12v outlet

Glider

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I post this for my new friend Camo!

I added 12v outlets to my m998 the pictures are in the "What have you done today" thread.

My question comes from which battery to pull from. I pulled 12v from forward battery, ran positive and negative wires to 12v outlets and fused the positive at battery. I used forward battery as that is where the alternator would send charge first and I figured the batteries would stay better balanced. People smarter than me tell me that it is potentially dangerous and I should at least pull from rear battery. That way 24v could not be introduced to the 12v outlets from a chassis ground. I understand the concept and concern. However this setup will lend itself to the rear battery not being balanced. My question is would the fused positive not blow before real damage could occur? Also would a fuse on ground provide any added safety?

Someone mentioned one of those fancy 24 to 12v converter things. I have one and don't really feel like messing with it. I'm only charging cell phones with the outlets.

Either way I have no problem changing the wiring to rear battery. I'm just looking to enjoy some good SS conversation.

Now let the beatings begin!
 

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It is advised to use the rear battery because it is 12V where the front battery since it is connected to the rear is 24V. The alternator is feeding 24V to both batteries. If you have the 200 AMP or 400 AMP alternator there is a balancing cable the balances the rear battery with 12V. The 4 speed transmissions use the rear battery at 12 V to power the transmission controller because there is the balancing cable to make sure there is not an imbalance. If you pull from the front battery there is nothing to prevent the imbalance.
 

Coug

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It is advised to use the rear battery because it is 12V where the front battery since it is connected to the rear is 24V. The alternator is feeding 24V to both batteries. If you have the 200 AMP or 400 AMP alternator there is a balancing cable the balances the rear battery with 12V. The 4 speed transmissions use the rear battery at 12 V to power the transmission controller because there is the balancing cable to make sure there is not an imbalance. If you pull from the front battery there is nothing to prevent the imbalance.
If it is the 60 amp system, there is nothing on the rear to prevent imbalance either.
I think what is being said here is with the 60 amp setup, due to resistances of series loads and whatnot, the front battery always ends up with higher charge than the rear over time, so would placing a very small load on the front battery, as opposed to the rear, cause any issues.
 

Coug

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placing that small of a load on either battery shouldn't be much of an issue in the short term. In the long term it can contribute to imbalance issues, but if you either swap your batteries front/rear every month or so, or put a 12V charger on each of them just as often to do an equalizing charge, then that minimal of a draw shouldn't be an issue.

Only caveat to this is make sure the USB adapter gets removed from the socket (if that is how you are doing it) if the truck is going to sit for any length of time. Even without anything plugged in, some of those USB adapters will still have a minimal amount of power being drawn from them. It doesn't matter in a car, because most modern automobiles have the 12V outlets on relays that only activate with the ignition switch turned on.
 

Glider

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It is advised to use the rear battery because it is 12V where the front battery since it is connected to the rear is 24V. The alternator is feeding 24V to both batteries. If you have the 200 AMP or 400 AMP alternator there is a balancing cable the balances the rear battery with 12V. The 4 speed transmissions use the rear battery at 12 V to power the transmission controller because there is the balancing cable to make sure there is not an imbalance. If you pull from the front battery there is nothing to prevent the imbalance.
That is good info. I have the 60amp alternator.
 

simp5782

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It will give you a bad cell over the course of a year or so drawing off the one. Just get a small step down or a equalizer.

Always pull off the positive post on the negative battery for 12v
 

Milcommoguy

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I post this for my new friend Camo!

I added 12v outlets to my m998 the pictures are in the "What have you done today" thread.

My question comes from which battery to pull from. I pulled 12v from forward battery, ran positive and negative wires to 12v outlets and fused the positive at battery. I used forward battery as that is where the alternator would send charge first and I figured the batteries would stay better balanced. People smarter than me tell me that it is potentially dangerous and I should at least pull from rear battery. That way 24v could not be introduced to the 12v outlets from a chassis ground. I understand the concept and concern. However this setup will lend itself to the rear battery not being balanced. My question is would the fused positive not blow before real damage could occur? Also would a fuse on ground provide any added safety?

