Lead acid battery charger (or alternator) switching to trick

[Peeler]

On Sun, 23 Jun 2019 01:30:41 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH another 209 !!! lines of senile bullshit unread again>

--
Sqwertz to Rodent Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID: <ev1p6ml7ywd5$.dlg@sqwertz.com>

 

[Bod]

Here, educate yourself;
https://www.swtc.edu/ag_power/electrical/lecture/parallel_circuits.htm

I knew all that before you were even born, thanks.

so it is still a load even when fully charged.

Not when its still taking 4A,

If the battery is *taking* 4 amps, then it *is definitely the load*.

But it wont be taking 4A WHEN THE BATTERY IS OUT OF THE
CAR WITH A BENCH SUPPLY. Because the battery voltage will
have risen once it has been charged so the original 4A will
have dropped significantly WITH A BENCH SUPPLY.

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.

No they aren't, unless one has been added.

--
Bod

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[TMS320]

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.

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.

 

[Commander Kinsey]

Modern car alternators seem to be able to give out a huge amount of current at engine idle speed. I'm sure my friend got his to give out pretty much the full 80 amps without revving the engine. He was powering a small disco on a campsite


On Sat, 22 Jun 2019 11:00:34 +0100, Brian Gaff <briang1@blueyonder.co.uk> wrote:

Yes indeed, the nominal output of an alternator can be as high as 15 volts,
but even a fully charged car battery is only 13.8v as far as I know and
these days, I'm sure the direction of current flow and voltages are
monitored very well by the computers. In the old days it was a bit of a
black art just relying on the ability of the alternator or dynamo in the old
bangers.
Normally the output will change due to engine speed, but in alternators
there is a voltage regulator inbuilt to keep the thing pretty nominal and
of course the thing that then suffers is the charging rate, ie its going to
be be slower when its not running very fast. I think if a battery dips below
about 11v outside of starter transients, you have to charge it or get a new
one. This very accurate sensing these days can often mask a battery on its
last legs though, as people tend to ignore warnings if the car still works,
then they leave it a couple of days and it won't start!

Brian

 

[Commander Kinsey]

On Sat, 22 Jun 2019 11:11:33 +0100, Rod Speed <rod.speed.aaa@gmail.com> wrote:

Brian Gaff <briang1@blueyonder.co.uk> wrote

Yes indeed, the nominal output of an alternator can be as high as 15
volts, but even a fully charged car battery is only 13.8v as far as I know

They are a bit higher than that just after being charged.

Depends what voltage you were charging them with. 13.8V is the recommended voltage for a continuous charge. 14.4V for fast, and 15V for very fast. But the last two need to be stopped before boil over.

I used to have a home made solar array, with thirty old car batteries in parallel. Bad idea. One of the batteries died - it lost a cell. The other batteries immediately then charged it very quickly as it was 10V and they were 12V, and evaporated the other cells one by one. There was eventually an explosion and the battery was blasted across the garage in several pieces, with a bloody strong smell of rotten eggs.

and these days, I'm sure the direction of current flow and voltages are
monitored very well by the computers. In the old days it was a bit of a
black art just relying on the ability of the alternator or dynamo in the
old bangers.
Normally the output will change due to engine speed, but in alternators
there is a voltage regulator inbuilt to keep the thing pretty nominal
and of course the thing that then suffers is the charging rate, ie its
going to be be slower when its not running very fast. I think if a battery
dips below about 11v outside of starter transients, you have to charge it
or get a new one. This very accurate sensing these days can often mask a
battery on its last legs though, as people tend to ignore warnings if the
car still works, then they leave it a couple of days and it won't start!

Brian

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"Rod Speed" <rod.speed.aaa@gmail.com> wrote in message
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Commander Kinsey <CFKinsey@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.

 

[Commander Kinsey]

On Sat, 22 Jun 2019 11:55:51 +0100, Mr Pounder Esquire <MrPounder@rationalthought.com> wrote:

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?

Asks the unemployable wanker/troll with a 20 year old worthless degree and a
stated IQ of 138. Odd that a few years ago your stated IQ was 142.

It has always been 135. And the degree is 22 years old.

 

[Commander Kinsey]

On Sat, 22 Jun 2019 17:03:08 +0100, TMS320 <dr6092@gmail.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?

