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Old 09-07-2011, 08:54 AM   #1
luifer76
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Hooking up two batteries together on my 73 c10?????

Kind of a dumb question and i have an idea on how i should do it but i just want to get some feed back or ideas fom all you guys to make sure i do it right as some of you seen my 73 c10 is bagged and running into a problem with my battery going dead everytime i fill up my air tanks i know that compressors could draw a lot of current specially when you running multiple compressors .....the battery doesn't completly die but but you can tell it drains it....now i only run the compressor when the truck is running since i added a toggle switch to be able to trun them off any time i want to..... long story short i want to run two batteries with the same altenator and i need to link both batteries together any ideas or pics would be great thanks.......
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Old 09-07-2011, 09:15 AM   #2
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Re: Hooking up two batteries together on my 73 c10?????

It should be just be a simple (+) to (+) and (-) to (-) for both the batteries. In other words, hook the (+) of one to the (+) of the other and the (-) to the (-). That's how we do it with car audio. Other input could be helpful though.
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Old 09-07-2011, 09:22 AM   #3
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Re: Hooking up two batteries together on my 73 c10?????

positive to positive and negative to negative is right. that's the way we do it here with the diesels and hydraulic lift school buses.
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Old 09-07-2011, 09:32 AM   #4
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Re: Hooking up two batteries together on my 73 c10?????

i just ground the drivers side - to the body or frame then run the + across to the passenger side + and the the passenger side ground to the engine in the factory location and the passenger side + to the starter like factory.
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Old 09-07-2011, 11:12 AM   #5
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Re: Hooking up two batteries together on my 73 c10?????

Either way will work. I ran both positive and negative cables through holes in the radiator core support and tie wrapped the cables to the underside of the radiator top panel, so the cables are out of sight.
You might want to check out a high output alternator, but you should also have heavier cables if you install one. Heavier cables for the battery and to the starter are also a good idea.
Two batteries will cost more than you might think: You should buy two new batteries or the old one will bring down the charge in the new one. You will need a battery tray for the second battery - the OEM ones are pricey but are way better than the aftermarket ones. You will need the extra set of cables and post adapters.
If you drive your truck a lot you will successfully keep a charge on two batteries. If you don't drive your truck much (like me) you will have difficulty keeping one battery well charged, much less two batteries. This is where the high output alternator comes in. You can search the internet for high output alternator and get advice on this, mostly from h.o. alternator vendors and car audio sites. Still, a high output alternator puts out most of its amps at higher RPMs, so city driving alone will not produce a lot of amps.
I have a high output alternator (140 amp, I think) and I find that for some reason the primary battery gets most of the charge and the secondary battery gets less of a charge - I have no isolator between them, which would be designed to charge the primary battery first, then the secondary battery. If you want info on isolators you can search that on the internet also, but I don't like isolators. I used a Ford solenoid between the two batteries instead of an isolator when my isolators kept failing. I had a toggle switch on the dash at one time to use two batteries for start up, but I don't think that is necessary.
Bottom line, two batteries ultimately won't help you much in the long run if you are providing the same amount of current as you were to one battery - you will just have two batteries with the same level of charge instead of one battery. Again, if you drive your truck a lot you will keep a good charge on both batteries, even with a stock alternator.
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Old 09-07-2011, 11:53 AM   #6
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Re: Hooking up two batteries together on my 73 c10?????

Quote:
Originally Posted by tucsonjwt View Post
Either way will work. I ran both positive and negative cables through holes in the radiator core support and tie wrapped the cables to the underside of the radiator top panel, so the cables are out of sight.
You might want to check out a high output alternator, but you should also have heavier cables if you install one. Heavier cables for the battery and to the starter are also a good idea.
Two batteries will cost more than you might think: You should buy two new batteries or the old one will bring down the charge in the new one. You will need a battery tray for the second battery - the OEM ones are pricey but are way better than the aftermarket ones. You will need the extra set of cables and post adapters.
If you drive your truck a lot you will successfully keep a charge on two batteries. If you don't drive your truck much (like me) you will have difficulty keeping one battery well charged, much less two batteries. This is where the high output alternator comes in. You can search the internet for high output alternator and get advice on this, mostly from h.o. alternator vendors and car audio sites. Still, a high output alternator puts out most of its amps at higher RPMs, so city driving alone will not produce a lot of amps.
I have a high output alternator (140 amp, I think) and I find that for some reason the primary battery gets most of the charge and the secondary battery gets less of a charge - I have no isolator between them, which would be designed to charge the primary battery first, then the secondary battery. If you want info on isolators you can search that on the internet also, but I don't like isolators. I used a Ford solenoid between the two batteries instead of an isolator when my isolators kept failing. I had a toggle switch on the dash at one time to use two batteries for start up, but I don't think that is necessary.
Bottom line, two batteries ultimately won't help you much in the long run if you are providing the same amount of current as you were to one battery - you will just have two batteries with the same level of charge instead of one battery. Again, if you drive your truck a lot you will keep a good charge on both batteries, even with a stock alternator.
thanks for the info both of the batteries are new i got an extra battery tray allready and i have a 120 amp altenator i think i may be fine with that altenator i think the extra battery will solve my problem since im running 4 380 compresors to fill up two 7 gallon tanks and everytime i get to run the compressors to get to at least 160 psi or 200 psi the one battery starts feeling it.....
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Old 09-07-2011, 11:55 AM   #7
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Re: Hooking up two batteries together on my 73 c10?????

