The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

The manual for the charger is unhelpfully vague, merely saying in poor
English that when the pointer is "in the left part of" the scale that
charging is complete.

Daniele

On Fri, 9 Oct 2009 13:40:27 +0100 someone who may be
(D.M. Procida) wrote
this:-

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.






--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54

D.M. Procida wrote:
The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

On some battery chargers - when the amp meter drops to zero (on the old one
that I use anyway)
When the batter hydrometer says so (if you can get at the individual cells)!
When a voltmeter says so!
When any indicator on top of the battery says so - usually turns green (on
the battery on my car at least)!

The manual for the charger is unhelpfully vague, merely saying in poor
English that when the pointer is "in the left part of" the scale that
charging is complete.

Or when you can start the car on a chilly morning using battery power alone.

Cash

When its terminal voltage is about 13.5 V off load.

In article ,
(D.M. Procida) writes:
The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

When it reaches a certain voltage.
The voltage varies slightly by battery temperature, battery type,
and if this is a cyclic charge (almost certainly what you're doing)
or a standby charge (where it's left permanently connected to the
charger).

If your charger is properly voltage regulated, the charge current
will drop to almost zero when charged. If it's not properly voltage
regulated (and many aren't), the charge current won't drop to zero
ever, and you may wreck the battery by leaving it charging too long.

You also need to be careful about the max charging current, again
depending on battery type. Charging at 1/7th of the battery capacity
is safe with just about any type. Some batteries (e.g. car) can
safely be charged at significantly higher rates. This is the max
current though when the battery is pretty flat. As it charges, the
current will drop.

Since you haven't said exactly what type of battery or charger,
can't be more specific.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel wrote:

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

If your charger is properly voltage regulated, the charge current
will drop to almost zero when charged. If it's not properly voltage
regulated (and many aren't), the charge current won't drop to zero
ever, and you may wreck the battery by leaving it charging too long.

I'm not sure. The instructions warn that it doesn't automatically stop
charging, but the current does diminish as it charges - whether this is
through regulation or the effect of the battery's increasing charge I
don't know.

You also need to be careful about the max charging current, again
depending on battery type. Charging at 1/7th of the battery capacity
is safe with just about any type. Some batteries (e.g. car) can
safely be charged at significantly higher rates. This is the max
current though when the battery is pretty flat. As it charges, the
current will drop.

Since you haven't said exactly what type of battery or charger,
can't be more specific.

It's a car battery.

Daniele

"David Hansen" wrote in message
...
On Fri, 9 Oct 2009 13:40:27 +0100 someone who may be
(D.M. Procida) wrote
this:-

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.


Ouch no!! That's the best way of wrecking a lead acid battery, especially
if the sealed types. Any current after it's fully charged will dry out a
battery.

The best charger has always been a constant voltage charger. This matter
has been discussed ad nauseum before in the NG.

"D.M. Procida" wrote in
message
...
The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

The manual for the charger is unhelpfully vague, merely saying in poor
English that when the pointer is "in the left part of" the scale that
charging is complete.

Daniele

For a cheapie charger, the best indication is terminal voltage. When it's
more that 14V, I'd disconnect the charger. 13.5V is too low, and the
battery won't have been fully charged.

On Fri, 9 Oct 2009 13:56:37 +0100
"Cash" wrote:

Or when you can start the car on a chilly morning using battery power alone.

Which is a lot of help if the battery if for a non-vehicle application.
R.

In article ,
(D.M. Procida) writes:
Andrew Gabriel wrote:

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?

If your charger is properly voltage regulated, the charge current
will drop to almost zero when charged. If it's not properly voltage
regulated (and many aren't), the charge current won't drop to zero
ever, and you may wreck the battery by leaving it charging too long.

I'm not sure. The instructions warn that it doesn't automatically stop
charging, but the current does diminish as it charges - whether this is
through regulation or the effect of the battery's increasing charge I
don't know.

Sounds like it isn't a proper voltage regulated one then,
so you need to be careful not to overcharge the battery.

You also need to be careful about the max charging current, again
depending on battery type. Charging at 1/7th of the battery capacity
is safe with just about any type. Some batteries (e.g. car) can
safely be charged at significantly higher rates. This is the max
current though when the battery is pretty flat. As it charges, the
current will drop.

