On Friday, June 21, 2019 at 6:44:36 PM UTC-4, Rod Speed wrote:
"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.


Because then there is an ammeter, dummy. I have yet to see a car
that has a sensor in the cable path to the battery. And obviously
it's not needed because lead acid car batteries worked for most of
a century BEFORE there was any computer to monitor or control anything
and the batteries worked fine, lasted just as long.



Ditto with an OBD2 dongle.

That is just a connection to the computer dummy and cars had batteries
for most of a century BEFORE OBD2.




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.

BS as proven by all the cars I've worked on over the years. Battery,
alternator, car loads all tied to one common point. And the VOLTAGE
regulator simply monitors that common point for VOLTAGE.