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GMC dual battery install

Bruce Smith February 21, 2012

Project Bedrock


Upgrading to dual batteries gives working Chevy/GMC 1500s a big electrical buffer; Odyssey and Cole Hersee make it easy

By Bruce W. Smith

Turning the key to discover nothing but a dead battery isn’t fun. But it happens.

Inverters, coolers, radios, warning strobes, laptops, battery chargers, printers and other necessary accessories put a big drain on any pickup’s stock electrical system when the truck is on a jobsite with the engine off.

Even with the engine running the amp load needed to power such an array of accessories can put a strain on the stock electrical system of today’s half-ton pickups.

Add a plow , connect to a weak trailer battery, or flip on auxiliary driving, fog, or work lights and the battery is going to take a hard hit. Sometimes hard enough to leave you stranded.

In preparation for adding an inverter, warning lights, and a few other work truck “necessaries” on Project Bedrock — our 2011 GMC Sierra 1500 Crew Cab 4×4—we decided it was a good idea to double-up the batteries.

Stock Chevy/GMC 1500s come with a single Group 48 battery located in the passenger’s-side rear corner of the engine bay. There’s also an unused battery tray on the driver’s front corner; there’s no TP2 (dual-battery option) for the 1500s, so it’s bit of a mystery why it’s there.

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  • Stacaz

    How would the following information affect adding an Aux battery to the system

    It discusses how the Silverado 1500 Electrical Power Management
    system automatically adjusts the output of the alternator to determine
    best rate of charge for the battery’s current State of Charge. It even
    has a amp-meter in line with the Neg main battery cable. I did not know
    that vehicles even had such “smart” charging systems these days, like
    the 3-stage chargers you can get for RV battery banks.

    I assume adding a second aux battery solenoid isolator would confuse
    the EPM, when it automatically switches the Aux battery in and out of
    the loop during starting, running, etc.

    I ordered one of these to install in my 2012 Silverado 1500. I assume
    no major problems, but what effect will it have on the EPMs algorithm
    for best charging and long life of BOTH batteries?


  • Stacaz

    I noticed that you flipped the isolator upside down after you realized that the main battery terminal must point toward the back of the truck. ;)


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