On 10/04/2020 22:35, The Natural Philosopher wrote:
On 10/04/2020 20:28, Bert Coules wrote:

Do I need to disconnect the car's own connecting leads
first?

no

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could upset
the onboard electronics.

Always connect the charger to the battery before switching on the mains
and switch off before disconnecting to avoid sparks at the terminals.
Especially after charging when there could be a build up of hydrogen
around the battery.

Robin asked:

If it's that old does it also have the means to select the mains voltage
between (say) 200-210, 220-30 and 240-250V?

No, there's no option to do that. I don't think it's ancient exactly, just
not totally up to date perhaps.

An update:

Charger connected at 9.45am, LEDs illuminated (though tricky to see in the
sunlight) up to 5A (6A being the highest).

There was no corrosion on or around either battery terminal, which I take to
be a good sign.

So now I suppose I wait and see. Many thanks for all the help.

Mike Clarke wrote:

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could upset
the onboard electronics.

Ah. I didn't do that...

Always connect the charger to the battery before switching on the mains...

....but I did do that, since it seemed the sensible sequence.

...and switch off before disconnecting to avoid sparks at the terminals.

And I shall do that. Thanks.

On 11/04/2020 08:30, charles wrote:
In article ,
Brian Reay wrote:
Brian Gaff \(Sofa 2\) wrote:

I've often wondered when new cars are made it is obviously months before
they go to a customer, so how do they look after all those batteries?

VW fit a better quality dashboard solar panel to at least some models- it
is removed before delivery to the customer and, I believe, returned for

Since there's a pretty solid bulkhead between the dashboard and the engine
compartment - where the battery lives - how do you connect tehtwo ? leads
out of the door and under the bonnet?

Via the OBD socket?

--
Spike

In the EU, only the future is certain, but the past is constantly changing.

In the Unprecedented Catastrophic Anthropogenic Climate Change Global
Heating
Emergency Alarm system, only the future is certain. The past is
constantly being revised.

Unite behind the science!

There is no pressure from anyone to reissue G8+3, G6+3 or G7+3 calls.
That tells you what you need to know about all calls being equal.

Narcissists can't deal with reality because it contradicts what
they want to be true.

If you actually examine the narcissist's narrative, you quickly
notice that they are full of crap.

Narcissists cant accept that they may not be wonderful people.
https://tinyurl.com/UKRA-narcissists

The maths teacher broke down in tears at
the North West Wiltshire Magistrates Court.

The Government has a secret system - a Machine - that spies on you,
every hour of every day. The Machine was designed to detect hate
crimes against minorities....but it sees everything: terrorism, violence
against ordinary people, returning militants, drug and sex trafficking.
The Government classes these latter groups as 'Irrelevant'.

On 11/04/2020 09:53, Mike Clarke wrote:
On 10/04/2020 22:35, The Natural Philosopher wrote:
On 10/04/2020 20:28, Bert Coules wrote:

Â* Do I need to disconnect the car's own connecting leads
first?

no

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could upset
the onboard electronics.

You need a hell of a lot of current to spike a battery over 14v

Always connect the charger to the battery before switching on the mains
and switch off before disconnecting to avoid sparks at the terminals.
Especially after charging when there could be a build up of hydrogen
around the battery.


--
€œThe fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

On 11/04/2020 09:59, Bert Coules wrote:
Mike Clarke wrote:

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could
upset the onboard electronics.

Ah.Â* I didn't do that...

You were correct. He's talking ********
#

Always connect the charger to the battery before switching on the
mains...

...but I did do that, since it seemed the sensible sequence.

...andÂ* switch off before disconnecting to avoid sparks at the terminals.

And I shall do that.Â* Thanks.


--
€œThe fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

On Sat, 11 Apr 2020 08:12:03 +0100, Brian Gaff \(Sofa 2\) wrote:

I've often wondered when new cars are made it is obviously months before
they go to a customer, so how do they look after all those batteries?

Modern cars have various "sleep" modes that power various sub systems
off after various lengths of time. AIUI there is also a deep sleep
mode that can be manually entered that effectively disconects the
battery for storeage. How you wake it back up I donno, but cars still
do have a physical key and lock.

