On Sat, 05 Jan 2019 15:43:57 -0000, Dave Plowman (News) wrote:

In article ,
Commander Kinsey wrote:
On Sat, 05 Jan 2019 11:47:26 -0000, Dave Plowman (News) wrote:

In article ,
Commander Kinsey wrote:
No alternator I've ever seen stays at 14.4v when the battery is
charged. It would very soon fry the battery. And modern batteries
are semi sealed and don't like gassing.

Maybe modern cars have a regulator to stop that,

Pretty well all cars - even in dynamo days - have a regulator. In most
alternators, it's built in.

I've heard the term "regulator" used for cars, but I thought it was to
change 3 phase AC into DC, just a big bridge rectifier.

They have both. Rectifier pack and regulator. Some older - or larger
alternators - had the regulator external to the alternator.

So it has some kind of intelligent sensor that detects when the battery is full and switches to trickle mode?

but older cars (and I mean around the turn of the century ones, not
vintage) don't. If you put a meter on the battery when the engine is
running, it's always over 14V. I assume batteries don't really mind
that as long as it's just for driving time - they'd be upset if you
did it 24/7.

If you check the battery volts just after a cold start, you'd be
right. You need to hook up your meter to show the volts after some
time running, when the battery is charged.

I wasn't aware lead acids were so fragile. I have my old car connected
to an old Bradex 4A charger 24/7, as the alarm runs the battery flat.
The charger indicates it's delivering 0.5 amps after it's been sat for a
while, and I've measured it at 14.4V. Surely charging a 60Ah battery at
0.5A (which is a 5 day charge!) can't possibly break it?

Something very odd indeed if you're seeing 14.4 volts and an 0.5 amp
charge at the same time.

What would you expect to see? The above is my experience with all lead acids, they simply don't take much current when they're full.