wrote:

On Sunday, May 3, 2020 at 9:12:35 AM UTC+10, Roger Hayter wrote:
The Natural Philosopher wrote:

On 02/05/2020 21:54, williamwright wrote:
On 02/05/2020 19:05, The Natural Philosopher wrote:
On 02/05/2020 17:31, Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage
between the alternator and battery, to achieve that and as the
battery attains a charge, its voltage rises quite rapidly.

The alternator will deliver whatever voltage it meeds to but of course
there would not need to be a particularly large voltage to charge a
battery that is capable of delivering over 700 A to starter motors
without crapping out

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven. Which is why it is always best
to put such a battery on a mains charger for 24 hours, if at all
possible.


Total crap. There is no pint in having a 150A capable alternator to do
THAT

You are forgetting the internal resistance of the battery.

I am the one with the degree in that subject, I am not forgetting it.
You simply have no idea of its value.

The fact is
that the most charge a car will give a flat battery is around 30A, it it
drops off very rapidly. The high alternator output is to support
accessories.

Like I said the battery has sufficiently low internal resistance to be
able to deliver 700A to a starter motor, it can sure handle 50A with
only a half a volt or so increase in charge voltage.

Bill
The charging rate must be deliberately limited to avoid damage to the
battery. The acceptable charge rate is much higher when fairly flat
than when nearly fully charged. Probably improved electronics is why
we can have much higher output alternators nowadays without risking
battery damage. The old system of just regulating the voltage could not
reliably avoid overcharging unless the maximum charge rate was
artificially limited.



--

Roger Hayter

Quite agree with the charging rate limitation. If one observes the meter
on a battery charger, the starting currents through the charger would be
around 4 amps in the worst case, coming down slowly to 0.5 amps in about
12/16 hours; if this is any guidance the alternator charging load would
be about the same, not of the order multiples of ten amps!!

Unfortunately, it isn't any guidance at all. Battery chargers are
limited in current by price, and thus the size of critical components.
They take a day to significantly charge a flat battery, while the
alternator has to recharge, say, a quarter of the capacity in a matter
of tens of minutes. I looked up maximum charge rate for lead acid wet
batteries and apparently 0.3C (a very few tens of amps for a car
battery) is recommended routinely but up to 1.5C (over 50A) can be used
for short periods with a partially discharged battery. (C of course is
a current in amps equal to the amp hour capacity of the battery to a
first approximation.)

--

Roger Hayter

On 02-05-2020 19:10, The Natural Philosopher wrote:
On 02/05/2020 19:05, The Natural Philosopher wrote:
On 02/05/2020 17:31, Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage
between the alternator and battery, to achieve that and as the
battery attains a charge, its voltage rises quite rapidly.

The alternator will deliver whatever voltage it meeds to but of course
there would not need to be a particularly large voltageÂ* to charge a
battery that is capable of delivering over 700 A to starter motors
without crapping out

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven. Which is why it is always best
to put such a battery on a mains charger for 24 hours, if at all
possible.


Total crap. There is no pint in having a 150A capable alternator to do
THAT

"Not long ago, an 80 amp alternator was considered a high output unit.
Most late model alternators produce 120 to 155 amps or more. Current
output increases with engine speed, from around 20 to 50 amps at idle up
to the unit's maximum output at 2,500 RPM or higher (refer to a service
manual for the exact charging output specifications for your vehicle)."

https://www.aa1car.com/library/charging_checks.htm



It's all in your tin foil head .

In article ,
Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage between
the alternator and battery, to achieve that and as the battery attains
a charge, its voltage rises quite rapidly.

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven.

6 to 10 hours driving is far more than many cars ever get.

Which is why it is always best to put such a battery on a mains charger
for 24 hours, if at all possible.

Given most cars these days have plenty alternator capacity, there really
shouldn't be the need to ever charge the battery externally. Unless the
car is not used for such a time as the battery goes flat.

--
*No word in the English language rhymes with month, orange, silver,purple

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
The Natural Philosopher wrote:
On 02/05/2020 18:15, Andy Burns wrote:
Dave Plowman wrote:

So you are guessing it charges a low battery at 140 amps? ;-)

Yuasa recommended rate is only 5A


Oh dear. Yuasa batteries are a couple of ampere hours

Yuasa is the posh brand Halfords sell for car batteries. Used to be Bosch.

--
*England has no kidney bank, but it does have a Liverpool.*

Dave Plowman London SW
To e-mail, change noise into sound.

On 03/05/2020 11:25, Roger Hayter wrote:
wrote:

On Sunday, May 3, 2020 at 9:12:35 AM UTC+10, Roger Hayter wrote:
The Natural Philosopher wrote:

On 02/05/2020 21:54, williamwright wrote:
On 02/05/2020 19:05, The Natural Philosopher wrote:
On 02/05/2020 17:31, Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage
between the alternator and battery, to achieve that and as the
battery attains a charge, its voltage rises quite rapidly.

