I would very much prefer 12V to the 24V, Can it be switched?

[freecr]

The lights are already 12V. The alternator already puts out 14v and 28v. Fooling the exiter relay just to engage the alternator may be a thing. Caterpiller engines are not exactly uncommon so finding a 12v starter that'll fit shouldn't be that hard. The real question is the electric transmission. Has anybody already looked into this? Does anybody know if the transmission is 12 or 24v? If its 24v can it be converted easily? The idea would be two 12v batteries in parallel. I have a M1079 that I will be turning into an RV and probably only need to use in the summer. While I'm at it, are there any freeze plugs on this engine that can be knocked out and a heater installed into JIC?

 

[Suprman]

If you have a heavy duty 24 volt system you can use a surepower 12-24 volt step up converter it can supply 24 volts at 40 amps off a 12 volt supply. I would think it draws 50 or so amps a full load to provide the 40 amps as long as your system can handle that you should be fine.

 

[freecr]

Thanks suprman, I'll definitely look into it. Seems like a good "end around" if needed. Hopefully the transmission is 12v.

 

[ke5eua]

If you have a heavy duty 24 volt system you can use a surepower 12-24 volt step up converter it can supply 24 volts at 40 amps off a 12 volt supply. I would think it draws 50 or so amps a full load to provide the 40 amps as long as your system can handle that you should be fine.

To provide a full 40 amps at 24 volts from 12 volts will require a minimum 80 amps 12v. No way to cheat the math.

 

[Suprman]

Yup you are right I was only thinking of the units overhead power use.

 

[ke5eua]

Yeah at an idle state it will have little power required.

Just like with inverters. That 2000 watt inverter will require a minimum of 200 amps on 12v.

Personally I'd stick with what is good. Granted I'm changing my 818 over to 12v but it's a mechanical engine so just swap a alternator and starter and a few bulbs.

I wish you the best in your conversion. Look in the -20 at the schematic to see what is 24v.

 

[Keith_J]

If you still have two batteries, conversion is nil savings. Even if you want to run 12 volt items, keep it dual. For high power items like inverters, 24 V rules. Remember, twice the voltage means half the current which is half the copper.

 

[freecr]

Keith_J,

I would keep the driving/starting batteries separate from the living space. Maintaining four batteries for starting/driving in my opinion is wasteful and unnecessarily complicated and expensive. If one battery develops a problem it can degrade the other three. If everything is 12v its just easier to deal with. One kind of spare relays, breakdown and more likely the local part store has what you need instead of having to order it. Two batteries are way cheaper than four. I can buy a lot of copper for the price of two batteries. One half the space, one half the weight. Except for the cost and work involved, which may very well preclude it, I can't come up with a reason not to ponder this conversion. This thread is all about seeing if its worth it. A new starter may be the vast majority of the expense. I know the saying...If it aint broke, don't fix it. But.....

ke5eua,

I'd prefer not using an end around if at all possible, but its good to identify if needed. I think Suprman was stating the unit could handle up to 40amps. The amperage needed to power the relay and to run the exciter probably isn't very high. I'm just guessing though. The amperage for the transmission I have no idea about but again I'll guess that its not overly high. I'll probably have to check the manuals to see, maybe even pull out the multi-meter and check the old fashioned way. I was being lazy and just hoped someone would just know. I was thinking others would have already pondered or done this conversion and thus did my homework for me, and would provide me with detailed step by step instructions complete with schematics and/or pictures. Possibly bring me beer and wipe my brow while I did the conversion.

I'm not holding my breath but...

Rochester MN
pretty much any kind of domestic beer as long as its cold.

 

[ke5eua]

I was just correcting the math. If something requires let's say 10 amps on 24 volts and you decided to power it using a step up converter off of 12v the total load on the 12v side will be 20 amps. Just the opposite if you used a step down converter to run something on 12 v from 24 v, the load on the 24v side would be half.

As far as saying the unit could handle 40 amps that means you would have to factor in 80 amps being used to generate that 40 amps.

Look at your circuit breakers to see the max amp load, look at the schematics to see what is on 12v and 24v. Personally with the design of the charging system the truck has already leaving it at 24v would be perfectly fine. Make a bank for your house batteries and tie in an isolator or a 100 amp continuous duty solendiod that ties in the house to truck batteries when the truck is running.

In a 12v setup if one battery goes bad in your bank it will take the rest with it. If your concern is 4 batteries vs 2 then take 2 out. The truck will run on 2 batteries in a 24v configuration.

Another option is get with the manufacturer and see if you can get the schematic for the civilian version of the truck they did.

When you look at the schematics for your truck you will he amazed of what all your s actually 12v and what is 24v. The trucks were designed to use the cots system. Only reason you have a 24v starting system is because that is a NATO standard.

Look in your battery box, three main wires, 12v blue, 24v red, and ground black. Just like on the cucv, 24v controls starting, everything else is 12v. That is also why you have a dual 24/12 volt alternator. Having the dual voltage alternator helps prevent the 12v from becoming unbalanced to the 24v side.

Your truck, do as you wish. I think your over thinking it though as the system was planed and tested and proven as it's still used on today's vehicles. Also look at motorhomes, the house and start batteries are separate, not a good idea to mix the two as you can find yourself needing a jump if not careful.

One last tidbit. If you do change from 24 to 12 volt and change the starter over you will have to run a heavier guage main battery cable to the starter as it is now requiring double the amperage it needed before. Depending on what size alternator you change to you may need to change that cable to.