Adding a Dual Battery

tenscourts · November 22, 2018

I have an ACR. Batteries are isolated when voltage is out of range.

Without a isolator then when the truck dies both batteries are dead. It will not start. Also one battery goes weak and the other will suffer. Charge system will have a hell of a time.

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RACERX7775 · November 22, 2018

18 minutes ago, Nasty said:

Are both grounds going through the battery current sensor? If not youll run into high charge issues

Nope. Basically the truck doesn't even know that the second batt is there. I have power from batt1 to batt 2 and power wire from alt stud to batt2. Im not worried about dead batteries if ever, i have a lithium jump pack.

Edited November 22, 2018 by RACERX7775

Nasty · November 22, 2018

Just now, RACERX7775 said:

Nope. Basically the truck doesn't even know that the second batt is there. I have power from batt1 to batt 2 and power wire from alt stud to batt2.

You only have 1 "frame ground" then? You didnt add another ground other than from battery 1 to battery 2?

RACERX7775 · November 22, 2018

No. No. No. I have all factory grounds. I have another ground from batt2 to engine. Another ground from batt2 to chassis. But no ground from batt1 to batt2.

Edited November 22, 2018 by RACERX7775
Content

Nasty · November 22, 2018

29 minutes ago, RACERX7775 said:

No. No. No. I have all factory grounds. I have another ground from batt2 to engine. Another ground from batt2 to chassis. But no ground from batt1 to batt2.

Hmm how long have you had it setup like this because you could be overcharging battery 2

RACERX7775 · November 22, 2018

About a year so far. I can watch the volt meter go up to normal and then down to the lowest setting. Just like normal.

csoldfield · November 23, 2018

I had that same concern, as I have mine very similar. Batt1+ via ACR to Batt2+, and Batt2- to engine block. Since the current sense is only on Batt1-, then when Batt1 needs charging it could potentially overcharge Batt2. But when Batt1 *is* charged/low loads, then Batt2 could be *undercharged* depending on its state of charge. So not ideal, but appears OK. Charge voltage at Batt2 starts off around 14.8-15.0, then will drop to ~14.0 after a short while. High voltage concerned me since I went for an AGM/deep cycle battery which dont like being over 14.6-14.8 for any length of time. Fingers x'd it'll be fine - plus I have a 3 year warranty :-)

RACERX7775 · November 24, 2018

I would add another ground from batt2 to chassis. I also have a cable from alt+ to batt2 +. In my excursion i have a DC POWER alt. It was Daves first prototype. I have the regulator set at 15.2v. Have had it that way for several years. It reliably puts out over 250 amps hot at idle. When cool at max load it puts out over 500. On my ammeter i would pull a hard 390 amps on a 32hz test tone. And voltage would only drop to about 14.4v. But it was over $1100.

1SLOW1500 · November 24, 2018

If you add a wire from alt to batt 2 then both batts see each other without a isolator in the middle.
As far as the charging issues. Fact is you will end up burning up a battery. And when it goes weak then it hurts the good battery and depending on if it is the batt 1 then the truck will max out the alt to charge it and that to is hard on a charged up batt 2. So Nasty is right on that. The fact it is working now or for a year has nothing to do with it. Next time I'm in my truck I will check my settings as mine is programmed for the two batteries.
But a poor man's if you will test is car off isolated or unhooked batts and load test them. I do this once a year as I have my own tester.
I have seen one batt dead in a friends truck. No isolator and he was having issues.

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RACERX7775 · November 24, 2018

Ok. I see your point. But i would never wanna isolate the batteries. I dont wanna only pull power through batt1 to charge batt2. Because on a heavy draw, you could harm batt1 because batt 1 technically, would be charging batt2. So recovery time on batt2 would be greatly increased. But since I have a charge cable between batt1 and batt2, the voltages will, over time, equal themselves out. And thats also the main reason why i have a charge cable from alt to batt2. As for the fact that i will burn up 1 battery. We will have to agree to disagree. I have never "burned up" a battery doing any of this stuff. Lastly, i dont think the alt will ever max out to charge either of the batts. Again, no harm here. Im not saying i know it all. Just merely what works for me and i have NEVER had ANY issues with any of my trucks. We/most are on here to learn and help each other out.

Edited November 24, 2018 by RACERX7775

1SLOW1500 · November 24, 2018

The isolator connects both batteries when truck is running running so then all is equal voltage and charge. Even in my old setup 2007 Silverado it had a non relay type isolator. It was a huge aluminum heat sink with 3 posts on it center isolator other posts are batteries. Inside it had huge diodes. So all can charge but batteries can NEVER see each other. My truck now has a relay isolator so when the low draw switched post gets power it throws and connects both batteries. Way I have it wired if the factory battery is dead truck will not start, I can throw a switch that gets power from batt2,start truck. Anytime key is in and relay has power batts see each other and it is just like one large batt. But charging,starting and running they connect.
I would like to agree with you on cant hurt anything and it is very much possible your setup will run for years till one battery slowly loses power. Same with mine. I will say these new trucks are 100% different, the charging system can be tuned. Like a performance car. And there a hundreds of settings just for that.
In audio world the big 3 wireing was the thing to have now just equal wire size.
Agree this talk is to help people understand and learn new tech. Your setup will be fine till go battery life goes down.

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RACERX7775 · November 24, 2018

Yup. I know what isolaters do. So, the one thing that you said is, which i had no clue about is, that the charging system can be tuned? Hmm. How? I was always one who wanted 14.8 or so, all the time. Apparently, thats not the case with these trucks. I dont like how the computer controls and lowers the voltage settings for charging. Im not sure i like it or not. There has been many threads on how to disable it. I think im just gonna leave mine alone the way i have it. Good discussion though.

RACERX7775 · November 24, 2018

I forgot to add, the one thing that i did not want to do is mess with the original truck wiring. Atleast for alternator and batt1. It was more to just ADD, for batt2.

1SLOW1500 · November 24, 2018

I think we where just miss understand the batt1 and batt2 thing when it came to use,charge and such. But sounds like we both are talking the same now.
There are setting in the software for the truck. I have seen some based on temp, idle, and amps. But I,m sure there are more.
I have HPT pro with latest software so I can mess around with settings.
Like in this cold weather I cant sit in the car with the key in and truck not running. Dash says cold weather batt protection and shuts off. Even though I have two batteries it over rides and shuts down then tells the alt to charge more after start. Also there are pids that can read the pcm and give you voltage stats of about everything.
As stated your setup is ok but some things arnt needed and you could do the same or better with one better battery. But each his own. My setup has a flaw in it connects the batteries when key in so I rely on the truck software to protect me. Once key is on I'm same as you other than the alt wire.

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Nasty · November 24, 2018

1 hour ago, RACERX7775 said:

Yup. I know what isolaters do. So, the one thing that you said is, which i had no clue about is, that the charging system can be tuned? Hmm. How? I was always one who wanted 14.8 or so, all the time. Apparently, thats not the case with these trucks. I dont like how the computer controls and lowers the voltage settings for charging. Im not sure i like it or not. There has been many threads on how to disable it. I think im just gonna leave mine alone the way i have it. Good discussion though.

If you turn on the lights the voltage wont drop. Its been like this since 2005 models. I had single alt setup in my 07c then went to dual setup. Leaving the oem alt just to run the truck and the second alt ran thr audio. Then or course i went to quad setup. If you have any grounds to the frame that arent ran through the sensor, it will charge high and the batteries will swell in time and go out.