[Vwdiesel] Wiring a VW alt in tandem with another

Tue Dec 4 09:36:24 PST 2012

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." :)

On Tue, Dec 4, 2012 at 8:47 AM, <lbaird119 at aol.com> wrote:

>
> 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
>
>
>
> -----Original Message-----
> From: Travis . <tgott at hotmail.com>
> To: Loren Vw <lbaird119 at aol.com>; eriklane <eriklane at gmail.com>
> Cc: vwdiesel <vwdiesel at vwfans.com>
> Sent: Tue, Dec 4, 2012 7:47 am
> Subject: RE:Wiring a VW alt in tandem with another
>
>
> I think I am understanding better then. So I will hook the D+ to the PTO
> power. The PTO uses an electric magnet to attract the clutch and start the
> spinning so without power it doesn't spin. I at this point could put the
> light inbetween just to make sure it is working as the light shouldn't turn
> on if the line isn't drawing power from either side even though it will be
> connected off the PTO line which will use power. Then I will hook the B+
> straight to the battery and then the power from the cab hook to the battery
> as well. And also run the cab in parrallel with the tractors alternator and
> battery? Would that hurt anything. Having both PTO's on the tractor-it
> won't allow for much charging of the battery which is why I want them in
> parrallel. At the same time-I don't want to fry the expensive Voltage
> regulator on the tractor, the VW alt and the two batteries. The tractor alt
> tends to like to charge right at 15 volts which is common on the JD 332.
> Keep the comments coming. I fi
>  gure it can work on this forum since it is a VW battery and alternator
> and the JD tractor is diesel-and my rabbits are parked for salt season.
>
> Travis
>
>
>
> To: tgott at hotmail.com; eriklane at gmail.com
> Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another
> From: lbaird119 at aol.com
> CC: vwdiesel at vwfans.com
> Date: Tue, 4 Dec 2012 02:10:32 -0500
>
>
>   Sounds like you could.  The field needs a little power to excite it
> until it starts turning and becomes self excited (that's what the bulb's
> for).  It only needs power when it starts running and yes, as you surmised,
> once it starts generating, the light goes out because it's not using power
> (nor sending any back through that D+ wire).
>   Thus the D+ wire will need to go to switched power and the B+ to the
> battery.  You must have a battery to an alt.  Not sure if it's to smooth
> out the AC ripple like with an inverter or if it's to make the regulator
> work properly but I've always been told "you'll burn up an alt without a
> battery, unlike a generator".
>      Loren
>
>
>
> -----Original Message-----
> From: Travis . <tgott at hotmail.com>
> To: eriklane <eriklane at gmail.com>
> Cc: vwdiesel <vwdiesel at vwfans.com>
> Sent: Mon, Dec 3, 2012 9:11 pm
> Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another
>
>
>
> o if the light is on-then the alt either isn't working or isn't spinning
> but if
> he light goes off the wire that does the exciting no longer draws
> electricity
> nd the light goes out? The VW alt will be running from the rear PTO which
> is
> an through a separate switched power source to turn the PTO on. Could I
> just
> ap into that as the alt wouldn't be turning unless the PTO is also
> energized?
> Travis
> > Date: Mon, 3 Dec 2012 20:44:39 -0800
>  Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another
>  From: eriklane at gmail.com
>  To: tgott at hotmail.com
>  CC: vwdiesel at vwfans.com
>
>  At least have the wire go through a little automotive light bulb. This
>  works as an 'idiot light' to tell you when it's working properly, and
>  also limits the current to the field while you're first starting up.
>  It's nice to keep it down some until the regulator has taken over and
>  is controlling the power output from the alternator. I would just hook
>  it up to the key switch so it was on whenever the engine was on, just
>  like how it's wired in a car. Dead simple, and it does a great job.
>
>  Erik
>
>  On Mon, Dec 3, 2012 at 8:37 PM, Travis . <tgott at hotmail.com> wrote:
>  >
>  > I almost have my JD L&G tractor wired up to run my VW alternator off the
> ear PTO (front PTO drives the snow blower). My question is on the exciter
> ire-does it need to have a diode on it or can it just be a switched power
> ource that can be turned on and left on while running, or should it be a
> omentary switch to excite it and then turn off? I am pretty sure the rest
> hould be easy just having the two alternators and batteries in parallel.
> The
> ractor alt has just enough power to run the PTO's and other functions to
> keep
> he tractor running so the VW alt is for the addition of the cab and its
> unctions (wiper, heater, fan, lights, etc). I will have another battery in
> a
> allast box behind the tractor (go figure-a vw rabbit battery).
>  >
>  > So-diode, momentary switch or just on/off switch for the the exciter
> wire.
>  >
>  > Travis
>  >
>  >
>  >
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