Someone mentioned one of those fancy 24 to 12v converter things. I have one and don't really feel like messing with it. I'm only charging cell phones with the outlets.

Either way I have no problem changing the wiring to rear battery. I'm just looking to enjoy some good SS conversation.

Now let the beatings begin!
WOOHOO... Friend OK. BUT Not advisable to make this connection (per conversions) to pull 12 Volts out of the battery bank this way. Puts the +12 volts referenced to ground on the negative of your plugs. Reference ground to ground and play it safe. Should the product you have be plugged in...Say CB or stereo set up ??? making contact with any metal parts of said accessory is going to be the Forth of July shit show of sparks.

Friend, then fire extinguisher, then fried and a sad face. Still pals, CAMO (y)

Let's look at the drawing.
 
Last edited:

Glider

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placing that small of a load on either battery shouldn't be much of an issue in the short term. In the long term it can contribute to imbalance issues, but if you either swap your batteries front/rear every month or so, or put a 12V charger on each of them just as often to do an equalizing charge, then that minimal of a draw shouldn't be an issue.

Only caveat to this is make sure the USB adapter gets removed from the socket (if that is how you are doing it) if the truck is going to sit for any length of time. Even without anything plugged in, some of those USB adapters will still have a minimal amount of power being drawn from them. It doesn't matter in a car, because most modern automobiles have the 12V outlets on relays that only activate with the ignition switch turned on.
So far I have been diligent to remove the usb chargers from sockets. I bought a 24v relay but didn't install it. Does anyone have any input concerning the fuse on negative side? I guess
WOOHOO... Friend OK. BUT Not advisable to make this connection (per conversions) to pull 12 Volts out of the battery bank this way. Puts the +12 volts referenced to ground on the negative of your plugs. Reference ground to ground and play it safe. Should the product you have be plugged in...Say CB or stereo set up ??? making contact with any metal parts of said accessory is going to be the Forth of July shit show of sparks.

Friend, then fire extinguisher, then fried and a sad face. Still pals, CAMO (y)

Let's look at the drawing.
Are the fireworks still relevant if all is fused? What is an equalizer?
 

simp5782

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So far I have been diligent to remove the usb chargers from sockets. I bought a 24v relay but didn't install it. Does anyone have any input concerning the fuse on negative side? I guess

Are the fireworks still relevant if all is fused? What is an equalizer?
Equalizer turns your standard 24v and turns it to 12v and charges the 12v side. This is a 100amp eaton. 24 to 12. Around $200.

They make 12 to 24v units as well
 

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Milcommoguy

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Glider

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This has been fun but...No one told me if fuses would stop the fireworks or fire. If there was enough current to start a fire, melt a wire, etc. would the fuse not blow? To me it sounds the same as making sure positive wiring 12v or 24v is properly fused to prevent fireworks.

Will pulling 12v from the forward battery reduce/slow the imbalance between batteries? If there is no difference I will absolutely move to rear battery and call it done.
 

Milcommoguy

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This has been fun but...No one told me if fuses would stop the fireworks or fire. If there was enough current to start a fire, melt a wire, etc. would the fuse not blow? To me it sounds the same as making sure positive wiring 12v or 24v is properly fused to prevent fireworks.

Will pulling 12v from the forward battery reduce/slow the imbalance between batteries? If there is no difference I will absolutely move to rear battery and call it done.
Yes... fuse would help protect the wire.

Bring a box, CAMO
 

simp5782

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Coug

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if putting on the rear battery, you need the fuse on just the positive.
If putting on the forward battery, you need fuses on both the positive AND the negative wires, as close to the battery as possible.
 

Retiredwarhorses

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ALWAYS a use the rear battery to pull 12v, same as what the factory does.
follow best practices as any electrical wiring in automobiles such as install fuse Inline on positive as close the power
source as possible, use correct gauge wiring, use common sense on wire routing, protect wires with split loom, use rubber grommets when passing fire Walls…
And never use the body of a hmmwv as a ground, use the negative off the rear battery.
 
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