Off-Grid Engineering Dual Battery System Q&A

Thanks for the answer.
Makes sense.

 

@CoWj
Recently installed your split dual battery kit for 3rd gen and have a couple questions about the system. To start, I went with odyssey pc1400 for both batteries and I've OV Tuned the truck and increased the alternator out and am reading 14.3v on my starter battery and 12.6v on my accessory batt with truck running and 12.6-13.1v on starter with 12.6v on accessory with truck off. I never hooked up the switch for the ML-ACR but grounded the ground for it. One of my questions is, am I supposed to hook up any of the other wires from the ML-ACR to allow my accessory battery to read same voltage? And also reading blue sea info it states that the relay will close after 2min of constant voltage but mine closes in under 30sec sometimes faster and will close if truck is in accessory mode. Been reading forms and trying to diagnose this but am having difficult time haha and am also not an electrical kinda guy. Any help would be much appreciated.

 

I cant speak to the wiring off the top of my head as its been a long time since Ive looked at the ML-ACR relay schematic. But the first thing I would try is the yellow lever on top. That can be turned to one side as a manual 'lock-out'. If its in that position it will not latch. There is some small lettering on the ML-ACR that tells which side is which

When its in 'normal' position, the center can be pushed down to manually latch the two batteries together.

 

@SR-71A
Yesterday I disconnected the ground for ML-ACR from fender and am just going to keep the ML-ACR closed until I can figure it out haha, since I'll just be driving to an from work with no accessory load. Been staring at the diagram for the ML-ACR and am thinking the isolation #1 brown wire needs to go on my ignition somewhere but idk.

 

So the way you have the ACR set up is in a fully auto mode. That is done by just grounding the single black wire coming out from the ACR. To me it sounds like it is functioning properly from what I gather in there post. The battery will read different voltages when they are disconnect. Yellow button UP (ACR not in lock off mode) means they are disconnect and they will be reading at there natural resting voltages. When you say you were getting 14.3 on the starting battery and 12.6 on the Aux, was the ACR actually locking down? Was is set in Auto mode? It looks at the battery voltage and anything above 13 for 2 minutes it latched and 13.5 for 30 seconds, and you will hear a very audible click and see the yellow button suck down. Then they should be reading identical voltages due to being in essence one battery. Then the ACR will disconnect the moment a battery drops below 12.7 which sounds like yours is doing in accessory mode. They reason that it still is closed in accessory mode, is because the batteries haven't dropped below that 12.7 mark. Healthy batteries with no draw can sometimes stay latched overnight if not longer. You can check the ability for it to unlatch by turning your headlights on to create a draw with the engine off, and once the starter is below 12.7 it should in latch. I will warn that when you are flipping the yellow knob back and forth it puts the ACR into a user control mode, which means it won't do anything automatically for 15 minutes after the yellow knob has been flipped. So to check all these, turn it to auto, then leave the truck for 20 minutes. Then start it, the yellow knob will latch down in around 30 seconds. Then kill the truck, turn on your headlights and they will draw down and in latch the ACR with a couple minutes. (LEDs will take longer) if it does all that the ACR is working as it should fully automatically.

 

I must be missing something, so I apologize if this is a dumb question.

My factory wiring harness pokes out really far. Like I can't get the battery in far. Has anybody else had this issue?

I might be able to squeeze the battery in but it's going to require a significant amount of force pushing aside that wiring harness.

 

I had to push mine out of the way. It is a pretty tight fit

 

As Per our fitting instructions, you do have to just push it out of the way and it will stay under the tray. Then you will be able to fit the battery just fine.
Feel free to shoot me an email if you have any other questions.

 

@CoWj I'm getting ready to install the Redarc BCDC dual system in my 2021 tacoma OR. I'm wondering whether or not I should connect the blue wire to ignition (variable voltage alternator) or not (fixed voltage)? The truck has a "smart" alternator controlled by the ECU IIRC.

 

In our testing, it is not needed, and when you purchase a prewired version from us we don't have it connected. The tacoma alternator is "smart" but it doesn't hit the levels needed to actually need that function of the redarc. It will charge the aux battery perfect without the blue wiring being hooked up.