Since you haven't said exactly what type of battery or charger,
can't be more specific.

It's a car battery.

If it's been taking 3A for a few hours, it will have 9Ahrs
(less a bit for inefficiency) added to it, which is plenty
enough to start a car many times, unless there's something
wrong. The car will then charge it properly, and much faster,
whilst you do your regular driving (don't sit on the drive
reving the engine, as that's pretty pointless).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel wrote:

It's a car battery.

If it's been taking 3A for a few hours, it will have 9Ahrs
(less a bit for inefficiency) added to it, which is plenty
enough to start a car many times, unless there's something
wrong. The car will then charge it properly, and much faster,
whilst you do your regular driving (don't sit on the drive
reving the engine, as that's pretty pointless).

It's a 60Ah battery. The terminal voltage isn't yet up to 13V.

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Daniele

On Fri, 9 Oct 2009 15:57:07 +0100, D.M. Procida wrote:

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Oh dear that doesn't bode well. One thing that car batteries hate is
having a deep discharge. A fairly new one should survive but one a
year or three old may not.

You need to find out if the car has a fault that is taking more than
a few 10's of mA when just parked up. You may need to measure this up
to half an hour after switching off and locking the car to allow it
to fully "go to sleep".

--
Cheers
Dave.

On Fri, 09 Oct 2009 15:57:07 +0100, D.M. Procida wrote:

Andrew Gabriel wrote:

It's a car battery.

If it's been taking 3A for a few hours, it will have 9Ahrs (less a bit
for inefficiency) added to it, which is plenty enough to start a car
many times, unless there's something wrong. The car will then charge it
properly, and much faster, whilst you do your regular driving (don't
sit on the drive reving the engine, as that's pretty pointless).

It's a 60Ah battery. The terminal voltage isn't yet up to 13V.

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Daniele

Had a Daewoo (yes I know but ...) and it had a known feature where the
bracket holding the brake light switch got tired and bend slowly out the
way so eventually the brake lights stayed on - battery flat next morning.

Not saying it is but ...

On Oct 9, 3:57*pm, (D.M.
Procida) wrote:
Andrew Gabriel wrote:
It's a car battery.

If it's been taking 3A for a few hours, it will have 9Ahrs
(less a bit for inefficiency) added to it, which is plenty
enough to start a car many times, unless there's something
wrong. The car will then charge it properly, and much faster,
whilst you do your regular driving (don't sit on the drive
reving the engine, as that's pretty pointless).

It's a 60Ah battery. The terminal voltage isn't yet up to 13V.

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Daniele


leave the battery on the car overnight again, but this time
disconnected. Then you'll know


NT

In article
,
D.M. Procida wrote:
It's a car battery.

Generally most home chargers are pretty weedy and car batteries are fairly
tolerant. All you really need to do is charge it sufficiently to start the
car and then let its charging system worry about topping it up. Overnight
is usually good enough for this.

Incidentally, Lidl have their rather fine chargers on sale again from next
Monday. They can be left on indefinitely since they switch to a
maintenance charge when the battery is 'full'. They've gone up since last
time - now 15 quid - but still very worth it. Enough output to charge most
batteries overnight.

--
*Starfishes have no brains *

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

On Fri, 9 Oct 2009 15:05:18 +0100 someone who may be "Fredxx"
wrote this:-

Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.

Ouch no!! That's the best way of wrecking a lead acid battery, especially
if the sealed types. Any current after it's fully charged will dry out a
battery.

I have been charging a set of sealed lead acid batteries in that way
for the best part of a decade. So far they remain fine. Obviously if
the charging voltage is set too high then it would indeed dry out
the battery, but I did a lot of research before deciding on that
form of charging to get the charging voltage right.

http://www.atbatt.com/sku_pdf/cyclon_application_manual.pdf



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54

On Fri, 9 Oct 2009 15:57:07 +0100 someone who may be
(D.M. Procida) wrote
this:-

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

I would suspect a fault in the car wiring and track this down. More
and more things are being connected directly to the battery,
sometimes without even a fuse, so are able to gently drain the
battery. If one of these has gone wrong then it will be able to
drain the battery more rapidly than designed to do. It may take a
while to track down what it is, but things which are available even
when the ignition is not turned on are where I would start looking.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54

In article ,
"Dave Plowman (News)" writes:
In article
,
D.M. Procida wrote:
It's a car battery.

