Dual battery setup

February 23, 2020

Here is the stock and added ground and current pics... sorry for how dirty the engine is... 8 years old this may...

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BrentH · April 2, 2021

@Gr8FrozenNorth : did you ever complete this operation of adding the auxiliary battery and increasing the alternator capacity?

I just purchased a 2021 2500HD LT and they "forgot" to install the package or couldn't due to missing parts. Anyway I have the parts ordered and a new 220 volt alternator on the way and will be doing this mod in a few weeks when everything arrives.

My truck arrived with the 170 Amp Alternator but has a 250 amp fuse for the alternator on the main battery. For a 170 amp alternator this would normally be a 175 amp fuse. For some reason my fuse block is from a 1500 Diesel with a 220 Alternator - for me, that is a good thing

I purchased the " J Block Auxiliary Battery" 84663447 - this part comes with a 30 amp fuse, a 100 amp fuse and a 175 amp fuse. The 100 amp fuse is connected to an isolator relay all as one assembly. The cover is Junction Block Cover 84471670

I am re-using the cable from the main battery positive to the terminal on the X50D (175 amp) it runs from the main battery over to the X50A Fuse Block (as per normal) and then a short pigtail will run from that connection to the 100 AMP fuse on the auxiliary battery J Block (X50E). this is the fuse attached to the isolator.

The isolator is supposed to be powered from a secondary relay that wires into a connector X136. I have to find all that on the truck first but I am away on business so it will take a bit. right now I am still in research mode but it looks like that is pretty much it other than connecting the trailer 30 supply power wire up.

From reading the battery relay will energize if you switch to tow/haul mode and it will charge the aux battery.

maybe someone with the factory install would have more intel. I will post pictures once things get underway.

Rozz522 · April 7, 2021

I'm wondering if anyone has had their dealer do an install much like the factory install? I just put a deposit on an in transit SLE with the Snow Plow Prep so I will have the 220A alternator. I would just need the battery, the new junction/fuse box and the additional leads. I know as a factory install its like a $135 install but looking at the parts list it looks significantly more as an after the fact installation. I just wasn't sure if there was a retrofit kit for the dealer to order of if you need to identify and order the individual parts needed.

Another JR · April 8, 2021

My new 3500HD gas truck arriving next week will have the factory dual battery installation. If you would like me to post photos of anything let me know. I'm going to be immediately installing 6awg wire to a slide in camper connector (for a 30 amp DC-DC converter/charger in the camper), so figuring out the battery, isolator, and fuse block arrangement on the truck will be one of the first things I get into.

Dare Wade · July 30, 2021

On 4/8/2021 at 7:09 AM, Another JR said:

My new 3500HD gas truck arriving next week will have the factory dual battery installation. If you would like me to post photos of anything let me know. I'm going to be immediately installing 6awg wire to a slide in camper connector (for a 30 amp DC-DC converter/charger in the camper), so figuring out the battery, isolator, and fuse block arrangement on the truck will be one of the first things I get into.

Please do post the set up.

03 Cobra · July 30, 2021

On 4/8/2021 at 10:09 AM, Another JR said:

My new 3500HD gas truck arriving next week will have the factory dual battery installation. If you would like me to post photos of anything let me know. I'm going to be immediately installing 6awg wire to a slide in camper connector (for a 30 amp DC-DC converter/charger in the camper), so figuring out the battery, isolator, and fuse block arrangement on the truck will be one of the first things I get into.

Yes, please post pics of your factory dual battery set up. Now that you've had it a few months are you happy with its performance? I have a 22 GMC HD ordered with that option and I'm very anxious to see what it looks like from the factory.

Another JR · July 31, 2021

I will take some pictures later this evening. I have not yet wired anything to the second battery. I ordered the option because it was way cheaper than adding the battery system later, and eventually I’ll use it to power an air compressor or refrigerator or both. The factory wires the trailer 12 volt supply to the aux battery. No other loads are on it right now, so I can’t give a report on using the aux battery yet.