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Originally Posted by juiceman650 View Post
It should be just be a simple (+) to (+) and (-) to (-) for both the batteries. In other words, hook the (+) of one to the (+) of the other and the (-) to the (-). That's how we do it with car audio. Other input could be helpful though.
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thats what i thought i just wanted some input from some of you guys thanks again....
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Old 09-07-2011, 02:13 PM   #8
Keith Seymore
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Re: Hooking up two batteries together on my 73 c10?????

Agree -

Positive to Positive, negative to negative in theory; in practice, it ends up being negatives routed to ground (ie, frame), postive on one battery to the postive on the other, then one positive routed to the starter.

Here's what it looks like in the trunk of my Chevelle:



Negatives are to the rear, and you can see them poking through the trunk floor headin' to the frame.

The positives are the forward post, and you can see the cable (inside the convoluted conduit) running across the rear of the trunk and through the latch area.

The side post/top post batteries make it a little easier, since it provides a place for all this stuff to hook up to.

Lastly, everything goes through that Moroso master cut off switch before heading to the rest of the car.

K
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Old 09-07-2011, 07:15 PM   #9
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Re: Hooking up two batteries together on my 73 c10?????

Has anyone rigged up a setup where one battery works when the car is shut off...so that even if you run that one down when the engine is off, you can still start the car with the other battery?
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Old 09-07-2011, 08:22 PM   #10
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Re: Hooking up two batteries together on my 73 c10?????

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Has anyone rigged up a setup where one battery works when the car is shut off...so that even if you run that one down when the engine is off, you can still start the car with the other battery?
That is just a simple isolator setup.
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Old 09-07-2011, 09:36 PM   #11
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Re: Hooking up two batteries together on my 73 c10?????

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Has anyone rigged up a setup where one battery works when the car is shut off...so that even if you run that one down when the engine is off, you can still start the car with the other battery?
That is typically the most common way of setting it up, either with a diode type isolator or with a relay. For example I run the stereo and trailer\camper plugs to the 2nd battery. I can run it down and still start the truck on the main battery. I personally prefer the diode type of isolator, but I'm sure there will be many opinions here as to what is best. In this situation, where you have very high current draw, it may be better for you to have your batteries hooked directly together to provide the amps to run the compressor. The only downside is that the batteries will discharge each other down when the truck is off.
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Old 09-07-2011, 10:42 PM   #12
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Re: Hooking up two batteries together on my 73 c10?????

+ to + - to -. if u went +to- ud create a 24v system. u want to create a "parallel bridge"
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Old 09-07-2011, 10:43 PM   #13
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Re: Hooking up two batteries together on my 73 c10?????

oh. and i have 1370 cold cranking amps
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Old 09-07-2011, 10:46 PM   #14
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Re: Hooking up two batteries together on my 73 c10?????

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Originally Posted by lilpoindexter View Post
Has anyone rigged up a setup where one battery works when the car is shut off...so that even if you run that one down when the engine is off, you can still start the car with the other battery?
i hate this idea. whats the point of having a seperate battery? u want more consistant voltage and more amperage? run 2 batterys in parallel and call it good. if not ur just drGging abound 70lbs for what?? " if u need it??" an alternator loves 2 batterys. its not harder on it.. its eaiser. less draw=less to recharge.
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Old 09-08-2011, 01:22 AM   #15
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Re: Hooking up two batteries together on my 73 c10?????

I've always ran 2 batteries by hooking them up + to + and - to - . Now what MOST PEOPLE do from here is simply go directly to the starter and ground off of one battery only. Which is fine if you want to double your reserve capacity.
But if you want to DOUBLE your COLD CRANKING AMPS... Hook the 2 batteries up the same way as described above BUT go to the starter (+) off of one battery and ground (-) off of the other battery.
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Old 09-08-2011, 02:10 AM   #16
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Re: Hooking up two batteries together on my 73 c10?????

I had the same problem on my truck. I used the isolator hook up and a 100amp alternater and have had no problems since. I have one battery running the truck and one runs my compressor, amp and switches. I also run optima yellow top batteries that can be recharged without damage to the battery.
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Old 09-08-2011, 03:32 AM   #17
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Re: Hooking up two batteries together on my 73 c10?????

[QUOTE=cr34t3d_by_d4rkd3n;4887806]i hate this idea. whats the point of having a seperate battery? u want more consistant voltage and more amperage? run 2 batterys in parallel and call it good. if not ur just drGging abound 70lbs for what?? " if u need it??" an alternator loves 2 batterys. its not harder on it.. its eaiser. less draw=less to recharge.[/QUOTE

It comes in handy on trucks with campers. You can run the camper off one battery and still be able to start the truck on the other one. Somebody correct me if I'm wrong, but I think usually the 2nd battery (the one that runs the camper) is a deep cycle battery and the other is just whatever you need to for the vehicle...it can be done that way because of the isolater. I have a camper on my C30 that I want to set up this way when time an money allows.