 

Awesome! Thanks a lot for replying. Can't wait to get this installed.

When I inevitably add a solar panel, I'm thinking the one from Cascadia 4x4 that mounts on the hood, what's the recommended way to connect to the yellow wire of the redarc? The pre-wired redarc assembly has the yellow wire covered all nicely and I don't want to cut it and see whats underneath until I need to. It looks like the solar panel has a positive and negative wire coming from it with some quick connects I'm not familiar with.

 

The prewired assembly just has a sealed heat shrink "cap" on it, when you go to connect the solar, simple cut that heat shrink off. Add the connector of your choice, and then negative to the chassis ground that the redarc uses. You may need to cut trim back the split loom that covers the wire, which is there for looks and abrasion resistance, cut off as much as you need and then just wrap electric tape around the end, like it has currently.
The connectors on the panel as known as MC4, you can either retain them, or because the panel is more "permanent" and not going to be removed. You can use Butt connectors to hard wire and resulting in no resistance through the connector. And extend the negative to that chassis ground I meantioned before.
One thing to note. When you buy the panel, there is no need to get the MPPT upgrade. It will not work with the Redarc and would be a waste of money. The Redarc is an MPPT solar controller so no need to buy another one.
When. If you have more questions when you go to install it, feel free to email me (in signature) I usually check it more often and can get back to your questions faster than TW.

 

I feel dumb, but I need help...

I bought the side by side kit about 3 years ago and had a local offroad shop install it along with my camper top, I told them to add an aux fuse panel and power the bed to the house battery. I've also installed a dual battery volt meter so I can keep track.

Over the last few years I've done a handful or two of multi-nights without starting my truck and never taxed the battery too much apparently. Fast forward to this weekend, 3 nights with lows in the teens. I ran my electric blanket a few times in the night and the last morning it stopped working, looking my my volt meter it appears that the house battery is at 5 volts and the starter is over 12. All good, that's what this is for.

Turn the key, NOTHING. I think this means that one of my two batteries has never even been used, just topped off by the alternator. The ACR looks to be hooked up correctly, B side goes to the "starter" battery (cables match up with stock to/from alternator) and A side goes to the "House" battery (cables continue on to fuse box). The ACR is always in the "Remote" position and I can hear it click a min or so after I kill the engine, so it's doing something. I don't have a switch inside the cab to control the ACR.







How/Where do I start my troubleshooting?

 

Hi David,
I would Start by first cleaning off the corrosion from all terminals and having both batteries tested. If the House battery is down at 5 volts then that battery is truly dead and likely can't be recovered. The Starter battery is also pretty low if it is only sitting at 12 volts that is also concerning. It is possible that both batteries are at the end of their lives, and being Optimas, from around 2016-2017 it is likely that it is at the end of its life cycle.
A heated blanket is very hard on batteries drawing a sustained 5-9amps all night. This will often drain a battery well past the deep cycle limit in a single night.
I would get the batteries tested by a shop, and see if either are still good and just need a good recharge. If they test bad, which for the house battery is highly likely. Then contact Optima and see if they are still in warranty. We have seen many of those aged optimas have rather short life cycles in recent years after they changed where the batteries were produced and quality seemed to drop around that time period.
I hope that helps, it sounds like the ACR is still trying to function as normal but is still try to protect the starter battery from the dead house battery.

 

Thanks for the response Wyatt.

I agree that both batteries are likely at the end of their lifecycle and could use a good cleaning. The electric blanket being used is a 12v cig lighter and only runs for 30 mins at a time, so yes it's a heavy draw, but not for as extended as I think you're imagining. I've used this method multiple nights (on apparently a single battery) without issue.

Where I lost is you is the ACR protecting the starter battery from a dead house battery. The truck didn't start, so I think the starter battery is being used as the house battery. The "starter" is sitting at 12.4 right now after not being driven since Sunday. Unless you're saying 12.4 isn't enough to start the truck?

