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Peeler
Guest

Sat Jun 22, 2019 12:45 am   



On Sat, 22 Jun 2019 08:57:52 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

Quote:

That's the way batterys work


That's the way how your and his trolling work, you senile asshole troll!

--
Bod addressing senile Rot:
"Rod, you have a sick twisted mind. I suggest you stop your mindless
and totally irresponsible talk. Your mouth could get you into a lot of
trouble."
Message-ID: <gfbb94Fb4a4U1_at_mid.individual.net>

Rod Speed
Guest

Sat Jun 22, 2019 12:45 am   



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rauixewdg98l_at_desktop-ga2mpl8.lan...
Quote:
On Fri, 21 Jun 2019 23:39:34 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q6mue3wdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 21:54:38 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:

Commander Kinsey <CFKinsey_at_military.org.jp> wrote

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

From the current the battery takes.

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?

You just look at the current going to the battery. The variably
loads like with lights isnt supplied by the battery when the
engine is running, its supplied by the alternator.

But how can the regulator on the alternator possibly know the current
it's
passing to the battery is going into the battery and not going straight
across to the lights?

The computer knows whats going to the battery and you can see that with
an ODB2 dongle.

My dongle only lists faults.


Because it's a steaming turd with wheels frog car.

Most show all sorts of things.

Quote:
If you look at the battery in your car, there are two or three thick
wires
coming off each terminal. One will go to the alternator, another to the
fusebox for all the lights etc.

And it's the voltage across the one going from the alternator to the
battery
that allows the computer to know how much current is going to the
battery.

Bullshit.


We'll see...

Quote:
How could it possibly know if the current flows into the battery or goes
to the other wire leading to the fusebox?


By measuring the voltage drop across those cables, stupid.

Quote:
Unless there's some clever circuitry monitoring each
battery wire individually and subtracting the currents,

Yes there is, its called the computer.

So what happened with older cars before they did that?


The voltage across the battery changes as the battery is charged.

Quote:
the alternator can't tell the difference between a battery taking 12
amps,
and a battery taking 2 amps plus lights taking 10 amps.

But the computer can. And knows if the lights are on too.

The second one requires switching to trickle charge, the first doesn't.


Commander Kinsey
Guest

Sat Jun 22, 2019 12:45 am   



On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed <rod.speed.aaa_at_gmail.com> wrote:

Quote:


"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q9fvpjwdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian <max_demian_at_bigfoot.com
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 the way batterys work, the battery voltage does change as its
charged.

That's determined by the alternator or charger.

Nope.


Yip. I can put any voltage I like across a battery's terminals. The battery then chooses how much current is drawn.

Quote:
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.

Its more complicated than that with the current going to the battery and the
battery is charged.

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.

No it doesn't even with a very crude battery charger.


For example, I'm currently keeping my car's battery topped up with a bench supply overnight. It's set to 13.8V, with a current limiter only to prevent overloading the supply. The voltage stays at 13.8V all the time, sometimes 100mA is drawn, sometimes up to 4A. The only way I or the supply can tell the battery is full, is by the current dropping to 100mA. But it's actually always full, as when 4A is drawn, that's going to a load.

Quote:
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?

By checking the current actually being delivered to the battery.


I guess that may be true, if the car's computer has two ammeters and subtracts one from the other. But AFAIK, the alternator regulator only works by it's own current sensor. And that current could be going into the battery, or past it to the loads.

Commander Kinsey
Guest

Sat Jun 22, 2019 12:45 am   



On Sat, 22 Jun 2019 00:26:13 +0100, Rod Speed <rod.speed.aaa_at_gmail.com> wrote:

Quote:


"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rauixewdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:39:34 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q6mue3wdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 21:54:38 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:

Commander Kinsey <CFKinsey_at_military.org.jp> wrote

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

From the current the battery takes.

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?

You just look at the current going to the battery. The variably
loads like with lights isnt supplied by the battery when the
engine is running, its supplied by the alternator.

But how can the regulator on the alternator possibly know the current
it's
passing to the battery is going into the battery and not going straight
across to the lights?

The computer knows whats going to the battery and you can see that with
an ODB2 dongle.

My dongle only lists faults.

Because it's a steaming turd with wheels frog car.


Which should adhere to the fucking OBD standards according to the frog's own EU regs!!

And a very basic OBD reader I bought to determine why a warning light was on.

Quote:
Most show all sorts of things.

If you look at the battery in your car, there are two or three thick
wires
coming off each terminal. One will go to the alternator, another to the
fusebox for all the lights etc.

And it's the voltage across the one going from the alternator to the
battery that allows the computer to know how much current is going to the
battery.

Bullshit.

We'll see...

