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2012 Suburban 2nd Battery

Robert A

By Robert A
in DIY Guides & Reference Library

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Robert A New Member

Robert A

Posted
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I know there are tons of threads on similar subjects, but I'm not finding answers that make me feel like I'm going to be able to get this going.

 

 I'm looking into adding a 2nd battery to my 2012 Suburban.  As technology changes, cars don't keep up!  I have several AUX loads that I want to keep powered with key off, but I don't want to drain my Optima starting battery (Damned RedTops don't like long term draws like USB chargers and the Stereo with key off) during park, and park and start short cycling (my wife drives 3 minutes to the kids school, then listens to the radio while charging her phone).  I want to run the entire truck off a deep cycle battery, while keeping my starting battery isolated from parasitic draws.  I'm basically hoping to stick the main battery wire running from the starting battery to the fuse block onto a feed from the AUX battery to run everything with key off from the AUX, but I'm having a hard time finding info on how to run the truck from the AUX battery.  I don't want to run the truck from the starting battery and a trailer or audio amp from the AUX battery, which is what these systems seem to be geared toward.  Maybe I'm over thinking this mess and should just hook a deep cycle battery to the Trailer post on the Fuse block and run a 7 foot ground back to the main battery ground post?  I'm worried about the computer being angry about voltages if it's drawing from the AUX.

 

It looks like the TP2 kit feeds specific additional loads directly from the AUX, not the typical key off loads that I'm trying to offload from the starting battery.  Help?

 

Basically, where I'm at is I can add a 2nd battery as referenced in several "Add TP2 to trucks without it" threads but I'm more worried about feeding the truck, than accessory loads off a trailer or plow from the trailer.  I don't want to rip apart any harnesses under the fuse block to feed the interior, I just want to power the X2 positive battery wire from a 2nd battery.  I was thinking about using a solenoid isolator or a diode charging relay and connecting the main fuse block to the saem side of the relay as the AUX battery and leaving the starting battery separate from the ECM, but from reading forums, the computer doesn't like not being connected to the starting battery.

swathdiver Senior Enthusiast

swathdiver

Posted
Posted
3 hours ago, Robert A said:

 I'm looking into adding a 2nd battery to my 2012 Suburban. 

A fella on the TYF forum just did something similar and posted about it with photos.  Our trucks were not made for AGM batteries and GM does not recommend them for the GMT900 platform.  You have to supplement your wife's driving schedule with a long highway trip or put the truck on a battery tender of some sort.  

 

The stock battery is ACDelco's 48PS and the highest reserve capacity is the 48HPG.  It has an extra 25 minutes reserve capacity and has 56.3 Amp-Hours versus 45.8 for the stock one and weighs 8.4 pounds more.  My 48PS is marching towards its 4th year of service.

 

Talk to Bill, InTheBurbs. @intheburbs

 

 

intheburbs Enthusiast

intheburbs

Posted
Posted

I was not aware of the AGM thing with GMT900.  I have two trucks, each with 2 AGM batteries.  ?

 

I've had the two AGM batteries in my Suburban for over 5 years with no issues.

 

Here's the writeup I used, and added some additional information of my own.  All OEM parts, so it's as if the truck came with TP2.

 

The 2nd battery is isolated when the ignition is off, so all aux loads pull from the primary, and the secondary is held in reserve as the start battery.

 

https://chevroletforum.com/forum/tahoe-suburban-diy-useful-threads-61/aux-battery-tp2-upgrade-65109/

 

 

Robert A New Member

Robert A

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So, the referenced write up is what brought me to this forum in the first place.  My concern here is the battery isolation.  From everything I've read, the interior accessories still run off the main battery, the TP2 battery is only wired to the trailer power line and has a post on the positive AUX battery terminal for adding additional accessories.  I'm not looking to power an inverter or a stereo amplifier, or anything else with a new power feed; I want to power the interior accessories for the AUX battery, unless this the the reason for the small fused wire from the AUX cable that is meant to be connected to one of the 2 posts on the fuse block.

 

I'm not a mechanic, I'm an electrician, but 12V systems in cars are not my area of knowledge. 

intheburbs Enthusiast

intheburbs

Posted
Posted

Not an electrician, just a geek who knows enough to be dangerous.  It sounds like what you want to do is the exact opposite of the way the truck is wired.

 

It would probably be easier and cheaper to just swap out the deep cycle battery and not try to swim upstream.  I have two AGM batteries (a total of 4) in each of my two trucks.  Have never had any issues in the last five years, and just recently, finally, had to replace one of them.  The only times I've even handled jumper cables or battery starters were to help others with dead batteries.

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