The alternator will deliver whatever voltage it meeds to but of course
there would not need to be a particularly large voltage to charge a
battery that is capable of delivering over 700 A to starter motors
without crapping out

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven. Which is why it is always best
to put such a battery on a mains charger for 24 hours, if at all
possible.


Total crap. There is no pint in having a 150A capable alternator to do
THAT

You are forgetting the internal resistance of the battery.

I am the one with the degree in that subject, I am not forgetting it.
You simply have no idea of its value.

The fact is
that the most charge a car will give a flat battery is around 30A, it it
drops off very rapidly. The high alternator output is to support
accessories.

Like I said the battery has sufficiently low internal resistance to be
able to deliver 700A to a starter motor, it can sure handle 50A with
only a half a volt or so increase in charge voltage.

Bill
The charging rate must be deliberately limited to avoid damage to the
battery. The acceptable charge rate is much higher when fairly flat
than when nearly fully charged. Probably improved electronics is why
we can have much higher output alternators nowadays without risking
battery damage. The old system of just regulating the voltage could not
reliably avoid overcharging unless the maximum charge rate was
artificially limited.



--

Roger Hayter

Quite agree with the charging rate limitation. If one observes the meter
on a battery charger, the starting currents through the charger would be
around 4 amps in the worst case, coming down slowly to 0.5 amps in about
12/16 hours; if this is any guidance the alternator charging load would
be about the same, not of the order multiples of ten amps!!

Unfortunately, it isn't any guidance at all. Battery chargers are
limited in current by price, and thus the size of critical components.
They take a day to significantly charge a flat battery, while the
alternator has to recharge, say, a quarter of the capacity in a matter
of tens of minutes. I looked up maximum charge rate for lead acid wet
batteries and apparently 0.3C (a very few tens of amps for a car
battery) is recommended routinely but up to 1.5C (over 50A) can be used
for short periods with a partially discharged battery. (C of course is
a current in amps equal to the amp hour capacity of the battery to a
first approximation.)

1.5C in a 75AH battery is around 110A.

I used to charge nickel chemistry batteries at 3C! LiPo at 1C, but even
those are now able to be charged harder

Anyway the point is that even at idle a big alternator is capable of
tens of amps. Not the 5A originally claimed.

Manufacturers have a trade off between having batteries fail through
being flattened in multiple cold starts or failing through overcharging.

But they are not limited by alternator technology.





--
Canada is all right really, though not for the whole weekend.

"Saki"

In article ,
williamwright wrote:
Total crap. There is no pint in having a 150A capable alternator to do THAT

You are forgetting the internal resistance of the battery. The fact is
that the most charge a car will give a flat battery is around 30A, it it
drops off very rapidly. The high alternator output is to support
accessories.

The internal impedance of a battery is a bit of a red herring. Given they
can deliver perhaps 600 amps at starting.

--
*Time flies like an arrow. Fruit flies like a banana.*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Algernon Goss-Custard wrote:
Fredxx posted
There is very little literature on battery charging, of when a charging
device might switch from constant current to constant voltage at
different initial charging currents.


My car battery charger, bought second-hand forty years ago for £5, has
just packed up. Can anyone recommend a suitable replacement? Doesn't
have to be portable, just plug into the mains and recharge a flat car or
lawnmower battery. Preferably for the same sort of price I paid for the
last one ...

Both Lidl and Aldi do a rather nice SMPS one for about £14. Aldi may have
it available online at all times - Lidl as a special offer a few times a
year. Similar in spec to a Ctek at 4 times the price. Much smaller than a
traditional charger, and better too.

--
*If love is blind, why is lingerie so popular? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
williamwright wrote:
I've just done a search for vehicle and marine ammeters. The vast
majority are 30-0-30. A few are 60-0-60. According to you they should
all be 150-0-150.

If it were to measure everything in a modern car, it would need to be 100
0 100 or more.

But a pure analogue ammeter is very expensive to fit, due to the very
heavy cable needed to the dash. Hence them not being fitted these days.

You can measure the voltage drop in a battery lead - either plus or minus
- and calculate the charge/discharge current to the battery. But doing
this to sufficient accuracy to be of use, likely not cheap.

--
*WOULD A FLY WITHOUT WINGS BE CALLED A WALK?

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
wrote:
Quite agree with the charging rate limitation. If one observes the meter
on a battery charger, the starting currents through the charger would be
around 4 amps in the worst case, coming down slowly to 0.5 amps in
about 12/16 hours; if this is any guidance the alternator charging load
would be about the same, not of the order multiples of ten amps!!

That is a crude charger. And a pretty small one if it peaks at 4 amps.

--
*If at first you don't succeed, avoid skydiving.*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
charles wrote:
In article ,
Andy Burns wrote:
The Natural Philosopher wrote:

There is no pint in having a 150A capable alternator to do THAT

Aren't such heavy duty alternators there for heated windscreens, bum
warmers, memory seats etc?

heated seats?

Brilliant devices. Work near instantly. Unlike the car heater.

