220 Amp Alternator Question - 2021 Silverado 2500HD Duramax

tortiseshell · April 1, 2022

I'm getting ready to add a DC to DC charger to my truck camper and need to tap into the truck alternator for a D+ (trigger) wire. My rig has a 220 amp alternator.

Wondering if the alternator is 3 or 4 terminals?

Any tips on which terminal to use on the alternator? (instructions say to use IGN for 3 terminal, use ON for 4 terminal. Thoughts? Yes... needs to be hot when the truck is on and off when the truck is not running.

Are the terminals labeled easily?

Are terminals toward the cab or front of the truck?

Routing wire? The space looks tight.

Any tricks to feed a wire (16awg) through the firewall into the cab (for a on/off switch) and back out again to the driver side cargo bed?

Someone must of done this or similar... I'd really like to learn from you any tips, tricks, consideration, advise, don't do's... etc... Yup I'm a rookie but determined to do this... So thank you for any insights. I feel like I have a good handle on the big picture of my project. Due to the alternator tight space it leaves me wondering a bit so checking here to see what others have experienced. Thanks so much!

Attached are two shots from the manual of what I am using - Renogy DC to DC 40 Amp Charger

sheath · April 1, 2022

That's a pretty old school schematic, and won't work for your new GM truck. There isn't an IGN signal (per se) at the alternator.

Chapter 5 of the Body Builder Electric manual explains how our charging systems function.

https://www.gmupfitter.com/wp-content/uploads/2021/05/20_Silverado_2500HD_3500HD_Electric-1.pdf

Contact Renogy Tech Support and give them model, year, etc. of your truck and get their input on how to correctly install. If they don't have those pages on the charging system, it might be helpful to supply them to the Tech Support Rep.

tortiseshell · April 1, 2022

Oh man... now I'm worried... perhaps I need to find a connection point other than the alternator for the trigger wire. Something that activates when the truck is on and shuts off when the truck is off. Wondering about some of the fuses that say not used... I can test to see if they light up while the truck is running and shut off when the truck is off.

Sheath do you have a recommendation of where to tap into without creating electrical mayhem on the system?

Renogy support is not helpful at all. My experience with them has not been impressive.

Really appreciate the link... thank you... for a rookie, thats a lot to digest and decode... am hoping to do this this weekend... YOW!

sheath · April 1, 2022

There are fuses that are powered only when the key is in run position (as an example F44-F48). A fuse tap off Fuse 46 (HVAC) would work. You can get fuse taps at the local auto parts store. Fuse 46 should be in the fuse box on the passenger side end of the dash.

Good luck with your setup.

I don't know how your DC/DC charger functions, but it would be best if it did not start a charge cycle until the truck battery voltage was a stable minimum voltage slightly above 13.8V. This will make sure you truck and batteries are kept in good condition during cold weather starts and if the BCM picks up a fault limiting output to 13.8V.

If you can adjust your cut in voltage for the converter, I'd set it to 13.9V - 14.1V.

Another JR · April 1, 2022

My Victron dc to dc charger has a programmable delay after engine running is detected to allow higher initial recovery current for the starter battery. On chargers with a hard wired trigger from a 12 volt circuit, you could achieve the same effect with a time delay relay.

Another JR · April 2, 2022

3 hours ago, sheath said:

...

I don't know how your DC/DC charger functions, but it would be best if it did not start a charge cycle until the truck battery voltage was a stable minimum voltage slightly above 13.8V. This will make sure you truck and batteries are kept in good condition during cold weather starts and if the BCM picks up a fault limiting output to 13.8V.

If you can adjust your cut in voltage for the converter, I'd set it to 13.9V - 14.1V.

The Renogy chargers do not have that capability. They have somewhat adjustable output voltages, but on/off is simply controlled by the D+ wire.

tortiseshell · April 2, 2022

Oh boy... now I'm getting more nervous...ugh... I very much appreciate sheath and another jr's insight... thank you so much! Just spent some time under the hood, fuse boxes and got the cabin fuse boxes open... yow! Wondering if I should use a Victron charger instead...ugh

Another JR · April 2, 2022

Victron’s Orion Smart dc to dc chargers are well built, have a lot of adjustability of the charging characteristics and the engine running detection logic and charging threshold voltages, and they don’t need a separate signal to tell them the engine is running.

They cost a bit more than the Renogy. The Orion Tr Smart 12/12-30 non-isolated 30 amp charger is $226 from PKYS.com, who provides excellent customer support. I have no affiliation - I’m just a satisfied customer.

If 30 amps is sufficient for you, it’s a great product. Also, you wouldn’t have to bother with finding a switched 12 volt D+ signal to tie into - you just need the two main wires and the software decides when to turn it on based on your settings.

However, you will be able to get the Renogy installed and it will do the job (with 10 more amps of output). A time delay relay on the control circuit can mostly address the start battery initial recharge current concerns Sheath mentioned in normal operation. The Renogy would make your system less tolerant to an alternator failure, but those are pretty rare, you get indication, and you just need to remember to immediately shut off the charger one way or another to avoid draining the truck battery.