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.

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.

 

[Commander Kinsey]

On Sat, 22 Jun 2019 00:57:57 +0100, Rod Speed <rod.speed.aaa@gmail.com> wrote:

"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3rc17q7wdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed <rod.speed.aaa@gmail.com
wrote:



"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3q9fvpjwdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian <max_demian@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.

I can if the charger / power supply is powerful enough.

The battery then chooses how much current is drawn.

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

Correct, it's the current it checks.

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.

No, it LIMITS the current. I set 13.8V, 2.5A. It will back off if either is exceeded.

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.

The faulty frog car with the dodgy alarm.

 

[Commander Kinsey]

On Sat, 22 Jun 2019 11:41:15 +0100, Xeno <xenolith@optusnet.com.au> wrote:

On 22/6/19 7:58 pm, Rod Speed wrote:


"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1@mid.individual.net...
On 22/6/19 9:57 am, Rod Speed wrote:


"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3rc17q7wdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed
rod.speed.aaa@gmail.com> wrote:



"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3q9fvpjwdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian
max_demian@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

Nope.

the *battery* is the *load*.

Not when the battery is fully charges and is being charged
with a bench supply that is delivering 4A to the battery.

Take the case of an alternator charging a battery at ~4 amps. The
battery is the load and it also provides, as part of that function, the
reference *voltage* that the alternator *must have* in order to control
the output.

I believe the reason Rod mentioned load as being seperate to the battery is this thread is about my car, with a fault that draws current from the battery, and it's also connected to a bench supply. In this situation, we refer to "load" as the faulty alarm system. I originally asked how an alternator could distinguish between the battery charging, and a load such as your headlamps being on.

In the process of being charged it is using electric current. That
makes it the load.

See above.

What happens to the charger when you disconnect the power with the
battery connected? It should, if designed correctly, shut down since it
no longer sees a load. Otherwise it may destroy itself.

Bullshit. You're telling me that a bench supply with a battery on the output and no 240V input will blow up if it doesn't shut down? Wrong. Absolutely wrong. The output end of the supply (which probably ends with smoothing capacitors) is just kept at the normal output voltage by the battery.

Even when it is fully charged it will still take a trickle charge

4A isnt a trickle charge.

That depends entirely on the amp hour rating of the battery.
Also, my bench charger will start off at 4 amps, its maximum capacity.
As the battery becomes charged, that current will drop down to *1 amp*
and, from that point, it will maintain a *trickle charge*.

How fucking big is that battery?! When I charge a 60Ah lead acid at 13.8V, it drops to about 150mA when full.

From Wikipedia;
For lead-acid batteries under no load float charging (such as
in SLI batteries), trickle charging happens naturally at the
end-of-charge, when the lead-acid battery internal resistance
to the charging current increases enough to reduce additional
charging current to a trickle, hence the name. In such cases,
the trickle charging equals the energy expended by the
lead-acid battery splitting the water in the electrolyte into
hydrogen and oxygen gases

Trouble is you might want to do a bulk charge first, at 14.4V.

The car alternator regulator is no different. It sees the battery as a
load, determines the voltage reference and pumps up its output.

All it can do is supply a certain voltage. 13.8V is safe. If it uses 14.4V or higher, it has to know when to back off to 13.8. It cannot do that if there is an external current draw like headlamp, as it won't know if they're switched on, or if the battery is drawing that current.

When the
regulator sees the battery voltage at the peak setpoint,

You can't tell a battery is full by voltage. You can only tell by it drawing less current. The voltage is determined by the charger.

it too will
drop the current to a trickle.

Actually it drops the voltage, to 13.8. I used to have a solar battery regulator which had very detailed instructions saying how it worked. It took the voltage of the solar cells and altered it up or down a bit to suit the battery condition.

If you add a load, say by turning
headlights on, that is in *parallel* to the battery and it will drop the
system voltage down a tad. The regulator will see that and pump up the
output current appropriately. The current will apportion itself to the
*two* loads as appropriate to their individual internal resistances.

But it can't tell the difference between current going to the lights and to the battery.