Though to be honest even a few mA drain will knacker a battery in few
months, Solar panel maybe, plugged into the ciggy socket or ODBII?
Actually disconnect the battery when parked up on the storeage field?
Would seem better options.

--
Cheers
Dave.

In article , Bert Coules
wrote:
newshound wrote:

The old fashioned transformer sort *usually* had a meter, you can
recognise those because they are always in a pressed steel box with big
ventilation louvres. The modern electronic ones (typically lightly
finned aluminium extrusions as heat sinks) will have electronic
regulation and usually have a coloured light.

Mine is in a plastic casing with no apparent heatsinks, externally at
least. It has six LEDs marked from 1A up to 6.

In either case the battery will not come to any harm if left on for a
day or two.

Tricky for me, since the car is in a very exposed paved area at the front
of my house. I don't suppose anyone would take advantage and stroll off
with the charger but I'd rather not leave the car with the bonnet
unlocked and cracked open overnight. But from what others have said, it
might be worth trying the starter after a few hours.

I'm sure you could close the bonnet if you put the charger in a suitable
place.

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

In article l.net,
Dave Liquorice wrote:
On Sat, 11 Apr 2020 08:12:03 +0100, Brian Gaff \(Sofa 2\) wrote:

I've often wondered when new cars are made it is obviously months
before they go to a customer, so how do they look after all those
batteries?

Modern cars have various "sleep" modes that power various sub systems
off after various lengths of time. AIUI there is also a deep sleep
mode that can be manually entered that effectively disconects the
battery for storeage. How you wake it back up I donno, but cars still
do have a physical key and lock.

Though to be honest even a few mA drain will knacker a battery in few
months, Solar panel maybe, plugged into the ciggy socket or ODBII?
Actually disconnect the battery when parked up on the storeage field?
Would seem better options.

the ciggy socket on my car is only live with 'aux' switched on.

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

In article ,
Bert Coules wrote:
wrote:

Don't know. A battery charger will usually solve it if you
can get your paws on one, and you or someone is physically
able to set it up.

I'd completely forgotten that I do in fact have a battery charger,
picked up I think at a boot fair on a whim years back, so I've no idea
if it works - I've certainly never used it for anything.

I'm not even sure that it's intended for cars: it's switchable between
six and twelve volts and is marked "Fast Charge 6 Amp". The clamps
strike me as a bit small and flimsy for a car terminals and the warning
"for indoor use only" doesn't inspire confidence either. Is it worth
giving it a go, do you think?


Lidl and Aldi sell a very nice little charger for about £14. Small enough
to fit in a large pocket. Pretty certain it's a stock item at Aldi online.

But you'd be unlikely to damage your battery any further even if your
charger doesn't work, so no harm in trying it.

Indoor only simply means don't use it where it could get wet - under the
bonnet etc will be fine, with the bonnet closed.

Depending on the charger, it may not even connect to a very flat battery,
though. Due to reverse polarity protection. A very basic old one should be
OK. Those usually have a low voltage fuse somewhere.

--
*I want it all and I want it delivered

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

In article ,
Bert Coules wrote:
"The Natural Philosopher" wrote:

And how can I tell when the battery is sufficiently charged?

when the terminal voltage is over 13V

But how do I tell that? There's no meter or any other indicator sort of on
the charger.

Leave it on for 24 hours.

A simple 6 amp charger will only charge at 6 amps for a short period (if
ever - many are extremely optimistic) and as the battery volts come up,
the charge rate will fall.

If the car won't start after 24 hours and the charger was working, chances
are the battery has had it.

You can check the charger is working with a simple DVM or other method of
measuring the volts. They will be higher on charge than off charge.

--
*Thank you. We're all refreshed and challenged by your unique point of view

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

In article ,
Brian Gaff \(Sofa 2\) wrote:
I've often wondered when new cars are made it is obviously months before
they go to a customer, so how do they look after all those batteries?

Not sure they do. I've never bought a new car, but a few just secondhand
with the original battery. And that never has the same life as its
replacement. A car sitting in the showroom etc, new or used, is not good
for the battery.

--
*A 'jiffy' is an actual unit of time for 1/100th of a second.

