Dual battery setup woes: Battery box fitment, charge controller and aux battery questions

Hey all,

I am looking to finish out a dual battery setup in my 2023 Off-Road. I have the Rago Fabrications second battery tray, mounted in the passenger side firewall location, and just need to purchase my Aux battery and a DC-DC charge controller to finish this project off.

I know many people run the Redarc BCDC1225D 25A DC-DC battery charger, but when I was looking around I also came across the Renogy IP67 50A DC-DC charger with MPPT. Aside from being a bit less expensive, it has selectable amperage and has a wider operating temperature range than the Redarc (-40℉ to 212℉ on the Renogy vs. 5°F to 176°F on the Redarc). I live in New England and plan to mount this in the engine by on the Rago box bracket so that alone seems like a benefit.

The Rago second battery box is also designed for group 34 & 35 batteries, but will also work with group 24 batteries since they share the same dimensions. This is my hope at least since Renogy also makes a moderately priced 100Ah LiFePO4 battery in that size that should be more than enough for my modest power needs (fridge & some roof rack lights). I have an ARB compressor but plan to keep that wired to the crank battery.

Does anyone have have experience with Renogy products? or see any reason why this shouldn't work properly? I welcome any advice!

 

I wouldn't mix battery chemistry. Either do 2 AGM, 2 Lead Acid, or 2 LIFEPO. Unless you're going to completely isolate the two systems. Then it doesn't matter.

 

I was under the impression that that point of using a DC-DC charger like the Redarc or the Renogy was so that you could run mixed configurations since they have different, selectable charging profiles for the type of AUX battery you select, no? I'm definitely no expert here so could be totally wrong on this but the Renogy does say it can support AGM/SLD, GEL, FLD, LIFEPO4 battery charging profiles. I think the Redarc has similar functionality but I guess that doesn't say anything about the input battery type. That is just listed as System Voltage:12V/24V - 12V/24V.

 

I've ran both set-ups... 2 AGMs under the hood using DC to DC charger (Redarc) and now AGM under the hood with Lifep04 in the bed. Originally the redundancy of having 2 AGMs appealed to me, and the battery location played a part in the chemistry I chose. The new DC to DC chargers have some added features that allow you to charge your starting battery from solar once your auxiliary battery is full. Also they have a recovery feature if your starting battery is dead. This swayed me toward Lifep04 the second time around. The location your going to place the batteries should be a consideration for you... from what I hear there are some Lifep04 batteries that will be okay under the hood but generally high heat environments is something you need to consider. As far as Renogy, I havent used them enough to form an opinion

 

If you’re running it through a dc-dc you should be fine. Beef up your alternator.

 

Yes, you're fine with a DC-DC charger.
Be aware LiFePO4 batteries also don't do well in freezing cold either... I recall they have circuits built into them that either disable charging entirely if too cold, or will instead redirect the charging current to a built-in heating element to bring the battery up to sufficient temp before actual charging will begin (this because charging in sub-freezing temps can damage LiFePO4 cells).

I would suggest stick with lead-acid (AGM) if you spend your winters in the north-east.

AGM = lead acid (maybe you meant flooded).
It's not impossible to combine AGM & flooded on a conventional relay-isolated setup, but no, I would not combine LiFePO4 with either lead-acid type on such a system.

 

Yup sorry. Retard moment.

 

This is all hugely helpful. LiFePO4 definitely appealed to me since I've read AGMs don't deal well with being discharged as much, but I think the temperature concerns about mounting an LiFePO4 in the engine bay might make this decision for me since I'm not planning to mount the battery in the bed.

 

I’m running 2 Lithium batteries under the hood. The starter battery is an Anti-Gravity battery with built in restart and the aux battery is a Dakota Digital with a Redarc BCDC1220 and Renogy 200W panel. I have a now discontinued Ring car camera that slowly drains my starter battery. If my truck sits for a couple weeks, I’ll probably need to use the restart, but I can do that with a remote from the driver’s seat. I haven’t had any engine related heat issues. I have the same starter battery on a heavily modded Subaru.

 

Sounds like I may just go AGM but a related problem:

I purchased the Rago Fabrications battery tray but due to the orientation of the lower AC line that goes into the fire wall, that hose rubs on the battery box. Given the angle of the weld sections of that tube, there is next to no movement and I can't get it out of the way.

I contacted Rago and they said it will eventually rub through and cause a problem so advised I wrap it with something to prevent abrasion. Problem is, there is already a fair amount of downward pressure on that line since it can't flex and wrapping it will only add thickness increasing that problem. I'm not sure if a different battery box wouldn't have the same problem given the location of that section of AC hose.

Anyone else run into this? What did you do?

 

If I'm seeing the angle of it right, would you be able to raise the box slightly by putting a few washers under the box brackets where it's bolted down at the bottom?
Usually it also is possible to bend the metal tube portions slightly on those lines, though this does carry a small risk of damaging it if you're not careful.
Failing all those, a couple wraps of Gorilla tape on the rubber hose should prevent a smooth metal surface (box) from abrading through the hose.

 

Over on YouTube "The Road Choose Me" I believe runs Renogy and has been traveling all over the world.

 

Same here. AG for the win.

 

That bodes well, especially since their price points are quite reasonable. I’ll check that channel out!

Yeah I tried that but there isn’t enough thread engagement on the studs after lifting it to where it needs to be. There are F-F cylindrical nuts that would allow me to raise it enough and then bolt into the new threaded stud, but I didn’t want to try that route just yet since it requires drilling new holes in the side supports (easy) and thus making this not returnable it doesn’t work out.

I did swing by an AC automotive shops and they definitely didn’t like the pressure on that fixed line and hose that goes into the firewall. I might just return the case and do a custom fabrication solution.

 

Yeah probably best to return it then.
Rago apparently needs to redesign their box if that A/C line is factory in it's factory position (have the box up a little higher, provided it doesn't create a clearance issue with the hood).