Date: Wed, 04 Jun 1997 12:22:41 -0600
Subject: Car Batterys these days...was Lucas bashing.
email@example.com (John Stevenson) wrote:
> We moan about quality and prices but has anybody noticed about
> batteries. I have just replaced the one on my 1990 diesel truck. It
> has done 120,000 miles which by US standards is not big but due to
> shorter distances has probably spent more time using the starter. This
> was the original battery and at 7 years old I think that's good.
It's partly improvements in battery technology, but a lot of it is due to
improved voltage regulators, and alternators that make life much easier
for the battery. Though I moan about the trend toward unmaintainable
batterys (euphamisticly marketed as "maintainance free") at least this
keeps bone heads from doing you a favor and topping it up with chlorine
and mineral laden tap water.
That buzzer that tells you you've left your lights on has a lot to do
with it too. Just takes one discharge to zero volts to start a battery's
Fuel injection helps also. I'ts rare that I engage the strater for as
much as a full second...one touch and she's running. Also doesn't die
unless I dump the clutch...so battery only has to start engine once per
trip. Unless you had the idle up way too high, carburators used to let
the engine load up and die at idle now and then.
It sounds like you are the mechanic, and the only driver. That situation
made the origional brakes last 140,000 miles on my car. Nobody goes as
easy on a vehicle as the man who will be busting his knuckles in the cold
and wind if/when it fails. Dad and I never could teach mom how to start
car without giving the starter & battery a workout. Superior engineering
is no match for the distructive influance of a committee....applys to
more than just cars.
Now if Detoit (or wherever) would temperature compensate the voltage
regulator at -24mV/C then even we desert dwellers could make batterys
last almost so long without having to pry up those one-shot caps so we
can add water. (distilled if you please)
Final tip is always buy the biggest battery that wil physically fit in
the available space. New technology batterys can be much smaller and
still start the car, but having lots of extra capacity will never be a
disadvantage. Take a tape measure to the auto parts store, and ignore
those application charts.
Subject: Re: Car Batterys these days...was Lucas bashing.
Date: 5 Jun 1997 18:43:54 GMT
In <3396C8E6.5B45@htc.honeywell.com>, Don Stauffer
>Whether the manuals specify it or not, yes, solid state voltage
>regulators are temperature compensated.
>The problem with the old electro-mechanical regulators was not poor
>operation, it was a failure mode that froze points together so contacts
>could not open. That really fries a battery.
Even the old electromechanical (relay type) regulators were
temperature compensated. At least the Delco one on my folk's
'72 Chevy was. I don't recall exactly how it was done, but
it had something to do with the arm that held the contact
on the votage regulator relay being bimetalic.
The top of the field winding went to B+, and the bottom went
to the moving contact, and also a resistor to ground. The outer
stationary contact went to ground, and the inner stationary
contact went to B+.
If the buss voltage was way down, the moving contact would
relax, and ground the bottom of the field winding - giving the
field full excitation. If the buss votage was intermediate, the
contact would float around between the two stops, and the
field would be energized thru the resistor. And if the voltage
was very high, the moving contact would suck down tight,
and the field would have B+ at both ends - no current.
But the real regulation was sort of a time-averaged thing, of
the moving contact bouncing around in between. So they
just modified the contact arm so when it was cold, the contact
wanted to move more towards the "full excitation" side.
But contacts for e/m relays, switches, and contactors is a
big business - they spend lots and lots of $ to keep them
from sticking like that. Silver is expensive, and cadmium is
toxic. Cheap relays stick more than expensive ones, I suspect.