Nick2 wrote:
On Fri, 29 Sep 2006 09:41:03 +0100, Dave Plowman (News) wrote:

I've got an accurate voltmeter sitting across my car battery at all times
the ignition is on, and I can assure you it never drops under nine point
something volts even on the coldest day when starting. Usually the high
10s. If you think about it, old cold start ignition systems are designed
for 9 volts minimum.

I wonder how responsive it is to transitions? I think you are right
though, most modern cars never seem to really load their batteries on
starting.

Doesn't always apply to diesels though... many a time I've heard a diesel
van start up after barely turning over.


We bought a second hand diesel, and tha battery was duff..I had to jump
it. Even at 10v it would not 'catch' - gloplugs too cold probably. I had
to fire up the 'donor' vehicle to get the volts up enough for it to
fire, and the bloody thing ran a bit rough for half a minute till the
volts came up on the battery. I had a meter on and that was about 10.5
volts that DIDN'T start it.

Strangely enough I had traded it for a jaguar with also a dead battery.

That fared even worse. Half the electronics didn't work properly even
with the engine running (finally) and I drove it to the garage with the
ABS and power brakes warning lights on, and the bloody windows wouldn't
stay closed till I got there and rebooted them..

Its not a question of the starter motor these days as much as the
likelihood that half the computers in the thing are designed for some
voltage above 10v at least.

Old cars are a lot more tolerant.