Generally most home chargers are pretty weedy and car batteries are fairly
tolerant. All you really need to do is charge it sufficiently to start the
car and then let its charging system worry about topping it up. Overnight
is usually good enough for this.

5 minutes charge with one of those was enough to get one start,
when a family member flattened their battery with lights left on.
IIRC, they charge at just under 4A.

Incidentally, Lidl have their rather fine chargers on sale again from next
Monday. They can be left on indefinitely since they switch to a
maintenance charge when the battery is 'full'. They've gone up since last
time - now 15 quid - but still very worth it. Enough output to charge most
batteries overnight.

I bought one for £12, IIRC (Aldi or Lidl, can't recall,
a year or two back). When I went back later, they were
reduced to half price, so I bought 2 more. They are very
nice units. Elsewhere, they could be found for around £40.

What would be _really_ nice is if they had a switch setting
to automatically start charging when mains is applied. That
could be the basis for an effective automatic emergency supply.
Sadly, they don't do this.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
The Nomad wrote:
Had a Daewoo (yes I know but ...) and it had a known feature where the
bracket holding the brake light switch got tired and bend slowly out the
way so eventually the brake lights stayed on - battery flat next
morning.

A car where the brake lights work without the ignition switched off? Mine
will when in the accessory position - but not when off totally.

--
*It's not hard to meet expenses... they're everywhere.

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

In article ,
David Hansen wrote:
I would suspect a fault in the car wiring and track this down. More
and more things are being connected directly to the battery,
sometimes without even a fuse, so are able to gently drain the
battery. If one of these has gone wrong then it will be able to
drain the battery more rapidly than designed to do. It may take a
while to track down what it is, but things which are available even
when the ignition is not turned on are where I would start looking.

If it's discharging overnight and nothing is obviously on one possible
cause is a failed diode in the alternator rectifier pack. They can fail
short circuit resulting in a permanent discharge of about 6 amps. Feel if
the alternator back is warm when the engine is cold, if you can't measure
the quiescent current.

--
*Lottery: A tax on people who are bad at math.

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

"David Hansen" wrote in message
...
On Fri, 9 Oct 2009 15:05:18 +0100 someone who may be "Fredxx"
wrote this:-

Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.

Ouch no!! That's the best way of wrecking a lead acid battery, especially
if the sealed types. Any current after it's fully charged will dry out a
battery.

I have been charging a set of sealed lead acid batteries in that way
for the best part of a decade. So far they remain fine. Obviously if
the charging voltage is set too high then it would indeed dry out
the battery, but I did a lot of research before deciding on that
form of charging to get the charging voltage right.

http://www.atbatt.com/sku_pdf/cyclon_application_manual.pdf



I can't see any mention of trickle charging. Float charging and constant
voltage charging are all that are mentioned or recommended.

You mix "trickle charging" with "charging voltage" in the same paragraph,
which suggests that your success in charging lead acid batteries has perhaps
been more by accident rather than through knowledge.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Dave Plowman (News)"
saying something like:

A car where the brake lights work without the ignition switched off?

Not unknown. For some reason peculiar to them, Commer of van fame wired
up the brake lights to do exactly that.

In message , "Dave Plowman (News)"
writes
Incidentally, Lidl have their rather fine chargers on sale again from next
Monday. They can be left on indefinitely since they switch to a
maintenance charge when the battery is 'full'.
Just had a look at them, they look extremely similar (different colour
case and different name) to the Aldi one I bought last year?
They've gone up since last
time - now 15 quid - but still very worth it. Enough output to charge most
batteries overnight.


--
Clint Sharp

Fredxx wrote:
"David Hansen" wrote in message
...
On Fri, 9 Oct 2009 13:40:27 +0100 someone who may be
(D.M. Procida) wrote
this:-

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?
Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.


Ouch no!! That's the best way of wrecking a lead acid battery, especially
if the sealed types. Any current after it's fully charged will dry out a
battery.