 

[Rod Speed]

Commander Kinsey <CFKinsey@military.org.jp> wrote

Rod Speed <rod.speed.aaa@gmail.com> wrote
Brian Gaff <briang1@blueyonder.co.uk> wrote

Yes indeed, the nominal output of an alternator can be as high as 15
volts, but even a fully charged car battery is only 13.8v as far as I
know

They are a bit higher than that just after being charged.

Depends what voltage you were charging them with.

We're discussing cars.

> 13.8V is the recommended voltage for a continuous charge.

That's wrong too.

> 14.4V for fast, and 15V for very fast.

And so is that.

But the last two need to be stopped before boil over.

I used to have a home made solar array, with thirty old car batteries in
parallel. Bad idea. One of the batteries died - it lost a cell. The
other batteries immediately then charged it very quickly as it was 10V and
they were 12V, and evaporated the other cells one by one.

Trivially easy to avoid that.

> There was eventually an explosion

That was the hydrogen you stupidly didn't get rid of.

and the battery was blasted across the garage in several pieces, with a
bloody strong smell of rotten eggs.

and these days, I'm sure the direction of current flow and voltages are
monitored very well by the computers. In the old days it was a bit of a
black art just relying on the ability of the alternator or dynamo in the
old bangers.
Normally the output will change due to engine speed, but in alternators
there is a voltage regulator inbuilt to keep the thing pretty nominal
and of course the thing that then suffers is the charging rate, ie its
going to be be slower when its not running very fast. I think if a
battery
dips below about 11v outside of starter transients, you have to charge
it
or get a new one. This very accurate sensing these days can often mask
a
battery on its last legs though, as people tend to ignore warnings if
the
car still works, then they leave it a couple of days and it won't start!

Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
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Blind user, so no pictures please
Note this Signature is meaningless.!
"Rod Speed" <rod.speed.aaa@gmail.com> wrote in message
news:gn4ugmFbofdU1@mid.individual.net...
Commander Kinsey <CFKinsey@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.

 

[Xeno]

On 23/6/19 2:03 am, 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.

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.

That's a bit *deep* for some people to comprehend.

--

Xeno


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

 

[Xeno]

On 23/6/19 1:30 am, Rod Speed wrote:

"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn6eudFlh2sU1@mid.individual.net...
On 22/6/19 7:58 pm, Rod Speed wrote:


"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1@mid.individual.net...
On 22/6/19 9:57 am, Rod Speed wrote:


"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3rc17q7wdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed
rod.speed.aaa@gmail.com> wrote:



"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3q9fvpjwdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian
max_demian@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

Nope.

the *battery* is the *load*.

Not when the battery is fully charged and is being charged
with a bench supply that is delivering 4A to the battery.

Take the case of an alternator charging a battery at ~4 amps.

That isnt what was being discussed there. What was being discussed
there was charging the battery out of the car with a bench supply.

The battery is the load and it also provides, as part of that
function, the  reference *voltage* that the alternator *must have* in
order to control  the output.

None of that is relevant to what was being discussed there,
charging the battery out of the car with a bench supply.

In the process of being charged it is using electric current. That
makes it the load.

See above.

What happens to the charger when you disconnect the power with the
battery connected?

With a BENCH SUPPLY, it continues to provide the
same voltage as it did with the battery connected.

It should, if designed correctly, shut down since it no longer sees a
load. Otherwise it may destroy itself.

That is just plain wrong with a BENCH SUPPLY.
None of those destroy themselves with no load.

Even when it is fully charged it will still take a trickle charge

4A isnt a trickle charge.

That depends entirely on the amp hour rating of the battery.

We're discussing a normal car battery in a steaming turd with
wheels frog car.

Also, my bench charger

We arent discussing a bench charger, we are discussing a bench SUPPLY.

will start off at 4 amps, its maximum capacity. As the battery becomes
charged, that current will drop down to *1 amp* and, from that point,
it will maintain a *trickle charge*.

So that is nothing like the situation being discussed
with a BENCH SUPPLY which is still delivering 4A to
a battery that has been removed from the car.

From Wikipedia;
    For lead-acid batteries under no load float charging (such as
    in SLI batteries), trickle charging happens naturally at the
    end-of-charge, when the lead-acid battery internal resistance
    to the charging current increases enough to reduce additional
    charging current to a trickle, hence the name. In such cases,
    the trickle charging equals the energy expended by the
    lead-acid battery splitting the water in the electrolyte into
    hydrogen and oxygen gases

Irrelevant to what is being discussed, 4A isnt a trickle charge.

