Question for the experienced - 24V alt. In CUCV

[PyroJoe]

I've searched and researched a lot the past week on the CUCV electrical system as well as those on multiple other vehicles. I really like having a 24v starter. I really like having an alternator that charges in 12V so I can run 12V accessories. My question is, are there any cons to replacing my GEN 2 isolated ground 12V alternator with a 24V alternator?

In the M35A2 deuce setup, if one sucks a bunch of juice out of the 1st battery for 12V, the first battery is undercharged while the second is overcharged. This is not good. So I wonder, can I charge battery 1 with the stock 12V alt, and use a 24V alt to charge both batteries? In my mind, the 12V alt would sufficiently charge battery 1, demanding less charging out of the 24V alternator, resulting in the 2nd battery not getting overcharged.

My plan: I'm swapping a 4BT into my M1031. I plan to install a 24V starter and 24V grid heater. The 2nd battery will power these 2 units, as well as the slave receptacle, as I have to jump various MV's quite often.

Why do I want to do it this way? I'm not sure I do. That's why I'm asking if anyone's tried it...

 

[rustystud]

If you get a 24 volt alternator then remove the 12 volt alternator and only use the 24 volt one. Then get a "Vanner" battery isolator/equalizer and run you 12 volt needs off that. That's what our busses do.

 

[NovacaineFix]

...

edit...I think I totally misread that, so I removed my reply.\

Carry on, nothing to see here.

https://www.youtube.com/watch?v=pdFl__NlOpA

 

[Recovry4x4]

In their stock form, the dual 12V isolated ground alts do exactly what you want. They keep both batteries charged with varying loads of 12V and 24V. If you only want to run one alt , do as Rustystud says and run the Vannar. Running 2 alts could be done with 2 iso ground 12V or a 12 and 24 iso ground units. Do some researching on the "plan b" mod used in the M1010. Good info there using Leece Neville alts.

 

[PyroJoe]

Awesome! Thanks for the Plan B and Leece and Vannar info! That's exactly what I was looking for. It would be nice to be able to carry this over to my 5 tons and deuces without having to remove the 24 alternators and slapping on 2 more. Ideally, I could leave the stock 24 and just add a 12v to them. The 24v and 12v combination wouldn't require any isolated grounding because they would share the same ground (first battery negative terminal). The other 'Pro' of the 12 + 24 setup over the 12 + 12 is that if your 12v alt. breaks on the road, you could theoretically drive indefinitely off the 24v alt., stopping and starting the engine included. In the 12 + 12 setup, if one alt. goes bad, you're no longer going to be able to start the engine once that battery depletes.

I'll read all 7 pages of the Plan B mod and get back to you with more thoughts.

 

[Recovry4x4]

If you were to run the CUCV on a straight 24V charging, you would eventually get a battery imbalance as one battery (front one) would have a constant drain vs the back battery. This would be similar to a center tap for power. With 2 12v alts even if one fails you could swap batteries back and forth to keep them both charged. Unique to ths ambulance, that Leece Nevills alt can be had at about any hour at about any Frieghtshaker dealership as they are very common on over the road trucks. My ambulancd has 2 12V Leece Nevillle alts and has charged dependably for years.

 

[PyroJoe]

That’s true, but that’s the reason for having the 12v alternator in the system, too. We’re only talking temporarily here as 1 alternator is dead in this example. As long as you refrain from using 12v accessories, you can run fine with just the 24v alternator. Driving without the radio on is a lot easier than having to swap batteries around. But with (2) 12v alt’s, you risk not being able to start the truck if your voltage goes too low in 1 battery – then you get to swap them around. This is what I experienced this week. And it sucks. If I had a 24v alternator, at least both batteries would still be getting charged.



On a side note, I just took my alternator to Autozone. Had them test it. I said 3 times in a row, “you need to put your ground on the ground stud, not the case”. They ignored me and put it on the casing and hurried up and ran it and then excitedly said, “you’re alternator’s shot, you need a new one!”

Frustrated, I stepped forward and hooked the ground cable up like I told them to and reran the test. Everything was good besides the voltage regulator. Just goes to show you can’t trust any of these kids nowadays. Even after telling them 3 times how to do it, they ignored me (or didn’t understand plain English) and did it their own way. Make sure you pay full attention if you’re getting an isolated-ground alternator tested.