--
*They told me I had type-A blood, but it was a Type-O.*

Dave Plowman London SW
To e-mail, change noise into sound.

The Natural Philosopher wrote:

On 03/05/2020 11:25, Roger Hayter wrote:
wrote:

On Sunday, May 3, 2020 at 9:12:35 AM UTC+10, Roger Hayter wrote:
The Natural Philosopher wrote:

On 02/05/2020 21:54, williamwright wrote:
On 02/05/2020 19:05, The Natural Philosopher wrote:
On 02/05/2020 17:31, Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage
between the alternator and battery, to achieve that and as the
battery attains a charge, its voltage rises quite rapidly.

The alternator will deliver whatever voltage it meeds to but of course
there would not need to be a particularly large voltage to charge a
battery that is capable of delivering over 700 A to starter motors
without crapping out

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven. Which is why it is always best
to put such a battery on a mains charger for 24 hours, if at all
possible.


Total crap. There is no pint in having a 150A capable alternator to do
THAT

You are forgetting the internal resistance of the battery.

I am the one with the degree in that subject, I am not forgetting it.
You simply have no idea of its value.

The fact is
that the most charge a car will give a flat battery is around 30A, it it
drops off very rapidly. The high alternator output is to support
accessories.

Like I said the battery has sufficiently low internal resistance to be
able to deliver 700A to a starter motor, it can sure handle 50A with
only a half a volt or so increase in charge voltage.

Bill
The charging rate must be deliberately limited to avoid damage to the
battery. The acceptable charge rate is much higher when fairly flat
than when nearly fully charged. Probably improved electronics is why
we can have much higher output alternators nowadays without risking
battery damage. The old system of just regulating the voltage could not
reliably avoid overcharging unless the maximum charge rate was
artificially limited.



--

Roger Hayter

Quite agree with the charging rate limitation. If one observes the meter
on a battery charger, the starting currents through the charger would be
around 4 amps in the worst case, coming down slowly to 0.5 amps in about
12/16 hours; if this is any guidance the alternator charging load would
be about the same, not of the order multiples of ten amps!!

Unfortunately, it isn't any guidance at all. Battery chargers are
limited in current by price, and thus the size of critical components.
They take a day to significantly charge a flat battery, while the
alternator has to recharge, say, a quarter of the capacity in a matter
of tens of minutes. I looked up maximum charge rate for lead acid wet
batteries and apparently 0.3C (a very few tens of amps for a car
battery) is recommended routinely but up to 1.5C (over 50A) can be used
for short periods with a partially discharged battery. (C of course is
a current in amps equal to the amp hour capacity of the battery to a
first approximation.)

1.5C in a 75AH battery is around 110A.

I used to charge nickel chemistry batteries at 3C! LiPo at 1C, but even
those are now able to be charged harder

Anyway the point is that even at idle a big alternator is capable of
tens of amps. Not the 5A originally claimed.

Manufacturers have a trade off between having batteries fail through
being flattened in multiple cold starts or failing through overcharging.

But they are not limited by alternator technology.

Exactly. The situation changed dramatically when alternators replaced
dynamos. After this the limitation was rather crude electo-mechanical
controls. Before that, everyone had a battery charger!
--

Roger Hayter

In article ,
Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
Dave Plowman (News) formulated on Saturday :
So you are guessing it charges a low battery at 140 amps? ;-)

No, there would need to be a rather large difference in voltage between
the alternator and battery, to achieve that and as the battery attains
a charge, its voltage rises quite rapidly.

I would suggest nearer an initial 20amps, which would rapidly fall to
maybe 3 to 6 amps. A flat to full charge time when being driven, can
require 6 to 10 hours of being driven.

6 to 10 hours driving is far more than many cars ever get.

Which is why it is always best to put such a battery on a mains charger
for 24 hours, if at all possible.

Given most cars these days have plenty alternator capacity, there really
shouldn't be the need to ever charge the battery externally. Unless the
car is not used for such a time as the battery goes flat.

It's now 7 weeks since I used my car.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

I guess everyone is talking Of the order 80 Amps and higher without thinking. A casual observation of cables that carry the currents are not thick to carry such high currents and such high current handling is a safety hazard.. Also, given the fact that cars move and hence the vibration will cause heavy sparking and damage the wiring.
Only the cable from battery to the starter motor is thick as it carries a peak current of upto 400 amps At engine cranking moment but then to a fraction of a second and not continuously!

wrote:

I guess everyone is talking Of the order 80 Amps and higher without
thinking. A casual observation of cables that carry the currents are not
thick to carry such high currents and such high current handling is a
safety hazard. Also, given the fact that cars move and hence the vibration
will cause heavy sparking and damage the wiring.

The idea that disturbing a fitted cable can cause huge electric
discharges and fires is a Hollywood meme with no basis in reality.



Only the cable from
battery to the starter motor is thick as it carries a peak current of upto
400 amps At engine cranking moment but then to a fraction of a second and
not continuously!