On my diesel burb I need 2 batteries to start the truck and they are wired in parrallell..although in reality I can get away with just one battery...gotta luv the optima red tops.
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Old 09-08-2011, 11:31 AM   #18
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Re: Hooking up two batteries together on my 73 c10?????

With the isolator setup the main battery is not being used so if it goes dead it does not kill the main battery to still be able to start the truck. the isolator separates the batteries until the isolator has power. I have always used this setup for high power add ons to vehicles like a stereo system or airrride. both ways will work but the isolator helps keep the main battery for starting the vehicle.
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Old 09-08-2011, 12:46 PM   #19
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Re: Hooking up two batteries together on my 73 c10?????

Isolators work as described but the ones I had (diode type) always failed after about one year of use. More expensive ($100+) isolators are supposed to last longer.

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Old 09-08-2011, 08:23 PM   #20
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Re: Hooking up two batteries together on my 73 c10?????

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i hate this idea. whats the point of having a seperate battery? u want more consistant voltage and more amperage? run 2 batterys in parallel and call it good. if not ur just drGging abound 70lbs for what?? " if u need it??" an alternator loves 2 batterys. its not harder on it.. its eaiser. less draw=less to recharge.
When you're parked in the bush a 100 miles away from civilization, it can come in kind of handy if you want to start your truck after a week of camping. It's a long walk home trying not to become grizzly snacks.
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Old 09-12-2011, 03:37 AM   #21
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Re: Hooking up two batteries together on my 73 c10?????

Instead of running an iso and power lines and bein that far n the bush seemsnlike a risk. When wed go to the desert wed just bring a generator. And for the cost and reliability id do that every day vs isolator this and that. Just another system to fail.
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Old 09-12-2011, 03:44 AM   #22
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Re: Hooking up two batteries together on my 73 c10?????

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I've always ran 2 batteries by hooking them up + to + and - to - . Now what MOST PEOPLE do from here is simply go directly to the starter and ground off of one battery only. Which is fine if you want to double your reserve capacity.
But if you want to DOUBLE your COLD CRANKING AMPS... Hook the 2 batteries up the same way as described above BUT go to the starter (+) off of one battery and ground (-) off of the other battery.
Hahah WHAT?! U need to open some books. 2 batterys parralled stays 12v and combines both batterys cca. The way u describe leaves insuffent grounds. BOTH BATTERYS NEED A CRAP LOAD OF GROUNDS AND EITHER A COMMON BUT EQUIL + JUNCTION POINT or EQUAL POSITIVE BRANCHES OFF POSTS. To say neg off one and pos to starter is a frog leap away from a in series system. Your 2000 posts are impressive, but if they contain incorrect instructons whats the point?
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Old 09-19-2011, 01:47 AM   #23
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Re: Hooking up two batteries together on my 73 c10?????

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Hahah WHAT?! U need to open some books. 2 batterys parralled stays 12v and combines both batterys cca.That's exactly what I said. The way u describe leaves insuffent grounds. Not at all if you will look at the attached diagram below.BOTH BATTERYS NEED A CRAP LOAD OF GROUNDS AND EITHER A COMMON BUT EQUIL + JUNCTION POINT or EQUAL POSITIVE BRANCHES OFF POSTS. To say neg off one and pos to starter is a frog leap away from a in series system. Your 2000 posts are impressive, but if they contain incorrect instructons whats the point?
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The diagram below is how I've always hooked up my batteries to DOUBLE MY COLD CRANKING AMPS.
I've ran like this for over 30 years and have never had a problem.
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Old 09-19-2011, 02:36 AM   #24
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Re: Hooking up two batteries together on my 73 c10?????

Ok excuse my languare i get irritated when one csnt see my point of view. Think of it this way... If 1 battery has 1 ground. 2 batterys should have ??...2 min. Ur method would work acceptably if it was an ac set up. But sense its dc the flow of power has to constantly work. Ur method increases reserve capicity. Think of it like hydrolics. Return line is always bigger than feed line.
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Old 09-19-2011, 04:53 AM   #25
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Re: Hooking up two batteries together on my 73 c10?????

the way u show is using the series principal. (flowing thru another) ur set up will work. but used to pull a winch on say a 4000lb 45 sec pull will turn that ground wire to a welding rod. the set up u show is best for a trunk sense grounding 2 batts at the sheet metal when theyre sitting right next to eachother is dumb. the more grounds u have the better. simple rule for every hot, the ground should b equil and 50 percent "fatter" .

in an engine compartment running that long of a ground is highly dangerous. surrounding positives will wanna jump to it. its better to ground both batterys to sheet or frame and jump the positives. but remember. share the load. brancch off each batt equil or else all will try to feed off one cable.
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