24 Volt battery????????

[joediveguy]

Okay, calling all Engineers………….
Here is the scenario, I have a buddy that is a pilot and has access to an infinite supply of 24 Volt small airplane batteries. Here is the question…..Seeing how about the only thing on the CUCV that uses the 24V power is the starter, would it be possible to replace one of the 12V’s with the 24V battery? I imagine you would have to do some rewiring to isolate the 12V and the 24V systems, but would it A, be possible, and B, be worth it.
In the above scenario, let’s assume that I have done the GP resistor bypass/removal and the Doghead starter relay mod.

Let the games begin………

 

[Darwin T]

First, you would also have to change the atenantor that charges the 24 volt battery, because the altenator that is there is a 12 volt.

 

[Darwin T]

this might be nice in the bigger trucks (my deuces) hooked together to keep it 24 volt.

 

[papercu]

You need to get a second job then maybe you'll to tired to think things up like this. Wayne

 

[appalacious]

you would need a voltage regulator for the fuel solenoid (12V) the glow plug module, and the starter relay input.
The alternators are both 12V, but they're in series, so you should get 24V out of them.
the headlights would probably be much more susceptible to RPM fluctuation since they'd only be running off the (first) alternator- unless you had some kind of voltage regulator on them too.

also since you've removed your GP resistor you'd have to use 24V GPs (do those exist?) or put the resistor back in.

 

[BIG_RED]

That would work, but it could be hard on the second alternators voltage regulator (and potentially the 24 volt battery) because the second alternator wouldn't have a battery to itself. Alternators are designed to have at least one battery connected to their outputs to help handle surges and regulate output. With your proposed set-up, your secondary alternator would effectively have half a battery.. I wouldn't recommend it.

If you left both 12 volt batteries in the truck (or installed smaller ones), you could add the 24 volt in parallel to the 12 volts (that are in series) and it would charge-up/help with starting. IMHO the split 12/24 volt system doesn't really lend itself to powering 24 volt things without using 2 12 volt batteries (one on each alternator) to sort-of load balance and surge-assist the two alternators.

 

[319]

Possible, yes. Practical, no!
What happens when the infinate supply of 24 volt batteries run out? Walmart doesn't stock them.

 

[Chief_919]

You would have to have a 24v alternator to charge it. The two 12v's only work because they charge separate batteries, won't work with a single 24v battery.


But a small 24v battery won't have the amperage to turn the 6.2 over with one small battery. you would need a 24v battery that could produce the CCA that the two 12v batteries in series do,

So all in all- not worth it.

Now if you want a use for the small 24v batteries, genset owners would love them for the MEP-701 and similar.

 

[joediveguy]

Please do not take my humor/sarcasm for disrespect. I value each and every comment and am just trying to interject a little humor to keep the thoughts coming.


I’m no electrical engineer but I would think that simply adding a 24V alternator to charge the 24V battery and leaving the 12V alternator to charge the 12V battery would suffice. Then somehow isolating the 24V circuit to only operate the starter, and or the starter relay. Isn’t everything else 12V?

“But a small 24v battery won't have the amperage to turn the 6.2 over with one small battery. you would need a 24v battery that could produce the CCA that the two 12v batteries in series do”
Don’t confuse “small airplane batteries” with “small batteries”. These are “big” 24V batteries used on “small” planes, like Lear jets and such.

“Now if you want a use for the small 24v batteries, genset owners would love them for the MEP-701 and similar.” Not sure what the CCa’s are but I will check with my friend later on that. Also, is the genset guy’s need 24V batteries, I might be able to hook them up……


“also since you've removed your GP resistor you'd have to use 24V GPs (do those exist?) or put the resistor back in.” Not sure what you mean, the GP’s are 12V supplied by 12V.
“you could add the 24 volt in parallel to the 12 volts (that are in series) and it would charge-up/help with starting.” I’m not interested in adding more batteries, I just want to save $$ by not having to buy 2 batteries at $100+ a pop.
“What happens when the infinite supply of 24 volt batteries run out?” infinite = endless supply. IThat being said, if the supply dries up, I could always just switch back….

 

[319]

Why go through the trouble. Regardless of the source of 24 volt batteries, if maintained, these trucks work fine the way they are designed. Perfect, no, buy why mix it up?
No offense or disrespect, but having a buddy that is a pilot with access does not equate to infinate supply.

 

[joediveguy]

Okay look, we can play the “why” game all night. That is not the goal of this exercise. We never would have made it to the moon if JFK listened to all the naysayers asking “why”. No, he said, here is what I want, get it done! No offense taken but I’m looking for answers, not people asking me why or saying it can’t be done with no explanation as to why. I’m not saying I am going to do it, I just want to know if it can be done and if so, how.
Think of it as a challenge, if you were going to do this, how would you proceed?