--

Roger Hayter

On 03/05/2020 06:47:18, harry wrote:
On Saturday, 2 May 2020 15:38:46 UTC+1, Andy Burns wrote:
The Natural Philosopher wrote:

Alternators are good for at least 15A. I wouldn't be surprised if they
can't mostly manage over 50A if needs be

Oh.. treble that

yep, mine is rated 140A

But only for a short time.

That's not my experience for a Chinese sourced Bosch replica on a boat
application, where the alternator will happily kick out 150A over a
prolonger period.

One of the reasons why high amperage alternators is specced is all the
electrical power needed when all the car appliances are used, rather
than just topping up the battery between starts.

On 02/05/2020 22:03:14, williamwright wrote:
On 02/05/2020 15:55, The Natural Philosopher wrote:
On 02/05/2020 15:44, Harry Bloomfield wrote:
The Natural Philosopher explained :
Alternators are good for at least 15A. I wouldn't be surprised if
they can't mostly manage over 50A if needs be

Oh.. treble that - apparently 45A - 200A is the range...

https://www.powerstream.com/car-battery-faq.htm

But not charge current into the battery.
Yes, charge current into the battery if its flat enough


A quick look at a few battery specs suggests that a charge rate above
50A can damage a lead acid battery if maintained for more than a few
minutes.

Most battery manufacturers suggest a charging current at C should be
considered a maximum, so an arbitrary 50A doesn't cover many battery specs.

YMMV

On 03/05/2020 12:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Andy Burns wrote:
The Natural Philosopher wrote:

There is no pint in having a 150A capable alternator to do THAT

Aren't such heavy duty alternators there for heated windscreens, bum
warmers, memory seats etc?

heated seats?

Brilliant devices. Work near instantly. Unlike the car heater.


The alternator on my car is 180A.

2x heated seats
1x heated steering wheel
2x heated mirrors
1x heated rear window
1x cabin heater booster
1x electric water pump
1x electric power steering

Plus dashboard/infotainment electronics and God knows how many
ECUs/processors elsewhere. 100% LED lighting.

The current for charging the battery is a small part of the current
drawn by the car. Full ECU controlled alternator with dynamic load
shedding and regenerative breaking.

Driving to work and back twice a day kept the battery well topped up and
the start/stop became active quickly as the engine/trans warmed and the
battery was charged enough. Driving short distances twice a week at
most, the start/stop never becomes ready. Not seen stop/start become
ready since I started working from home, a week before lockdown.

On 03/05/2020 04:22, williamwright wrote:
On 02/05/2020 23:50, The Natural Philosopher wrote:

A quick look at a few battery specs suggests that a charge rate above
50A can damage a lead acid battery if maintained for more than a few
minutes.

Bill
I see you just make that statement with no link to back it up.


Look it up yourself then.

Bill
How dare you question the turnip.... he's got a special degree.

On 03/05/2020 09:22, The Natural Philosopher wrote:
On 03/05/2020 08:52, Harry Bloomfield wrote:
williamwright was thinking very hard :
You are forgetting the internal resistance of the battery. The fact
is that the most charge a car will give a flat battery is around 30A,
it it drops off very rapidly. The high alternator output is to
support accessories.

Correct! I have taken the trouble to actually measure it and have seen
20 to maybe 30amps delivered by a 130amp alternator, into a near flat
battery. That level of charge current rapidly declines as the flat
battery gains in voltage.

I have battery chargers that will dump full permitted current into a
battery until it is =99% full.


Yes, intelligent chargers with a temperature sensor strapped to the side
of the battery.

Bill

In article ,
Roger Hayter wrote:
But they are not limited by alternator technology.

Exactly. The situation changed dramatically when alternators replaced
dynamos. After this the limitation was rather crude electo-mechanical
controls. Before that, everyone had a battery charger!

The peak output of a dynamo on the average car fitted with one was under
30 amps - 24 being a common size. Plenty 50s cars didn't have enough
output to drive all the electrical bits then - let alone what we are used
to now.

Rolls did fit an adequate size dynamo with electro mechanical regulator.

An alternator is much cheaper to make than an equivalent dynamo. But had
to wait for cheap enough rectifiers to be practical. So saying, electronic
control can improves the performance of a dynamo too - if not the peak
output.

--
*I don't suffer from insanity -- I'm a carrier

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
wrote:
I guess everyone is talking Of the order 80 Amps and higher without
thinking. A casual observation of cables that carry the currents are
not thick to carry such high currents and such high current handling is
a safety hazard. Also, given the fact that cars move and hence the
vibration will cause heavy sparking and damage the wiring. Only the
cable from battery to the starter motor is thick as it carries a peak
current of upto 400 amps At engine cranking moment but then to a
fraction of a second and not continuously!

If you have a 100 amp alternator - quite modest these days - the output
cable will be capable of handling 100 amps. But that goes straight to the
battery.

Other circuits in the car use the appropriate cable size.

--
*I don't feel old. I don't feel anything until noon. Then it's time for my nap.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Dave Plowman (News) wrote:
In article ,
Roger Hayter wrote:
But they are not limited by alternator technology.

