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Dual Battrey/Dual Alternators

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Hi all according to my dealer I should have my 2022 Silverado 2500HD in 2 weeks. (I have a build date of 8/30/21!)

 I ordered the dual Battery/Alternator option. Dose anyone on here know how this setup works? (Just incase my dealer is not suer) Is one battery just for the truck and one for a camper? I have had dual battery setup in some of my other vehicles but I installed them with a battery isloator. I plan on having a slide in pop up truck camper that I will be putting to good use this winter! Im from Michigan so its south or west for me! Thanks all!



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18 hours ago, hdhp said:

OH and one more thing. Why is there so many adds on this fourm? Every time Iclick on a new page there are like 5-10 of the same add. It is very Irrtating!





I use Ad Blocker Plus, its free and stops all of the ads.

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  • 2 weeks later...

I just received my 3500 last weekend and I too ordered the dual battery and alternators. My application was for the snow prep, and I did ask the dealer about the camper package that it was included in. So according to the dealer, your camper should benefit from the 2nd alternator keeping the 2nd battery fully charged

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Short time lurker, first time poster... lol

Thanks for the input from everyone on this thread and the other aux alternator thread I read.


I did some study on this because it is something I'm very interested in for a new order.

Reviewing the schematics and the T of O, it appears there are two different ways the Aux Alt works.


W/o Snow plow package the 170A Auxiliary Alternator is in parallel operation with the 200A main alternator. The same control signal is sent from the BCM to both alternators through the "L" terminal.  Output operation is monitored through the F terminal from only the main alternator, and current sensor of primary battery, input to BCM.

I don't see a current sensor for C1B battery, nor a connection from F terminal to BCM of aux alternator.

Auxiliary Alt schematic is page 5-7 of the Electrical Body Builder Manual, and Main Alt schematic is page 5-6.  So you can see how they work in concert.


With Snow plow package (option VYU) the 170A Auxiliary Alternator will only be active when the controller from the Snow plow presents B+ at the "Snow Plow Relay".  The relay then closes allowing a path from BCM to "L" terminal. 

The output is still in parallel, but the control circuit is interrupted by that relay.

Snow Plow Aux Alt schematic is page 5-10 of the Electrical Body Builder Manual


There is not a separate charging schematic for Camper Package only, so most likely dual alt with camper only option would be as standard (Both alternators working in concert).


I've not seen an actual truck to see if the schematic is accurate, but GM schematics are normally pretty reliable.  Also I find nothing on the duty cycle rating of the Snow Plow Relay.  If it is not rated 100% that could be an issue for situations where long term use is needed.  Also how that relay would handle loading if connected to the Run circuit instead of the Accessory circuit.

I'm a bit disappointed in GMs choice, as they are way ahead of Snow Plow electronics technology that I've seen, so this was not necessary.  When possible it is always better not to modify the truck electrical so that defects in materials or workmanship of electrical/electronics are still covered by warranty.  i'll probably remove the snow plow relay on my truck and jumper terminal 30 to 87A.  But if an issue with anything in the electrical system comes up during the warranty period, the claim could be denied.

One thing that is pretty cool, is it looks like the main alternator uses an overrun clutch. 


If something I've stated is not correct, please feel free to correct me.




Auxiliary Charging Diagrams.pdf Auxiliary Charging T o fO.pdf Snow Plow Schematic.pdf

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