[T3] Voltage Regulator

Mike Fisher fisherfarms at gmail.com
Tue Nov 9 12:19:41 PST 2010


Theddb.com in Portland, OR is back in business under new management
selling a complete alternator conversion for Type 3's.  The glowing
battery light is common and usually can be Ignored.  My JVC unit works
fine in my 69 FI/AT with a generator.

On Tue, Nov 9, 2010 at 12:07 PM, Tim Keohane <rheorojo at wildblue.net> wrote:
> Did some more fussing on this. I hope I didn't trash my battery. It's a 500
> CCA 625 Amp/hour battery. I have been charging my batteries when needed
> thinking my charger "senses" the state of charge and reduces the input as
> necessary. So I assumed @ 2 amps the battery never received more than 2
> amps, and that was reduced as the battery neared capacity. I may have
> screwed up more batteries than I helped.
> I drove the car at night several times this past week. I've observed that
> the idiot light is faintly glowing. I had to dim my dash lights to be
> certain. It makes no discernible difference between high and low beams. (
> 110 x 2 or 55 x 2 ). I do notice the lights brighten when rpm's are
> increased. Again high/low seems the same. Electrically the V R connections
> shouldn't make any difference, but physically if the V R has an issue,
> swapping the terminal connections at the V R ( fuse and battery circuits )
> would produce a noticeable change. I'll try that next. I'm also earth
> strapping the components so I'm not chasing a bad/faulty ground.
> I've seen some conversions to alternators. Are there any comments regarding
> this. It seems that if I had 50 amps charging capacity I could eliminate
> this problem.
> I'm researching lower wattage bulbs, and have yet to power up the radio/cd
> player. Standard alpine unit, but does need 12 volts.
> Thanks Tim
> On 1 Nov 2010 at 21:45, Tim Keohane wrote:
>
>> I charged the battery @ 10 amps for 24 hours, then 2 amps for 3 days.
>> 4 hours after removing the charger these are the results:
>> Battery charge          13.5 volts
>
> That was actually quite hard on the battery. You put more than 240
> amp-hours into a 45 amp-hour battery. The result has to be lots of
> hydrolyzed water and probably some battery plate damage. (Plate
> damage occurs when hydrolization occurs inside the sintered plates,
> causing them to flake off bits of plate material.)
>
>> @ 2500 RPM  No Load
>> Battery                                 14.5 volts
>> Gen.                            14.5 volts  10.5 Amps
>> Battery circuit                 1.6 Amps
>> Fuse Panel circuit        8.5 Amps
>
> This seems pretty normal. I'm surprised that the V at the generator
> isn't a bit higher than the V at the battery, but the low voltage
> drop was probably due to the low current. Still, from the numbers
> below, I would have expected ~0.4 V difference.
>
> Note that the current out of the generator = the sum of the currents
> out of the VR. As it should be.
>
>> @ 2500 Low Beams ( 2x 55 watts)
>> Battery                         14.5 volts
>> Gen.                            15.2  volts   20.5-21.5 amps
>> Battery circuit                1.5 - 2.5 amps
>> Fuse panel circuit         19.3 amps
>
> Again, this is pretty normal. At the same voltage the battery is
> taking about the same current, while the excess is going to the 2
> headlights via the fuse panel, and the currents in and out of the VR
> sum the same.
>
>> The generator light only comes on when I turn the key to start. Once
>> started it goes out, and does not indicate when the generator is
>> insufficient to maintain the battery @ 12.5 volts or higher. I can
>> visualize the generator light remaining out if it V R is receiving
>> ample current regardless of the circuit out except when the battery
>> goes down during use. I would also think more amperage would flow to
>> the battery to maintain it.
>
> I'm guessing that you're expecting more out of your idiot light than
> it can actually deliver. It's exactly the same as any other
> automotive charging system idiot light and they are not a perfect
> system.  They only tell you when there is a difference between the
> generator output voltage and the battery voltage. When they both go
> down together the light does not light.
>
>> My first impression is everything here seems within parameters, but
>> the battery dies then the car without an indication. When a fresh
>> battery is installed the car starts and runs without a hic-up.  I have
>> not checked the strength of the battery. I guess I'll have to replace
>> the bulbs with something requiring a little less.
>
> I think you're on the right track. The electrical system on our cars
> cannot support those lights for extended drives. If you drove with
> those headlights for no more than a half hour at a time, followed by
> several hours of no headlights, they would probably be fine. You just
> need to give the charging system and battery a chance to recover.
> Note that nothing much happens at idle; the generator needs decent
> rpms to put out its rated current. 2500 rpm was a good choice for
> your tests.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
> Tim & Paula Keohane
> Purveyors of:
> Wild Alaska Salmon & Halibut
> AKC/FDSB/CKC Irish Setters
> rheorojo at wildblue.net
>
>
>
>
>
>
>
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