10 replies to this topic

[Jon R]

My new truck finally arrived, so I'm now able to look at the factory dual battery arrangement.  This truck has a single 220 amp alternator (base is 175 amp).  I thought I'd describe it in case it's useful to someone in the future. 

 

The battery isolator appears to be a simple relay that is part of the fuse housing on top of the aux battery, and it connects the batteries only when the engine is running according to the manual. 

 

The main battery has a fuse assembly on top of the battery with the main fuses, and it includes a spare fused 1/4" post with an 80 amp fuse installed.  I plan to connect my 6 awg positive wire to the camper's DC to DC converter to this post (I may reduce the fuse to 60 amps).  The negative battery connector has a single unused 1/4" inch post on it.  There does not appear to be a conventional negative bus bar anywhere under the hood.  I plan to use the post on the negative connector for the 6 awg negative wire to the camper.  I plan to run the camper wires in split plastic conduit across the top rear of the engine compartment alongside the factory bundle and then down and back along the left side on top of the frame attached to the existing factory bundle.  The exhaust is on the right side, so the left stays cool, and that's where it needs to end up anyway at the camper.  I still haven't decided what connector to use at the bed, but I'm leaning to a fixed SB50.  

 

The auxiliary battery is connected to the main battery by a 100 amp fused (at both ends) positive wire that runs through the isolator relay.  The aux battery fuse housing has a 30 amp fused post that connects to the trailer/camper connectors in the bed and at the trailer hitch.  It has a spare position for one more fuse and post in the plastic housing.  I expect there is a GM part that can be bought to add to the fuse block in that position. 

 

I don't plan to associate the truck auxiliary battery with the camper electrical system.  I plan to connect to the aux battery a 12 volt cigarette lighter style connector for a portable fridge/freezer in the back seat area, and eventually hope to power a permanently installed air compressor from it as well.  Hopefully I can obtain the GM part to add the post and supply those items.  I hope to have it all looking like factory work when I'm done. 

[DavidGraves]

Congrats on the NEW TRUCK !

 

What color ?

 

David Graves

[Jon R]

It’s dark blue “pacific blue metallic”

[Mighty Dodge Ram]

Great color (says the guy with an Indigo Blue Metallic Chevy 😂). I’ve been impressed with the GM HD models and the included amenities. Sounds like you’ve got yourself a great truck, I’ll be following your progress. 

[ntsqd]

If you were going to charge direct (doubt that's advisable in this vintage truck) I'd say 6 ga. is just about right. For charging with a DC-DC converter is it excessive overkill? How many amps can the converter draw?

[Jon R]

6 awg is overkill for the 35 amp current the converter will draw, and overkill for voltage drop regarding the basic function of the converter. However, the engine running detection function of the Victron converter can detect excessive voltage drop as an engine shutdown, shutting of the converter, and it can cycle on and off. Victron has addressed that with a software change allowing you to set the engine (not) running detection voltage threshold lower, so I probably could have used 8 awg, but by the time I found out about this improvement I had already bought my wire. 6 awg is still what Victron recommends for the wiring.

[jeep364]

Congrats on the new truck!  Is it diesel?  Reason I ask is the secondary alternator (if ordered) also requires spec'ing a second battery which I assume is not present on gas trucks.

[Jon R]

Thanks, Jeep364.  It's a gas truck. I have the optional single 220 amp alternator (the base one is 170 amps), and a second optional battery wired as an auxilliary battery with isolator (unlike the diesel, which apparently needs two batteries to start).  I bought the second battery thinking it would be good for powering a truck fridge and a compressor.  The second battery option is only $135, and retrofitting one is expensive and a lot of work.  They offer a second alternator on the gas truck but I didn't see a need for it.  Other camper-relevant options I ordered were the one step heavier front camper springs, and the high idle switch.  The payload on the placard is 4,054 lbs!  It drives very smoothly despite the heavier springs. 

 

Camper arrives in two weeks!

[jeep364]

Thanks, Jeep364.  It's a gas truck. I have the optional single 220 amp alternator (the base one is 170 amps), and a second optional battery wired as an auxilliary battery with isolator (unlike the diesel, which apparently needs two batteries to start).  I bought the second battery thinking it would be good for powering a truck fridge and a compressor.  The second battery option is only $135, and retrofitting one is expensive and a lot of work.  They offer a second alternator on the gas truck but I didn't see a need for it.  Other camper-relevant options I ordered were the one step heavier front camper springs, and the high idle switch.  The payload on the placard is 4,054 lbs!  It drives very smoothly despite the heavier springs. 

 

Camper arrives in two weeks!

Thanks that is a great setup.  Please post pics of the combo!  Payload on these new trucks is great.  It seems strange GM does not offer different axle ratios on the gas (not that it's needed for most) or the ext cab / short bed in the 3500.

 

I was a bit confused and didn't realize the extra battery was available as a stand-alone option, I know when I was 'building' a new 3500 online and selected the second alternator with gas it forced the second battery.

 

How does the high idle work with the gas, do you get to select the RPM via the 'computer' controls on the dash?  I can see that being useful for charging from the vehicle and from what I have read, the new trucks literally do not let you idle the truck for >30 minutes unless you trick the system.  Guys online (gm-trucks.com) are suggesting putting in neutral and parking brake allowing the truck to run for hours which seems like a bad idea, but I think putting it in high idle accomplishes the same thing with a slight increase in gas consumption.

Edited by jeep364, 15 May 2021 - 01:14 AM.

[Jon R]

The high idle setting is turned on using the cruise control switches when the truck is in park. I believe it’s a fixed rpm and not adjustable, but i haven’t actually tried it yet. I’ll mess with it tomorrow and report back. I don’t know if the auto shutdown you describe is defeated when high idle is selected. I’ll see if I can find out from the manual.