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

Mine turns clicks off within 5-10 seconds

 

Yeah, I have read all of that too.

In the field tho, there many factors that could impact this. For example, how well matched are the two batteries. And how much voltage drop difference is there between the starting battery and the house battery and the runs to those batteries. I suppose it is even possible that a brand new ML-ACR "loosens up" over time and use, meaning, it disengages easier over time.

I will also add, I have reads comments in this thread (can't remember who said it) that he could hear it disengage as he walked away from the truck which might support what you are saying.

That is what prompted me to ask this question. To see if there are some patterns that consistently true.

FWIW, mine is taking almost 48 hours to automatically disengage. I have two brand new, identical Northstar 24Fs connected with 1/0 ga. One is in the stock location and one is in the bed of the truck.

 

Interesting. Has it always been about that long?

 

Gotcha.

Wow that's a long time. Do you know what voltage they are at when truck is off?

 

Actually let me clarify. My aux battery has recently gone to shit. Only reads 10 volts unless the ML-ACR connects the two. Replacement battery has been sitting in my garage for a week. I'm assuming the low voltage on the aux battery is causing it to disconnect quickly.

I would say, I'll report back after I swap the new battery in, but I'm hooking up solar to the aux battery too, so I'm sure that'll affect connect/disconnect time

 

Based on the Peak DBI monitor, which is only a rough estiamte, as long as they each stay above 12.6v, they stay engaged.

But you're right, I can't really tell from that monitor when they go below 12.7v. It is a stack of lights for each battery, one for 14.2, then 13.0, then 12.6, then 12.3, ultimately 11.8.

Edited for accuracy the voltage readout numbers printed on the Peak DBI monitor.

 

Yeah, the voltage drop from the bad battery is causing it to disengage for sure. I'll be interested to hear how that changes for you with the new battery.

 

i have a dual drivers tray with one yellow top and one red top. the acr usually wont separate them till i come out in the morning and stick the key in to let the electronics warm up for a minute before cranking it over.

@HeliMedic i summon you! please explain to us exactly what is going on with the ML-ACR.

 

So something like 12 hours or so? And only then because you put some load on one of the two batteries?

 

@adanfon nailed it in the post below this one. The ML-ACR will disconnect the batteries when it detects a voltage lower than 12.75 for more than 30 seconds. In a perfect world, with fresh batteries, and no draw on either battery, your ACR should stay connected for quite some time... 12 - 16 hours... depending on temperature and other factors. With old batteries or any sort of draw whatsoever, you'll see the ACR kick off fairly quickly.

On the flip side, the ACR will connect as soon as it detects a charging source above 13 volts (your alternator)... with one caveat. The ACR allows the starting battery to recover from the cranking process for approximately 30 seconds and then it engages, allowing both batteries to benefit from the charging source.

So, it is completely normal for your ACR to stay connected all night if you're not drawing on the batteries at all. If it isn't, you may have less than healthy batteries.

 

Yes. AGM batteries are much more efficient at taking a charge... meaning they charge faster... meaning they will reach their full charge before a flooded cell battery. The charging source will continue to charge the flooded cell battery until it is also full... in the mean time, you will be overcharging the AGM battery that is wired in parallel... thus damaging it.

 

This is normal for your setup. You have two brand new, healthy batteries. The longer it takes for you ACR it disengage, the longer your batteries are staying over 12.75 volts.

The ACR has no way of loosening up. It is a simple "smart" solenoid that can only disengage when programmed to or told to.

 

Thanks for the input. What you say seems to confirm my own experiences so far.

 

Can i just put a jumper on my original batt?

 

Yes you can but the additional safeties and monitoring of both batteries is where the systems shine.

 

Is your house battery permanently mounted somewhere in your vehicle? How do you keep it charged?

 

I have my starter and aux battery in the cab now. I also have jumper studs under the hood if I need to jump someone. That way I don't have to empty the cab to get to batteries.

If you have the batteries connected and running on a "smart solenoid" it will charge the aux battery automatically once the truck is running.

 

It is slowly getting there....

 

Guy's, for those of you using this Monitorwhen you hook it up to one battery did both of the bottom red lights come on? I hooked the blue to neg and the red to pos. I had the yellow lights come on for the main battery.