pulling 12v without a batt imbalance

[wilsonmotors]

ok here is my problem i need 12v from my 09 for off road lights and a headlight relay upgrade and a stereo with some high power amps. i might need to pull other stuff off of this later to but, i am really not shure of all the amps or load i am pulling if the 12v lug on the fire wall will handle it or not. i did have my stereo hooked to the first batt for awhile and caused a batt imbalance and fryed a batt and a alt i really dont want to go through this again i want to pull 12v some how and not cause a imbalance but i am unshure of the amps i need to run my hid off road lights with relays, radio, and my hid headlights with the relay upgrade, and what ever else i put on it i just dont wanna tax the stock system to much does anyone have any ideas how to get a good 12v source to run all these things and not cause a imbalance in my batteries?

 

[Moto4Life]

HIDs don't draw that much current, maybe 3-5amps per light. You can use a step down transformer to take your 24 volts and convert it to 12 volts (much like they do on golf carts when they put lights/stereos on them). Another, probably better, option would be to run a standalone 12v system and keep everything separate. I'm sure someone with more knowledge on this can chime in! Also, since someones bound to say it, try searching for this topic, it's most likely covered on SS somewhere.

 

[cpf240]

You could run power directly from the rear battery terminals, but you would have to run *both* hot and ground to the battery, and make sure that the items being powered by it are isolated from the chassis ground. There was a post a while ago from a member who did this, I think for his CB setup.

 

[JH1]

There are some 24v to 12v downconverters available. Check www.MPJA.com for some. They will not create any imbalance. Jim

 

[doghead]

You need to determine what your additional loads are before you can improve your power supply.

 

[swbradley1]

HIDs don't draw that much current, maybe 3-5amps per light. You can use a step down transformer to take your 24 volts and convert it to 12 volts (much like they do on golf carts when they put lights/stereos on them).

A transformer only works on AC. A converter works on DC and converts DC to DC. An inverter works on DC and converts DC to AC. A power supply works on AC and converts it to DC.

 

[MarcusOReallyus]

A transformer only works on AC. A converter works on DC and converts DC to DC. An inverter works on DC and converts DC to AC. A power supply works on AC and converts it to DC.

Bingo.


Just because some ignorant eBay seller calls something a transformer doesn't make it a transformer. If it's DC it's NOT a transformer.


That's like calling a transmission a differential.

 

[MarcusOReallyus]

You need to determine what your additional loads are before you can improve your power supply.

Exactly.

Wilsonmotors, it's not difficult to get the info about loads. Without that, you are shooting in the dark. Any solution you implement will be a roll of the dice.

The info should be available from the manufacturer.

 

[sandcobra164]

The Cucv escapes normal thinking in the realm of adding 12V DC electronics to a 24V system and keeping batteries topped off and balanced. Most of us think of a Deuce or 5 ton where the Alt or Gen send 24V power to one battery wired in series to the "trailing" battery. I agree with what was posted earlier, do just as GM did, install an ungrounded terminal block connected to the rear batteries negative post and run the accessories from the rear batteries positive post. The front battery supplies positive power to your mostly 12V truck and the factory run 12V components and it's alternator keep it charged. You're rear battery is serviced by an ungrounded 12V alternator, provides the power to you're accessories if you add some, and it's dedicated alternator keeps it charged. Now keep in mind, said accessories will be toast if the insulating shims in the passenger side alternator fail. You could pull straight from the fuse panel if you feel your electrical needs will be under the amperage draw and the driver's side alt could keep up. If you wire it this way, keep your eyes peeled for a constant Gen 1 light, that indicates you've overdrawn that circuit and need to re-wire as I've described.

 

[41cl8m5]

Why not change the alt with one that has a higher apm rating? The alt that charges the front battery is a 100amp 12v from factory. Both alternators are ground isolated from the factory but you could get a new one that is not ground isolated and use it for the front battery charging only. Others have done this to save $ on getting a replacement when one fails.

 

[sandcobra164]

Driver's side alt is not "ungrounded". Take a test meter and put the negative lead on it and the positive lead on the back battery positive post. You'll wind up with much more than 12V. The passenger side on is the insulated one if I don't have it backwards.

