Trailer Alternator

[Little Lost in the Woods]

I purchased an overland trailer thats made out of a 1988 Toyota truck bed and rear end. One of the things that him and I got to talking about is mounting an alternator to the pumpkin and powering it off of the input for the rear diff. Has anybody here had any experience with this?

Thanks
John

 

[Billiebob]

That was a common thing when hot rodders wanted to clean up the open engine. Running an alternator off the drive shaft. But they only work on the highway. 1950s, 1960s. Maybe earlier too.

 

[Shakes355]

I love the spirit, but chances are that the reduction wouldn't spin it fast enough to excite the field coil, as mentioned above.

You could theoretically get the reduction you need through gearing and pulley sizing to get it to charge at trail speed, sure. But it would most likely over spin at highway speeds and self detonate.

It would be much cheaper and more efficient just to run a larger alternator on your rig.

 

[Little Lost in the Woods]

Thats what I was thinking, he made it sound like there was a kit out there that regulated this. I, not knowing crap about overland trailers, figured he knew what he had it all figured out. Assumed the kit had some sort of digital regulator or some sort of transmission to it... lol

Thanks for the reply guys.

 

[Brianj5600]

Can you not upgrade the alternator on your tow vehicle?

 

[Little Lost in the Woods]

Maybe... its a 2017 Ram 5.7... everything is electronically controlled. Even then I have to run wires down the truck frame, across the hitch gap and then to the trailer... That seems sketchy to me lol

 

[Billiebob]

Maybe... its a 2017 Ram 5.7... everything is electronically controlled. Even then I have to run wires down the truck frame, across the hitch gap and then to the trailer... That seems sketchy to me lol

Not sketchy at all. Thats how it is done. Visit yer local retail trailer seller, RV mechanic.

Back to the trailer alternator, depending on how much/often you drive it could work. Coolers do not need to always have power. Mine is only plugged in driving, 6-10 hours a day. If the cooler is full of cold food it'll hold temperature pretty well over night. And buying cold food will help so nothing is wasted cooling the contents, just maintaining the temperature. Adding a cold 6pak can also help as a cold sink, just like an ice block. A cooler full of cold food will stay cold a long time.

And apways know what you want before opening it.

 

[Shakes355]

Just a note, does your truck have a factory 7 way trailer plug? If you do, then you have a factory charging circuit for an aux battery. Red wire I believe (pin 4? Double check) should already be wired to a separate charging relay in the TIPM with a dedicated fuse.

Easy peasy to just wire up your trailer with a 7 pin and integrate the charging circuit to the second battery. No need to run wires down the frame.

 

[JDGreens]

I was kicking the idea around when I started my trailer build out of a Xj body. I was going to go ahead and use the rear axle run the drive shaft up to the tongue area and fab a pulley system. But I decided that if I did that I would have to keep the hump down the middle of the floor board. And decided I would rather be able to gain the extra foot by tubbing it out instead. I believe solar would be a better way to keep things charged anyways.

But I think that's some out of the box thinking for sure!

 

[MazeVX]

Maybe... its a 2017 Ram 5.7... everything is electronically controlled. Even then I have to run wires down the truck frame, across the hitch gap and then to the trailer... That seems sketchy to me lol

Here's a real high power alternator, ready to bolt in for your ram

320 amp high output alternator for Ram Hemi 5.7L

320 amp high output alternator for Ram Hemi 5.7L

www.mechman.com

 

[Brianj5600]

Here's a real high power alternator, ready to bolt in for your ram

320 amp high output alternator for Ram Hemi 5.7L

320 amp high output alternator for Ram Hemi 5.7L

www.mechman.com

That's a lot of overkill.

 

[smritte]

Ok so how would I build this...
1. graft a crank pulley onto the pinion end.
2. make brackets to hold alternator.
3. use overdrive pulley on alternator (smaller)
4. on my 7 wire trailer plug, use the lead commonly used for the back up lamp to turn it on with the ignition. Or run a 78 amp, mid 80's GM alternator. They self energize real easy.
5. run an 8 gauge wire to the battery with a 100 amp manual reset breaker. That way you can disconnect power to it when your parked if you want/need to.
OR
1. install solar panel and controller.
Or
Wire your truck to charge it like the rest of the world.
When your calculating how much alternator you need. average vehicle at night, wipers on, draws 20-30 amps + any add on accessories. Add in 40 amps per battery in vehicle. Add in 40 amps per battery in trailer. Add in 10% over the total just because and there you go.

Personally i like the extra charging system at the trailer and a solar panel. One of my buddies at work drew up the plans to install motors at the trailer hubs to give it power. Great idea, stupid expensive. the downfall is, too hard to do regenerative breaking and the battery pack is too difficult to charge. OH and its real heavy.

 

[Little Lost in the Woods]

Holy Crap! You all are amazing!!!! Thank you so much for the responses!!! I believe that having the trailer alternator has some merit for how we plan on doing things. Not sure if its worth the cost of admission, but it could be fruitful. That said, I never new thats was what the power wire was for on the seven pin, I need to look into that now. I was planning on running a solar system as well, Still figuring all the out. 370 Amp alternator you say... I like it, but Im a grunt and I thoroughly believe over kill is under rated! lol

Thank you again, you guys are amazing.