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

On 11/04/2020 10:21:52, The Natural Philosopher wrote:
On 11/04/2020 09:53, Mike Clarke wrote:
On 10/04/2020 22:35, The Natural Philosopher wrote:
On 10/04/2020 20:28, Bert Coules wrote:

Â* Do I need to disconnect the car's own connecting leads
first?

no

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could
upset the onboard electronics.

You need a hell of a lot of current to spike a battery over 14v

If flat, yes. If open circuit, a common failure mode then no current at all.

A good fully charged battery can see the volts rising to beyond 16V
without any trouble at just a modest current.

I would suggest rather than putting the battery on charge and leaving it
to regularly monitor the terminal voltage.

In article ,
Tim Lamb wrote:
In message , "Brian Gaff (Sofa 2)"
writes
Some of the home rescue folk are helping keep Ambulances going and the like.
Personally I'd charge the battery up. How long has it been flat for?
I remember the old battery lawnmower batteries did not like being flat over
the winter.

Ride on mower curiosity. Laid up for Winter and then the house move.
Mower battery flat! Charged up OK but I decided to remove a battery lead
for storage. No visible splash on disconnection and I don't have access
to a DC ammeter.

Re-connected and started with no trouble yesterday!

A battery can still start a vehicle when well past its best. I have a very
sophisticated tester made by ACT. That calculates the true battery
capacity in amp.hrs. The nominal new capacity is normally printed on the
battery case. Once it has dropped to about 2/3rs on a fully charged
battery, it won't be long for this world.

--
*Half the people in the world are below average.

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

In article ,
Bert Coules wrote:
Brian Gaff (Sofa 2) wrote:

Personally I'd charge the battery up. How long has it been flat for?

I last started the car four days ago.

How long did you run it for?

With a modern car, it will generally replace the amount taken to start it
by the time the engine is thoroughly hot.

--
*To be intoxicated is to feel sophisticated, but not be able to say it.

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

On 11/04/2020 09:53:03, Mike Clarke wrote:
On 10/04/2020 22:35, The Natural Philosopher wrote:
On 10/04/2020 20:28, Bert Coules wrote:

Â* Do I need to disconnect the car's own connecting leads
first?

no

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could upset
the onboard electronics.

I would hope the electronics are designed and tested to a variant of
ISO7637.
https://en.wikipedia.org/wiki/ISO_7637

It shouldn't be a problem.

In article ,
charles wrote:
In article ,
Brian Reay wrote:
Brian Gaff \(Sofa 2\) wrote:
I've often wondered when new cars are made it is obviously months
before they go to a customer, so how do they look after all those
batteries? Brian


VW fit a better quality dashboard solar panel to at least some models-
it is removed before delivery to the customer and, I believe, returned
for

Since there's a pretty solid bulkhead between the dashboard and the
engine compartment - where the battery lives - how do you connect tehtwo
? leads out of the door and under the bonnet?

Many cars have a power outlet inside the car which is always live. Some
fag lighters and so on. But some power down.

--
*How many roads must a man travel down before he admits he is lost? *

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

In article ,
Mike Clarke wrote:
Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could upset
the onboard electronics.

You'd need an awfully large charger to get voltage spikes past the very
low impedance of a car battery.

Properly designed car electronics should have voltage regulators (and
components) rated up to 40 volts.

--
*CAN AN ATHEIST GET INSURANCE AGAINST ACTS OF GOD?

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

In article ,
charles wrote:
Tricky for me, since the car is in a very exposed paved area at the front
of my house. I don't suppose anyone would take advantage and stroll off
with the charger but I'd rather not leave the car with the bonnet
unlocked and cracked open overnight. But from what others have said, it
might be worth trying the starter after a few hours.

I'm sure you could close the bonnet if you put the charger in a suitable
place.

Even with an under engine tray, you can usually feed the mains extension
into the compartment from underneath. Assuming it's not a cable reel. If
the battery is in the boot, tough. But I doubt anyone would nick a car
boot sale charger.

