Dual Battery Question

revrnd · November 20

Just curious as to the thinking behind the dual batteries & 220 amp alternator as options on my 2024 2500HD gasser. It doesn't have either the snow plow prep package or 5th Wheel prep.

The only truck of my previous 7 that had an aux' battery was my '82 K15. I added a winch w/ a 2nd battery, so winching wouldn't kill the primary battery.

I have had previous trucks w/ the VYU option, but none included an aux' battery.

I have read in the past that the electrical loads on the 12V batteries were getting higher for 1 battery to handle (talk at the time was going to higher voltages). Are certain systems and/or accessories powered by the aux' battery on my truck?

rjgvt · November 20

The aux battery on my truck supplies 12v to the trailer connectors at the bumper and inside the bed. My truck has the plow prep package and fifth wheel options. I used the bed connector to provide power to my ARE cap lights. I installed a 12v socket in the cab that I connected to the aux battery.

lineman1234 · November 20

I have the plow/camper prep but it just came in bags, not installed.

I did add a second battery same as original just to have more power for a DC cooler and my front/rear dashcams.

The cooler can run when i get cooled stuff needed and not going home right away as stopping places with the pickup off, the dash cams are on all the time, if it moves its recorded, so that takes some power.

The dash cam can be set to shut off when it detects a certain voltage to not kill the batt/s.

rjgvt · November 21

The snow plow prep/camper package comes with a 220 amp alternator, increased front GAWR and roof emergency light provisions. I’m not sure how to hook up the roof light without having the upfitter option which is not available for my truck.

revrnd · November 21

12 minutes ago, rjgvt said:

The snow plow prep/camper package comes with a 220 amp alternator, increased front GAWR and roof emergency light provisions. I’m not sure how to hook up the roof light without having the upfitter option which is not available for my truck.

That seems odd. Any of the trucks I had w/ VYU had a switch in the overhead 'console' to control it. My crew cab has the console where the dome light controls are.

Looking @ the manual:

No mention of higher trimmed trucks.

rjgvt · November 21

Those are the upfitter switches. That option was not available for the 2024 AT4 and Denali.

64BAwagon · November 21

As I understand the 2 battery setup on my 2024 L8T the second battery is isolated. I dont have the schematic but there are electronics on the battery box that apparently control the flow of power in and out. It is not like previous generations where the batteries are simply wired together. This setup is meant to provide power for high loads like a plow and isolate the primary chassis battery in order to buffer the loads.

Pryme · November 21

I have the plow prep and camper packs in my poverty model truck with the 220a alt and probably the light provisions but I’d never use that. The empty spot for the second battery would be a nice place to put a tool kit or a six pack for ice fishing haha.

revrnd · November 21

1 hour ago, 64BAwagon said:

As I understand the 2 battery setup on my 2024 L8T the second battery is isolated. I dont have the schematic but there are electronics on the battery box that apparently control the flow of power in and out. It is not like previous generations where the batteries are simply wired together. This setup is meant to provide power for high loads like a plow and isolate the primary chassis battery in order to buffer the loads.

That's similar to how I wired my 2nd battery for powering the winch. Not sure if it's still used, but I used a battery isolator like this:

I could draw down the winch battery, but not affect the starting battery.

Do you think that the wiring/electronics would allow power to flow from the aux' battery during cold temp' starts?

The truck includes the True North Pkg, but the 220 A alternator & aux' battery are not part of it.

64BAwagon · November 21

I havent really delved into it deeply but the basic explanation I got was that it would under certain circumstances. I have ordered the 220a alternator on both trucks but my first one was the single battery. I figured after the discount the 2nd battery was around $130 and the last time I priced an AGM around here it was a little more than that for just the battery. I also got it for towing so I didnt have to worry about the trailer drawing the main battery down. On previous trucks where the trailer battery feed was hot at all times I would remove the line and add a relay to feed it only when the ignition was on. That way if we stopped for a rest I didnt have to unhook the battery in fear of the trailer drawing it down.

This truck has the heavy front torsion bars, the 220a alternator and dual batteries on a 3500 chassis. It broadens the market when I sell them

revrnd · November 21

5 minutes ago, 64BAwagon said:

I havent really delved into it deeply but the basic explanation I got was that it would under certain circumstances. I have ordered the 220a alternator on both trucks but my first one was the single battery. I figured after the discount the 2nd battery was around $130 and the last time I priced an AGM around here it was a little more than that for just the battery. I also got it for towing so I didnt have to worry about the trailer drawing the main battery down. On previous trucks where the trailer battery feed was hot at all times I would remove the line and add a relay to feed it only when the ignition was on. That way if we stopped for a rest I didnt have to unhook the battery in fear of the trailer drawing it down.

This truck has the heavy front torsion bars, the 220a alternator and dual batteries on a 3500 chassis. It broadens the market when I sell them

On the 1st bold, I started a thread asking if other True North owners have the aux battery and HD alternator.

This is the 1st truck that I didn't order otherwise I would've ordered it w/ RPO VYU. Since my GMT400 in ''94, I've ordered the plow prep for the same reason.

lineman1234 · November 21

As i really wanted to custom order my WT but no dealer had any clue on when the regular cab line would run, i found one 186 miles away. Very close to what i wanted, or close enough. ( I LOVE my WT ) simple fun pig.

It does have the camper/snow plow prep, the stuff came in 2 bags, looks like it should be on a space ship, no directions. No one ordered the $135 second batt option that is cheaper than just getting the darn batt hold down alone after. Let alone no up fitter switches, to get and install that seems a bit of a chore. Thank goodness i dont need any of that.

As mentioned, i added the second batt, made my own redneck hold down, had napa make cables to tie the second to the fuse box on the top of the other batt. I ran the positive cable across the rear fire wall in that split duct plastic wire protecting stuff.

I used 2 fuses from the kit to fuse at each end of the cable. The second batt is tied hot all the time to the main batt.

I made the lighter plug hot all the time to run the dash cams and cooler as needed.

revrnd · November 21

55 minutes ago, lineman1234 said:

As i really wanted to custom order my WT but no dealer had any clue on when the regular cab line would run, i found one 186 miles away. Very close to what i wanted, or close enough. ( I LOVE my WT ) simple fun pig.

It does have the camper/snow plow prep, the stuff came in 2 bags, looks like it should be on a space ship, no directions. No one ordered the $135 second batt option that is cheaper than just getting the darn batt hold down alone after. Let alone no up fitter switches, to get and install that seems a bit of a chore. Thank goodness i dont need any of that.

As mentioned, i added the second batt, made my own redneck hold down, had napa make cables to tie the second to the fuse box on the top of the other batt. I ran the positive cable across the rear fire wall in that split duct plastic wire protecting stuff.

I used 2 fuses from the kit to fuse at each end of the cable. The second batt is tied hot all the time to the main batt.

I made the lighter plug hot all the time to run the dash cams and cooler as needed.

Is that similar to how the 'dual' batteries are wired on the diesels?

lineman1234 · November 21

3 hours ago, revrnd said:

Is that similar to how the 'dual' batteries are wired on the diesels?

Having come from a diesel it isnt that way, its more fancy.

I am just supplementing what the main one does.

64BAwagon · November 21

I suspect that the upfitter instructions will have the exact operation of the second battery and how to wire accessories to it. I can say that its a different setup than my 2005 Duramax.

Edited November 24 by 64BAwagon