Exactly. The situation changed dramatically when alternators replaced
dynamos. After this the limitation was rather crude electo-mechanical
controls. Before that, everyone had a battery charger!

The peak output of a dynamo on the average car fitted with one was under
30 amps - 24 being a common size. Plenty 50s cars didn't have enough
output to drive all the electrical bits then - let alone what we are used
to now.

I fitted an alternator to my Anglia - in which I took part in motor rallies
The extra load on the driving belt broke the pressed metal take off pulley.
Luckily Ford made a competition version which was a casting.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

mm0fmf wrote:

On 03/05/2020 12:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Andy Burns wrote:
The Natural Philosopher wrote:

There is no pint in having a 150A capable alternator to do THAT

Aren't such heavy duty alternators there for heated windscreens, bum
warmers, memory seats etc?

heated seats?

Brilliant devices. Work near instantly. Unlike the car heater.


The alternator on my car is 180A.

2x heated seats
1x heated steering wheel
2x heated mirrors
1x heated rear window
1x cabin heater booster
1x electric water pump
1x electric power steering

Plus dashboard/infotainment electronics and God knows how many
ECUs/processors elsewhere. 100% LED lighting.

The current for charging the battery is a small part of the current
drawn by the car. Full ECU controlled alternator with dynamic load
shedding and regenerative breaking.
^^^^^^^^^^^^^^^^^^^^^

Presumably after the warranty period?


Driving to work and back twice a day kept the battery well topped up and
the start/stop became active quickly as the engine/trans warmed and the
battery was charged enough. Driving short distances twice a week at
most, the start/stop never becomes ready. Not seen stop/start become
ready since I started working from home, a week before lockdown.


--

Roger Hayter

On Sunday, 3 May 2020 07:23:49 UTC+1, Algernon Goss-Custard wrote:
tabbypurr posted
On Saturday, 2 May 2020 17:52:41 UTC+1, Algernon Goss-Custard wrote:
Fredxx posted

There is very little literature on battery charging, of when a charging
device might switch from constant current to constant voltage at
different initial charging currents.


My car battery charger, bought second-hand forty years ago for 0 just packed up. Can anyone recommend a suitable replacement? Doesn't
have to be portable, just plug into the mains and recharge a flat car or
lawnmower battery. Preferably for the same sort of price I paid for the
last one ...

Yes. Any modern car battery charger will work. All there is to choose
is cheapos versus high MTTF ones, £12 versus £40+.

I might fix the old one.

The metal enclosure is riveted together so I can't open it up. Anyway

A drill bit would remove those in no time.

IMLE the failure mode for devices based on a transformer is nearly
always shorting or burning out of the windings which can't be fixed.

It can be any of the parts, including just a bad connection.


NT

On 03/05/2020 16:50, Roger Hayter wrote:
mm0fmf wrote:

On 03/05/2020 12:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Andy Burns wrote:
The Natural Philosopher wrote:

There is no pint in having a 150A capable alternator to do THAT

Aren't such heavy duty alternators there for heated windscreens, bum
warmers, memory seats etc?

heated seats?

Brilliant devices. Work near instantly. Unlike the car heater.


The alternator on my car is 180A.

2x heated seats
1x heated steering wheel
2x heated mirrors
1x heated rear window
1x cabin heater booster
1x electric water pump
1x electric power steering

Plus dashboard/infotainment electronics and God knows how many
ECUs/processors elsewhere. 100% LED lighting.

The current for charging the battery is a small part of the current
drawn by the car. Full ECU controlled alternator with dynamic load
shedding and regenerative breaking.
^^^^^^^^^^^^^^^^^^^^^

Presumably after the warranty period?


Driving to work and back twice a day kept the battery well topped up and
the start/stop became active quickly as the engine/trans warmed and the
battery was charged enough. Driving short distances twice a week at
most, the start/stop never becomes ready. Not seen stop/start become
ready since I started working from home, a week before lockdown.



Why?

On 02/05/2020 16:53, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
The Natural Philosopher explained :
Alternators are good for at least 15A. I wouldn't be surprised if they can't
mostly manage over 50A if needs be

Oh.. treble that - apparently 45A - 200A is the range...

https://www.powerstream.com/car-battery-faq.htm

But not charge current into the battery.

Remember it is Turnip. Never reads or understands a question.

But he's got a degree in this!

On Sunday, 3 May 2020 13:42:29 UTC+1, wrote:

I guess everyone is talking Of the order 80 Amps and higher without thinking. A casual observation of cables that carry the currents are not thick to carry such high currents

every cable in every car I've encountered has been thick enough to carry the current it carries.


and such high current handling is a safety hazard. Also,

it isn't


given the fact that cars move and hence the vibration will cause heavy sparking and damage the wiring.

nonsense


Only the cable from battery to the starter motor is thick as it carries a peak current of upto 400 amps At engine cranking moment but then to a fraction of a second and not continuously!

alternator output cabling is also fairly thick.