--
*I couldn't repair your brakes, so I made your horn louder *

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

charles wrote:

In article ,
Brian Reay wrote:
Brian Gaff \(Sofa 2\) wrote:
I've often wondered when new cars are made it is obviously months before
they go to a customer, so how do they look after all those batteries?
Brian


VW fit a better quality dashboard solar panel to at least some models- it
is removed before delivery to the customer and, I believe, returned for

Since there's a pretty solid bulkhead between the dashboard and the engine
compartment - where the battery lives - how do you connect tehtwo ? leads
out of the door and under the bonnet?

Presumably if you're a car manufacturer you install a suitable socket
(fuse protected but unswitched) on the wiring loom under the dashboard.
It doesn't have to be particularly high current for a small solar
charger.


--

Roger Hayter

Dave Plowman wrote:

How long did you run it for?

Less than a minute. It simply occurred to me to see if it would start.

On 11/04/20 11:21, Dave Plowman (News) wrote:
In article ,
Bert Coules wrote:
"The Natural Philosopher" wrote:

And how can I tell when the battery is sufficiently charged?

when the terminal voltage is over 13V

But how do I tell that? There's no meter or any other indicator sort of on
the charger.

Leave it on for 24 hours.

A simple 6 amp charger will only charge at 6 amps for a short period (if
ever - many are extremely optimistic) and as the battery volts come up,
the charge rate will fall.

If the car won't start after 24 hours and the charger was working, chances
are the battery has had it.

You can check the charger is working with a simple DVM or other method of
measuring the volts. They will be higher on charge than off charge.

The OP said that he doesn't have any method of measurement,
unfortunately. Might be simplest to charge for 4 or 5 hours, then turn
off the charger and turn the headlights on for a minute:
1. Headlights don't come on - battery buggered. Replace asap.
2. Headlights come on and stay on - battery ok. Continue charging.
3. Headlights come on and slowly fade - battery on the way out. The car
might start and get you from A to B, but I wouldn't guarantee getting
back from B to A! Replace battery asap.

--

Jeff

Jeff Layman wrote:

Might be simplest to charge for 4 or 5 hours, then turn
off the charger and turn the headlights on for a minute:
1. Headlights don't come on - battery buggered. Replace asap.
2. Headlights come on and stay on - battery ok. Continue charging.
3. Headlights come on and slowly fade - battery on the way out. The car
might start and get you from A to B, but I wouldn't guarantee getting
back from B to A! Replace battery asap.

Thanks for that. Sounds like a good scheme.

"Dave Plowman (News)" wrote:
You'd need an awfully large charger to get voltage spikes past the very
low impedance of a car battery.

If the battery is knackered, won't that impedance increase? As an endpoint,
imagine if the battery was completely dry - it's open circuit and so
wouldn't accept any current at all, and all the current would be put into
the car electronics.

Would sulphation raise the impedance?

Properly designed car electronics should have voltage regulators (and
components) rated up to 40 volts.

Indeed. Although I wouldn't be surprised if some weren't as
tolerant as they should be (also that aftermarket radio you got from
China...)

Theo

On Sat, 11 Apr 2020 10:48:49 +0100, charles wrote:

Though to be honest even a few mA drain will knacker a battery in
few
months, Solar panel maybe, plugged into the ciggy socket or ODBII?
Actually disconnect the battery when parked up on the storeage
field?
Would seem better options.

the ciggy socket on my car is only live with 'aux' switched on.

Ah, but is that via the physical steering colum switch or a
relay/solid state one buried in a BCU that could be set to "on" in
deep leep mode?

--
Cheers
Dave.

In article l.net,
Dave Liquorice wrote:
On Sat, 11 Apr 2020 10:48:49 +0100, charles wrote:

Though to be honest even a few mA drain will knacker a battery in
few
months, Solar panel maybe, plugged into the ciggy socket or ODBII?
Actually disconnect the battery when parked up on the storeage
field?
Would seem better options.

the ciggy socket on my car is only live with 'aux' switched on.

Ah, but is that via the physical steering colum switch or a
relay/solid state one buried in a BCU that could be set to "on" in
deep leep mode?

I have a dashboard push button; but no idea about the deep sleep mode.