The best charger has always been a constant voltage charger. This matter
has been discussed ad nauseum before in the NG.

I am going to take one of our two cars off the road at the end of this
month. I had thought of running a mains extension under the bonnet and
leaving a charger there. The extension will be plugged into a timer to
control how long the chargers is on.

How long a time should I power up the charger, per day/week?

Dave

"Dave" wrote in message
...
Fredxx wrote:
"David Hansen" wrote in message
...
On Fri, 9 Oct 2009 13:40:27 +0100 someone who may be
(D.M. Procida) wrote
this:-

The charger says it's running at about 3 amps. When can I consider the
battery properly charged?
Lead-acid batteries are best left being trickle charged. Of course
that implies that the charger is capable of doing that, which many
cheap ones are not.


Ouch no!! That's the best way of wrecking a lead acid battery,
especially if the sealed types. Any current after it's fully charged
will dry out a battery.

The best charger has always been a constant voltage charger. This matter
has been discussed ad nauseum before in the NG.

I am going to take one of our two cars off the road at the end of this
month. I had thought of running a mains extension under the bonnet and
leaving a charger there. The extension will be plugged into a timer to
control how long the chargers is on.

How long a time should I power up the charger, per day/week?

Dave

The trouble is cheap chargers generally wreck batteries if left attached for
long lengths of time. I don't know what's currently on the market. But a
charger designed for "float charging" is one you can permanently leave
connected to the battery.

I have known good lead-acid batteries keep their charge for nearly a year,
but it's rare.

I have seen it suggested that a unconnected battery should be topped up
every 6 weeks. I would disconnect the charger if the terminal voltage gets
much above 14V and then assume the battery is then close to being fully
charged.

In article ,
Andrew Gabriel wrote:
What would be _really_ nice is if they had a switch setting
to automatically start charging when mains is applied. That
could be the basis for an effective automatic emergency supply.
Sadly, they don't do this.

Yes. Wonder how easy it would be to modify?

--
*Save a tree, eat a beaver*

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

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Dave
saying something like:

I am going to take one of our two cars off the road at the end of this
month. I had thought of running a mains extension under the bonnet and
leaving a charger there. The extension will be plugged into a timer to
control how long the chargers is on.

How long a time should I power up the charger, per day/week?

Half an hour per day would be fine. That's exactly what I do on one of
mine. So far, that particular battery's remained good for a couple of
years after being laid up.
An alternative is a decent sized solar panel inside the windscreen and
charging either through the lighter socket or via flyleads to the
disconnected battery. Again, another of my vehicles has just that.

All depends on the battery's self-discharge rate and of course if
anything's slightly draining it on the vehicle.

In article ,
Fredxx wrote:
I have known good lead-acid batteries keep their charge for nearly a
year, but it's rare.

According to an expert on another group the average lead acid car battery
loses 60% of its charge per month. I'm only quoting this FWIW as it's not
my experience. I have a clever electronic battery tester which works out
the actual capacity and that shows nearer 20% per month.
Of course if the battery is left connected in a modern car, the quiescent
drain may well flatten it in less than a month.

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

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

It happens that Dave Plowman (News) formulated :
In article ,
Andrew Gabriel wrote:
What would be _really_ nice is if they had a switch setting
to automatically start charging when mains is applied. That
could be the basis for an effective automatic emergency supply.
Sadly, they don't do this.

Yes. Wonder how easy it would be to modify?

Not that easy - the button needs to be pressed several times, depending
on the model, to set it for car battery charging. There are other types
which do start charging as soon as the mains come back on, but the down
side is that they discharge the battery if they remain connected whilst
the mains is off.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Sat, 10 Oct 2009 08:44:32 +0100, Dave Plowman (News) wrote:

According to an expert on another group the average lead acid car
battery loses 60% of its charge per month.

Naw, thats worse than NiCd!...

I'm only quoting this FWIW as it's not my experience. I have a clever
electronic battery tester which works out the actual capacity and that
shows nearer 20% per month.

I'd say even that is high, no doubt that also includes the energy
taken by the tester. Lead acid batteries have a very low self
discharge, Battery University say 40% per year (3%/month average):

http://www.batteryuniversity.com/partone-6.htm

Of course if the battery is left connected in a modern car, the
quiescent drain may well flatten it in less than a month.

