24-12v conversion diagram any help?

[pipeandwire]

200a dual voltage alt.
Hey all... common 24v to 12v question here but I’ve yet to see a thread with the conclusion I’ve come up with and am looking for feedback on my setup. Basicly I’m looking at utilizing the 14v output of the alternator to a seperate 3rd battery and using another 24v to 12v converter to keep it going when the vehicle is not running. Any comments or concerns on my thoughts??

 

[TOBASH]

Huh? Keep what going? The truck? The fuel pump? The lights and electrics?

You can absolutely run a 12 V system with its own battery, but what is the other stuff about?

 

[springer1981]

What is the stuff in the red?
I'm not sure what you are trying to accomplish but unless the 24v to 12v converter uses a common ground, you have no ground to your 12v battery circuit.

 

[NormB]

Fuse as close to source as possible, otherwise wiring/connections frequently sacrifice themselves in fire under high current draw to save the life of the fuse.

 

[Coug]

I'm kind of new to 24V wiring in trucks, but since it's a dual output alternator, can the alternator be hooked up to the starting batteries as normal, then wire a third battery in parallel with the second battery, and possibly use some type of an isolation relay to separate it from the system when the vehicle isn't running? Something like https://www.powerstream.com/battery-isolator.htm ? Not sure if it would work properly due to the 12/24 split nature of the alternator.

As for utilizing a 24/12V converter to keep the third battery charged up when the vehicle isn't running, I would if you are going to use an additional battery it would be specifically NOT drain the primary batteries when the vehicle is off.

 

[Milcommoguy]

Sounds like a lot of trouble to me. How many amps are you planning to draw off the 12 feed and for how long? The dual alternator will equalize your two batteries and allow for reasonable 12 volts circuits loads.

Reasonable... Not a 12 volt winch or a lot of incandescence flood lighting, but all the 12 volt consumer goodies (CB's, stereo, ham rigs, LED's, etc. Need to keep an eye on the discharge of the 12 volt battery so to get restarted.

I see what your thinking and IMO might be a bit overkill. Having the third 12 volt battery would eliminate any chance of getting stuck with the 12 volt half of the 24 volt system starting / run batteries being drained. Ditch the 24 to 12 converter. You will need contractors / relays / solid state for isolation buss management and I am scratching my head as to why? LOL

Keep it simple and start the truck to recharge, CAMO

 

[pipeandwire]

That was just suppose to show to common ground. Just happened i drew the other battery right next to it. All of the grounds will be actually bonded and the same.

What is the stuff in the red?
I'm not sure what you are trying to accomplish but unless the 24v to 12v converter uses a common ground, you have no ground to your 12v battery circuit.

View attachment 760627

 

[pipeandwire]

I have a wetsounds marine audio system that will draw up to 50 along with a backup camera and couple small things like a 12v to usb charger fro phone

 

[pipeandwire]

The objective would be the small 3rd battery would be fine while the humvee is running put out 50a but if i happens to turn it off and run the audio its going to dream quickly so by having the converter would give me power from the main batts temporarily

 

[pipeandwire]

Definitely fuses would be near the source, just drawn like that from my couch.

Fuse as close to source as possible, otherwise wiring/connections frequently sacrifice themselves in fire under high current draw to save the life of the fuse.

 

[pipeandwire]

Been doing a bunch of reading and end result is best advice is not to grab power from the 12v between batts. Leaving only the converter as the option of an actual power source when the vehicle is off. There is no 12v from the alternator unless its running. The beast is quite noisy and if i run audio when its off it will require 12v.

Sounds like a lot of trouble to me. How many amps are you planning to draw off the 12 feed and for how long? The dual alternator will equalize your two batteries and allow for reasonable 12 volts circuits loads.

Reasonable... Not a 12 volt winch or a lot of incandescence flood lighting, but all the 12 volt consumer goodies (CB's, stereo, ham rigs, LED's, etc. Need to keep an eye on the discharge of the 12 volt battery so to get restarted.

I see what your thinking and IMO might be a bit overkill. Having the third 12 volt battery would eliminate any chance of getting stuck with the 12 volt half of the 24 volt system starting / run batteries being drained. Ditch the 24 to 12 converter. You will need contractors / relays / solid state for isolation buss management and I am scratching my head as to why? LOL

Keep it simple and start the truck to recharge, CAMO

 

[pipeandwire]

Ironically im an electrician, and a controls guy at that. So any relays or contractors and wiring is no problem, but i dont see needing any of those with the setup. That’s the whole reason I’m posting is to get others opinions and eyes on my design. I really appreciate all the feedback so I’m not tryin to be defensive or rude. I’m very thankful for input from everyone. I’m a newbie to the humvee and appreciate having the forum as a resource.
basicly it boils down to 12v when vehicle isn’t running. A converter is of course option 1 and maybe the straight easy way to go.