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

The Natural Philosopher wrote:
On 11/04/2020 09:53, Mike Clarke wrote:
On 10/04/2020 22:35, The Natural Philosopher wrote:
On 10/04/2020 20:28, Bert Coules wrote:

Do I need to disconnect the car's own connecting leads
first?

no

Some manufacturers recommend that you do disconnect the battery. Some
cheapo chargers might have a very spiky voltage pattern that could
upset the onboard electronics.

You need a hell of a lot of current to spike a battery over 14v

Car electrical systems need to have a wide voltage tolerance.
Thus occurs during "load dumps".

The voltage seen on a car electrical bus *can* spike, but
the electronics are also specified to survive this.

This is one reason you should not connect relatively "naive"
electronics to the raw electrical system of the car.
(A "car stereo" is not the same as a "home stereo" from
a "width of supply rating" point of view. The "car stereo"
is just a bit armored by comparison.)

You might ask yourself, if the car battery impedance is as low
as we think it is, how do *70V spikes* appear on the car
electrical bus ? As a Natural Philosopher, you can go find
an answer for us. I haven't seen any oscilloscope pictures
of car electrical systems which prove these spikes are present.

As an illustration of this, the specsmanship, we can use a
TDA2003, an audio amplifier intended for cheap car radios.

UTC TDA2003 LINEAR INTEGRATED CIRCUIT

ABSOLUTE MAXIMUM RATINGS(Ta=25°C)

PARAMETER SYMBOL VALUE UNIT
Peak Supply Voltage Vs 40 V
DC Supply Voltage Vs 28 V
Operating Supply Voltage Vs 18 V

Nominal

Supply Voltage Vs 8 to 18 V

Now, that's an integrated circuit, where the nominal battery
voltage might be 12.6V, or maybe 14.4V fully charged or under
charge or whatever.

The 18V value is what results, if you jam the field winding
to battery, as an alternator test. The alternator can run
the battery up to around 18V, by forcing a lot of current
into the battery. Your mechanic at the shop might try this.
That's why this stereo expects on occasion, to see 18V, and
the car radio will continue to play.

Well, what do the other voltages mean ?

The 40V value is a measure of load dump. If there is a
transient on the car electrical bus, the 40V value can be
achieved. The TDA2003 is designed to disconnect itself,
at the 40V level, in an attempt to protect the IC innards.
The behavior of some part of the IC changes, when the supply
goes over 18V.

BUILT-IN PROTECTION SYSTEMS

LOAD DUMP VOLTAGE SURGE

The UTC TDA2003 has a circuit which enables it to withstand a
voltage pulse train, on pin 5, of the type shown in Fig. 23.

If the supply voltage peaks to more than 40V, then an LC filter
must be inserted between the supply and pin 5, in
order to assure that the pulses at pin 5 will be held
within the limits shown in Fig.22.

A suggested LC network is shown in Fig.23. With this network,
a train of pulses with amplitude up to 120V and width of
2ms can be applied at point A. This type of protection is ON
when the supply voltage (pulsed or DC) exceeds 18V. For
this reason the maximum "operating" supply voltage is 18V.

There can be spikes on battery, but you would hope that things
like CANBUS or whatever, the spikes would not be seen there.

What is the battery doing when those spikes are present ?
You got me there. Looks like the battery impedance at
frequency, is insufficient to deal with the spike in any
useful way. It suggests an impedance versus frequency curve,
of weird shape or behavior. Even bench DC power supplies,
have impedance versus frequency curves.

A cheap battery charger, is a half wave or full wave rectified device
running off a transformer. A pulsating DC waveform is being applied
to battery, but staying at relatively low voltage levels. A good reason
for not making sparks around the battery area, is igniting any
evolved hydrogen (more of a problem around the battery types
where the battery caps are removable, as those have vents). It's
for that reason, you could connect the charger while it's off.
The electrical spike issue, the car design has taken some
of that into account, with load dump specs and the like.

If you're jump starting a car, that's usually done with "hot" cabling.
The cabling is connected in a particular sequence, to keep "sparks"
away from the battery. You can connect the "hot" to the "hot" first,
without sparks. The "ground" alligator jaw, gets fastened to a screw
on the metal framework, rather than to the battery terminal, and this keeps
the spark away from the very top of the battery. As it's when the
second lead is connected (or disconnected), when a small spark flies.
When jump starting a car, those "sparks" near the frame, also
hint about the state of the two electrical systems on the cars,
such as if the second car is a dead short or something. You might
see very large sparks or "welding behavior", if the second car
had a dead short of some sort. It's better to be making sparks like
that, near the frame, than near the top of the battery.

