[Vwdiesel] Wiring a VW alt in tandem with another

Wed Dec 5 05:10:05 PST 2012

I will just keep them separated. I think the tractor-although getting close the the limit having both PTO's on-will survive. At the moment I will not have a volt meter on each system. I may someday-but not right now. I will test it though while running everything. And-I hate electrical stuff. 

Travis 

To: tgott at hotmail.com; vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another
From: lbaird119 at aol.com
Date: Wed, 5 Dec 2012 02:23:28 -0500

  I suppose you could get really creative and run the feed wires from both alts, to a separate, regulator, that would load each alt equally but that's more wiring and not your strong point already.
  Combining both grounds is fine.  The electrons don't know and don't care, so long as the positive sides don't mingle.  If they mingle then you're bridging the two systems, just as if you tie both B+ leads to the same battery.  
  If you have a volt meter on each system, if your JD starts to draw down (beyond full load on the alt and then drawing down the battery) you could have a switch to tie the VW system to the JD's for charging, extra power etc, for a manually determined time.  Just be sure the switch and wire are large enough to handle the discrepency in load.
  I love electrical stuff!
     Loren

-----Original Message-----
From: Travis . <tgott at hotmail.com>
To: vwdiesel <vwdiesel at vwfans.com>
Sent: Tue, Dec 4, 2012 6:14 pm
Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another

The reason I am/was considering the system in parallel is the JD alt will be 
maxing out with both PTO's running, the tractor lights, the fuel solinoid and 
the fuel pump along with charging after starting/glow plugs. They didn't have 
the room to put the larger alt on like the JD 430 L&G tractor has under the side 
covers. The cab came off a JD 420 L&G tractor which was an air cooled engine 
with a stator and voltage regulator (Onan engine). My 332 has an alternator 
which is like a stator with a couple of magnets glued to the housing and then a 
5 pin VR it connects to. I may be able to lower the voltage on the regulator by 
putting in a relay on the green sensing wire that tells the VR what to output at 
as that is a known issue. Back to the 420-it had a GM alt hooked up to a gear 
drive rear 2000 RPM PTO and they also had a salter spreader and a battery and a 
rats nest for wiring. There was a positive wire coming off the tractors battery 
and it looks like that may have driven some 
 things while the rear battery/alt drove other things like the salter and cab 
heater and cab lights. I think the wiper, stob light, doom light and fan were 
driven off the tractors battery. The GM alt isn't pretty with the years of salt 
hitting it but I assume it works. My rear PTO I want to use runs a belt drive to 
a hyd pump that then drives a tiller (JD 30 Hyd tiller). So I figured I have a 
nice looking almost new VW alt, the salt spreader is NOT getting installed and I 
have a rear JD weight box to put a VW battery. I was trying to copy the 420 best 
I could but I don't think I should after digging in more. The 420 did come with 
another new voltage regulator so I am wondering if they had had battery problems 
before on the tractor with not enough charge for the draw they were using-it 
only had 601 hours. 

So-keep the systems separate then and just keep an eye on the tractors battery 
to see if it is draining. Is there any problem with both systems grounding on 
the frame just as long as the two positive sources aren't in tandem? There is a 
lot of things I don't think I could get by with not grounding to the frame like 
the strob light (which wasn't working due to a bad rivots not grounding). 

I will run the alt charging wires to the battery then up to the cab with a 
switched main line and I will run off that switch another line back to the alt 
exciteder with a light inbetween and the electronics can run off that main feed 
line from the battery. Anyone see any problems with that? 

I love turning wrenches as I can visually see what is going on-but electronics 
scare me as you can't see electricity and the things it runs-isn't cheap and it 
can be hooked up wrong easier then most mechanical components and depending on 
the voltage/amps it can also be more deadly as I can see a mechanical thing vs 
the electricity. 

Thanks for the help everyone. I need to get some toggle switches now. The OEM 
Cozy cab has 8 pre-drilled holes for toggle switches/lights and a 7 slot fuze 
pannel with leads on both ends of the powered side. I want to make it look nice 
and not add more holes and get rid of a few of the added cords (no just wires 
but cords). The cab has a window wiper, fan, electric heater, 3 cab lights, 
strob light and doom light. I am also running and electric shoot discharge 
control. If I can figure out how to properly string heater hose without drilling 
holes I will also change the electric heater to a coolant heater. 

Travis 

> Since the JD alt charges at 15V it's going to be working pretty hard since the 
VW alts tend to charge in the high 13's to low 14's. You could use a separate 
battery for your cab/pto system, even if it's a small motorcycle or lawn tractor 
battery. Not sure how well they share the load when regulated at different 
voltages. Might be time for Roger to comment! :-)
> Loren
> 

> So if they're wired in parallel, what's the need for an additional battery?
> 
> If there are two alternators regulated at different voltages, I would
> expect (disregarding voltage drop in the wiring/junctions) the JD alt would
> be doing all the work and the VW alt would be loafing, at least until the
> JD is maxed out on amps and its output voltage starts to drop. This gets
> back to your comment about frying the JD regulator.
> 
> FWIW, a personal anecdote re: "running an alternator without a battery will
> destroy the alternator", when I was young(er) and stupid(er), I swapped
> batteries in my POS AMC Concord with the engine running... I think because
> the "new" battery was dead and I didn't have jumper cables? Don't really
> remember, but the point is I was able to start the car, remove the old
> battery and install the new one with no apparent ill effect to the
> alternator, so maybe that conventional wisdom should be amended to
> "...*eventually* destroy the alternator." :)
> 
>

> Wouldn't be wired in parallel then. VW would have a battery it's wired to 
(either one could go to the D+) and the JD would go to the normal battery. That 
way the VW alt can generate away, at it's voltage and the JD do likewise, both 
on basically separate systems thusly not interfering with the operation of the 
other with the simple addition of a small (or not so small) battery.
> Loren
> 

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