How could it possibly know if the current flows into the battery or goes
to the other wire leading to the fusebox?

By measuring the voltage drop across those cables, stupid.

Unless there's some clever circuitry monitoring each
battery wire individually and subtracting the currents,

Yes there is, its called the computer.

So what happened with older cars before they did that?

The voltage across the battery changes as the battery is charged.


Wrong. Say the alternator can produce 14V at up to 50 amps. When the battery has been used to start the car and perhaps run some lights when the engine was off, it takes maybe 25A, and the voltage is 14V, regulated by the alternator's circuitry. When the battery becomes full, it takes only a fraction of an amp, but the voltage is still 14V. What needs to be measured is the current going into the battery, and that cannot be done by just measuring the current coming from the alternator, as that could also be going to lights, heaters, spark plugs, etc, etc.

Quote:
the alternator can't tell the difference between a battery taking 12
amps,
and a battery taking 2 amps plus lights taking 10 amps.

But the computer can. And knows if the lights are on too.

The second one requires switching to trickle charge, the first doesn't.


Peeler
Guest

Sat Jun 22, 2019 1:45 am   



On Sat, 22 Jun 2019 09:26:13 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the two clinically insane asshole's latest trollshit unread>


--
Richard addressing Rot Speed:
"Shit you're thick/pathetic excuse for a troll."
MID: <ogoa38$pul$1_at_news.mixmin.net>

Rod Speed
Guest

Sat Jun 22, 2019 1:45 am   



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rc17q7wdg98l_at_desktop-ga2mpl8.lan...
Quote:
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q9fvpjwdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian <max_demian_at_bigfoot.com
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 the way batterys work, the battery voltage does change as its
charged.

That's determined by the alternator or charger.

Nope.

Yip.


Nope.

> I can put any voltage I like across a battery's terminals.

Nope.

> The battery then chooses how much current is drawn.

And that current changes depending on the how charged the battery is.

Quote:
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.

Its more complicated than that with the current going to the battery and
the
battery is charged.

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.

No it doesn't even with a very crude battery charger.

For example, I'm currently keeping my car's battery topped up with a bench
supply overnight. It's set to 13.8V, with a current limiter only to
prevent overloading the supply.


It actually specify the current being supplied.

Quote:
The voltage stays at 13.8V all the time, sometimes 100mA is drawn,
sometimes up to 4A. The only way I or the supply can tell the battery is
full, is by the current dropping to 100mA. But it's actually always full,
as when 4A is drawn, that's going to a load.


What load ? There no load with a battery being charged with a bench supply.

Quote:
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?

By checking the current actually being delivered to the battery.

I guess that may be true, if the car's computer has two ammeters


It has more than one wire to the positive terminal of the battery.
So it can see what current is going to the rest of the car.

Quote:
and subtracts one from the other. But AFAIK, the alternator regulator
only works by it's own current sensor. And that current could be going
into the battery, or past it to the loads.


Not when there is more than one wire going to the
positive terminal of the battery, and there always is.

Rod Speed
Guest

Sat Jun 22, 2019 1:45 am   



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rc8ux1wdg98l_at_desktop-ga2mpl8.lan...
Quote:
On Sat, 22 Jun 2019 00:26:13 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rauixewdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:39:34 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q6mue3wdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 21:54:38 +0100, Rod Speed
rod.speed.aaa_at_gmail.com
wrote:

Commander Kinsey <CFKinsey_at_military.org.jp> wrote

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

From the current the battery takes.

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?

You just look at the current going to the battery. The variably
loads like with lights isnt supplied by the battery when the
engine is running, its supplied by the alternator.

But how can the regulator on the alternator possibly know the current
it's
passing to the battery is going into the battery and not going
straight
across to the lights?

The computer knows whats going to the battery and you can see that with
an ODB2 dongle.

My dongle only lists faults.

Because it's a steaming turd with wheels frog car.

Which should adhere to the fucking OBD standards according to the frog's
own EU regs!!


Steaming turd frog cars don't work like that.

Quote:
And a very basic OBD reader I bought to determine why a warning light was
on.


Should still show that other stuff.

Quote:
Most show all sorts of things.

If you look at the battery in your car, there are two or three thick
wires
coming off each terminal. One will go to the alternator, another to
the
fusebox for all the lights etc.

And it's the voltage across the one going from the alternator to the
battery that allows the computer to know how much current is going to
the
battery.

Bullshit.

We'll see...

How could it possibly know if the current flows into the battery or goes
to the other wire leading to the fusebox?

By measuring the voltage drop across those cables, stupid.

Unless there's some clever circuitry monitoring each
battery wire individually and subtracting the currents,

Yes there is, its called the computer.

So what happened with older cars before they did that?

