[T3] Voltage Regulator

[Tim Keohane]

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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