The car alternator regulator is no different.

We arent discussing that there.

It sees the battery as a load, determines the voltage reference and
pumps up its output. When the regulator sees the battery voltage at
the peak setpoint, it too will drop the current to a trickle. If you
add a load, say by turning headlights on, that is in *parallel* to the
battery and it will drop the system voltage down a tad. The regulator
will see that and pump up the output current appropriately. The
current will apportion itself to the *two* loads as appropriate to
their individual internal resistances.

All irrelevant to charging a battery out of the car with a BENCH SUPPLY.

Here, educate yourself;
https://www.swtc.edu/ag_power/electrical/lecture/parallel_circuits.htm

I knew all that before you were even born, thanks.

so it is still a load even when fully charged.

Not when its still taking 4A,

If the battery is *taking* 4 amps, then it *is definitely the load*.

But it wont be taking 4A WHEN THE BATTERY IS OUT OF THE
CAR WITH A BENCH SUPPLY. Because the battery voltage will
have risen once it has been charged so the original 4A will
have dropped significantly WITH A BENCH SUPPLY.

If you have a battery connected to a bench supply, it is still the load
because it will always be taking *some* current. If it is taking 4 amps
it is definitely loading the BENCH SUPPLY.

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)

 

[Rod Speed]

"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn84kjF24gkU1@mid.individual.net...

On 23/6/19 1:30 am, Rod Speed wrote:


"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn6eudFlh2sU1@mid.individual.net...
On 22/6/19 7:58 pm, Rod Speed wrote:


"Xeno" <xenolith@optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1@mid.individual.net...
On 22/6/19 9:57 am, Rod Speed wrote:


"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3rc17q7wdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed
rod.speed.aaa@gmail.com> wrote:



"Commander Kinsey" <CFKinsey@military.org.jp> wrote in message
newsp.z3q9fvpjwdg98l@desktop-ga2mpl8.lan...
On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian
max_demian@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

Nope.

the *battery* is the *load*.

Not when the battery is fully charged and is being charged
with a bench supply that is delivering 4A to the battery.

Take the case of an alternator charging a battery at ~4 amps.

That isnt what was being discussed there. What was being discussed
there was charging the battery out of the car with a bench supply.

The battery is the load and it also provides, as part of that function,
the reference *voltage* that the alternator *must have* in order to
control the output.

None of that is relevant to what was being discussed there,
charging the battery out of the car with a bench supply.

In the process of being charged it is using electric current. That
makes it the load.

See above.

What happens to the charger when you disconnect the power with the
battery connected?

With a BENCH SUPPLY, it continues to provide the
same voltage as it did with the battery connected.

It should, if designed correctly, shut down since it no longer sees a
load. Otherwise it may destroy itself.

That is just plain wrong with a BENCH SUPPLY.
None of those destroy themselves with no load.

Even when it is fully charged it will still take a trickle charge

4A isnt a trickle charge.

That depends entirely on the amp hour rating of the battery.

We're discussing a normal car battery in a steaming turd with
wheels frog car.

Also, my bench charger

We arent discussing a bench charger, we are discussing a bench SUPPLY.

will start off at 4 amps, its maximum capacity. As the battery becomes
charged, that current will drop down to *1 amp* and, from that point, it
will maintain a *trickle charge*.

So that is nothing like the situation being discussed
with a BENCH SUPPLY which is still delivering 4A to
a battery that has been removed from the car.

From Wikipedia;
For lead-acid batteries under no load float charging (such as
in SLI batteries), trickle charging happens naturally at the
end-of-charge, when the lead-acid battery internal resistance
to the charging current increases enough to reduce additional
charging current to a trickle, hence the name. In such cases,
the trickle charging equals the energy expended by the
lead-acid battery splitting the water in the electrolyte into
hydrogen and oxygen gases

Irrelevant to what is being discussed, 4A isnt a trickle charge.

The car alternator regulator is no different.

We arent discussing that there.

