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Dual battery setup questions? Need some Opinions.

Jones1972

By Jones1972
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Jones1972 Enthusiast

Jones1972

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Okay, been reading around on the forums and I'm really impressed with some of the information found on here so I decided to make an account and chime in. I'm just gonna throw out my situation and what I've got going on and hopefully I can get some good advice and tips from you guys. 

 

I have a 2014 GMC Sierra 1500, 5.3, single cab SWB, base model pickup with all the basic features, nothing crazy. 

 

I'm trying to install a dual battery setup. its going to have a simple battery isolator, the large relay or continuous solenoid style. That will power on with the ignition, or preferably when the engine is running. Allowing the two batteries to be split while the truck isn't running.

 For the Isolator ill be using a 500 amp continuous working load relay, in hopes that the extra beefiness will help increase longevity of the unit, overbuilt is always better right? 

unless you guys say otherwise. ill also be using another of these isolators for the winch power cutoff that ill be installing aswell.

 

for the aux battery ill be going with a second starter battery matching the main battery, after reading a few very lengthy posts arguing about deep cycle vs starter battery's vs only using single battery's etc,etc,etc.... I've decided that for the amount of time that ill be using the winch a second starter batt will be sufficient. seeing as a big part of the reason for adding a dual battery is to help with cold starting since ill be relocating to Wyoming within the next 6 months. much colder there than we see in Oklahoma from what I've heard..

 

I've made up a quick diagram of what the wiring will look like in Microsoft paint, excuse the crudeness of it. it should explain it pretty well I hope. I've also included a screenshot of the "current draw sensor". I couldn't actually find a lot on this, most posts ignore that its there and some say you MUST run your aux battery's ground through that sensor, top to bottom, and then connect it to the block or frame. some also state that it can be connected directly to the main battery ground terminal for the same effect. however wouldn't that cause double the current load through that factory ground lead? 

 

after all my reading on the forums I've decided that this setup should do a decent job. however id really like if I could hear some other peoples 2 cents on the whole thing. also with the battery isolator, is there a terminal in the fuse box that will get power only when the engine is running? is that a thing on these newer engines? do they only have Ignition key hot terminals? I know if it was a small block 350 I could just tap into the low oil pressure dummy light. so surely with all of these electronics they would have a something similar to that, id think anyways. 

 

so to sum it up my main questions are: Is running the aux battery ground through the current draw sensor the proper way to let the computer "recognize" the battery and adjust the charging rate? and then, is there a fuse or terminal to tap into in the fuse box that only has power when the engine is actually running?

 

lastly id just be happy to hear yalls input and opinions on this setup.

 1003815565_WiringfordualBattery.thumb.jpg.be7501f7b8478f747b988d5bf5e33404.jpg2102824695_2014currentdrawsensor.thumb.jpg.8ffcc72352656028c0edba3675c578cf.jpgcurrent draw sensor548120927_2014batterybusbar.jpg.3e348eba91ce189a4e09acd149a617c1.jpg

 

 

 

 

bdbake01 Senior Enthusiast

bdbake01

Posted
Posted

Everyone is gonna have their own opinion on this, but, by using only a relay to isolate the second battery, you're going to make to make sure that you keep the two batteries pretty close in voltage, otherwise you'll run into issues - which could be major if the difference between the two is major.  Imagine if you had your secondary battery fail while it was just sitting in the garage (trust me, it happens), and then you parallel the two by closing in the relay.  Fire, explosion are both possibilities.  And this is just one scenario.  This is just one type of protection that a battery isolator provides.  Also in this scenario, if your primary battery is too low to pull in your relay, then having a second battery there won't help without a set of jumper cables or a manual bypass of some sort.  As for using the current sensor for both, I can go either way on this one.  You may struggle to get both cables in there for one.  The factory control algorithm is tuned for one battery, and adding a second to the current monitor doesn't change this.  But, it also shouldn't cause any issues.    

Jones1972 Enthusiast

Jones1972

Posted
  • Author
Posted
39 minutes ago, bdbake01 said:

Everyone is gonna have their own opinion on this, but, by using only a relay to isolate the second battery, you're going to make to make sure that you keep the two batteries pretty close in voltage, otherwise you'll run into issues - which could be major if the difference between the two is major.  Imagine if you had your secondary battery fail while it was just sitting in the garage (trust me, it happens), and then you parallel the two by closing in the relay.  Fire, explosion are both possibilities.  And this is just one scenario.  This is just one type of protection that a battery isolator provides.  Also in this scenario, if your primary battery is too low to pull in your relay, then having a second battery there won't help without a set of jumper cables or a manual bypass of some sort.  As for using the current sensor for both, I can go either way on this one.  You may struggle to get both cables in there for one.  The factory control algorithm is tuned for one battery, and adding a second to the current monitor doesn't change this.  But, it also shouldn't cause any issues.    

okay so for the manual override on the isolator, a simple toggle switch to provide power to the coil would suffice to link the two as long as its getting power from the aux bat. 

 

cramming the aux bat ground wire into the current draw sensor seems to work on the other threads I've seen, was hoping to get someone's input who has hands on with it? but your info is enough to convince me on it. 

