Dual Battery Setups! Let's see them! Multiple Batteries Thread!

Starting to get it sealed up. then its time to cut some access holes and construct some storage boxes.

 

Just finishing a removable powerstation set up charged from the start battery through a dcdc charger.

 

Updates on my dual battery/bed storage system.
Was able to find a water jug with the right dimensions to fit in the cabinets, then got it plumbed up with a quick disconnect for the Dometic faucet.

got the electrical covered with polycarbonate…

and finally got around to cutting out the storage entry and piecing together some doors…

hopefully get this finished up in another few days.

 

Upgraded (or, changed) the house electrical system from AGM to LiFePO4 and finally got the write-up posted. Was a fun project!

• Choosing components: https://www.tacomaworld.com/threads...-and-adventures.484602/page-277#post-30719720
• Installation: https://www.tacomaworld.com/threads...-and-adventures.484602/page-277#post-30719731

Happy to answer any questions!


As a result, no longer using - and so selling - my ML-ACR if anyone's interested: https://www.tacomaworld.com/threads...ic-charging-relay-with-manual-control.861892/


For anyone not wanting to read the posts above, here's a quick TL;DR.

Wiring diagram for the new system:



Cabinet I built to hold everything:


Electrical components installed (covers missing on the various bus bars/fuse panels):


Happy to answer any questions!

 

Enjoyed the read. Very detailed and informative. I currently have the mg-acr so I was curious regarding your switch to the other system. Very informative. I have to outfit my wife’s vehicle so have some things to consider.

 

Your project is very inspiring! I’m in the middle of my own battery project, relocating both batteries from the engine bay to the inside of the cab. One thing I kept going back and forth on is incorporating a LifePO4 Battery or not. Ultimately I chose to stay with a AGM Battery because of potential Winch Use.

Relocating because of the 2nd Gen Inner Fender Core collapse problems..


Almost Ready to run Cable to the front..


Question for the 2ndGen Owners, where are y’all installing your ML-ACR switch?

 

Love to see a picture of your battery collapse from the engine bay side. Do you do a lot of fast driving over rough roads/trails? Or what have you attributed the sheet metal damage to? Were both batteries in the original battery position? How were the batteries fixed in position.

 

What is a good voltage to use as a low voltage cut-off for the starter battery (OEM AGM)?

I have a single-battery set-up, but have several auxiliary items running off of it through a Victron Smart Battery Protect 12/24V 65A. It's configurable for the low voltage cut-off and restart voltage thresholds. Curious what folks tend to use for their low voltage isolate/cut-off settings on dual battery set-ups to ensure they can still start off the starter battery.

 

Well, on a dual battery system, all of the aux items (or as many as possible) are hooked up to the second (house) battery. That house battery can be run down to nothing and the starting battery will still start the vehicle. That's the whole point.

If you've just got a single AGM starting battery and you're running your accessories off of that, I'd make sure to keep it above 11.5v at a bare minimum on a strong (reasonably new) battery. 11.8v would be safer.

 

Voltage is one factor. The other is the battery’s CCA. You can have a battery that shows 12 volts at the terminals but will not crank over the engine if it only tests at 300 CCA’s.

 

This is true, but hard(er) to measure in the field since many might bring a multimeter, but rarely a CCA tester. It's also not what any of the devices that @wradar wants to hook up to his battery are basing their on/off state on; those are all using voltage, hence my suggestion to keep the voltage reasonably high.

 

No doubt, low voltage is a general indicator of a battery’s health. Measuring cca’s in the field is easier than ever. You can get a small cca tester for under $20 now. I have three but never carry them in the vehicle. I measure at every oil change and before a long trip.

 

Thanks, all. Agreed, a CCA cut-off would be amazing, but until Victron, RedArc, or the others get to cracking on the production of such a beast, the next best thing (voltage) is what I’m left with for automated load-shedding engine-start-up security. I went with 12.2V cut-off and 12.5V restart just to really hedge my bets.

 

12.2v might be a little high; keep an eye on it when you're in camp. An AGM/Lead-Acid can get pulled down into the 12v range pretty easily when loads are running (fridge, etc.) and then climb back up when they are off. I noticed that my Dometic Fridge has a "high" cutt off of 11.8v, which is Dometic really saying "be 100% sure the fridge doesn't kill the battery," which is why I started there.

Also, a lot of the victron stuff can show voltage over time via Bluetooth. You could watch that graph as devices turn on/off to see how things end up over the course of ~8-12 hours (to simulate overnight).

Something like this that I get from my Victron Solar setup:

 

Solar panel is mounted and working perfectly. Fridge running 24/7 and per the solar charger app battery is still at 100%. Since I use a smart isolator it charges BOTH batteries as well

 

Great info, thanks! I'll make the tweak.

I installed a shore power connection for a battery charger in order to let me keep a very low-draw radio scanner running when I park at home. On the (likely) chance that I forget to turn the scanner off when I park at work or elsewhere, I just want to be sure I don't run the battery down so low it won't start. Since it's not powering a fridge or anything I actually need to keep running, a higher-level cut-off would probably suffice, since my priority is vehicle starting, not aux power.

I've been letting it sit unplugged in the driveway today and monitoring the voltage as it drops (the Victron has a BT-enabled app that has a current voltage readout), and I'm several hours in and it's only dropped about .3V. If it makes it ~8 hours and stays above cut-off, great, but as long as the cut-off ensures it starts, that's key.

While the experiment runs, I'll keep researching small form-factor LiFePo4 batteries to give me 50-100A of "I don't need to worry about this anymore."

 

That's a handy feature! That clinches it: guess I need to get a solar set-up.

 

I have that very same battery gauge in that same exact spot, and I'm pretty sure you were the inspiration for that when I did my first dual battery setup a few years ago!! Unfortunately my ARB Locker Switches occupies those slots. I'm thinking about removing the Inverter Switch to make room for the ACR Switch. I have used the Inverter once or maybe twice previously, not even sure if it still works to be honest.

Some progress made... 2/0 Gauge Cable x2 27M AGM Batteries

 

I jumped the clutch bypass switch at the pedal and tucked the switch up behind the dashboard

The inverter is kinda useless so that route isn’t a bad idea.

Theres enough slack in the harness you can hang the button right above the “ashtray” and just remove the pocket if you need access.