Jump starting a car, is a very good time to be testing the
limits of load dump specs.

Paul

In article ,
Bert Coules wrote:
Dave Plowman wrote:

How long did you run it for?

Less than a minute. It simply occurred to me to see if it would start.

Ah - that's why it wouldn't the next time. It's also bad for the engine to
start it just for a short time. Ideally, take the car for a drive, or warm
it up fully before stopping it. Blip the throttle a few times to while
doing this - don't just let it idle.

--
*Ham and Eggs: Just a day's work for a chicken, but a lifetime commitment

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

In article ,
Theo wrote:
"Dave Plowman (News)" wrote:
You'd need an awfully large charger to get voltage spikes past the very
low impedance of a car battery.

If the battery is knackered, won't that impedance increase? As an
endpoint, imagine if the battery was completely dry - it's open circuit
and so wouldn't accept any current at all, and all the current would be
put into the car electronics.

Would sulphation raise the impedance?

Yes to both. But then that is two faults. An incredibly crappy charger and
a totally knackered battery.

Properly designed car electronics should have voltage regulators (and
components) rated up to 40 volts.

Indeed. Although I wouldn't be surprised if some weren't as
tolerant as they should be (also that aftermarket radio you got from
China...)

The old chestnut that only China makes rubbish. ;-)

--
*I want it all and I want it delivered

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

On 11/04/2020 10:24, Dave Liquorice wrote:
On Sat, 11 Apr 2020 08:12:03 +0100, Brian Gaff \(Sofa 2\) wrote:

I've often wondered when new cars are made it is obviously months before
they go to a customer, so how do they look after all those batteries?

Modern cars have various "sleep" modes that power various sub systems
off after various lengths of time. AIUI there is also a deep sleep
mode that can be manually entered that effectively disconects the
battery for storeage. How you wake it back up I donno, but cars still
do have a physical key and lock.

Though to be honest even a few mA drain will knacker a battery in few
months, Solar panel maybe, plugged into the ciggy socket or ODBII?
Actually disconnect the battery when parked up on the storeage field?
Would seem better options.


BMW have special depot at Southampton where news cars are 'woken up'
as part of the PDI. heard this phrase used on a documentary not that
long ago.

On 11/04/2020 10:41, charles wrote:
In article , Bert Coules
wrote:
newshound wrote:

The old fashioned transformer sort *usually* had a meter, you can
recognise those because they are always in a pressed steel box with big
ventilation louvres. The modern electronic ones (typically lightly
finned aluminium extrusions as heat sinks) will have electronic
regulation and usually have a coloured light.

Mine is in a plastic casing with no apparent heatsinks, externally at
least. It has six LEDs marked from 1A up to 6.

In either case the battery will not come to any harm if left on for a
day or two.

Tricky for me, since the car is in a very exposed paved area at the front
of my house. I don't suppose anyone would take advantage and stroll off
with the charger but I'd rather not leave the car with the bonnet
unlocked and cracked open overnight. But from what others have said, it
might be worth trying the starter after a few hours.

I'm sure you could close the bonnet if you put the charger in a suitable
place.

I have always done that. Or the boot, depending where it is..


--
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.

Its inherent virtue is the equal sharing of misery.

Winston Churchill

On 11/04/2020 11:57, Jeff Layman wrote:
On 11/04/20 11:21, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Bert Coules wrote:
"The Natural Philosopher" wrote:

And how can I tell when the battery is sufficiently charged?

when the terminal voltage is over 13V

But how do I tell that?Â* There's no meter or any other indicator sort
of on
the charger.

Leave it on for 24 hours.

A simple 6 amp charger will only charge at 6 amps for a short period (if
ever - many are extremely optimistic) and as the battery volts come up,
the charge rate will fall.

If the car won't start after 24 hours and the charger was working,
chances
are the battery has had it.

