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2nd alt for dual battery?

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Old Apr 8, 2009 | 08:03 PM
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2nd alt for dual battery?

I'm thinking instead of running some system with battery isolators, why not just put in a second alternator. Trying to remember how many wires come off the alt, anyone remember? The body is connected to the chassis ground and there's the wire that goes straight to the battery (right?), but then there's also a plastic plug (green i think) that hooks to the alternator, what is it's job? How would that work if the alt was being used to keep a deep-cycle juiced up for dual batteries.
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Old Apr 8, 2009 | 08:10 PM
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i only have two wires hooked up to my alternator the obvious charge wire and a 12v exciter wire that is activated with the key inthe on position that is all you really need to get a altrenator to run
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Old Apr 8, 2009 | 09:55 PM
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Rather than wasting money and time trying to put in two alternators, just have your existing alternator rewound. Boyles Future tech does that
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Old Apr 8, 2009 | 10:44 PM
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The idea is to avoid a battery isolator by having two completely separate electrical systems. I don't want to ship my alternator down and back from Canada. I can get alternators for cheap- just find someone with a "dead" alt and replace the brushes at a cost of $7 and you have a $20 working alternator. I have room in my engine bay beside my York compressor if i recall.

Last edited by Matt16; Apr 8, 2009 at 10:46 PM.
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Old Apr 9, 2009 | 12:09 AM
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but why? what do you need that for? do you have a huge sound system, winch and or a big power converter of some kind to run something big like a welder? I am confused by why you would need this.
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Old Apr 9, 2009 | 12:11 AM
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http://images.google.com/imgres?imgu...a%3DX%26um%3D1
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Old Apr 9, 2009 | 01:30 AM
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not sure how you'd run two batteries in parallel (regardless of separate charging systems) without some sort of isolator, considering you're looking to run the electrical system off of either battery (switching to the charged one when the other is discharged), no?
... or you'd have to split the electrical system so some circuits draw from one battery, and other circuits draw from the other.
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Old Apr 9, 2009 | 01:33 AM
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and the wiring to the factory alt, IIRC, is one charge line to the battery, one reference line to the regulator, one 'indicator' wire and one wire switched hot by the ignition... oh, and the ground.
The charge line is the large wire to the stud on the alt, and the reference, indicator and switched are all in one plug, and the ground is to the body of the alt (or usually the mounting bracket)
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Old Apr 9, 2009 | 06:53 AM
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From: Shoreline, Wa
Originally Posted by abecedarian
not sure how you'd run two batteries in parallel (regardless of separate charging systems) without some sort of isolator, considering you're looking to run the electrical system off of either battery (switching to the charged one when the other is discharged), no?
... or you'd have to split the electrical system so some circuits draw from one battery, and other circuits draw from the other.
I think he needs something like this. http://www.amarket.com/imbs001.htm

then when he goes somewhere he can run on one battery, and on the way back he can switch. and he can also turn the whole thing off as a theft deterrent.
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Old Apr 9, 2009 | 08:14 AM
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theres a guy running around town here who has dual alt/bat setup.
i was thinking about doing the same. except his is setup like abe was describing in his first post. he is using a gm 1 wire (mounted where the ac used to be).

i would like the stock alt/bat to run only the stock equipment. then have a second bat/alt to run all my accessories, winch, lights, etc.
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Old Apr 9, 2009 | 09:30 AM
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From: Da UP, eh?
I believe you do need the indicator light, just so you know. You can rig up a little bulb you can get from radioshack. I ran two alts on my old daewoo...if you don't put that indicator light inline, that wire or connector doesnt have enough resistance and will burn up your alt. quicker then normal...
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Old Apr 9, 2009 | 12:43 PM
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Originally Posted by abecedarian
not sure how you'd run two batteries in parallel (regardless of separate charging systems) without some sort of isolator, considering you're looking to run the electrical system off of either battery (switching to the charged one when the other is discharged), no?
... or you'd have to split the electrical system so some circuits draw from one battery, and other circuits draw from the other.
That's the idea. The second electrical system would power an electric heater for camping and some of my aux. lights that i use when the engine is off and relatively frequently kill the battery.
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Old Apr 9, 2009 | 12:46 PM
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Having a bit of a brain fart at the moment. There wouldn't be any issues with running a common ground for both batteries (considering they different systems and are not connected) ?
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Old Apr 9, 2009 | 01:11 PM
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Originally Posted by Matt16
Having a bit of a brain fart at the moment. There wouldn't be any issues with running a common ground for both batteries (considering they different systems and are not connected) ?
Naw, not at all (so long as everything was kept 12v).

Think of it as two cars jump-starting. When you clip the grounds, they're sharing a common ground with two independent battery+charging systems.
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Old Apr 9, 2009 | 08:20 PM
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a common ground between the two is perfectly fine. you have to isolate the positives though else you will be sharing draw between the two batteries. additionally, having a common ground gives you the option of installing switches to allow you to change which battery supplies which circuits so you could disconnect a discharged battery and use the other to provide voltage to the other circuits.
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Old Apr 9, 2009 | 08:51 PM
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From: detroit lakes minnesota
Originally Posted by Matt16
I'm thinking instead of running some system with battery isolators, why not just put in a second alternator. Trying to remember how many wires come off the alt, anyone remember? The body is connected to the chassis ground and there's the wire that goes straight to the battery (right?), but then there's also a plastic plug (green i think) that hooks to the alternator, what is it's job? How would that work if the alt was being used to keep a deep-cycle juiced up for dual batteries.
lol just gave me an idea with ur second alternator take the air conditioning out an weld ur alternator there or weld a plate an drill some holes
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Old Apr 9, 2009 | 09:36 PM
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Maybe just for a 22re but surely not for a 3vze it just wont fit anywhere.
1 bigger and better alt and 2 good batteries should work fine for almost anything you thow at it. I hope !!!
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Old Apr 10, 2009 | 07:23 AM
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From: Da UP, eh?
Originally Posted by j0hNnI
lol just gave me an idea with ur second alternator take the air conditioning out an weld ur alternator there or weld a plate an drill some holes
Thats what i did on my old daewoo, took the ac off and made a bracket to hook an alt. up. That alt. ran a second battery in the trunk for my stereo, it worked great. The only hard part was aligning the pulley for the serpentine belt...
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Old Apr 12, 2009 | 08:59 AM
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You mentioned running a Deep Cycle battery as your second battery. I'm currently running one as my primary. I've only driving the truck a couple times since the install, but I don't anticipate any issue, especially with my 170 amp alternator.

Good Luck, I look forward to seeing how you end up going about this and how it works.
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