"trader_4" wrote in message
...
On Friday, June 21, 2019 at 4:54:51 PM UTC-4, Rod Speed wrote:
Commander Kinsey wrote

How does a lead acid battery charger (or car alternator) know when to
switch to trickle charge?

From the current the battery takes.

Except that the alternator doesn't know how much current
is going into the battery and how much is being used to
power the car.At least not in any car I've had.

Have fun explaining how you can have an ammeter
which shows the current that is going to the battery.

Ditto with an OBD2 dongle.

The alternator is tied directly to the battery

Yes.

and that common point supplies the car.

Nope. And there isnt normally just the
one wire at the positive battery terminal.