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Auxilary Battery

armyhockeynut

By armyhockeynut
in Ask A GM Technician

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armyhockeynut New Member

armyhockeynut

Posted
Posted

I have a 2001 Chevy Silverado 2500HD LB CC that I bought used about 6 years ago. In that time I have had the Auxilary battery replaced twice. Yet, I still do not know, and cant seem to find an answer to what exactly the auxilary battery does and how it recharges?

 

I have read something about it having to do with if you use a camper mounted into the truckbed. I dont. But I do tow a 35 Ft Travel Trailer.

 

Could you please explain what the purpose of this auxillary battery is and why it would need to be replaced so soon? I am only assuming this battery was dead when I bought the truck too???

builderpaul Enthusiast

builderpaul

Posted
Posted

There are a few different axillary battery options.

 

The d-maxs come with the one that has both batteries connected all the time. This gives more starting power. It is also a good option for plowing or any activity that draws a lot of power for a short time. I think this option RPO is TP2

 

Another option is the isolated battery option. This allows drawing from the aux bat only, when the engine is off. This is good for camper/trailer use since your can run your lights, refer, etc and not draw off the main battery so you will always be able to start. I have this option hooked into an inverter to run power tools. Some with high powered stereos use this option so they can "jamb out" without running the truck. The aux battery charges when the truck starts just like the main battery. This options RPO is 8BO.

 

If you have the trailer option Z82 and the isolated option 8BO the aux battery is wired into the 7 pin trailer plug though a fuse in the under hood fuse box.

 

If you need to replace the isolated battery often here are few possible problems.

There may be corrosion on the 7 pin trailer plug. This can make a path for a slow trickle discharge. I had this problem and noticed it by my brake lights being on really dim. You can check for a slow discharge by disconnecting the aux battery. Any sparking indicates a discharge.

 

The isolator could be bad so the battery is not being charged. You can check this with a volt meter. Both batteries should read the same with the engine running.

 

I have heard of the aux batteries boiling do to removal of the header heat shield.

 

hope this helps

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