 

Now for the big one. If the main battery somehow gets completely drained, which I agree is a possible situation, and I then start the engine, linking both batteries, the charging system and aux battery will become overworked trying to charge a depleted battery that wasn't designed to be depleted that low. therefore possibly causing an explosion or fire. on all of the posts I've seen with people connecting the two battery's straight in parallel with only cables, no isolator of any sort, I feel id see at least one instance of a catastrophic issue? and there's been some setups I've seen very similar to the one I'm suggesting, that have claimed to have no issues? is this a highly likely scenario that I've never seen or heard of? What style and brand of isolator would you recommend to keep this from happening? 

 

Or is this an issue that occurs after a lot of neglect to the battery?

 

Hope that's not to much of a ramble, I only know a few basics when it comes to electronic know how, especially on charging systems and batteries. I completely agree on EVERYONE having a different opinion, my plan changes every time I hear a new one. 

bdbake01 Senior Enthusiast

bdbake01

Posted
Posted
12 minutes ago, Jones1972 said:

okay so for the manual override on the isolator, a simple toggle switch to provide power to the coil would suffice to link the two as long as its getting power from the aux bat. 

 

cramming the aux bat ground wire into the current draw sensor seems to work on the other threads I've seen, was hoping to get someone's input who has hands on with it? but your info is enough to convince me on it. 

 

Now for the big one. If the main battery somehow gets completely drained, which I agree is a possible situation, and I then start the engine, linking both batteries, the charging system and aux battery will become overworked trying to charge a depleted battery that wasn't designed to be depleted that low. therefore possibly causing an explosion or fire. on all of the posts I've seen with people connecting the two battery's straight in parallel with only cables, no isolator of any sort, I feel id see at least one instance of a catastrophic issue? and there's been some setups I've seen very similar to the one I'm suggesting, that have claimed to have no issues? is this a highly likely scenario that I've never seen or heard of? What style and brand of isolator would you recommend to keep this from happening? 

 

Or is this an issue that occurs after a lot of neglect to the battery?

 

Hope that's not to much of a ramble, I only know a few basics when it comes to electronic know how, especially on charging systems and batteries. I completely agree on EVERYONE having a different opinion, my plan changes every time I hear a new one. 

Toggle switch would work to close the coil from the backup battery, just make sure that this switch doesn't itself parallel the two batteries as it would fry pretty quickly.  It needs to be a SPDT to select it's power source from either the fuse box (your "truck running" source from Battery A) to only battery B.  Remember, this would leave them tied together in that position until you turned the switch off.

 

As for the batt ground, if two cables don't fit, you can just upsize the factory ground lead and tie the to grounds together on the battery side of the sensor.  May even be easier to practically implement.

 

But you're missing something here with tying two batteries together all of the time.  If they're always tied together with cables, you can't run into the scenario where one is very depleted, and the other is charged.  In your scenario with the relay, you could have one battery at 10V and another at 13.8V, and THEN you would be tying them together.  That means LOOOOOOTS of amps!!!  Battery isolators also prevent this scenario.  As for others who have done this or done that with all kinds of success and no problems, maybe they've been lucky is all I gotta say.  Russian Roulette is tons of fun....until it isn't.  

 

It's the lot of neglect to one battery with your setup.  

 

And don't take my comments as arguing or anything, just trying to help :)  I have just a bit of experience with cars, batteries, electrical systems in general.  

PPK Enthusiast

PPK

Posted
Posted (edited)

Nothing wrong with isolating the second battery. My approach will be to add the second battery when my '18 gets a little weak. I will put two new AGMs in there. i will probably use #2 AWG wire to parallel them. It is very important to keep a low impedance between the batteries to avoid long term charging issues.. I won't use isolation.. if i have enough amp hours in the batteries, i will be okay. 

 

Two new batteries in parallel will last quite a while. The toughest duty they perform is cranking the engine.. you have two of them in there.. that amperage and impact on the battery is halved. A battery has only so many starts in it... 

Edited by PPK
Jones1972 Enthusiast

Jones1972

Posted
  • Author
Posted
1 hour ago, PPK said:

Nothing wrong with isolating the second battery. My approach will be to add the second battery when my '18 gets a little weak. I will put two new AGMs in there. i will probably use #2 AWG wire to parallel them. It is very important to keep a low impedance between the batteries to avoid long term charging issues.. I won't use isolation.. if i have enough amp hours in the batteries, i will be okay. 

 

Two new batteries in parallel will last quite a while. The toughest duty they perform is cranking the engine.. you have two of them in there.. that amperage and impact on the battery is halved. A battery has only so many starts in it... 

I've decided I wont be using isolation either. 2/0 gauge welding cable between the two batteries, and if I can get it to fit through the current sensor I'll be upgrading the factory main battery ground to a 4/0 gauge cable. Definitely overkill I think but it cant hurt. Ill be upgrading the alternator wire to 2/0 as well. 

 

Only thing I'm curious of now is if anyone has an opinion on running an extra charging cable to the Aux Battery from the alternator as well as keeping the factory cable to the main BAT? since I will be running the winch cables from the Aux battery. Any opinions on that? Definitely over doing it for how little Ill be using the winch, but if someone thinks it would help with the current flow etc. why not... Since Ill be running cables anyway what's one more.  Any experience with that? Thanks for the tips and input guys!

PPK Enthusiast

PPK

Posted
Posted

i will use 2-#2 on pos and neg. It is easier to bend than the big wire...

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