Charging System upgrade (?)

[v12venator]

Evening all, relatively new poster and lurker here and, like many other members here, I'm having some issues with the electrical systems on my M1031. I've chowdered up the stator in my P/S 27si alternator and am waiting for a "new" alternator to come in from the parts store so I can rip the rotor and stator out of there and slap them in my isolated ground 27si for the truck.

This got me wondering, though, could I just get a 24v alternator, rip out some wires in the engine bay, and have myself an alternator delete on the beast. I'm going to be scouring the colored wiring diagrams from the CUCV forum to see what I could possibly eliminate, but I think I've got a good chance at this. The 24v alternator that I also ordered when I purchased my replacement 12v 27si is supposed to also meet the 27si standard, just in a 24v configuration. This would eliminate the need for the D/S alternator and belt, as well as some assumedly crusty wiring out of the engine bay.

Another option I was considering is a CAT 24v alternator that looks like it comes with isolated POS and GND posts, but that would require a bit more research. Part number will be added once I'm done poring over the starting circuit diagrams.

Figuring I could remove one excite wireset and charging wire set from the mix altogether and make the truck a bit simpler, electronically speaking. This would also mean re-engineering the voltage gauge (simple enough) and the Gen 1/2 lights on the dash.

My concerns are, if I am successful with this conversion to a single alt starting/charging system, would that reap any havok on the cab's 12v systems? Has anyone else tried this modification before? Any recommendations? Constructive feedback?

 

[Recovry4x4]

If you go that route, you will need to find something that steps the voltage back to 12V to run the rest of your truck. It's a hybrid 12/24V system. Except the starter and resistor that already steps glow plug voltage down, the rest of the truck is 12V. Toss 24V in there and plan on spending coin to fix it.

 

[Curtisje]

I've thought about that as well. With my current setup I could do it. There is probably some good info here if your interested.

24 volt conversion... sort of

I bypassed the glowplug resistors a while back because others had done it. I also have a volt meter on each battery so I can see how each is doing. I didn't like watching the front battery drop to 10V or lower during startup nor am I a fan of swapping the battery positions every few months. I...

www.steelsoldiers.com

Good luck.

 

[v12venator]

If you go that route, you will need to find something that steps the voltage back to 12V to run the rest of your truck. It's a hybrid 12/24V system. Except the starter and resistor that already steps glow plug voltage down, the rest of the truck is 12V. Toss 24V in there and plan on spending coin to fix it.

Interesting, I think I might be able to make something like that work. Just isolate the charging and starting circuit to the bus bars and one-wire it to a step down transformer. There's a couple 24v to 12 transformers on Amazon that say they're rated for up to 100A peak, so I could probably get something like that to run the small amount of electrical components in the cab with zero implementation issues. Manufacturer defects may pose some problems, though, but hopefully not.

I might have to invest in another CUCV to see if I can't engineer a new starting/charging circuit for it. Would be a pretty invasive surgery, though, but I think it would be worth it. Maybe after I do the engine overhaul and transmission and t-case swap on the 1031.

 

[Curtisje]

Interesting, I think I might be able to make something like that work. Just isolate the charging and starting circuit to the bus bars and one-wire it to a step down transformer. There's a couple 24v to 12 transformers on Amazon that say they're rated for up to 100A peak, so I could probably get something like that to run the small amount of electrical components in the cab with zero implementation issues. Manufacturer defects may pose some problems, though, but hopefully not.

I might have to invest in another CUCV to see if I can't engineer a new starting/charging circuit for it. Would be a pretty invasive surgery, though, but I think it would be worth it. Maybe after I do the engine overhaul and transmission and t-case swap on the 1031.

I think you need a 120 amp converter. The glowplug system starts pulling 126 amps on my truck but quickly drops to around 80. 126 amp pull on a 100 amp converter may be too much, even for a short period, but I don't know for sure.

 

[v12venator]

I think you need a 120 amp converter. The glowplug system starts pulling 126 amps on my truck but quickly drops to around 80. 126 amp pull on a 100 amp converter may be too much, even for a short period, but I don't know for sure.

I'd have to check and see if that is a 12v draw or 24v draw more in-depth. My surface look at the glow plug circuit diagram leads me to believe that it's 12v because it's "behind" the resistors on the circuit. In which case, I would probably get a second step down transformer dedicated to the glow plugs so it wouldn't interfere with the cab circuitry when starting. And I would probably pop a flip switch to open the cab circuit so it didn't draw too much power at once from the batteries.

 

[Recovry4x4]

The factory system works fairly well and there are many folks who can help troubleshoot it. What do you think you will gain with using a single 24V system?

 

[Curtisje]

I'd have to check and see if that is a 12v draw or 24v draw more in-depth. My surface look at the glow plug circuit diagram leads me to believe that it's 12v because it's "behind" the resistors on the circuit. In which case, I would probably get a second step down transformer dedicated to the glow plugs so it wouldn't interfere with the cab circuitry when starting. And I would probably pop a flip switch to open the cab circuit so it didn't draw too much power at once from the batteries.

Yes, that is 12 volt draw.

 

[Skinny]

Sounds like you are trying to create more work for yourself. Should have just fixed the alternator and keep it stock. Granted you had to fix the rotor, not sure how that even happens but you are talking $45 worth of rebuild parts and an afternoon.

Or

Just go 12v and be done. Either way going to a single 24v alternator and using a DC to DC converter to run the truck 12v system is making for a pretty bastardized setup and creating more expense for no reason.



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[v12venator]

The factory system works fairly well and there are many folks who can help troubleshoot it. What do you think you will gain with using a single 24V system?