If it was me and I felt 30 amps was sufficient and I could return the Renogy for a refund, I’d go with the Victron because of its more sophisticated controls and easier installation, but the Renogy is not a bad choice if you are committed or need the 40 amps.

tortiseshell · April 2, 2022

awesome jr.. thanks... chewing on it. wiring tomorrow on the truck side... the victron sounds like a smart way to go. hmmmm.... ugh....

Another JR · April 2, 2022

If you decide to switch to the Victron 30 amp charger, I can confirm that 6awg wiring is adequate from end to end and the associated voltage drop still allows the engine running detection logic to work without having to do the test cycling it does with a greater voltage drop. This is for a slide in truck camper with the charger and camper battery in the rear corner on a cclb truck, so a nearly 30 foot wire run.

if you don’t know what that means I can explain it further.

tortiseshell · April 2, 2022

hey thxs another jr… i already got all my stuff and ready to install… so thinking im going to proceed with what i have…

todays the day for round one… thank you for all your help… gonna see how this works out… will let you know

sheath · April 2, 2022

Great input from JR. Going with your Renogy, you could always add an adjustable Voltage Sensing Relay (VSR) in the future to connect the D+ signal to.

An adjustable VSR will allow you to set the voltage that the D+ gets a trigger. It is very easy to connect, and the solid state electronic versions are very reliable.

Just something to consider for the future.

Best of luck getting everything setup. :cheers:

tortiseshell · April 3, 2022

I so appreciate all your input, experience and advice... Thank you!

So.... today got some good things accomplished, Not done yet. Today was prepping the truck with the help of an amazing neighbor and friend. Goal was to complete wiring with a switch for a trigger wire to the charger. Complete a wire run from rear truck running lights into the bed for camper marker lights. Run battery cables from engine to cargo bed. The three wire runs in the cargo bed will be connected to the camper. I have anderson connectors for the battery cable run to the camper. Will use weather tight smaller connectors for the trigger wire and marker lights. So a total of three connections in the cargo bed.

The wires emerge out of the forward driver side of the bed through one of the removable caps on the sidewall. The switch was the tricky part but is done and tested. It looks great and I'll post pics when done. Truck running light to camper marker light connection is raced and just needs a connection. Tomorrow we run the battery cables and terminate all the truck wires with the appropriate connector.

For the trigger wire switch, we were able to use an empty fuse slot that is hot on the driver side fuse panel. That wire exits the firewall via the hood release boot. It will race down with the battery wires to the cargo bed. The key to that is using the switch when I want the charger on or off. The switch is a simple lighted push button. So it's easy to determine if it is on or off. I like that I can manually trigger the charger on or off from the cab at will.

After the truck comes the camper. Install lithium batts, wire in charger, tap into camper marker lights, make a pigtail connection that allows all three plugs to come together in the truck bed. Once done I won't need to use the camper 7 way trailer wire at all. My camper is small enough to close the tailgate, Viola'!

So far good... just slow and methodical. I really appreciate your help, ideas and cheering me on. So thank you. More to come with pics hopefully soon. I learned so much today that i really admire the facets revealed in putting this together. Hopefully it will be a clean productive install. The joy in DIY is the fact of understanding what is going on and what to be aware of now and later.

Thanks much! Oh... and yes... the VSR is a great idea... that may be an add on after I figure this out for a bit.

tortiseshell · April 5, 2022

So just an update... I got the truck fully wired 95%.. Battery cable from under the hood to mid cargo bed with anderson connector done. Trigger wire from driver side fuse box to push button switch in dash installed. Switch wire runs from dash through firewall, thru hood release boot and joins battery wire to cargo bed. Rear driver side running light tapped into for camper marker lights. That wire is raced to meet the other looms to the cargo bed. So I have a total of two connections between truck and camper. Battery wire to charger. Double plug for switch to turn charger on/off and camper marker lights. I just need to add the double plug, loom it and fuse tap my connection for the switch. Overall it looks great and is super clean. Many thank you all of you and an amazing neighbor/friend.

I didn't need to make a physical connection to the alternator. My HD was set up for adding accessories onto the battery. The fuse panel on the driver side provided a needed trigger wire signal for the charger. Adding a switch inline between the fuse panel and charger will let me turn it on/off from the cab.

Next phase is the camper. Again... thanks so much all. I've learned a lot!

tortiseshell · April 30, 2022

OK... finally got it and done. Sooooo happy and it came out great! Many thanks to my fantastic neighbor and friend who was instrumental throughout the project. On top of that he made a CAD drawing of my setup. Way better than my 6th grade science paper representation! So, sharing this in hopes it may help others. There is no way I could have done this without help from outside... Another JR and Sheath... thank you so much! Overall the whole system is terrific and super clean install. I greatly appreciate everything everyone has done to help navigate this rookie though my project. The best take way? I know this system inside and out since it was a DIY. I feel good about every wire placement, how it was done and how to think about troubleshooting if needed. So many thanks to everyone.