03 Cobra · July 31, 2021

1 hour ago, Another JR said:

I will take some pictures later this evening. I have not yet wired anything to the second battery. I ordered the option because it was way cheaper than adding the battery system later, and eventually I’ll use it to power an air compressor or refrigerator or both. The factory wires the trailer 12 volt supply to the aux battery. No other loads are on it right now, so I can’t give a report on using the aux battery yet.

From research I've done recently including chatting in another forum with a guy that has a 2020 Chevy HD with the factory dual batteries I believe that the second battery powers the trailer connections (4 pin and 7 pin) when the truck is turned off and when the truck is running both batteries get charged. That way you can power your RV with the truck off and not worry about draining your starting battery. He traced the wiring using schematics he found online and then tested his truck with a meter to confirm it. I haven't been able to check it myself yet but he seemed to be confident and knowledgeable on what he was talking about. Is that aligned with your understanding?

Another JR · July 31, 2021

I believe all of that is correct except my understanding is that only the trailer positive (pin 4) is powered from the aux battery, and pin 7 is reverse lights. That’s my understanding of standard 7 pin trailer connector wiring, but I have not tested pin 7 to see how it’s actually wired on my truck.

03 Cobra · July 31, 2021

10 hours ago, Another JR said:

I believe all of that is correct except my understanding is that only the trailer positive (pin 4) is powered from the aux battery, and pin 7 is reverse lights. That’s my understanding of standard 7 pin trailer connector wiring, but I have not tested pin 7 to see how it’s actually wired on my truck.

Did a quick search and found the below diagram. It will be interesting to know which pins have power when the truck is completely off.

Another JR · July 31, 2021

I just used a voltmeter and confirmed that only pin 4 has 12 volts on it when the truck is off and no lights are on.

i’m not sure what you would like pictures of, so to start here is a view of the general battery installation and one of the i fuse block. The 30 amp fuse is connected to pin 4 of the trailer connector. The 100 amp fuse comes from the main battery fuse block.

My truck has a gas engine with single alternator. The aux battery option includes a larger 220 amp alternator. My understanding is that on diesels the second battery is a parallel wired starter battery with no isolator.

Edited July 31, 2021 by Another JR

03 Cobra · July 31, 2021

8 hours ago, Another JR said:

I just used a voltmeter and confirmed that only pin 4 has 12 volts on it when the truck is off and no lights are on.

i’m not sure what you would like pictures of, so to start here is a view of the general battery installation and one of the i fuse block. The 30 amp fuse is connected to pin 4 of the trailer connector. The 100 amp fuse comes from the main battery fuse block.

My truck has a gas engine with single alternator. The aux battery option includes a larger 220 amp alternator. My understanding is that on diesels the second battery is a parallel wired starter battery with no isolator.

Another JR, hey thanks for checking the volts and confirming that only pin 4 is hot. Also, the pics are great. I just wanted to see what the factory set up looks like. The aux battery definitely fills the hole that is in that corner of the engine bay when the battery isn't there. I like that it's wired so the aux battery is disconnected without us needing to do anything.

Edited July 31, 2021 by 03 Cobra

hdhp · August 31, 2021

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! I posted this in other sections a lot of views but no reply....

HDHP

redwngr · August 31, 2021

On the dmax they are all dual the batteries which behave as one big one.

Not sure about on the gasser

Edited August 31, 2021 by redwngr

03 Cobra · September 1, 2021

15 hours ago, hdhp said:

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! I posted this in other sections a lot of views but no reply....

HDHP

On the gas trucks the aux battery is charged when the truck is running. When the truck is off only pin 4 on the 7 pin round trailer connections is powered by only the aux battery (it is disconnected from the starting battery when the truck is off). This way you can power your camper or other items using the 7 pin connector(s) without draining your main battery.