The voltage across the battery changes as the battery is charged.

Wrong.


Nope,

Quote:
Say the alternator can produce 14V at up to 50 amps. When the battery has
been used to start the car and perhaps run some lights when the engine was
off, it takes maybe 25A, and the voltage is 14V,


Yes.

> regulated by the alternator's circuitry.

Nope, buy the battery, and you can prove that with the bench supply.

> When the battery becomes full, it takes only a fraction of an amp,

Yep, because the battery voltage has risen.

> but the voltage is still 14V.

Nope, and you previously said it wasn't.

> What needs to be measured is the current going into the battery,

That's what the computer does.

Quote:
and that cannot be done by just measuring the current coming from the
alternator,


Yes, that's why there is more than one wire on the battery positive
terminal.

> as that could also be going to lights, heaters, spark plugs, etc, etc.

Yes, that's why there is more than one wire on the battery positive
terminal.

Quote:
the alternator can't tell the difference between a battery taking 12
amps,
and a battery taking 2 amps plus lights taking 10 amps.

But the computer can. And knows if the lights are on too.

The second one requires switching to trickle charge, the first
doesn't.


Rod Speed
Guest

Sat Jun 22, 2019 2:45 am   



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rc8ux1wdg98l_at_desktop-ga2mpl8.lan...
Quote:
On Sat, 22 Jun 2019 00:26:13 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rauixewdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:39:34 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q6mue3wdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 21:54:38 +0100, Rod Speed
rod.speed.aaa_at_gmail.com
wrote:

Commander Kinsey <CFKinsey_at_military.org.jp> wrote

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

From the current the battery takes.

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?

You just look at the current going to the battery. The variably
loads like with lights isnt supplied by the battery when the
engine is running, its supplied by the alternator.

But how can the regulator on the alternator possibly know the current
it's
passing to the battery is going into the battery and not going
straight
across to the lights?

The computer knows whats going to the battery and you can see that with
an ODB2 dongle.

My dongle only lists faults.

Because it's a steaming turd with wheels frog car.

Which should adhere to the fucking OBD standards according to the frog's
own EU regs!!


Steaming turd with wheels frog cars don't. And that isnt an EU reg anyway.

Quote:
And a very basic OBD reader I bought to determine why a warning light was
on.


That will still show more than just faults.

Quote:
Most show all sorts of things.

If you look at the battery in your car, there are two or three thick
wires
coming off each terminal. One will go to the alternator, another to
the
fusebox for all the lights etc.

And it's the voltage across the one going from the alternator to the
battery that allows the computer to know how much current is going to
the
battery.

Bullshit.

We'll see...

How could it possibly know if the current flows into the battery or goes
to the other wire leading to the fusebox?

By measuring the voltage drop across those cables, stupid.

Unless there's some clever circuitry monitoring each
battery wire individually and subtracting the currents,

Yes there is, its called the computer.

So what happened with older cars before they did that?

The voltage across the battery changes as the battery is charged.

Wrong.


Nope.

Quote:
Say the alternator can produce 14V at up to 50 amps. When the battery has
been used to start the car and perhaps run some lights when the engine was
off, it takes maybe 25A, and the voltage is 14V,


Yep.

> regulated by the alternator's circuitry.

Nope, by the battery.

> When the battery becomes full, it takes only a fraction of an amp,

Yep, because the battery voltage is now higher.

> but the voltage is still 14V.

The battery voltage isnt.

> What needs to be measured is the current going into the battery,

Nope, the current drops automatically.

Quote:
and that cannot be done by just measuring the current coming from the
alternator, as that could also be going to lights, heaters, spark plugs,
etc, etc.


That's why there is more than one wire to the battery positive terminal.

Quote:
the alternator can't tell the difference between a battery taking 12
amps,
and a battery taking 2 amps plus lights taking 10 amps.

But the computer can. And knows if the lights are on too.

The second one requires switching to trickle charge, the first
doesn't.


The Natural Philosopher
Guest

Sat Jun 22, 2019 7:45 am   



On 21/06/2019 22:57, Max Demian wrote:
Quote:
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.

Definitely. One of the simplest ways to msake a vcarger is to have a
constant voltage source in series with somem form of resistor. As the
terminal voltage rises so too does the charge current drop.

The problem that brings is when a heavy cirrent is siltanoeusly drawn
from the battery.

Which is why car alternator control is a little more spohisticated than
that.


--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

Peeler
Guest

Sat Jun 22, 2019 9:45 am   



On Sat, 22 Jun 2019 09:26:13 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


> We'll see...

We'll see YOU trolling on these groups like there was no tomorrow, you
85-year-old senile pest!

