24 volt to 12 volt

Going to need 12 volt in the 5 ton. Looked at a couple of different options. So I decided the least inexpensive and simple way to go for me is a DC to DC transformer. I will be using a continuous heavy duty solenoid to power the transformer and 2 separate fuse panels. One fuse panel will be 24 volt, and the other will be 12 volt. That way when I turn of the battery switch "off" on the dash it will power down anything wired to either fuse panel, so the batteries won't be drained.

Transformer, solenoid.





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Both auxiliary fuse panels came in the mail today!





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Getting things installed.





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All the wiring is hooked up, just need to clean up the wiring. Tapped into the battery switch to power the solenoid.

A little worried the solenoid is getting up to 165 degrees. All the terminals are cool, but the solenoid is very hot.

Also got the 12 volt cigarette lighter / power hooked up! Getting 12.5 volts!






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Well I just found this about solenoid temps:

Standard DECCO coils are rated class 105[SUP]o[/SUP]C, which means that they can safely reach and sustain temperatures up to 105[SUP]o[/SUP]C or (221[SUP]o[/SUP]F) -temperatures hotter than boiling water! Therefore, a solenoid too hot to touch may not be overheated.
[h=3]Solenoid Troubleshooting Directions - ROSS Decco[/h]

I just read this thread. Why did you go through all this expense, when you could have just ran a fuse panel off of one battery? With a disconnect, if you are prone to leave things running.

Running off of one battery is a good way to ruin both your batteries. So don't do it. there are many threads why this is a bad idea

Can you post where you got your parts and how much they costs?

Sephirothq said:

Can you post where you got your parts and how much they costs?

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Got everything off an auction site. The transformer was $82 with free shipping, the solenoid was $68 with free shipping, and both fuse blocks where $20 a piece for a total of $40 with free shipping. The cigarette lighter socket was $10 with free shipping. So grand total is $200.

If you add the cost of wires, connectors, a 50 amp maxi fuse coming of battery. Then it would probably add about another $200 dollars. I bought rolls of wire and large boxes of different type of connectors, so I probably spent a little more than I needed to but I wanted to make sure I had enough wire, etc.

jimbo66348 said:

I just read this thread. Why did you go through all this expense, when you could have just ran a fuse panel off of one battery? With a disconnect, if you are prone to leave things running.

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Without an alternator charging the 12 volt side, it will slowly drain that battery causing it to fail or short out. Spent a lot of money on some really nice batteries in the spring, not going to do something that would fry it. There are 12 volt alternator kits or dual charging 12/24 volt alternators for the NHC 250, but they are expensive, $1500. If I went that route I would still need both fuse panels, plus wiring, so I saved a lot of money going the route I did. Probably will switch to a dual alternator later on, but for now this will get me by.

Sephirothq said:

Running off of one battery is a good way to ruin both your batteries. So don't do it. there are many threads why this is a bad idea

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This is nonsense. Running 12 volts off of one battery will just put a bit of a drain on one, but they are in series and the other battery will aid in back up and their charge will balance out. Many 24 volt trucks also have split systems, with both 12 and 24, with the 12 coming from one battery.

jimbo66348 said:

This is nonsense. Running 12 volts off of one battery will just put a bit of a drain on one, but they are in series and the other battery will aid in back up and their charge will balance out. Many 24 volt trucks also have split systems, with both 12 and 24, with the 12 coming from one battery.

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Yes, cucv and some humvee have split systems. But they also have two alternator's, or a dual voltage alternator to charge both the 12 volt and 24 volt at the same time. I am pretty sure the engineers would not have used two alternator's if pulling off the 12 volt side could be charged with just a 24 volt alternator.

It's your truck do what you want. But I'm not going to take a chance and fry a battery. I bought 4D's in the spring and they weren't cheap.

So it cost me $200 to add the transformer, solenoid, etc. Lot cheaper than having to replace a battery every couple of months because it was drained or shorted out.

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jimbo66348 said:

This is nonsense. Running 12 volts off of one battery will just put a bit of a drain on one, but they are in series and the other battery will aid in back up and their charge will balance out....

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Nope. The battery you tap will become undercharged. The other battery will become overcharged.

https://www.waytekwire.com/datasheet/extend battery life.pdf

jimbo66348 said:

This is nonsense. Running 12 volts off of one battery will just put a bit of a drain on one, but they are in series and the other battery will aid in back up and their charge will balance out. Many 24 volt trucks also have split systems, with both 12 and 24, with the 12 coming from one battery.

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It is called the evil wire. You can get away with running a phone charger for up to 3 to 5amp but after a year or so the battery will have a bad cell early in life. Even on big 8D's i have had good luck with just small stuff like phone chargers but when I tried running my fuel gauge, oil temp gauge and cig lighter thru it it died a week after its 1 yr warranty expired. The other battery went about a month later.

Hey Iceman,

How many watts do plan on running off that converter? I’ve been curious on how those cheap ones hold up myself.

Also, you might as well pull the low speed fan wire off the one battery and connect it to your 12v as well, I never run mine on low just for the battery balance reason...

It's rated for 1200 watts, 1600 surge, and 100 amps. But I don't plan on pulling that much power through it at one time. It had great reviews online verses the other models with less watts and amps.

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You are drawing off of one. The other will back charge it to keep them balanced out. The alternator charged both batteries at the same time. Heck, the lmtv has both 12 and 24 volt systems. You can do whatever you want, but your assumptions are incorrect.

jimbo66348 said:

You are drawing off of one. The other will back charge it to keep them balanced out. The alternator charged both batteries at the same time. Heck, the lmtv has both 12 and 24 volt systems. You can do whatever you want, but your assumptions are incorrect.

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Your argument is invalid in my thread. Why, because it's my truck and I did what I wanted. You do what ever you want to your truck.

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jimbo66348 said:

You are drawing off of one. The other will back charge it to keep them balanced out. The alternator charged both batteries at the same time. Heck, the lmtv has both 12 and 24 volt systems. You can do whatever you want, but your assumptions are incorrect.

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You apparently don't have a clue sir. I can tell you flat out if you hook up a 12v item with a decent draw i guarantee you that you truck will run all day long but when you turn it off it will NOT start back up. One battery will be dead. You understand that LMTVs have dual voltage alternators right? They charge 14/28. Just like what comes on the M915 series trucks. Charges 24v for starting to adhere to military standard and 12v for everything else.

You do understand that 24v amps are half of 12v amps right?