 

My mistake, most time people leave the heated blankets in all night, but running for 30 minutes wouldn't hurt the battery and is the right way to run it.
The ML-ACR is a Smart solenoid and monitors the Voltage of both batteries at all times. It has a built in protection system that when a battery is below 10 volt it wont combine because combining a "dead" battery with a full one can result in damage to the full one. So Currently if you went to start your truck with that battery at 5 volts, the ACR shouldn't combine the batteries, thus that house battery is likely not getting any charging in the system because it is below the undervoltage cutoff.
So the Start is sitting at 12.4 volts which is low, however, if there is internal damage to some of the lead plates, it may mean that a resting voltage is okay, but the moment any load is put through the battery is could tank to well below that voltage. Based on the fact the starter isn't even slowly turning but the relay is clicking tells me that it is somewhere around 10v or lower when you actually put a load through the battery.
The starter battery shouldn't be being used as the house battery currently unless you have the ACR force combined on either the switch or the unit itself. The if all your accessories are wired to your house battery then all the circuits should be separate once the the Batteries hit 12.7 which is where the ACR automatically disconnects them.

 

Ok, so it sounds like what you're saying is still the 12.4 from the "Starting" battery might not even be enough to start the vehicle. I didn't even hear the relay clicking when I tried to start it the other day.

I added this to my above post, but it should probably go on it's own:

I did some more investigation and here is what I found:

There is an additional positive wire coming from the House battery that I can't tell where it goes, it makes a stop by the factory fuse box, so maybe that contains the starter? But that doesn't align with my next point.

I started the truck while watching the meters and the Starting battery dips quite a bit when I start (down in the 11v range) and the House stays generally the same. After a few seconds and the Starter voltage comes back up, I can hear (and see) the ACR click at around 12.4ish and then they are both at 13.something, so that means the alternator is charging both, right?

 

Both batteries need to be Load tested, you can't tell very much about a battery when just measuring the resting voltage.

I can only speak on our battery system, so I don't know where any of the wires that you or the shop that installed it goes. If the system was installed per our instructions, All factory systems should have been connected to the starter battery only. Start cable, Fuse box cable, Alternator Cable should only be hooked up to the starter battery to keep the factory systems and auxiliary systems you add separate from each other. In your photos is looks like it might not be hooked up like that. Just based on the pictures, it does look like there is a cable coming off the positive terminal of the house battery and going to the fuse box or starter.
It also looks like some of the cables have been modified, or changed from what they were originally shipped with the kit.
But I can only say what I see in the pictures provided. Without seeing the entire system I am limited in truly saying where the exact issue may be coming from. But it doesn't quite look right to me, and I would check to make sure that all factory systems come from the starter battery, and all auxiliary systems come off the house battery.

Finally, yes it sounds like both are being charged. So I am guessing the house battery was above 5v when you tried to start the truck. The ACR should connect about 30 seconds after starting the truck which it sounds like it is doing. But when you turn the vehicle off, how long does the ACR stay latched? It should remain latched until the batteries hit 12.7, if you are running accessories or headlights that should take about a minute on good batteries, if it happens almost right away without any draws on the battery, then the batteries likely have internal damage and aren't able to hold a normal resting voltage. For example, with really high quality batteries and no draws on either the ACR often stay latched overnight. But that doesn't sound like your batteries are able to stay above 12.7 for any amount of time.

 

This is great, and exactly what I needed to know.

I'll do some more digging for the instructions that were provided with the kit when I bought it. Are they posted on the site? I did a quick look the other day and didn't see them. I can double check those with my current wiring and correct see where the differences are. My hunch is that the house is routed through the stock fuse panel, and powering stock items because I can see the volt meter move around for the house battery when i open doors or put any other stress on what should be the starter battery.

And you are correct that the ACR unlatches almost immediately (1 min tops) from turning off the truck.

My plan:
1. Clean
2. Load test
3. Compare wiring with diagram
4. Probably get new batteries.

To #4 do you have any recommendations? Sounds like the yellow tops are not held in as high of a regard as they once were.

 

That sounds like the wiring might be different to what we designed it around. If you can't find your instructions, shoot me an email and I can send them over to you.

As far as batteries Odyssey, Northstar, and Full Throttle are the batteries we recommend and have had very good reliability with in the past few years. We sell Full throttles on our site but you can also likely get Odyssey and Northstar locally compared to Full Throttle.
Yellow tops unfortunately have gone down high in our experience in the past few years.