 

[vtdeucedriver]

As a aircraft mechanic............................All of it!!!

 

[vtdeucedriver]

Gill Products

Concorde Battery - Aircraft Batteries

For those who are considering this, I will let the MV engineers sort it all out.

 

[Keith_J]

How does the NATO slave receptacle work? Yes, all but the 1010 have two 12 volt alternators, one for each battery BUT they are also connected in series so they "act" as a single 24 volt alternator.

It still would require two 12 volt batteries.

 

[mistaken1]

These trucks are COTS vehicles. Everything is 12V except the starting system.

You have changed the glow plug part of the charging system to 12V.

You would have to replace the passenger 12V alternator with a 24V alternator. It would ground to the engine block just like the drivers side does. You would have to dig through the wiring diagrams and cap off all of the 12V feeds to the original negative side of the original alternator.

You would have to replace the rear battery with your 24V battery. The negative side would connect to the negative bus and the frame just like the front battery does. The positive side would connect to 24V bus.

At that point the only thing connected to the 24V bus should be the 24V gauge, the starter and the slave receptacle (and maybe a radio bus). If you tried to slave start you would have 24V for the starter but the isolated 12V battery will not get any real boost. You could bypass the resistor and feed the glow plug 24V and use the 24V HMMWV glow plugs. Now as long as your 12V battery had enough juice to pull in a few relays you should be able to slave start.

Am I missing something? It seems simple to me.

The hardest part is making the 24V battery fit and the 24V alternator. Would a HMMWV alternator fit in the same spot as passenger alternator? Belt issues?

 

[joediveguy]

Good stuff Mistaken1! That is about what I was thinking, seems simple in theory. A few questions for the MV challenged:
1. What does COTS stand for?
2. Is the HMMVW a pure 24V system? 2 X 12V’s like the CUCV or 1 X 24V battery?
3. Why would a 12V alt not charge the 24V battery? The alt is pushing current into the battery to charge, right? Will a 24V alt push more current, or are the two just plain not compatible?


I like your signature, Monty Python and the Holy Grail is one of my favorite’s!

 

[mistaken1]

COTS = Common Off The Shelf (meaning not custom designed like a HMMVW). They are just plain jane gm trucks with a modified starting system.

My understanding is that the HMMVW is all 24V.

Because voltage is EMF (Elctro Motive Force). It is what pushes electrons through things creating current flow. A 12V alternator does not have enough EMF to overcome the 24V battery's internal resistance to cause current flow. That is why 12V alternators produce 14.x volts so they can overcome the 12V (13.2V) battery's internal resistance and push electrons onto the negative plates.

How much current an alternator can push is a function of the design of the alternator (winding size, winding turns, magnetic field, etc). The more current it produces the larger the load applied to the prime mover.

The CUCV system is two 12V systems in series. One battery/alternator combination floats 12V above the other battery/alternator combination. The negative of the front battery is the chassis ground. The positive of the front battery is 12V above chassis ground and powers most of the truck. The negative of the back battery is the front battery's positive. The front battery positive and the back battery negative are electrically the same point. The positive of the back battery is just 12V above the positive of the front battery but is also 24V above the front battery negative (which is the chassis ground). The two batteries together power the glow plugs and the starter.

A negative charge is an excess of electrons. A positive charge is an absence of electrons. Only valence electrons are involved in current flow. Conductors have only a few, easily dislodged electrons in their valence shell. Insulators have full or nearly full valence shells (making their valence electrons hard to dislodge).

 

[73m819]

could you run big 24v batteries hooked up parallel in our 24v systems, in stead of 2/4 12vs

 

[eagle4g63]

Just use a SI style alternator in 24 volt, just like us deuce guys switch to instead of the military alternator. Looks just like a GM alternator just a little bigger and 24 volt.

Then like stated above one alt-24v the other alt-12v, split voltage 2 batteries and put the jumper(slave recept) on the 24 side only that is the side you need to start with anyway no need on the 12 volt side to start it. That is the same concept on a duel voltage deuce why not a cucv?

To me it sounds like a logical thing to do anyway instead of all the hassle with the 2 alternators the way they are that seem to give a few cucv owners troubles!!

 

[papercu]

"That is not the goal of this exercise. We never would have made it to the moon if JFK listened to all the naysayers asking “why”."
No, the goal as you stated was to save you about 100.00 every three years or so.
Just skip one coffee (@1.00 per) a week for those 3 years and you have enough for one 12v battery and more than half for the second.
No fuss, no mess.
O, you could also just recyle the endless supply of 24v and just have free batteries for your truck. Wayne