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24v vs 12v systems

Austin

Austin

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The Unimog I bought were built 24v. Some do a 12v conversion ... of what I don't know yet.

One of the previous owners welded up the battery box and the only access is through the top ... which is now covered by the floorboard for the whole rig.

I stuck my phone up in there and got a few pics, I can see two batteries, but can't tell how they are wired.

They ran a cord out to two bolts to use as a jumper contacts. Those read 12v.

So .. how do I tell what voltage the system is running?

Any pros to 24 vs 12?
 
Volts x Amps = Watts. The higher the voltage, the less the amperage needed to create the same wattage. Higher amps requires thicker wire which costs more. Building a bugout rig?
 
The M1031 and M1028A2 CUCV'S I own are both a 12/24V system in that the only component on the trucks was the starters but they had two 12v batteries and two isolated ground alternators basically so they could interact with the 5 ton trucks that the military used.

You can wire batterys many different ways but the two most common are series and parallel.

Series gives 24v from two 12v batteries parallel gives twice amperage or current than that of one standard 12v battery.


https://www.google.com/search?clien...JgBAKABAcgBB8ABAQ&sclient=mobile-gws-wiz-serp
 
Can you look at your data plate on your alternator/s?
The 12 volt on your jumper lugs might be just hooked to one battery

A relay from the dash usually would have a voltage stamped on it too. If it’s a factory relay that should start us with a clue
Your headlights might have a voltage stenciled on them

Take a picture of your wires to the starter
 
NOODLES said:
Start truck. Check alternator output.
Click to expand...

NOODLES said:
Unless you have a half dead 24 volt system, you have a 12v system.
Click to expand...

Can't start it, converting to propane at the moment.

It's got a marine battery tender (built into the rig) and it's been plugged in for over a week. charging point still says 12v


Given this:
RV-battery-in-series-and-parallel.jpg


if the jumper cable wire is attached to only one battery in either situation, it would still read 12v or 24v right?
 
Austin said:
if the jumper cable wire is attached to only one battery in either situation, it would still read 12v or 24v right?
Click to expand...

12v is correct if you were to connect to only one battery in either config. My bus was set up similarly. Two batteries in series to make the 24v. A balancer between the two batteries to keep them charged the same. Charging just one battery in a 24v, series config will really only charge that one battery (at least they don't balance well). The pair of batteries on my bus had wires coming from between them to supply 12v to items that needed it. Discharging 12v off a series 24v bank also causing an imbalance. I don't know the rig at all, but I'm imagining you're measuring off the 12v between two batteries unless it's a 12v only system.
 
Austin said:
if the jumper cable wire is attached to only one battery in either situation, it would still read 12v or 24v right?
Click to expand...

It jumpers were hooked to only one battery 12 volt only.

A 12v battery has six 2 volt cells in series. =12 vdc
When you series two 12 volt batteries in series you have twelve 2 volt cells in series. =24 vdc
If you hook into that series circuit in the midway whatever cells your between is what voltage you get
 
IGT said:
12 volt would be coming off of one battery unless the batteries are in parallel.
Between then as in parallel?
Click to expand...

Between them in series, but yeah, coming off one battery. Felt like I wasn't typing that out correctly.
 
Third pic sure looks like you have a heavy red jumping from + on the batt in front to - on the batt in back. Then a heavy black off the + of the batt behind. Suggests series config for 24v. That's about all I can tell.
 
Can you get to the + post on the starter motor? Measure your voltage between there and any given ground point on your frame/chassis.

Going off one battery without knowing if they're in parallel or series is fairly useless info.
 
No way said:
Can you get to the + post on the starter motor? Measure your voltage between there and any given ground point on your frame/chassis.

Going off one battery without knowing if they're in parallel or series is fairly useless info.
Click to expand...

Doesn't it have to be running to do that? I have the fuel system ripped out right now
 
It's likely got constant positive at the starter so I'm thinking if it recently ran it probably will have at least close to normal voltage.
 
I don't understand why you haven't already cut open that battery box ? You're going to have to service/replace them at some point. what's you're plan, pull the body every time you have to clean the battery terminals ?
 
Stephen Wilson said:
I don't understand why you haven't already cut open that battery box ?
Click to expand...

No doubt it has to be done, It's not going to be a quick task. I'm working on other stuff on it and wanted to get some parts ordered and sitting here for when I'm done.
 
So back to the second question .... aside from cost, is there a reason to leave it 24v vs converting to 12V?

I'm thinking two batteries to reach 24v is silly when you could have 2 12v wired to last longer ......
 
Not unless you're gonna run a mill that needs more juice to crank.
More voltage is more betterer but.. less practical.

My bus is 24V but i run a 12v bank on board for general electricity needs.

There are more 12v parts and accessories available
 
Big displacement, military, and industrial engines are where the 24v systems originated.

I believe yours would have been in the military part.

Where you live? I’m sending a electrician over to figure this 12 or 24 out before you worry yourself to drinking.
:flipoff2:
 
could it be as simple as looking at a couple of light bulbs to see what voltage they are?
 
pjaf said:
could it be as simple as looking at a couple of light bulbs to see what voltage they are?
Click to expand...

ahh thats a good idea.

I pulled several of the radiator hoses last night and that allowed me to see a 24v stamp on the alternator ....
 
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