24v to 12v dilema

[85-m1028]

I have a 98 military hmmwv turbo 6.5 diesel drive train I want to put in a blazer project. I have everything radiator to t-case "including all the wiring and computer box"

this engine and components run with 24v and everything on the blazer is 12v

do I just need to hook it up 24v and then step it down to 12v?

any suggestions on how to best go about this??

 

[HeadWizard]

I've got NEW US made, high quality 24v to 12v inverters, 35 amp available. See the classifieds for details.

 

[Blythewoodjoe]

Put the stock HMMWV dual voltage alternator on and you'll have all the juice you would need. If I understand your post you are putting the HMMWV engine in a chevy? You wouldn't be changing anything on the engine that way. I put one on my deuce.

 

[85-m1028]

I want to run the engine 24v but everything else in the blazer is 12v. I just need a 12v inverter?

simple as that!!

 

[mangus580]

Like joe said... I would use a 12/24 alternator. They bolt right on the humvee engine. Matter of fact... If you are running the computerized engine, it may already have it!

 

[85-m1028]

how do I know if I have a dual voltage alt? and how exactly does that work? sounds like the way to go.

 

[mangus580]

it has a 'dual voltage' regulator. Do some seaching... me & joe both put them on our deuces, and Joe has a thread with pics.

 

[85-m1028]

with a dual voltage alt do I connect two batts in series and run them like the cucv set up essentialy having one alt doing charging duties instead of two??

heres what I'm looking at

 

[mangus580]

The dual voltage, you will need 3 batteries. 2 used for 24v, 1 used for 12v. Looks like you have a 24v alternator? What transmission is that, do you know?

 

[85-m1028]

3 batts!! hmmm!

It's whatever trans comes with the 98 hmmwv 6.5 turbo diesel.. I think it's a 4l80e or a 4l85e??

 

[mangus580]

I had been under the impression that the 4L80's used the dual voltage alt. I am by far not an expert.... so who knows.

 

[JasonS]

Do you really need three batteries? Can't you tie the 12V out from the alternator to the mid point of the existing two batteries in a 24V system?

 

[ida34]

You should not fun the 12 out from the alt back to one battery. The two batteries need to be balanced or the 24 volt side of the alt will fry them. When one batter is charge more than the other one the alt works hard to bring the weak battery back up. When it does so it over charges the other battery. I will be using a small motorcycle battery for my 12 volt side. It will be enough to handle all my 12 volt needs and small so I can hide it away somewhere.

 

[JasonS]

You should not fun the 12 out from the alt back to one battery. The two batteries need to be balanced or the 24 volt side of the alt will fry them. When one batter is charge more than the other one the alt works hard to bring the weak battery back up. When it does so it over charges the other battery. I will be using a small motorcycle battery for my 12 volt side. It will be enough to handle all my 12 volt needs and small so I can hide it away somewhere.

I don't see why it wouldn't work. I have done the same thing with series capacitors in power supplies (FWB doubler). Putting 14V on the first battery and 28V on the series combination should serve to better balance the batteries.

 

[ida34]

I am sure is you did some fancy electronic regulation it might work, but as I said, if the batteries get unbalanced then you are going to fry them both. Its your batteries and your truck so do as you wish.

 

[JasonS]

I am sure is you did some fancy electronic regulation it might work, but as I said, if the batteries get unbalanced then you are going to fry them both. Its your batteries and your truck so do as you wish.

Alright, ignoring for the moment whether or not this particular alternator is capable of the desired task... There will be no imbalance by supplying 14V to the center connection between two series batteries. The voltage there is already 14V (for good batteries).

Take it to an extreme: What if you could charge each cell independantly at 2.3V. No cell would get too much or too little charge/ voltage. Would you still argue that there is imbalance?

 

[rmgill]

So you're charging the first battery with 12 volts from one source point and the second one with 24 volts across both batteries right? How do you proportion the charging current. Because your 1st battery will have twice the current running across it no?

 

[JasonS]

So you're charging the first battery with 12 volts from one source point and the second one with 24 volts across both batteries right? How do you proportion the charging current. Because your 1st battery will have twice the current running across it no?

No, not necessarily. Lets say that you apply 14V to a point that is already 14V; nothing happens; no additional current will flow. I don't know how the current will share upon startup; probably depends on if one battery is weaker and discharges more than the other. Maybe someone knows more about how the alternator is developing dual voltages or how much it can source?