I look forward to seeing what you find out.

It's looking like a cool MOD! :up:

Ray
When I had an RV. We just charged the RV batteries from the truck when the engine was running. The isolation box only cost $30 CDN including tax. It was good for about 30 amps continuous and 50 amps peak for about 5 minutes. Do they still make these simple devices for the old schools types.

Yep, I used to have one on my old camper van. But as battery bank size grows and lithium type is being used some sort of regulation between the alternator and batteries is recommended or the alternator can risk being damaged. So, many people are using DC-DC converters versus the old school simple solenoid isolation switch. This is an example - https://www.renogy.com/12v-dc-to-dc-on-board-battery-charger/ Since I have the old Bogart solar controller kicking around now I'm going to reuse it for the same purpose.

I'm curious to see what the voltage to the Bogart is. Alternators are around 13.6v? I think. With line loss I am thinking there will still be enough voltage to charge the battery. I think that's key advantage to the dc-dc chargers like the Renogy is that they boost voltage. The video should be interesting. Look forward to seeing what it does. :)

In my latest RV mod, I install a high amperage 30A 12VDC port into the bed of my 2018 Ram 3500 pickup truck. I also test out using an old Bogart SC2030 solar charge controller I have laying around for alternator charging.

Bogart Engineering Test showing the SC2030 solar charge controller acting as a DC-DC converter - https://www.youtube.com/watch?v=2yhC-43P_Uk



Disclaimer: Working with electricity can be dangerous. The following is for entertainment purposes only and should not be taken as instructional. If you decide to do the same, then research and beware of the risks involved. I don’t advise it without advanced knowledge of electricity. I accept no liability. You have been warned! – Ray

I explain how I ran various cables and installed the connections and then show the results of my amperage tests. I saw a charging current of between 9-15 amps. Not too bad but nowhere near the solar controller maximum of 30 amps.

My theory for why the low results are the .6V drop I'm getting in the wires or the fact my truck's smart alternator regulates the alternator charge voltage. So, at the truck battery, I see anywhere from 13.8V to 14.3V DC. Furthermore, I'm charging lithium batteries, which have a higher resting voltage than the lead-acid type.

I'll continue to play around with the system and experiment and come back with another video if my results improve.

Related Links:

My RV Mod Videos - https://www.loveyourrv.com/love-your-rv-mods-and-upgrades/

Boondocking Videos - https://www.loveyourrv.com/boondocking-archive/

Bogart Trimetric WiFi Monitor Demo - https://www.loveyourrv.com/new-wifi-add-on-for-the-trimetric-battery-monitor-installation-and-demo/

VIAIR 12V Trolling Motor Plug Install - https://www.loveyourrv.com/viair-450p-rv-12vdc-air-compressor-review-and-rv-hookup-mod/

My Ram Truck Videos - https://www.loveyourrv.com/category/new-ram-truck/

Uni-T Clamp Meter - https://www.loveyourrv.com/electrical-test-gear-aboard-rv-uses/

Last Sept we dry camped overnight in cold weather while running the furnace, when I got up the following morning I noticed by the solar monitor that the voltage had dropped substantially(can't remember that number). Because my umbilical cord was hooked up to the truck I started the truck and almost Immediately the voltage came up. Fired up the furnace and the truck was able to maintain voltage to the batteries while running the truck.
We have a 170 watt solar panel with PWM2 and 2x12 volt led acid batteries.
This was my by guess and by gully method,, who would know I did not until I tried it.
Would I be stressing the alternator ?

Hey Ray,

Love your vids! Thanks for putting them out there for all of us.

A different HACK I have considered is putting an Inverter in or near the engine bay near sized not to cause harm to the alternator/truck (1000w??). Short heavy-gauge DC cables with appropriate fusing etc. Then run 110v back to the trailer to the charger that has the correct profile for the trailer. It might be tough to protect it from weather or heat.

My rig's converter/charger is 55A located in the electrical bay upfront like yours. I'd be on the edge of a 1000w inverter at full charge. This would keep the gauge of wire down required to go from the truck to the trailer. I have a recessed female AC plug on the front of my trailer that only powers the converter (not the trailer 110v). My converter is not connected by default when the trailer is plugged in as solar looks after charging the batteries most of the time.

The converter designed for the batteries would control the charge profile. This would allow a fairly hefty charge rate to the batteries. Assuming the alternator could deliver 70ish amps continuous while charging,

I suppose firing up a secured Geni in the truck box could do the same thing. ;)

Jake

I've had several people comment that is what they have done and works for them.
I decided against it as I didn't want to try and wire an inverter into the engine bay and was looking at adding the 12V truck bed port. Also, I was thinking my 60A charger draws about 1000 watts when charging lithium bank, so may pull 80 amps or more off my alternator, was a little high for my taste.

I've actually decided to buy and review the Renogy DC-DC charger 40A model - https://amzn.to/39PFIl1 Its on its way. :)

I look forward to the renogy dc-dc charger review. Looking at the instructions for this it looks like the lithium setting is a basic dip switch setting and wouldn't be ideal for my non BMS DIY battery pack.

Victron make the Orion which is a programmable dc-dc charger. I have been sort of kicking it around for a while.

Is this necessary account of running the Lithium batteries?

I've heard hooking lithium batterie straight to an alternator isn't a good idea since they have such a low internal resistance its easy to damage the alternator, especially if the wire gauge is large. I doubt the little OEM tow cable wire would hurt anything as its so small of gauge.
It's why people use something between the two as a controller, like the solar controller I tried and the DC-DC charger I'm going to try. Victron also makes some gear called a Battery Isolation Manager for their systems. https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/

Look forward to your review of the Renology. I wasn't aware on a DC-DC boost solution. This makes a lot of sense to me. Look forward to your amps into the battery result. :).

Looks like it's going to work well, plugged it into the existing cobbled together wiring from my previous testing and got 39 amps, the feed to it dropped from 14.3V at the truck battery all the way to 11.8V at the Renogy charger input but it boosted the voltage back up to deliver the 39 amps to the RV battery bank.
On the input side, it drew 54 amps from the alternator. So it does work drawing extra current to boost the voltage but of course, was heating up things, so now I'm in the process of beefing up my wiring to handle the extra current, better connectors, and higher amp circuit protection, etc. I will kick out a video when I get it all wired up.

Thanks for letting us know. That is a very good outcome. I like your approach to do it 'right'.