Really just aiming for simplicity, isolating and clearing out wires out of the charging system and engine bay.

Now I'm wondering if I could use the existing resistors (so long as they're not shot) to run everything that's 12v in the truck and it would probably be easier on the batteries.

Sounds like you are trying to create more work for yourself. Should have just fixed the alternator and keep it stock. Granted you had to fix the rotor, not sure how that even happens but you are talking $45 worth of rebuild parts and an afternoon.

Or

Just go 12v and be done. Either way going to a single 24v alternator and using a DC to DC converter to run the truck 12v system is making for a pretty bastardized setup and creating more expense for no reason.

What if I'm doing this because I want to?

Also, the PO tried rebuilding this alt before I got it and went happy swinging with metal hammers because he didn't have a press or 3 jaw pulller. Turns out he chowdered up the threads real good on the rotor and pulley nut. Kids these days.

 

[Skinny]

Still not sure how they f'd the rotor up. You can rebuild the entire thing with a 10mm socket and a paper clip. Only the bearings require force but even then they are little.

I guess if you want to sure but you say you are doing this for simplicity but still need a DC to DC converter to run pretty much the entire truck minus the starter. Thanks doesn't make sense to me and isn't making things simple. You are actually making an entire truck contingent on a 12v converter. So you can advocate because you want to and don't let my opinion that doing that isnt a bright idea get in the way. To each there own but simplicity is not the outcome.

With the stock 12/24v system you can run the truck for a really long time if the 2nd alternator fails because it only runs the starter. Unless you still have the resistor in the GP system which you shouldn't.

In the event the 1st alternator fails you can literally swap the identical 2nd alternator road side to get home. Lot of redundancy built. Can't say the same for a 24v only system running a 12v truck.

Why even stay 24v? I'm not advocating converting a perfectly good running CUCV but if you are going through all this why even stay 24v? Do you plan on getting a jumpstart from another military truck anytime soon?

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[antennaclimber]

Constructive feedback:

I agree with Skinny, keep the electrical system stock or switch it to a documented 12 volt conversion.

 

[Curtisje]

Really just aiming for simplicity, isolating and clearing out wires out of the charging system and engine bay.

Now I'm wondering if I could use the existing resistors (so long as they're not shot) to run everything that's 12v in the truck and it would probably be easier on the batteries.



What if I'm doing this because I want to?

Also, the PO tried rebuilding this alt before I got it and went happy swinging with metal hammers because he didn't have a press or 3 jaw pulller. Turns out he chowdered up the threads real good on the rotor and pulley nut. Kids these days.

You cannot use the existing resistors to power the 12v side of the truck. Measure the voltage on output side of the resistor bank and you will find 24v. It only works in conjunction with the glowplug system.

 

[v12venator]

Still not sure how they f'd the rotor up. You can rebuild the entire thing with a 10mm socket and a paper clip. Only the bearings require force but even then they are little.

I guess if you want to sure but you say you are doing this for simplicity but still need a DC to DC converter to run pretty much the entire truck minus the starter. Thanks doesn't make sense to me and isn't making things simple. You are actually making an entire truck contingent on a 12v converter. So you can advocate because you want to and don't let my opinion that doing that isnt a bright idea get in the way. To each there own but simplicity is not the outcome.

With the stock 12/24v system you can run the truck for a really long time if the 2nd alternator fails because it only runs the starter. Unless you still have the resistor in the GP system which you shouldn't.

In the event the 1st alternator fails you can literally swap the identical 2nd alternator road side to get home. Lot of redundancy built. Can't say the same for a 24v only system running a 12v truck.

Why even stay 24v? I'm not advocating converting a perfectly good running CUCV but if you are going through all this why even stay 24v? Do you plan on getting a jumpstart from another military truck anytime soon?

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This was more of a personal electrical engineering challenge that I wanted to see if I could accomplish, stupid or not. Wanted to mirror it off of more over-the-road commercial electrical systems. A good DC to DC transformer doesn't cost an arm and a leg anymore, either.

I cooked up this thought experiment to try and see if I could improve the 24v system in the CUCV just based off of complaints often found here about the stock charging systems in the CUCVs. In all reality, I will probably never see this engineering project come to fruition unless I find another CUCV that I wouldn't mind attempting this one, but after the results, I would probably just go ahead and do a good 12v conversion to the truck like AnternnaClimber said.

Being right outside of an Army installation, chances are pretty good that if I were to have dead batteries on the side of the road, I could indeed get a jump from a humvee/fmtv running around in the training area, but I certainly wouldn't bet my life on it.

 

[Recovry4x4]

Well, there is one more alternative. My CUCV has been flawless for the last 12 years I've owned it. Rebuilt one alternator. With that said, I did have an M1010 with the wonky charging system. The guy I got it from swapped out both 24V Leece Neville alternators for 12V isolated ground ones and did away with the duvac. It was flawless and had a boatload of juice. You could also buy the alts most anywhere, especially all night Freightliner dealers. The system was flawless, so much to the point that I bought all the brackets and pulleys from another M1010 and plan on doing the same system for my SECM should I run out of alternator for that. I still run quite a few LED lights off the back battery as well, just need to ground them directly to the back battery.

 

[Skinny]

But what you are saying is I'm trying to engineer a 24v charging system on a truck that is literally 99% 12v by only having one 24v alternator. To me that isn't great engineering. I get why people keep the stock 24v system but the stock system is two 12v systems in series. A lot of redundancy built in.

The M1010 bracket setup is the best kept secret in CUCV trucks. Those alternators run $180 on Amazon and are 160 amps. Plus you have a compressor bracket for AC. It's literally the best of all world's.



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