On Mon, 24 Jun 2019 02:26:38 +0100, trader_4 wrote:

On Sunday, June 23, 2019 at 3:07:53 PM UTC-4, Commander Kinsey wrote:
On Sun, 23 Jun 2019 14:39:09 +0100, trader_4 wrote:

On Saturday, June 22, 2019 at 5:22:54 PM UTC-4, Commander Kinsey wrote:
On Sat, 22 Jun 2019 16:45:08 +0100, Rod Speed wrote:



"trader_4" wrote in message
...
On Friday, June 21, 2019 at 6:48:31 PM UTC-4, wrote:
On Fri, 21 Jun 2019 23:15:21 +0100, "Commander Kinsey"
wrote:

On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian
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? 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?

The voltage perhaps.

Why would the voltage change? That's determined by the alternator or
charger. Let's say the charger/alternator gives out 14.4V initially, to
charge the battery quickly. It'll just sit at 14.4V forever, providing
the charger can give out enough current to charge the slightly flat
battery and power any connected loads. If the battery had no loads
connected, it would take a lot less current when it became full, but the
voltage would stay the same. If the charger monitored the current it
was providing, how does it know if the battery is still charging at 10
amps, or if the battery is full and there's a 10 amp load?

Not really true with anything but the most primative regulator like
you might see on an old outboard. Voltage is regulated somewhere
between 13.x and 14.x, not just reflecting what the alternator can do
against the load.
Rod is right, they look at current from the alternator

Every car I've seen, the the alternator, the battery
and the rest of the car are tied to one point

But there is normally more than the one wire
at the the positive terminal of the battery.

and there is no monitor for what current
is going to the battery vs to the car load.

Wrong when there is normally more than the one
wire at the the positive terminal of the battery.

And Rod is talking computers,

Because thats what his car has.

so how did cars work prior to the 80s?

The regulator uses the voltage it sees which varys
with the load and the charge of the battery.

That was my original question - on an old car, there is no way for the regulator to tell the difference between the battery still charging at 10 amps and the headlamps being switched on.

Probably on most or all new cars too. Why change what works?

But it didn't work. Stop start activities like short shop runs, taxi drivers, etc, everyone got flat batteries. Modern cars presumably do a fast charge after starting. So they need to know when to slow down the charge rate.

And so far I haven't seen any evidence presented here that shows modern
ones can tell the difference and care about it either. The ones I've
seen, still have a voltage regulator in the alternator that functions
like it has for most of the last century. Rod claims to know so much,
including that they use the resistance of the battery cable to measure
current, but he can't produce anything other than his own flapping BS
gums and he's likely just doing the usual, making it up on the fly
and lying.

What he says sounds very easy to implement, and it would make sense to allow the battery to be put on fast charge after starting it, then go back to trickle later. And my own car certainly does change the voltage after a while. 14.4 then 13.8.

I disagree, what he says makes no sense for obvious reasons that another
poster described. And AFAIK, the VR just targets voltage, that Rod is
bloviating his usual BS doesn't change that.
But heh, if you or Rod have a reference that describes this
"new" system, that uses the resistance of the battery cable to measure
current and then the computer controls the VR, let's see it. Otherwise,
I say your question is answered,
the VR doesn't know or care where the current is going, it just maintains
a system voltage of ~14V.

Wrong, I've ****ing well measured it myself, for the fifth time!!