I read through all of Plan B. Sounds like everyone is satisfied, and it is the exact same thing I’m suggesting here, so I think that’s the route I’m going to go. I’m going to look into the Vannar isolator/equalizer option a little deeper, but at least now I have a rough idea of how I can improve upon the M35A2/M939 trucks.

And for any 5-ton guys, it’s worth mentioning here that your heater fan has 2 speeds, controlled by supplying 12 or 24 V, so I guess after all this research, my advice would be to only run it in 24 V (HIGH) mode, as to not overtax your 1[SUP]st[/SUP] battery.

 

[Recovry4x4]

That’s true, but that’s the reason for having the 12v alternator in the system, too. We’re only talking temporarily here as 1 alternator is dead in this example. As long as you refrain from using 12v accessories, you can run fine with just the 24v alternator. Driving without the radio on is a lot easier than having to swap batteries around. But with (2) 12v alt’s, you risk not being able to start the truck if your voltage goes too low in 1 battery – then you get to swap them around. This is what I experienced this week. And it sucks. If I had a 24v alternator, at least both batteries would still be getting charged.




I read through all of Plan B. Sounds like everyone is satisfied, and it is the exact same thing I’m suggesting here, so I think that’s the route I’m going to go. I’m going to look into the Vannar isolator/equalizer option a little deeper, but at least now I have a rough idea of how I can improve upon the M35A2/M939 trucks.

And for any 5-ton guys, it’s worth mentioning here that your heater fan has 2 speeds, controlled by supplying 12 or 24 V, so I guess after all this research, my advice would be to only run it in 24 V (HIGH) mode, as to not overtax your 1[SUP]st[/SUP] battery.

Only problem with not using 12V is that is what the truck needs to run. Rather than invent another wheel, keep a spare alt on hand or keep a charged jump box onboard. What if your 24v fails?

 

[PyroJoe]

Like I mentioned above, the pro of the 12 + 24 is that if the 12 fails, you're still OK. Obviously if the 24V fails, you're in the same boat as either alternator failing in the 12 + 12 system.

Now that I've gotten a chance to read some more about Vanner's offerings, I am going to start price searching their equalizers. Sounds like you could run just the 24V alternator and get away with sucking 12V with your accessories. This would also be perfect for the deuce/5tons. I'm sure I'll be sticker-shocked on the prices, though.

 

[Recovry4x4]

Another notable mention about the CUCV factory system is both alts are the same. Keeping a spare alt and a rebuild kit or two sure makes things easy. I need to practice what I preach on this.

 

[rustystud]

If you were to run the CUCV on a straight 24V charging, you would eventually get a battery imbalance as one battery (front one) would have a constant drain vs the back battery. This would be similar to a center tap for power. With 2 12v alts even if one fails you could swap batteries back and forth to keep them both charged. Unique to ths ambulance, that Leece Nevills alt can be had at about any hour at about any Frieghtshaker dealership as they are very common on over the road trucks. My ambulancd has 2 12V Leece Nevillle alts and has charged dependably for years.

Actually running a "Vanner" equalizer you will not get a battery imbalance as it charges each battery individually giving each one just what it needs. Buses through-out the country use this system and it is very dependable.

 

[PyroJoe]

After price searching the Vanner equalizers... YIKES! They are not feasible new. But used on Ebay, very reasonable. I found some for $100-$200. Their product info is pretty vague, but it looks like you can get them where they just equalize, or they put out a lot of amps from the 12v battery, too, with the more amps being more expensive. Winches and off-road lights are the things that immediately come to my mind. Too bad the deuces/5tons didn't come with these things! In an application where real estate is limited on the motor to mount 2 alternators, this is probably the best solution. I think 2 volt meters should be incorporated, as well.

 

[NovacaineFix]

I was watching a lot of equipment on GL that included about 8 24/12V converters that were rated for 1K watt output, that would be nice for for those high amperage devices without the worry of causing the imbalance effect. No sure about running an electric winch from one, but several other devices it could work for.


Those equalizers are quite pricey, if you look at any local auto electric shops, they may have some "gently" used ones for a lot better price, or try a boneyard that specializes in large trucks and buses.

 

[rustystud]

Yes the Vanner is a bit expensive but it is the best on the market and is a very dependable and long lasting unit. Unlike cheaper models that don't have the quality of components the Vanner has. I have also seen some on eBay going for a very reasonable price. Just like "NovacaineFix" said, I would look at wrecking yards for a good used unit. They usually last the life of the bus. I have only replaced 2 units in 25 years and one was a factory recall.