 

[Shakes355]

An extra note: Tread carefully and consult your manual/service information. Chrysler had a real problem with their Totally Integrated Power Modules (TIPM ie. The main fuse block) burning up and failing.

Make sure to double and triple check your setup to ensure you don't exceed the limit of that circuit. Its designed precisely for that purpose, for sure, but no need to put any extra stress on that module than you need to, if you get my drift.

 

[Billiebob]

Here's a real high power alternator, ready to bolt in for your ram

320 amp high output alternator for Ram Hemi 5.7L

320 amp high output alternator for Ram Hemi 5.7L

www.mechman.com

[/QUOT

Just a note, does your truck have a factory 7 way trailer plug? If you do, then you have a factory charging circuit for an aux battery. Red wire I believe (pin 4? Double check) should already be wired to a separate charging relay in the TIPM with a dedicated fuse.

Easy peasy to just wire up your trailer with a 7 pin and integrate the charging circuit to the second battery. No need to run wires down the frame.

Depends on the draw. Most 7pin trailer plugs are good to charge the electric brake battery but not substantial enough to run a house of RV appliances. Once you add that draw you need separate cables sized for the load and length of the run, and an Anderson Connector is an ideal way to move that load.

 

[Billiebob]

Ok so how would I build this...
1. graft a crank pulley onto the pinion end.
2. make brackets to hold alternator.
3. use overdrive pulley on alternator (smaller)
4. on my 7 wire trailer plug, use the lead commonly used for the back up lamp to turn it on with the ignition. Or run a 78 amp, mid 80's GM alternator. They self energize real easy.
5. run an 8 gauge wire to the battery with a 100 amp manual reset breaker. That way you can disconnect power to it when your parked if you want/need to.
OR
1. install solar panel and controller.
Or
Wire your truck to charge it like the rest of the world.
When your calculating how much alternator you need. average vehicle at night, wipers on, draws 20-30 amps + any add on accessories. Add in 40 amps per battery in vehicle. Add in 40 amps per battery in trailer. Add in 10% over the total just because and there you go.

Personally i like the extra charging system at the trailer and a solar panel. One of my buddies at work drew up the plans to install motors at the trailer hubs to give it power. Great idea, stupid expensive. the downfall is, too hard to do regenerative breaking and the battery pack is too difficult to charge. OH and its real heavy.

A choice means it charges only while driving.
B choice means it charges only when sunny....

Stupid expensive is, well stupid expensive.

Personally I like the solar charger.

 

[B-R]

Another idea if worried about factory wiring being enough to handle the load is you could run a second alternator (GM one wire or Zena ) and isolate it from factory wiring with an Anderson plug to connect trailer

Then would charge any time truck is running and plugged into trailer

 

[Shakes355]

Yeah that's my bad. I should have clarified further for safety's sake. @Billiebob is correct. Its limited by the factory circuit and is mainly designed for maintaining/topping off a battery. The amperage needed to charge it if it's dead would most certainly overload the circuit. Obviously, that includes loads as well. Using a winch off the aux battery, for example, will draw more amperage than the circuit can replenish in short order.

Using in conjunction with another charge source such as solar is preferred and potentially required depending on use (as pointed out by multiple other members).

 

[smritte]

I wouldn't worry about overloading the circuits while charging. Due to internal resistance, batteries only draw about 40 amps max and the factory output wire is normally slightly over kill for the stock alternator. The biggest issue is the feed to the back. Even with a towing package most OEM power feed to the rear is a 10 gauge. Those don't normally melt trying to charge only one battery but, due to the length and wire size, they normally lose a bit of power by the time they get to the back. When I set up a rear charging feed, i find 8 gauge has very little loss charging a single battery and 6 gauge works on dual batteries.

Adding a second alternator is a great idea as long as you have an older vehicle. Modern belt/pulley configurations make it real hard to do. The modern engines don't have a bunch of extra mounting holes either. When I have added in on board air or secondary alternators for welding systems, getting the pulley exact is a pain. I bought a small laser that mounts to the pulley. this way you can check square to the other pulley grooves. If your of by as little as .020 your belt will squeak, more and the belt runs off the pulley.

If your stock alternator is over 100 amps your probably good. See if the factory optioned something in the 140 amp range for a towing package. This should bolt in without issue. Upgrading the alternator output wire at the same time would be a good thing.

 

[Little Lost in the Woods]

1) As for adding an alternator to the truck. I wouldn't mine upgrading it to a 140ish amp, if its not there already.
2) I can see the Voltage Drop of 12 volt being shoved through 30ish feet of #10 being a thing and its why I never really considered using that before. Though I am looking into more.
3) I wont touch the fuse box on the truck... period.... the high end electronics in cars these days are finicky as shit. you fuck around and parallel a circuit and steel to much amperage and fun things can happen. I am installing a separate fuse box for all my after market needs.
4) I dont think we need 2 batteries, and with a fixed Solar panel and possibly a blanket with a long drop cord , it should stay fairly charged already. if I dins that this is not the case I will go from there.

Again, you all are great!