You can check the charger is working with a simple DVM or other method of
measuring the volts. They will be higher on charge than off charge.

The OP said that he doesn't have any method of measurement,
unfortunately. Might be simplest to charge for 4 or 5 hours, then turn
off the charger and turn the headlights on for a minute:
1. Headlights don't come on - battery buggered. Replace asap.
2. Headlights come on and stay on - battery ok. Continue charging.
3. Headlights come on and slowly fade - battery on the way out. The car
might start and get you from A to B, but I wouldn't guarantee getting
back from B to A! Replace battery asap.

Depending on the motor it takes about 200A to start a car for about 5
seconds.

If a reasonable charge current once started is 5 A that needs 200
seconds to replace the charge.

Or about 3 1/2 minutes.

These figures are well within an order of magnitude. If you start a car
you should not routinely stop it within 5 minutes if you can avoid it


--
In todays liberal progressive conflict-free education system, everyone
gets full Marx.

In article ,
Paul wrote:
You need a hell of a lot of current to spike a battery over 14v

Car electrical systems need to have a wide voltage tolerance.
Thus occurs during "load dumps".

This is more commonly referred to after jump starting a car. Not using a
battery charger.

And I'd take that with a pinch of salt too.

--
*Why is it that doctors call what they do "practice"?

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

In article ,
Paul wrote:
You might ask yourself, if the car battery impedance is as low
as we think it is, how do *70V spikes* appear on the car
electrical bus ? As a Natural Philosopher, you can go find
an answer for us. I haven't seen any oscilloscope pictures
of car electrical systems which prove these spikes are present.

Nor have I. Despite playing with car electrics more than most. Except if
you were stupid enough to disconnect the battery with the engine running.

As the saying goes, you can make things fool proof. Idiot proof, even. But
not c**t proof.

As an illustration of this, the specsmanship, we can use a
TDA2003, an audio amplifier intended for cheap car radios.

UTC TDA2003 LINEAR INTEGRATED CIRCUIT

ABSOLUTE MAXIMUM RATINGS(Ta=25°C)

PARAMETER SYMBOL VALUE UNIT
Peak Supply Voltage Vs 40 V
DC Supply Voltage Vs 28 V
Operating Supply Voltage Vs 18 V

Nominal

Supply Voltage Vs 8 to 18 V

Now, that's an integrated circuit, where the nominal battery
voltage might be 12.6V, or maybe 14.4V fully charged or under
charge or whatever.

The 18V value is what results, if you jam the field winding
to battery, as an alternator test. The alternator can run
the battery up to around 18V, by forcing a lot of current
into the battery. Your mechanic at the shop might try this.
That's why this stereo expects on occasion, to see 18V, and
the car radio will continue to play.

I don't know of any modern alternator where it's remotely possible to
bypass the regulator. Certainly not by the average grease monkey. Who
knows very little about car electronics, other than fitting new parts.

Well, what do the other voltages mean ?

The 40V value is a measure of load dump. If there is a
transient on the car electrical bus, the 40V value can be
achieved. The TDA2003 is designed to disconnect itself,
at the 40V level, in an attempt to protect the IC innards.
The behavior of some part of the IC changes, when the supply
goes over 18V.

BUILT-IN PROTECTION SYSTEMS

LOAD DUMP VOLTAGE SURGE

The UTC TDA2003 has a circuit which enables it to withstand a
voltage pulse train, on pin 5, of the type shown in Fig. 23.

If the supply voltage peaks to more than 40V, then an LC filter
must be inserted between the supply and pin 5, in
order to assure that the pulses at pin 5 will be held
within the limits shown in Fig.22.

A suggested LC network is shown in Fig.23. With this network,
a train of pulses with amplitude up to 120V and width of
2ms can be applied at point A. This type of protection is ON
when the supply voltage (pulsed or DC) exceeds 18V. For
this reason the maximum "operating" supply voltage is 18V.

There can be spikes on battery, but you would hope that things
like CANBUS or whatever, the spikes would not be seen there.

What is the battery doing when those spikes are present ?
You got me there. Looks like the battery impedance at
frequency, is insufficient to deal with the spike in any
useful way. It suggests an impedance versus frequency curve,
of weird shape or behavior. Even bench DC power supplies,
have impedance versus frequency curves.