It sees the battery as a load, determines the voltage reference and
pumps up its output. When the regulator sees the battery voltage at the
peak setpoint, it too will drop the current to a trickle. If you add a
load, say by turning headlights on, that is in *parallel* to the battery
and it will drop the system voltage down a tad. The regulator will see
that and pump up the output current appropriately. The current will
apportion itself to the *two* loads as appropriate to their individual
internal resistances.

All irrelevant to charging a battery out of the car with a BENCH SUPPLY.

Here, educate yourself;
https://www.swtc.edu/ag_power/electrical/lecture/parallel_circuits.htm

I knew all that before you were even born, thanks.

so it is still a load even when fully charged.

Not when its still taking 4A,

If the battery is *taking* 4 amps, then it *is definitely the load*.

But it wont be taking 4A WHEN THE BATTERY IS OUT OF THE
CAR WITH A BENCH SUPPLY. Because the battery voltage will
have risen once it has been charged so the original 4A will
have dropped significantly WITH A BENCH SUPPLY.

If you have a battery connected to a bench supply, it is still the load
because it will always be taking *some* current. If it is taking 4 amps it
is definitely loading the BENCH SUPPLY.

It wont be taking 4A when charged unless
you have completely fucked up the voltage.

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]

On 23/6/19 5:47 am, Commander Kinsey wrote:

Modern car alternators seem to be able to give out a huge amount of
current at engine idle speed.  I'm sure my friend got his to give out
pretty much the full 80 amps without revving the engine.  He was
powering a small disco on a campsite

No way to get a full 80 amps out of an alternator *at idle*.

On Sat, 22 Jun 2019 11:00:34 +0100, Brian Gaff
briang1@blueyonder.co.uk> wrote:

Yes indeed, the nominal output of an alternator can be as high as 15
volts,
but even a fully charged car battery is only 13.8v as far as I know and
these days, I'm sure the direction of current flow and voltages are
monitored very well by the computers. In the old days it was a bit of a
black art just relying on the ability of the alternator or dynamo in
the old
bangers.
 Normally the output will change due to engine speed, but  in alternators
there is a voltage regulator inbuilt to keep the  thing pretty
nominal and
of course the thing that then suffers is the charging rate, ie its
going to
be be slower when its not running very fast. I think if a battery dips
below
about 11v outside of starter transients, you have to charge it or get
a new
one. This  very accurate sensing these days can often mask a battery
on its
last legs though, as people tend to ignore  warnings if the car still
works,
then they leave it a couple of days and it won't start!

Brian

--

Xeno


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

 

[Peeler]

On Sun, 23 Jun 2019 16:07:14 +1000, Xeno, another brain damaged,
troll-feeding, senile Australian idiot, blathered:

No way to get a full 80 amps out of an alternator *at idle*.

Every way for him to get YOU to suck him off time and again, every time he
wants to be sucked off by one of you seniles infesting these groups! <BG>

 

[Peeler]

On Sun, 23 Jun 2019 10:02:37 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

We're discussing cars.

We're discussing your and his clinical insanity, whenever one you opens his
stupid perverted gob!

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

 

[Peeler]

On Sun, 23 Jun 2019 12:59:55 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

It wont be taking 4A when charged unless
you have completely fucked up the voltage.

You clinically insane auto-contradicting asshole disagree? Well, that's a
novelty! LMAO!

--
Keema Nam addressing nym-shifting senile Rodent:
"You are now exposed as a liar, as well as an ignorant troll."
"MID: <0001HW.22B654E7000BF12E70000F4CC2EF@news.giganews.com>"

 

[Peeler]

On Sun, 23 Jun 2019 12:07:05 +1000, Xeno, another brainless, troll-feeding,
senile Australian idiot, blathered:

Ohm's law.

That's a bit *deep* for some people to comprehend.

Like you being unable to comprehend that you've turned into another
miserable troll-feeding brainless senile asshole? <BG>

 

[Peeler]

On Sun, 23 Jun 2019 12:59:55 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


<FLUSH another 223 !!! lines of the two senile Ozzie cretin's latest sick
shit>

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

 

[Peeler]

On Sun, 23 Jun 2019 11:57:35 +1000, Xeno, another brain damaged,
troll-feeding, senile Australian idiot, blathered:


> If you have a battery

Shove your battery up your arse, that will keep you quiet for a while, you
endlessly blathering senile idiot!