On Sun, 23 Jun 2019 14:53:00 +0100, trader_4 wrote:

On Saturday, June 22, 2019 at 5:58:02 PM UTC-4, Commander Kinsey wrote:
On Sat, 22 Jun 2019 17:03:08 +0100, TMS320 wrote:

On 21/06/2019 21:19, Commander Kinsey wrote:
How does a lead acid battery charger (or car alternator) know when to
switch to trickle charge?

It doesn't.

Mine does, if I start my car when the battery is say 80% full, the voltage will be 14.4V. After a while, something causes that voltage to drop to 13.8, because something knows the battery is full and should no longer be charged at a high rate.


Go find a description of the voltage regulator/alternator and/or a
schematic for that car.

No idea where to find that.

Give us the references. If something is telling
the VR/alternator what voltage to target, then there must be an additional
wire or connection of some kind.

Agreed. And it could well have a sensor in the fusebox etc.

I have not seen that. The other possibilities
are that the VR itself lowers the target voltage, based on? Makes no sense
and I've never seen it mentioned anywhere. I just googled for VR and looked
at half a dozen references, all just say the VR targets a specific voltage
period. The other possibility is that when you read the voltage later,
some other load is present that is lowering the system voltage that you see.

No, all I did was to start the car when the battery was almost full. The battery terminal voltage was immediately 14.4V. 20 minutes later it dropped to 13.8V. I added no loads. I think it actually dropped gradually if that means anything. I actually did that test because someone in one of these groups (although some troll has deleted half the groups, so I've added them back in AGAIN) told me that a car alternator changes voltage, this was in a post 6 months ago.

I can understand it noticing a drop in
charging current if the battery is on its own, but what if a random
changing load is connected, as there is in a running car?

Ohm's law.

Explain how an alternator or charger can use ohm's law to distinguish between:
1) A car battery which is full, with a load of 10 amps connected to it, like two headlights.
2) A car battery with no load, which is not full yet and draws 10 amps for the charge.

Rod claims that they have an extra sensing wire at the battery terminal
and use the voltage there versus the voltage at the other end of the
cable, to determine the current. I seriously doubt that, for obvious
reasons involving the very large gauge cable and current of interest.

It could only be mV, but easy enough to sense with modern electronics. Or how about an amp clamp?

And he can't produce a damn thing from anywhere that says that's what
they do, except his own worthless statements. If it's done that way
anywhere, it's not done on the cars I've seen here, that have just one
battery cable on the positive terminal.

Every UK car has 2 or 3 cables on the battery positive. America is infamous for being behind the times. We all know your cars can't go round corners, and get way less HP for the same engine size.

Why doesn't someone show us
an example, a description of one of these alleged fancy voltage regulators
that are computer controlled?