FWIW starter motor cable thickness is as much due to voltage drop as ampacity.


NT

On Sun, 03 May 2020 05:42:26 -0700, gopalansampath wrote:

I guess everyone is talking Of the order 80 Amps and higher without
thinking. A casual observation of cables that carry the currents are
not thick to carry such high currents and such high current handling is
a safety hazard. Also, given the fact that cars move and hence the
vibration will cause heavy sparking and damage the wiring.
Only the cable from battery to the starter motor is thick as it carries
a peak current of upto 400 amps At engine cranking moment but then to a
fraction of a second and not continuously!

People forget about - or are unaware of - the importance of cable
*length* in this respect. You can get away with quite astonishing
amperage levels with short runs of alarmingly thin cable, especially when
the current is pulsed or of short duration. For example, there are some
TO-220 packaged MOSFETs now which will handle close to 200A through their
sub 1mm diameter leads provided those leads are cropped as short as
possible.

On Sun, 03 May 2020 12:47:32 +0100, charles wrote:

It's now 7 weeks since I used my car.

Those A4 sized solar panels are great for keeping a car battery's charge
topped-up if you make only infrequent short trips in the car. And with
just a few cheap external components you can modify the charging current
to prevent the battery getting cooked on very bright days. Add just a few
more components on top and you can fit it and forget it - the car will
always be 'on the button' no matter how long you leave it standing.

On 03/05/2020 13:42, wrote:
I guess everyone is talking Of the order 80 Amps and higher without thinking. A casual observation of cables that carry the currents are not thick to carry such high currents and such high current handling is a safety hazard. Also, given the fact that cars move and hence the vibration will cause heavy sparking and damage the wiring.
Only the cable from battery to the starter motor is thick as it carries a peak current of upto 400 amps At engine cranking moment but then to a fraction of a second and not continuously!

carries more than that a part of start up current.
Voltage at alternator can go high enough at 150+ A to render extremely
think cable not necessary.

Again simple minded armchair engineers confuse 'breaking' with
'becoming operationally unusable'. In things like sagging floors, and in
terms of electrics.

A thick wire gives you two things: less power dissipation so it doesn't
melt and less voltage drop so it doesn't affect operations



--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 03/05/2020 15:36, mm0fmf wrote:
On 03/05/2020 04:22, williamwright wrote:
On 02/05/2020 23:50, The Natural Philosopher wrote:

A quick look at a few battery specs suggests that a charge rate
above 50A can damage a lead acid battery if maintained for more than
a few minutes.

Bill
I see you just make that statement with no link to back it up.


Look it up yourself then.

Bill
How dare you question the turnip.... he's got a special degree.

How dare I question the Bill,. He is plain right at all times eh?

--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 03/05/2020 15:50, williamwright wrote:
On 03/05/2020 09:22, The Natural Philosopher wrote:
On 03/05/2020 08:52, Harry Bloomfield wrote:
williamwright was thinking very hard :
You are forgetting the internal resistance of the battery. The fact
is that the most charge a car will give a flat battery is around
30A, it it drops off very rapidly. The high alternator output is to
support accessories.

Correct! I have taken the trouble to actually measure it and have
seen 20 to maybe 30amps delivered by a 130amp alternator, into a near
flat battery. That level of charge current rapidly declines as the
flat battery gains in voltage.

I have battery chargers that will dump full permitted current into a
battery until it is =99% full.


Yes, intelligent chargers with a temperature sensor strapped to the side
of the battery.

Bill


No Bill. They dont have that.
Wrong again.


--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 03/05/2020 18:05, mm0fmf wrote:
On 02/05/2020 16:53, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Harry Bloomfield wrote:
The Natural Philosopher explained :
Alternators are good for at least 15A. I wouldn't be surprised if
they can't
mostly manage over 50A if needs be

Oh.. treble that - apparently 45A - 200A is the range...

https://www.powerstream.com/car-battery-faq.htm

But not charge current into the battery.

Remember it is Turnip. Never reads or understands a question.

But he's got a degree in this!

Not in not reading questions no.



--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

In article ,
Cursitor Doom wrote:
On Sun, 03 May 2020 12:47:32 +0100, charles wrote:

It's now 7 weeks since I used my car.

Those A4 sized solar panels are great for keeping a car battery's charge
topped-up if you make only infrequent short trips in the car. And with
just a few cheap external components you can modify the charging current
to prevent the battery getting cooked on very bright days. Add just a few
more components on top and you can fit it and forget it - the car will
always be 'on the button' no matter how long you leave it standing.

even if it's in the shade for most of the day?

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

In article ,
The Natural Philosopher wrote:
On 03/05/2020 15:50, williamwright wrote:
On 03/05/2020 09:22, The Natural Philosopher wrote:
On 03/05/2020 08:52, Harry Bloomfield wrote:
williamwright was thinking very hard :
You are forgetting the internal resistance of the battery. The fact
is that the most charge a car will give a flat battery is around
30A, it it drops off very rapidly. The high alternator output is to
support accessories.