 

[cpf240]

Driver's side alt is not "ungrounded". Take a test meter and put the negative lead on it and the positive lead on the back battery positive post. You'll wind up with much more than 12V. The passenger side on is the insulated one if I don't have it backwards.

Perhaps it could have been worded differently. In stock configuration, both alternators are isolated ground units, meaning that the case is not connected to the ground terminal on the back of the alternator. They have one NSN / part number, easier to stock one part instead of two different parts. The driver's side alt, GEN 1, does have its ground lug connected to a ground strap running to the engine though.

 

[sandcobra164]

Perhaps it could have been worded differently. In stock configuration, both alternators are isolated ground units, meaning that the case is not connected to the ground terminal on the back of the alternator. They have one NSN / part number, easier to stock one part instead of two different parts. The driver's side alt, GEN 1, does have its ground lug connected to a ground strap running to the engine though.

I'm so glad I read your post twice before breaking out my Fluke, Flashlight and Camera to prove you wrong and make a fool of myself in the process!!! I know I've used the driver's side alternator case as a ground in the past when testing the glowplugs. Great information and you're absolutely correct, I could have worded it differently.

 

[cpf240]

... I know I've used the driver's side alternator case as a ground in the past when testing the glowplugs.

In that sense, yes, the *housing* of the alternators *are* the same as the chassis ground, since they are bolted to the engine, etc. The only difference being that these alts have their internals isolated from their housings. Thus no continuity between the alternators housing and its ground lug, which is made a moot point in the case of GEN 1, as the ground lug is connected to the engine block.

 

[allenhillview]

So now? To whom may I ask this question? can I just connect my 12v stereo amp to 12v on rear battery as long as I know the risk of the said mentioned isolating shims in the pass. alt.? I don't need terminal block if Its one single connection do I? Making sure to ask first this is new amp 300.00 JL

 

[doghead]

Use the front battery for 12v loads.

 

[allenhillview]

So flat out don't use rear For Any!!! 12v because of possible unforeseen breakdown in alternator, don't be dependent on something that can fail and cause further and more severe damage, Is that it Doghead?, Thanks and I just want to understand more as I travel down this road of CUCV

 

[MarcusOReallyus]

The rear battery positive terminal is 24v with respect to the vehicle's ground. If you hook up a 12v device to that battery, you must carefully isolate it completely from every part of the truck that is grounded. That's very hard to do. You must also run its ground wire to the negative terminal of the rear battery, which is connected to the positive terminal of the front battery. The ground (chassis) of your 12v device will be at +12v. If it touches any part of the vehicle that is grounded, you'll have melting wires and possibly a fire.

If you REALLY know what you're doing with electricity, you can get away with it, but it's really not worth the risk.

So, don't do it, NOT because it's not reliable, NOT because it might cause a problem for your alternator, but because it's dangerous.

 

[allenhillview]

So now I'm confused bad, there is 12 v on rear battery right?, power goes to 12v block on fire wall, can I use it? just at the battery post as a connection point?

 

[richingalveston]

the 12 volts on the rear battery is at the negative terminal. when you put 12 volts into the negative terminal you get 24 from the possative terminal.
the wire to the 12 volt terminal block does come from the back battery but it comes from the 12 volt negative post which is no longer a negative post it is actually a 12volt possitive post since the batteries are wired in serries. Dont think of a battery as a possative and negative. think of it as an input and an output and it will make more sense.
The front battery has 0 volts input (wired to the chassis ground) and thus it has 12 volts at its output terminal which then goes to the second batteries input. The second battery adds another 12 volts and has 24 volts at its output. If you added a third battery in the serries you would end up with 36 volts output. You can run power through the batteries backwards and get a negative 12 volts and negative 24volts at the output terminals instead of possative voltage. Telecom systems use negative voltage. In a negative volt system, the possative terminal is the one strapped to ground.
It also helps not to think of negative being ground, it is actuall the return. In a DC system you have a supply and a return and input and output terminals. The polarity of the terminal can be irrelevant.