridge at 34 degrees as I find that frozen items (like meats) on the bottom stay frozen, yet water, etc., do not freeze. Running time would be longer if for example the fridge was set at 40+ degrees.
• As far as keeping the fridge full-time in my Tacoma, I do have to plug the fridge into a garage outlet each night. I do like having the fridge as for example, I can stop at a local butcher over my lunch hour and buy steaks for dinner and put them in the fridge for when I’m home. I have even bought ice cream over lunch and turn the fridge down to 30 degrees!
• I could seeing integrating a solar panel in to help power the fridge while parked outside, however with plugging in the fridge to AC overnight, that works for my use.

 

So, just plopped the money down for one of these battery systems and realized that you can only run a group 35 or so in the tray. Anyone have any input if this is a big enough Ah battery to run fridge, accessories, and propex heater for cold weather camping?

 

I think you'd be okay if you're driving everyday to recharge the one Group 35 battery. My experience with cold weather camping and a quality AGM battery is that my 42L fridge uses hardly any power overnight as the compressor rarely runs. It runs mostly during the day when the cab interior heats up.

It looks like Propex heaters draw about 1.7 amps per hour for the fan. So say you run it for eight hours, that's 14 amps for that. That should leave you plenty to run a fridge for say 14 hours while parked at a campsite.

I don't think you'd make it for two days, unless you don't run the heater that much? For my previous trips with my fridge, I usually drive daily and charge iPhones, etc., while driving.

 

The fridge would be in a moderately insulated camper on the back of my tacoma. I think that if I add a 200w or even a 100w solar panel, most of my power consumption would be at night. eg) Fridge in the summer, propex for about 15 min / hr in winter. I reckon they would have similar Ah usage on the opposite seasons. So, if I can recharge the battery during the day with solar (live in CO) then I should be a-ok with a 74 ah group 65 battery if my usage is about 20 amps at night.

 

Adding solar is also something I'm thinking about?

Oh, not sure if it was in this thread or somewhere else, but someone said that they switched cabling so that the auxiliary becomes the starter, and then where the starter is now, they were able to fit a 100 ah battery in that spot to use as the auxiliary.

 

God, that would be a big "duh" thing to do. You could also just run LiFePo4 as well, it seems. Saw some YouTube Aussie videos doing just that. I guess there are options...

 

I ended up building my own "kit". Used the Off Grid aux battery holder. All wiring is 4 gauge with crimped lugs and connectors as well as battery terminals with multiple 4/8/12 gauge holes for connecting your secondary loads or distribution blocks. Dual fuse holders with fuses. WirthCo Battery Doctor 150A isolator/auto relay with manual override. This automatically connects the batteries and charges the secondary battery while the engine is running, disconnects when not. Push a button to connect and jump start if your main battery goes dead. No longer have a need for it and probably going to sell it. Worked awesome.