Correct! I have taken the trouble to actually measure it and have
seen 20 to maybe 30amps delivered by a 130amp alternator, into a near
flat battery. That level of charge current rapidly declines as the
flat battery gains in voltage.

I have battery chargers that will dump full permitted current into a
battery until it is =99% full.


Yes, intelligent chargers with a temperature sensor strapped to the
side of the battery.

Bill


No Bill. They dont have that.
Wrong again.

my one does. It displays temperature along with battery voltage & charge
current, If it thinks the temperature is too high, it turns on an internal
fan.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

"mm0fmf" wrote in message
...
On 03/05/2020 12:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Andy Burns wrote:
The Natural Philosopher wrote:

There is no pint in having a 150A capable alternator to do THAT

Aren't such heavy duty alternators there for heated windscreens, bum
warmers, memory seats etc?

heated seats?

Brilliant devices. Work near instantly. Unlike the car heater.


The alternator on my car is 180A.

2x heated seats
1x heated steering wheel
2x heated mirrors
1x heated rear window
1x cabin heater booster
1x electric water pump
1x electric power steering

Which car is that ?

Plus dashboard/infotainment electronics and God knows how many
ECUs/processors elsewhere. 100% LED lighting.

The current for charging the battery is a small part of the current drawn
by the car. Full ECU controlled alternator with dynamic load shedding and
regenerative breaking.

Driving to work and back twice a day kept the battery well topped up and
the start/stop became active quickly as the engine/trans warmed and the
battery was charged enough. Driving short distances twice a week at most,
the start/stop never becomes ready. Not seen stop/start become ready since
I started working from home, a week before lockdown.

mm0fmf wrote:

On 03/05/2020 16:50, Roger Hayter wrote:
mm0fmf wrote:




The current for charging the battery is a small part of the current
drawn by the car. Full ECU controlled alternator with dynamic load
shedding and regenerative breaking.
^^^^^^^^^^^^^^^^^^^^^

Presumably after the warranty period?


Driving to work and back twice a day kept the battery well topped up and
the start/stop became active quickly as the engine/trans warmed and the
battery was charged enough. Driving short distances twice a week at
most, the start/stop never becomes ready. Not seen stop/start become
ready since I started working from home, a week before lockdown.



Why?

Because if it breaks you won't be able to use it. Not even for
regenerative braking.

--

Roger Hayter

On Mon, 4 May 2020 05:16:36 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH the trolling senile asshole's latest troll**** unread

--
FredXX to Rot Speed:
"You are still an idiot and an embarrassment to your country. No wonder
we shipped the likes of you out of the British Isles. Perhaps stupidity
and criminality is inherited after all?"
Message-ID:

Algernon Goss-Custard wrote:
posted
On Saturday, 2 May 2020 17:52:41 UTC+1, Algernon Goss-Custard wrote:
Fredxx posted
There is very little literature on battery charging, of when a charging
device might switch from constant current to constant voltage at
different initial charging currents.


My car battery charger, bought second-hand forty years ago for 0
just packed up. Can anyone recommend a suitable replacement? Doesn't
have to be portable, just plug into the mains and recharge a flat car or
lawnmower battery. Preferably for the same sort of price I paid for the
last one ...

Yes. Any modern car battery charger will work. All there is to choose
is cheapos versus high MTTF ones, £12 versus £40+.

I might fix the old one.

The metal enclosure is riveted together so I can't open it up. Anyway
IMLE the failure mode for devices based on a transformer is nearly
always shorting or burning out of the windings which can't be fixed.


That's not the only mechanism.

The transformer laminations are dipped in lacquer, then dried.
Then the laminations are fastened together to make the core.

The purpose of the lacquer is to prevent eddy currents from
forming. The assembly is clamped together to make a soft
steel core with the desired magnetization behavior (B-H curve).

If the laminations happen to rust, it can cause the lacquer to be
punctured. Then eddy electrical currents start to flow in a loop, between
laminations. Perhaps a bit of a buzz is heard. The eddy currents heat
up the laminations (which is why the lacquer was there in the first place).

This makes the transformer get hot, even at no load.

I had a RadioShack transformer fail this way. Sitting
in the junk room for 20 years, dry conditions, and
still it managed to have an eddy current problem. You couldn't
leave it plugged in for an hour, as it would get scalding hot.
When it gets hot, *then* there's some room for the other
failure modes to happen. I had to buy another, and today
they're not cheap (the cost spoils the fun of building
your own gadgets).

The selenium rectifiers get pretty hot in those dumb chargers too.
The reason selenium seems to be used, is the relatively high
resistance in the conducting state. They're not efficient
like a semiconductor diode. But the selenium rectifier also
helps "tame" the output behavior, making for a better
battery charger.

Selenium is a kind of impedance protection. Not perfect, but better.
Semiconductor diodes are too "stiff" for this usage (making a
dumb charger with a minimum of components).

