Date: Fri, 4 Aug 2000 11:44:38 -0600
Reply-To: "Jon B. Kanas" <kanas@quality.qadas.com>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "Jon B. Kanas" <kanas@quality.qadas.com>
Subject: Battery/Alternator/Regulator
Content-Type: TEXT/PLAIN; charset=US-ASCII
Good day Tinkerman and the list,
Regarding the charging problems you posted recently:
It is very important that you verify that your alternator output is
appropriate. When you have the alternator tested, make sure that you test
if off of the Vanagon. This insures that loose belts and localized wiring
problems in the Vanagon (particularly the exciter), or a problem on the
printer circuit board (air-cooled only) are not causing the alternator to
misbehave. Be sure that the alternator is tested at full load and full
RPM.
When the original alternator failed in my Syncro, there was a problem in
the armature which only appeared when the alternator was at full speed.
The first shop which tested it said it was OK. It turns out that they
never spun it up as fast as it normally runs in the Vanagon. My
alternator was charging when the engine was under 3000RPM, but quit
charging at higher RPMs. There were no idiot lights, just a discharged
battery at the most unexpected times (like during long trips!).
Your symptoms sound like you are exceeding the output capability of the
alternator. A small short in either the stator or armature of the
alternator can reduce it's output capacity in the manner you describe. An
alternator malfunctioning in this manner must work very hard to maintain
voltage and amperage; It is drawing too much horsepower from the engine
and may also be overheating.
My 1987 Syncro has a 90A alternator; I charge at about 14.25 volts with
nothing on, and about 14.0 volts with everything (including the fridge,
which is a BIG current pig) on.
If all is well, I would select the 15V charge option for the regulator.
In my experience, unless you frequently operate the Vanagon for extended
periods of time with little or no electrical loads the negative effects of
this slight overcharging will be mitigated by insuring that the battery is
fully charged each time you use the Vanagon. You should make it a habit
to check the electrolyte level in the battery regularly, like when you
change the oil while you are 'experimenting' with different solutions. If
the top of the battery is moist, evidence of liquid splattering in the
battery compartment, or frequent light bulb failures, you are charging way
too high for your application. If you do a lot of short, local trips, you
want to be charging at the higher rate because you are not running the
Vanagon long enough to fully charge the battery at the nominal voltages
cited in your post.
Constant undercharging is a bad thing: Running the battery in a condition
that infrequently fully charges promotes "sulfating" of the plates. On
that infrequent occasion that you then charge the battery fully, the
sulfur is "baked" onto the lead plates, the surface area of the plates
which is in contact with the electrolyte is reduced, and the battery never
fully charges again. You want the get the battery charged as fully as
possible every time you start the Vanagon.
I have two old Porsches, one with a generator and one with an alternator.
These cars are infrequently used and I have both set up for a high charge
rate (between 14.75 and 15.0) volts. On those occasions I do drive them,
I am reasonably confident that I fully charge the battery with each use.
I recently returned from an mid-mileage (+/- 300 miles) daytime trip in
the 914 and had no evidence of overcharging.
Best wishes,
Jon Kanas
