Can 12 and 24 V share same ground?

[Warthog]

That can be said for many things...................

Jesus nut - Wikipedia, the free encyclopedia

 

[zout]

seeing as I have one foot in the grave already - I just tie on a copper ground cable to my copper anke braclet for my ground. What a better ground than that.

Thought you were going to ask if you could ground 12v & 24v to the same post along with having an electrical distribution box for 120v and ground that to the same post.

 

[KaiserM109]

Yes, but only when you have a 24v alt hooked to two batterys and a second 12v alt hooked to one(of those two) battery.

The 12v alternator HAS TO HAVE ITS OWN BATTERY. You cannot charge one of the batteries in the 24v string with a separate alternator; that will overcharge it and boil off the electrolyte. You also cannot use one of the batteries in the 24v string separately to get 12v for any serious amount of current because that will overcharge the other battery and boil it off. You have to keep the 2 batteries balanced.

A 24v battery (2 12v batteries in a series) and a 12v battery (which is really 6 2v batteries in a series) can certainly have the same ground. Any good solid connection is okay as long as you remember the chassis is shock mounted from the frame and has a ground strap somewhere to the frame. The same is true with the engine. Make sure those ground straps are good. I don't remember where the chassis-to-frame strap is but the engine-to-chassis strap is near the Right-Rear engine mount. ABSOLUTELY do not start the engine if there is any doubt that the engine-to-frame ground is solid. It can blow out things like the turn signal box, etc.

Arlyn

 

[DUG]

The 12v alternator HAS TO HAVE ITS OWN BATTERY. You cannot charge one of the batteries in the 24v string with a separate alternator; that will overcharge it and boil off the electrolyte. You also cannot use one of the batteries in the 24v string separately to get 12v for any serious amount of current because that will overcharge the other battery and boil it off. You have to keep the 2 batteries balanced.

A 24v battery (2 12v batteries in a series) and a 12v battery (which is really 6 2v batteries in a series) can certainly have the same ground. Any good solid connection is okay as long as you remember the chassis is shock mounted from the frame and has a ground strap somewhere to the frame. The same is true with the engine. Make sure those ground straps are good. I don't remember where the chassis-to-frame strap is but the engine-to-chassis strap is near the Right-Rear engine mount. ABSOLUTELY do not start the engine if there is any doubt that the engine-to-frame ground is solid. It can blow out things like the turn signal box, etc.

Arlyn

All great advice. The main reason I grounded everything to the seat was - that's where everything was grounded when I bought the truck. I used it for about two years and when I added the 12 volt system I went with what had already been working.

I know the alts to frame grounds are good since I reinstalled those in the same place when I installed the new alts.

I did change the seat ground bolt to something less rusty when I added the 12 volt ground. Maybe I should have kept the old one?

 

[JasonS]

The 12v alternator HAS TO HAVE ITS OWN BATTERY. You cannot charge one of the batteries in the 24v string with a separate alternator; that will overcharge it and boil off the electrolyte. You also cannot use one of the batteries in the 24v string separately to get 12v for any serious amount of current because that will overcharge the other battery and boil it off. You have to keep the 2 batteries balanced.


Arlyn

Why? This is EXACTLY how battery equalizers work.

 

[rat4spd]

you forgot harry potter has to be there too?

Hey now, isn't that my line? My gawd, we now have the seat bolt, and Jesus nut. What are we coming to? I may have to go to church this Sunday and pray over this one.

 

[Kasper31]

YES,,,,it will work, I have replaced the 25amp 24vdc GENERATOR with a 100amp 24 vdc single wire alternator and added a 65amp 12 vdc single wire alternator for the 12 volt system. Both share the same ground as they are both mounted to the engine block on their respective mounts with the ground wires going to the engine which is also grounded to the frame.
I guess what I forgot to mention is, the 24v alternator goes to its own batteries ( 2-#27 series ) for running the truck equipment and the 12v alternator goes to its own battery ( 1-deep cycle ) that runs my 12v equipment, I/e two complete and separate voltage systems.

 

[mendo]

Why? This is EXACTLY how battery equalizers work.

no, it is not.

if you run a constant 24V through 2 batteries in series (24v) both batteries will see 12V and the same amperage if they are the same size and age. when you are putting 14.5 or so volts on one of them and 24 something through both you will drop the voltage of the 2nd battery down so that they only add up to 24 v or so. this is rough math just to give you the ideer. bottom line is that it is pretty hard on the batteries to run it like this. it may be cheaper in the long run to add one extra battery just for the 12V, and keep the 2 for the 24v nice and equal.