--
Keema Nam addressing nym-shifting senile Rodent:
"You are now exposed as a liar, as well as an ignorant troll."
"MID: <0001HW.22B654E7000BF12E70000F4CC2EF_at_news.giganews.com>"

Peeler
Guest

Sat Jun 22, 2019 9:45 am   



<FLUSH another 142 !!! lines of absolutel trollshit unread again>

--
gfretwell_at_aol.com addressing nym-shifting senile Rodent:
"You on the other hand are a heavyweight bullshitter who demonstrates
your particular prowess at it every day."
MID: <rufg9ep6ggjdt3uek8k5rnu41ca081rvce_at_4ax.com>

Peeler
Guest

Sat Jun 22, 2019 9:45 am   



<FLUSH another 137 !!! lines of the two asshole trolls' latest trollshit
unread>

--
Richard addressing Rot Speed:
"Shit you're thick/pathetic excuse for a troll."
MID: <ogoa38$pul$1_at_news.mixmin.net>

Peeler
Guest

Sat Jun 22, 2019 9:45 am   



On Sat, 22 Jun 2019 09:57:57 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the two prize idiots' endless trollshit>

Quote:
Not when there is more than one wire going to the
positive terminal of the battery, and there always is.


In auto-contradicting mode again, you clinically insane auto-contradicting
senile asshole? <G>

--
MrTurnip_at_down.the.farm about senile Rot Speed:
"This is like having a conversation with someone with brain damage."
MID: <ps10v9$uo2$1_at_gioia.aioe.org>

Xeno
Guest

Sat Jun 22, 2019 10:45 am   



On 22/6/19 9:33 am, Commander Kinsey wrote:
Quote:
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed <rod.speed.aaa_at_gmail.com
wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q9fvpjwdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian <max_demian_at_bigfoot.com
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 the way batterys work, the battery voltage does change as its
charged.

That's determined by the alternator or charger.

Nope.

Yip. I can put any voltage I like across a battery's terminals. The
battery then chooses how much current is drawn.

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.

Its more complicated than that with the current going to the battery
and the
battery is charged.

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.

No it doesn't even with a very crude battery charger.

For example, I'm currently keeping my car's battery topped up with a
bench supply overnight. It's set to 13.8V, with a current limiter only
to prevent overloading the supply. The voltage stays at 13.8V all the
time, sometimes 100mA is drawn, sometimes up to 4A. The only way I or
the supply can tell the battery is full, is by the current dropping to
100mA. But it's actually always full, as when 4A is drawn, that's going
to a load.

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?

By checking the current actually being delivered to the battery.

I guess that may be true, if the car's computer has two ammeters and
subtracts one from the other. But AFAIK, the alternator regulator only
works by it's own current sensor. And that current could be going into
the battery, or past it to the loads.


Nope, the alternator regulator is sensing only *voltage*.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

Xeno
Guest

Sat Jun 22, 2019 10:45 am   



On 22/6/19 9:57 am, Rod Speed wrote:
Quote:


"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3rc17q7wdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed
rod.speed.aaa_at_gmail.com> wrote:



"Commander Kinsey" <CFKinsey_at_military.org.jp> wrote in message
news:op.z3q9fvpjwdg98l_at_desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian <max_demian_at_bigfoot.com
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 the way batterys work, the battery voltage does change as its
charged.

That's determined by the alternator or charger.

Nope.

Yip.

Nope.

I can put any voltage I like across a battery's terminals.

Nope.

The battery then chooses how much current is drawn.

And that current changes depending on the how charged the battery is.

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.

Its more complicated than that with the current going to the battery
and the
battery is charged.

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.

No it doesn't even with a very crude battery charger.

For example, I'm currently keeping my car's battery topped up with a
bench supply overnight. It's set to 13.8V, with a current limiter
only to prevent overloading the supply.

It actually specify the current being supplied.

The voltage stays at 13.8V all the time, sometimes 100mA is drawn,
sometimes up to 4A. The only way I or the supply can tell the battery
is full, is by the current dropping to 100mA. But it's actually
always full, as when 4A is drawn, that's going to a load.

What load ? There no load with a battery being charged with a bench
supply.


Correction - the *battery* is the *load*. In the process of being
charged it is using electric current. That makes it the load. Even when
it is fully charged it will still take a trickle charge so it is still a
load even when fully charged.
Quote:

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?

By checking the current actually being delivered to the battery.

I guess that may be true, if the car's computer has two ammeters

It has more than one wire to the positive terminal of the battery.
So it can see what current is going to the rest of the car.

and subtracts one from the other. But AFAIK, the alternator
regulator only works by it's own current sensor. And that current
could be going into the battery, or past it to the loads.

Not when there is more than one wire going to the
positive terminal of the battery, and there always is.


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

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