If you were to replace the selenium rectifiers with a non-selenium
solution, you would have to make sure the behavior of the output
was modified with additional electronic components. Which kinda
spoils the "I only paid £5 for this".

At 9V, maybe the dumb charger makes 6 amps.
At 12V, maybe 2-3 amps.
At 18V, about 0 amps (end of charging, when knackered battery is present.
A good battery shouldn't rise to 18V.)

If you used semiconductor diodes in place of
the selenium ones, at 9V you might get 20 amps
and a fuse blows or smoke comes out or...
Some additional resistance to current flow
is needed, somehow, but without eroding the
good characteristics as the charge operation
continues and the battery fills up.

You paid £5 40 years ago. If the inflation rate
caused a doubling of the value every 10 years,
your "budget" today would be £80. Since the
new chargers don't use nearly as much copper
wire inside (SMPS, high frequencies, small transformer),
they can do considerably better than £80 a unit.

The device also has to be selected for the task.
The lawnmower battery isn't a lot of amp-hours.
Maybe even the cheap 1 ampere charger would work
(charger is switchable between 6V and 12V battery types).
But to do a good job of charging the car battery,
you would probably enjoy using more current than that.
I have a 3 amp one, which is sufficient for car battery
top-up. It would take a whole day if the battery
was flat (run-down by inattention during COVID).

The Lidl one is probably a bit more current than that.

The car battery type matters to. There are regular batteries,
and there are "start/stop" batteries. Cars that stop the
engine at intersections are the "start/stop" case. Older
cars left the engine running all the time until you got
home and removed the key. The older cars are easier
on their battery, calling for bulk current less often.
The advert for the charger may mention whether it's
compatible with "start/stop". I saw one float charger,
that said it was not intended for start/stop battery types.
That suggests you'd also want to monitor *any* charger,
for aberrant behavior when the main charging sequence is complete.

In the graph here, phase 2 (topping charge) is CV (constant
volts) at 14.4V.

https://batteryuniversity.com/learn/...d_acid_battery

Phase 3 (float charge) is supposed to be CV 13.5V. Some
of the chargers you buy today, don't do phase 3 quite
correctly, and some batteries are "resting" at 15V with
the charger connected. I checked mine, and I did see it
float-charging at 13.5V.

You would not leave the smart charger connected forever,
unless you'd verified (somehow), that it wasn't abusing
the battery (wrong float charge behavior).

Phase 1 CC (bulk charge, 9V rising slowly towards 14.4V)
(if the battery is full, it gets to 14.4V within
the first five minutes or so)
Phase 2 CV (topping charge, 14.4V in a CV mode)
Phase 3 CV (float charge, 13.5V)
Phase 4 (some chargers switch off, leaving battery at 12.8V
if it's in good shape)
(when the battery self-discharges to 11.8V, some
chargers automatically start Phase 1 again, others
need the user to press the button)

The purpose of these user manuals, is to check and see what
ampere-hour size of battery they charge with each. The 5 amp one,
handles a battery up to 120 amp-hours. The 2 amp one is shown
charging a 40 amp-hour battery. You'd check your car battery
rating on the label, to see what ballpark it's in, like 60Ah.
If it was 60Ah, you'd likely want a bit more than a 2 amp charger.

https://no.co/media/nocodownloads/fo...er_guide_1.pdf
https://no.co/media/nocodownloads/fo...er_guide_2.pdf
https://no.co/media/nocodownloads/fo...er_guide_1.pdf

Since for the cheap ones, AldiLidl buys them in "lots" and how
they work could change from lot to lot, you want to find a
discussion thread for the "current" one, to see whether it's
a good deal or a dud in terms of the whole charge sequence. I've
been paying more attention to mine, and notice it's not as "saintly"
as I thought. The "full" light comes on, while it's still
pumping current. It shouldn't do that. I ended up disconnecting
it while it was doing "verification phase". No idea what would have
flashed if it wasn't holding well. Mine could use a LED that
says it's stopped faffing about. But at least so far, I've not
caught it using a wrong voltage.

The dumb chargers, the human operator had to guess at the
fullness, and disconnect the alligator clips before it
was too late. That's why we have smart chargers - in theory,
to do the job well enough, they can be ignored once connected.
You want to be able to walk away for a year, and come back to
a properly charged battery, and no battery damage.

Paul

On Sun, 03 May 2020 19:07:06 +0100, charles wrote:

In article ,
Cursitor Doom wrote:
On Sun, 03 May 2020 12:47:32 +0100, charles wrote:

It's now 7 weeks since I used my car.

Those A4 sized solar panels are great for keeping a car battery's
charge topped-up if you make only infrequent short trips in the car.
And with just a few cheap external components you can modify the
charging current to prevent the battery getting cooked on very bright
days. Add just a few more components on top and you can fit it and
forget it - the car will always be 'on the button' no matter how long
you leave it standing.

even if it's in the shade for most of the day?

It doesn't matter if the car's parked in the shade - it's where the solar
panel is mounted that counts! :-D