 

[swbradley1]

Just put three commercial batteries in the box like the pics show. Connect the two normally and connect the 12v stuff to the third and it will work just fine.

sw

 

[DUG]

Hey now, isn't that my line? My gawd, we now have the seat bolt, and Jesus nut. What are we coming to? I may have to go to church this Sunday and pray over this one.

I'm not sure they would know what to do with you in a church.

 

[treeguy]

If you wanted to charge/ top off 2 extra 12V batteries you keep at home, could you just throw them in your truck, connect the pos to the other neg and run jumper cables respectivly to them and your truck batteries while you drive around all day?

 

[JasonS]

no, it is not.

if you run a constant 24V through 2 batteries in series (24v) both batteries will see 12V and the same amperage if they are the same size and age. when you are putting 14.5 or so volts on one of them and 24 something through both you will drop the voltage of the 2nd battery down so that they only add up to 24 v or so. this is rough math just to give you the ideer. bottom line is that it is pretty hard on the batteries to run it like this. it may be cheaper in the long run to add one extra battery just for the 12V, and keep the 2 for the 24v nice and equal.

No, look at the installation manual for a battery equalizer. They apply 1/2 of the 28V (ie. 14V) to the lower battery.

Here is a link for ya:

http://www.allbatterysalesandservice.com/graphics/52109-52204-52206-52208-52210.pdf

 

[steelandcanvas]

If you wanted to charge/ top off 2 extra 12V batteries you keep at home, could you just throw them in your truck, connect the pos to the other neg and run jumper cables respectivly to them and your truck batteries while you drive around all day?

Yes, can't see why not.

 

[DUG]

What's the price for say a 60 amp equalizer? I still think it's cheaper in the long run to add a 12 volt alt and another battery. My replacement costs on a 24 volt 1one alt is $123 - cheap enough to carry a spare.

And no matter what I run on the 12 volt side or how bad I screw it up, the truck is still gonna start and take me home.

 

[steelandcanvas]

What's the price for say a 60 amp equalizer? I still think it's cheaper in the long run to add a 12 volt alt and another battery. My replacement costs on a 24 volt 1one alt is $123 - cheap enough to carry a spare.

And no matter what I run on the 12 volt side or how bad I screw it up, the truck is still gonna start and take me home.

I agree. I have been debating this issue for days. Your last sentence sums it up DUG.

 

[doghead]

An alternator is not equivalent to a Battery equalizer.

JasonS, this is about the 4th thread that you have debated the merits of alternators, batterys, and equalizers.

Why don't you either let it rest, or modify your MV whatever way you figure out with your "advanced degree" , and experience(or lack there of). Then post that up, instead of theories and math and whatever else you've posted lately.

 

[rat4spd]

And no matter what I run on the 12 volt side or how bad I screw it up, the truck is still gonna start and take me home.

Or you could just do what I did with the screamo on subbase when it had electrical issues,.....park on a hil.

 

[cyruscat]

Thanks for the answer(s) and glad to start an entertaining thread

 

[JasonS]

An alternator is not equivalent to a Battery equalizer.

JasonS, this is about the 4th thread that you have debated the merits of alternators, batterys, and equalizers.

Why don't you either let it rest, or modify your MV whatever way you figure out with your "advanced degree" , and experience(or lack there of). Then post that up, instead of theories and math and whatever else you've posted lately.

Doghead,

I won't belabor this any further. Have it your way.

 

[coachgeo]

was searching about common grounds between 12v and 24v... for a different project.... Found this thread. Answered my question. you can have common ground between 12v and 24v.


For shiats and grins will bring this ancient thread up and throw a monkey wrench between the battery lugs and let it spark.

FMTV's and a few other military rigs have dual volt alts that do essentially what in this thread eludes to and seems to say "you can't have" two alts / Two voltages...... same battery bank:
> 24v alt to whole bank of various cells = 24v
> second 12v alt to one half of said bank.)

Though in defense..... @JasonS discussed in his post about what equalizers do .. these dual alts also go about splitting power down the middle and sending it to the battrey all the 12v only things are pulled from... aka - logically the battery to end up the lower voltage of a pair..... anddd the bank is wired in series / parallel.

PS- many folk hate the dual volt alts LOL