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Xeno
Guest

Sat Jun 22, 2019 11:45 am   



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


"Xeno" <xenolith_at_optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1_at_mid.individual.net...
On 22/6/19 9:57 am, Rod Speed wrote:


"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

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.
Quote:

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.
Quote:

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*.
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

The car alternator regulator is no different. 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.

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

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*.
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)

Peeler
Guest

Sat Jun 22, 2019 11:45 am   



On Sat, 22 Jun 2019 20:11:33 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

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


You ALWAYS have to go one better, eh, you abnormal senile asshole? Can't you
see that that's the very reason why you got NO ONE in real life to talk to?
<BG>

--
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 11:45 am   



On Sat, 22 Jun 2019 19:15:56 +1000, Xeno, another brain damaged,
troll-feeding, senile Australian idiot, blathered:

Quote:

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


Nope, it's the Scottish wanker sensing that he can have all you senile
troll-feeding idiots on, time and again! <BG>

Rod Speed
Guest

Sat Jun 22, 2019 11:45 am   



Brian Gaff <briang1_at_blueyonder.co.uk> wrote

Quote:
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.

Quote:
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

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1_at_blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Rod Speed" <rod.speed.aaa_at_gmail.com> wrote in message
news:gn4ugmFbofdU1_at_mid.individual.net...
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.



Peeler
Guest

Sat Jun 22, 2019 11:45 am   



On Sat, 22 Jun 2019 19:58:32 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

Quote:

Correction

Nope.


LOL Clinically insane 85-year-old senile pest!

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID: <XnsA97071CF43E3Fadmin127001_at_85.214.115.223>

Brian Gaff
Guest

Sat Jun 22, 2019 11:45 am   



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

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1_at_blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Rod Speed" <rod.speed.aaa_at_gmail.com> wrote in message
news:gn4ugmFbofdU1_at_mid.individual.net...
Quote:
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.


Rod Speed
Guest

Sat Jun 22, 2019 11:45 am   



"Xeno" <xenolith_at_optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1_at_mid.individual.net...
Quote:
On 22/6/19 9:57 am, Rod Speed wrote:


"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


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.

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


See above.

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

4A isnt a trickle charge.

> so it is still a load even when fully charged.

Not when its still taking 4A,

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.


Mr Pounder Esquire
Guest

Sat Jun 22, 2019 12:45 pm   



Commander Kinsey wrote:
Quote:
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.

Xeno
Guest

Sat Jun 22, 2019 12:45 pm   



On 22/6/19 8:00 pm, Brian Gaff wrote:
Quote:
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


A 12 Volt lead acid battery will show 13.2 volts straight off the
charger, about 2.2 volts per cell. That will drop to about 12.7 volts
after a day or so, a tad over 2.1 volts per cell.

On the other hand, a vehicle's nominal *system voltage* is 14 Volts.
That's because the *alternator typically operates in the 13.8-14.2 range.

Due to increasing loads on vehicle electrical equipment, manufacturers
were pushing to a nominal 42 Volt electrical system on cars. They were
to be equipped with a 36 Volt battery. It may not happen now.
https://en.wikipedia.org/wiki/42-volt_electrical_system


Quote:
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

Most batteries fail gracefully as they progressively lose *capacity*.
The first sign of impending doom is a lack of gusto on the first turn of
the engine on the first cold start of the day. Batteries don't like cold
weather, their chemistry just isn't happy. The rest of the day they will
start pretty much as normal. Most people however aren't as attuned to
this so fail to observe that subtle change. It won't get better however
and it will eventually be noticeable by all and sundry as it will, one
slightly colder morning, fail to start the car at all.

--

Xeno


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

Rod Speed
Guest

Sat Jun 22, 2019 4:45 pm   



"Xeno" <xenolith_at_optusnet.com.au> wrote in message
news:gn6eudFlh2sU1_at_mid.individual.net...
Quote:
On 22/6/19 7:58 pm, Rod Speed wrote:


"Xeno" <xenolith_at_optusnet.com.au> wrote in message
news:gn6a5eFkg1fU1_at_mid.individual.net...
On 22/6/19 9:57 am, Rod Speed wrote:


"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

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.

Quote:
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.

Quote:
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.

Quote:
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.

Quote:
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.

Quote:
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.

Quote:
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.

Quote:
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.

Quote:


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

Quote:
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.

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.


TMS320
Guest

Sat Jun 22, 2019 5:45 pm   



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


It doesn't.

Quote:
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.

Bod
Guest

Sat Jun 22, 2019 5:45 pm   



Quote:
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

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

Peeler
Guest

Sat Jun 22, 2019 5:45 pm   



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_at_sqwertz.com>

Commander Kinsey
Guest

Sat Jun 22, 2019 9:45 pm   



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_at_blueyonder.co.uk> wrote:

Quote:
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
Guest

Sat Jun 22, 2019 9:45 pm   



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

Quote:
Brian Gaff <briang1_at_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.

Quote:
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_at_gmail.com> wrote in message
news:gn4ugmFbofdU1_at_mid.individual.net...
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.



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