Agreed, modern cars have a "deep sleep" mode that they can be put
into. The makers use this when brand new cars are spending weeks on a
boat traveling the world or parked up on disused airfields waiting to
be sold.

--
Cheers
Dave.

In article ,
"Dave Plowman (News)" writes:
In article ,
Fredxx wrote:
I have known good lead-acid batteries keep their charge for nearly a
year, but it's rare.

According to an expert on another group the average lead acid car battery
loses 60% of its charge per month. I'm only quoting this FWIW as it's not
my experience. I have a clever electronic battery tester which works out
the actual capacity and that shows nearer 20% per month.

Sounds far too high to me, unless it includes the quiescent drain.

Of course if the battery is left connected in a modern car, the quiescent
drain may well flatten it in less than a month.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article o.uk,
Dave Liquorice wrote:
I'm only quoting this FWIW as it's not my experience. I have a clever
electronic battery tester which works out the actual capacity and that
shows nearer 20% per month.

I'd say even that is high, no doubt that also includes the energy
taken by the tester.
Dunno exactly how it works but I suspect it puts on a very heavy load for
a fraction of a second only. I checked its reading against a 5 year old
battery by doing a 20 hour rate test - and it was spot on.
Lead acid batteries have a very low self
discharge, Battery University say 40% per year (3%/month average):

http://www.batteryuniversity.com/partone-6.htm

Dunno how the slope of self discharge goes, though.

--
*You're just jealous because the voices only talk to me *

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

In article , Andrew Gabriel
wrote:
In article , "Dave Plowman (News)"
writes:
In article , Fredxx
wrote:
I have known good lead-acid batteries keep their charge for nearly a
year, but it's rare.

According to an expert on another group the average lead acid car
battery loses 60% of its charge per month. I'm only quoting this FWIW
as it's not my experience. I have a clever electronic battery tester
which works out the actual capacity and that shows nearer 20% per
month.

Sounds far too high to me, unless it includes the quiescent drain.

Me too. But he came out with all sorts of lab tests to prove it. Makes no
difference - I've been using them long enough to know he's wrong.

--
*I was once a millionaire but my mom gave away my baseball cards

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

"Dave" wrote in message
...


I am going to take one of our two cars off the road at the end of this
month. I had thought of running a mains extension under the bonnet and
leaving a charger there. The extension will be plugged into a timer to
control how long the chargers is on.

How long a time should I power up the charger, per day/week?

Dave


I have a boat - that is not used over winter - I have a modern 12V pulse
charger .. I just put it on an overnight charge once a month.
It initially take a couple of amps, but drops very quickly to trickle
charge.

Boat starts no problem come spring.

Far better to keep battery in good nick ... don't keep it permananently
trickle charging, and avoid large current charging form flat, as that can
damage the plates.

"Dave Plowman (News)" gurgled happily, sounding
much like they were saying:

I have known good lead-acid batteries keep their charge for nearly a
year, but it's rare.

According to an expert on another group the average lead acid car
battery loses 60% of its charge per month. I'm only quoting this FWIW as
it's not my experience.

Nor mine.

I've left cars in lockups regularly for the winter, occasionally for 18
months or more, with either no drain (no clock, no stereo memory etc) or
with battery disconnected - and they've started happily come spring.

The battery in 'erselfs 2cv has been on for roughly a decade - it's used
occasional weekends through the summer, usually with at least one week+
trip per year. The battery earth is normally disconnected over the
winter, but left connected through the summer - with a stereo with memory
fitted. It's not had to be jumped or charged for years.

As far as the original question goes - just disconnect the battery and
reconnect when you want to use it again.

"Dave Liquorice" wrote in message
ll.co.uk...
On Sat, 10 Oct 2009 08:44:32 +0100, Dave Plowman (News) wrote:

According to an expert on another group the average lead acid car
battery loses 60% of its charge per month.

Naw, thats worse than NiCd!...

I'm only quoting this FWIW as it's not my experience. I have a clever
electronic battery tester which works out the actual capacity and that
shows nearer 20% per month.