 

[pipeandwire]

I updated the drawing showing common grounds. Also beginning to think that eliminating the converter all together OR only having the converter is the way to go. Not sure I like the backfeed thru the converter when its running

 

[Retiredwarhorses]

Let me make this simple...you have no need for a 3rd battery or a 12v converter with the 200amp and 14tap tied to the rear battery. Just run all your 12v items to a power strip off the pos of the REAR battery, pull the ground from the shunt.
done...that 200amp gen was designed to run way more then anything you are going to wire into the truck.
the 14v tap will keep your batterys equalized.

 

[Valley Rock]

Let me make this simple...you have no need for a 3rd battery or a 12v converter with the 200amp and 14tap tied to the rear battery. Just run all your 12v items to a power strip off the pos of the REAR battery, pull the ground from the shunt.
done...that 200amp gen was designed to run way more then anything you are going to wire into the truck.
the 14v tap will keep your batterys equalized.

Could you possibly dumb this down to laymens terms / 3rd grade level of understanding as I may need to also do this with my truck, or at least have it as an option, I am NOT an electrician as you may have already gathered .

Thanks .

 

[NormB]

Could you possibly dumb this down to laymens terms / 3rd grade level of understanding as I may need to also do this with my truck, or at least have it as an option, I am NOT an electrician as you may have already gathered .
Thanks .

The "shunt" is the candy-bar shaped "block" of flat plates on the tunnel side of the battery compartment, left side of the commander's seat.



[FONT=DDG_ProximaNova]"In electronics, a shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path The term is also widely used in photovoltaics to describe an unwanted short circuit between the front and back surface contacts of a solar cell, usually caused by wafer damage. The origin of the term is in the verb 'to shunt' meaning to turn away or follow a different path." (wikipedia edit)[/FONT]



Battery ground goes through this, the ammeter taps off it with very low current drain.

Of course, you could just run a ground wire to the rear-most battery if that's clearer or easier.

I'm using a 35AH gel cell (about $50 on the jungle shopping site) tied down underneath the right rear passenger seat.

I then ran a battery tender fuse/2-wire connector off it through the side of the seat into one of these: https://smile.amazon.com/gp/product/B0031BOTFC/ref=oh_aui_search_asin_title?ie=UTF8&psc=1 for ease of use and/or trickle-charging the 12v circuit (I have two I mounted up front for the mains).

The 14V wire from the regulator I ran through 8 gauge milspec wire (Erik's military had it) positive to that battery (fused up front by the alternator).

If you are going to run a lot of 12v accessories, use a fuse block like this: https://smile.amazon.com/gp/product/B072Q3GLVJ/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

or a power strip for ground: https://smile.amazon.com/gp/product/B000K2MA9M/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

insulated for hot: https://smile.amazon.com/gp/product/B000K2MA9M/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

Or cigarette lighter outlet/connection, whatever.

Remember, disconnect battery ground before messing with ANY electrical wiring on your truck.

NB

 

[sue]

What warhorse said, that’s what we do
also, those batteries ( if there original)
have a LOT of reserve.

 

[pipeandwire]

Without offending anyone, can someone explain why half the planet suggests taking 12v from the main batts and the other half says never to do it as eventually it will create problems? I understand electronics fine but I’m not an engineer to be able to weigh the facts and create a basis either way. To me they both make sense. I just want to get this right and wire it 1 time.

 

[NormB]

Without offending anyone, can someone explain why half the planet suggests taking 12v from the main batts and the other half says never to do it as eventually it will create problems? I understand electronics fine but I’m not an engineer to be able to weigh the facts and create a basis either way. To me they both make sense. I just want to get this right and wire it 1 time.

Hooh, boy.

Imagine a line of AA batteries laid end to end, 16 of ‘em, so as to make up 24 volts (a bit more with fresh alkaline AAs, lower with recharchables).

Tapped from + to -, you get full voltage. Regulator stops pumping electrons as resistance to flow increases as batteries charge.

Now, you want twelve volts? Where do you tap? From battery #1-8, or 9-16? 4-12?

As you’re pulling current out of THOSE cells, the regulator sees a drop in voltage, adds more, BUT, the resistance in the cells before/after - those cells being “full” - keep the cells you’re draining from benefitting from full charge.

Eventually you kill those cells.

Just ask everyone who’s done it, and why voltage balancers for these 24-12V circuits are made and sold to PREVENT battery damage.

If a normal flooded lead-acid or AGM battery, current/voltages balance internally under normal operation.

add more end-to-end and then you drain ONE cell? Eventually the cell fails, shorts, sulfates, taking your $400 lump of toxic waste with it,.

Simplistic, but correct me if I’m wrong.

Norm

 

[Retiredwarhorses]

AM General feeds ALL 12v components from the rear battery...TCM primarily, the 14v tap from the gen takes care of the imbalance. If it’s so bad, why does the mfg do it?