On Fri, 21 Jun 2019 23:44:24 +0100, 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.

Er that's what he just said, it can't. The car must have more than one meter, on every wire coming from the battery, so it knows what's being consumed and what's used for charging.

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.

I believe mine has three. Alternator, starter, everything else. The alternator itself can't know where it's current goes once it reaches the battery terminal. Does it go to the lights or into the battery itself?