A cheap battery charger, is a half wave or full wave rectified device
running off a transformer. A pulsating DC waveform is being applied
to battery, but staying at relatively low voltage levels. A good reason
for not making sparks around the battery area, is igniting any
evolved hydrogen (more of a problem around the battery types
where the battery caps are removable, as those have vents). It's
for that reason, you could connect the charger while it's off.
The electrical spike issue, the car design has taken some
of that into account, with load dump specs and the like.

Love to know where you'd by a cheap battery charger that has a transformer
these days. SMPS have been cheaper for many a year.

--
*Gun Control: Use both hands.

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

In article ,
The Natural Philosopher wrote:
Depending on the motor it takes about 200A to start a car for about 5
seconds.

If a reasonable charge current once started is 5 A that needs 200
seconds to replace the charge.

Or about 3 1/2 minutes.

These figures are well within an order of magnitude.

I have a very accurate voltmeter fitted to the old Rover. Alternator on
that is a slightly more modern unit with 100 amp output. Assuming the
battery is reasonably fresh to start with, the voltage, after a cold start
will have dropped back to the normal point after a drive to the shops. Say
a couple of miles of town driving.

--
*Cover me. I'm changing lanes.

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

Bert Coules presented the following explanation :
And I shall do that. Thanks.

Better to make the negative connection last and make it first. It is
also better practice to make/break the negative connection away from
the battery, assuming the battery is connected to the car - connect the
negative of the charger, to the car chassis/engine block or etc.. It
minimises the chance of a spark igniting gas from a battery.

If you cannot connect away from the battery, always try to waft some
air across the battery, to dispel any gas.

Dave Plowman (News) formulated the question :
You'd need an awfully large charger to get voltage spikes past the very
low impedance of a car battery.

Properly designed car electronics should have voltage regulators (and
components) rated up to 40 volts.

.....and if the battery is faulty and open circuit???

Bert Coules was thinking very hard :
There was no corrosion on or around either battery terminal, which I take to
be a good sign.

That is neither a good, nor bad sign. Corrosion just means there has
been some acid leakage around the terminal post.

On 11/04/20 14:18, The Natural Philosopher wrote:
On 11/04/2020 11:57, Jeff Layman wrote:
On 11/04/20 11:21, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Bert Coules wrote:
"The Natural Philosopher" wrote:

And how can I tell when the battery is sufficiently charged?

when the terminal voltage is over 13V

But how do I tell that?Â* There's no meter or any other indicator sort
of on
the charger.

Leave it on for 24 hours.

A simple 6 amp charger will only charge at 6 amps for a short period (if
ever - many are extremely optimistic) and as the battery volts come up,
the charge rate will fall.

If the car won't start after 24 hours and the charger was working,
chances
are the battery has had it.

You can check the charger is working with a simple DVM or other method of
measuring the volts. They will be higher on charge than off charge.

The OP said that he doesn't have any method of measurement,
unfortunately. Might be simplest to charge for 4 or 5 hours, then turn
off the charger and turn the headlights on for a minute:
1. Headlights don't come on - battery buggered. Replace asap.
2. Headlights come on and stay on - battery ok. Continue charging.
3. Headlights come on and slowly fade - battery on the way out. The car
might start and get you from A to B, but I wouldn't guarantee getting
back from B to A! Replace battery asap.

Depending on the motor it takes about 200A to start a car for about 5
seconds.

If a reasonable charge current once started is 5 A that needs 200
seconds to replace the charge.

Or about 3 1/2 minutes.

These figures are well within an order of magnitude. If you start a car
you should not routinely stop it within 5 minutes if you can avoid it

Nothing wrong with your figures, but I don't understand the relevance
here. All I was trying to point out is a battery which will charge -
sort of - but won't hold a charge for very long. It'll lose that charge
over a period of several minutes or maybe an hour, and so needs
replacing. If the OP stops for less than a minute after driving around
with that battery and then tries to restart the car he /might/ get away
with it. He might not. The headlight test should show if the battery is
dodgy enough that it could fail to restart the car.

--

Jeff