I'd say even that is high, no doubt that also includes the energy
taken by the tester. Lead acid batteries have a very low self
discharge, Battery University say 40% per year (3%/month average):

http://www.batteryuniversity.com/partone-6.htm

Of course if the battery is left connected in a modern car, the
quiescent drain may well flatten it in less than a month.

Agreed, modern cars have a "deep sleep" mode that they can be put
into. The makers use this when brand new cars are spending weeks on a
boat traveling the world or parked up on disused airfields waiting to
be sold.


I've not heard of this. But not saying it doesn't happen. My experience is
that new batteries have electrodes of high purity, such that batteries have
a very low rate of self discharge. They may well retain their charge over
an extended time. One issue when fitted to a car is that some of the car's
gadgets do consume a small current.

I had believed that batteries were generally shipped dry, with the
electrodes in their formed state, where on importation or before sale, were
topped up with the correct strength of sulphuric acid. A dry battery will
quite literally last years on the shelf. Again I could be wrong.

Dave Liquorice wrote:

On Fri, 9 Oct 2009 15:57:07 +0100, D.M. Procida wrote:

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Oh dear that doesn't bode well. One thing that car batteries hate is
having a deep discharge. A fairly new one should survive but one a
year or three old may not.

You need to find out if the car has a fault that is taking more than
a few 10's of mA when just parked up. You may need to measure this up
to half an hour after switching off and locking the car to allow it
to fully "go to sleep".

Well, since I gave it about four hours on the charger on Friday it's
been fine. If there is something draining it, it doesn't seem to be at
work now.

How much use does a car need to keep its battery charged?

Daniele

In article
,
D.M. Procida wrote:
Well, since I gave it about four hours on the charger on Friday it's
been fine. If there is something draining it, it doesn't seem to be at
work now.

How much use does a car need to keep its battery charged?

IIRC, BMW won't entertain a claim for a new battery if the car's not been
run for over three weeks. I've read somewhere.

--
*Caution: I drive like you do.

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

On Oct 9, 8:21*pm, "Dave Plowman (News)" wrote:
In article ,
* *Andrew Gabriel wrote:

What would be _really_ nice is if they had a switch setting
to automatically start charging when mains is applied. That
could be the basis for an effective automatic emergency supply.
Sadly, they don't do this.

Yes. Wonder how easy it would be to modify?

--
*Save a tree, eat a beaver*

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

Here are some numbers recalled from working days.
When one typically dealt with 24 cell, nominal 48 volt, large capacity
telecomm. batteries and occasionally with other varieties/sizes!

Voltages per cell and for a six cell car battery.
Charging voltage; 2.3 to 2.4 volts/13.8 to 14.4 volts.
Floating/trickle charge to keep batteries alive and fully ready for
service, 2.15 (British Post Office) to 2.17 (US. ATT&T etc.) 12.9 to
13.0. Just a few milliamps going to battery bank to offset natural
self discharge tendency. A non trickled battery in good condition can
self discharge in several months.
In other words any 14.5 volts and over can boil a wet battery dry.
A trickle voltage below say 12.5 not much use.

Another yard stick read somewhere was; after some 12 to 24 hours after
being fully charged (not over-charged) a battery in good condition
should settle down and assume a nominal voltage of around 11.8 to 12
volts.
If it's anything below that or down to say 10.7 volts or below,
battery is shot! Haven't tried that myself, although got several old
truck batteries that were refreshed recently, so must try it!

PS. Forget nonsense about modern encased batteries discharging if
stored on a cool cement floor. Old wives tale due to earlier, probably
porous rubber encased batteries of an earlier era!

BTW Apropos the "Save a tree ................. " Try this: "Save fish,
hunt some seals". The 500 year old fishery off the east coast on
Canada/North America has been decimated by a) Overfishing and b) The
millions of seals who will eat almost anything marine!

On Oct 9, 8:21*pm, "Dave Plowman (News)" wrote:
In article ,
* *Andrew Gabriel wrote:

What would be _really_ nice is if they had a switch setting
to automatically start charging when mains is applied. That
could be the basis for an effective automatic emergency supply.
Sadly, they don't do this.

Yes. Wonder how easy it would be to modify?

--
*Save a tree, eat a beaver*

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

We have a fast garage style charger that we salvaged and modified. It
came equipped with a simple timer.