OK, so we all know cordless power tool batteries have a limited life
governed by the discharge cycle.

What's the best way to prolong life? Discharge completely on a regular
basis? Recharge immediately after each use?

And where does one get the individual cells from if you want to replace?

Dave

David Lang wrote:
OK, so we all know cordless power tool batteries have a limited life
governed by the discharge cycle.

What's the best way to prolong life? Discharge completely on a regular
basis? Recharge immediately after each use?

And where does one get the individual cells from if you want to replace?

If your tool does not have a low-voltage cut-off, then do not
use it once it starts to fade rapidly.
This will reverse charge one or more cells, and do terrible
things to the life.
For both NiMH, and NiCd, occasional deep discharges are not a bad
idea.
http://www.cpc.co.uk/ has cells.

David Lang wrote:

OK, so we all know cordless power tool batteries have a limited life
governed by the discharge cycle.

What's the best way to prolong life? Discharge completely on a regular
basis? Recharge immediately after each use?

If you can do a full charge discharge cycle most of the time this will
help. If you start out with a good quality pack this is easier to do
anyway since the self discharge rate will be low, so you can use half
the charge, put the tool down, come back a week later and still use most
of the other half. Many of the cheaper packs encourage partial charging
on the grounds that you need to charge packs in an unknown state just
the be sure they will be ready when you want them.

Not overcharging is one of the most important things. With most NiCds
you can charge at a low rate (i.e. 16 hour charge) and not worry too
much about going over. Obviously this is not much use for a power tool
though - most people want faster chargers. The worst examples are the
"mid speed" ones - often these will charge in 2 to 5 hours and have no
control over the charging. These will kill batteries fast. A good
intelligent charger with delta peak detection and thermal sensors will
work best.

Don't run packs completely flat. Don't leave them flat for long periods.
Don't subject them to extremes of temperature.

And where does one get the individual cells from if you want to replace?

RS / CPC/ Farnell / Maplin / and any decent model shop.

Failing that send the complete pack to http://www.re-cell.co.uk/ and
they will rebuild it for you.


If you equip a poor or medium spec tool with a decent set of cells and
buy it a good charger (Makita and the like sell them separately if
required) you will not only get much better life from the batteries, but
also improve the performance of the tool by sometimes a very substantial
margin.

(I note that many budget tools have copied the same terminal arrangement
as used by Makita, since their chargers are universal and will typically
charge anything in the range of 7.2 to 14/18/24V (depending on model)
you can often use a Makita charger on these other packs as well)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
David Lang wrote:
OK, so we all know cordless power tool batteries have a limited life
governed by the discharge cycle.

What's the best way to prolong life? Discharge completely on a regular
basis? Recharge immediately after each use?

1/10th capacity charge rate for 14 hours and use a timer. They should only
be discharged to the point where the performance suffers - not completely.
Fast charging may reduce the number of packs you need for any one heavily
used tool, but IMHO still reduces life no matter how well done.

And where does one get the individual cells from if you want to replace?

Any electronics supplier like Maplin, RS, CPC etc. Maplin own brand tagged
cells are pretty good - although my favourite make is Sanyo.

--
*Growing old is inevitable, growing up is optional

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

On Sat, 30 Jul 2005 23:14:23 GMT, David Lang wrote:

What's the best way to prolong life? Discharge completely on a
regular basis? Recharge immediately after each use?

Self discharge is one of the most damaging things for NiCds, note that
come discharged. If you know your are not going to use the tool for a
period(*) then it's best to take the charge level down low, but then
of course you need to charge it before you use it. No more whip it out
and off you go...

As I want the convience of instant use I always charge when flat, I
don't do partial charges.

And where does one get the individual cells from if you want to
replace?

Others have mentioned the big general suppliers but there are a quite
a few smaller battery/cell specialists out there that offer
competative prices and my well recell for you. Recelling might not be
as straight forward as it looks, especially if the case is welded
together, rather than glued or screwed. Yellow pages, batteries are
heavy so postage high.

(*) Months rather than days or weeks but it depends on the quality of
the cells. Some will self discharge completely in a couple of months
others much longer.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:
On Sat, 30 Jul 2005 23:14:23 GMT, David Lang wrote:

What's the best way to prolong life? Discharge completely on a
regular basis? Recharge immediately after each use?

Self discharge is one of the most damaging things for NiCds, note that
come discharged. If you know your are not going to use the tool for a
period(*) then it's best to take the charge level down low, but then
of course you need to charge it before you use it. No more whip it out
and off you go...

What do you mean by this?
Discharging deeply harms cells, by reverse charging them.
Sustained charging converts one of the metals in the battery to a different
form, and makes it harder to discharge rapidly.
Self-discharge does not harm cells.

Huge wrote:
Ian Stirling writes:
Dave Liquorice wrote:
On Sat, 30 Jul 2005 23:14:23 GMT, David Lang wrote:

What's the best way to prolong life? Discharge completely on a
regular basis? Recharge immediately after each use?

Self discharge is one of the most damaging things for NiCds, note that
come discharged. If you know your are not going to use the tool for a
period(*) then it's best to take the charge level down low, but then
of course you need to charge it before you use it. No more whip it out
and off you go...

What do you mean by this?
Discharging deeply harms cells, by reverse charging them.
Sustained charging converts one of the metals in the battery to a different
form, and makes it harder to discharge rapidly.
Self-discharge does not harm cells.

Yeah. Right. That'll explain why the Nicads on my 144MHz and 432MHz handhelds, which
have been sitting on a shelf for 10 years, are as dead as doornails.



Self discharge, unless they go totally flat for long periods does not harm
cells.
This does not seem to be what the Dave was saying.

Huge wrote:
Ian Stirling writes:
Huge wrote:
Ian Stirling writes:
Dave Liquorice wrote:
On Sat, 30 Jul 2005 23:14:23 GMT, David Lang wrote:

What's the best way to prolong life? Discharge completely on a
regular basis? Recharge immediately after each use?

Self discharge is one of the most damaging things for NiCds, note that
come discharged. If you know your are not going to use the tool for a
period(*) then it's best to take the charge level down low, but then
of course you need to charge it before you use it. No more whip it out
and off you go...

What do you mean by this?
Discharging deeply harms cells, by reverse charging them.
Sustained charging converts one of the metals in the battery to a different
form, and makes it harder to discharge rapidly.
Self-discharge does not harm cells.

Yeah. Right. That'll explain why the Nicads on my 144MHz and 432MHz handhelds, which
have been sitting on a shelf for 10 years, are as dead as doornails.



Self discharge,

[The sound of goalposts moving]

unless they go totally flat for long periods does not harm
cells.
This does not seem to be what the Dave was saying.

Nicads also self-discharge very quickly.


No, they don't.
NiMH cells self-discharge very quickly.
NiCd cells left on the shelf at room temperature for a year will have
a significant amount of charge left.

In article ,
Huge wrote:
Nicads also self-discharge very quickly.

It very much depends on the quality. I've got a 7.2 volt drill kept for
electronics stuff (clean ;-)) which was re-celled with Maplin's finest
ages ago and hasn't been charged this year. Worked fine yesterday.

Rubbish cells - or damaged by poor charging - can self discharge in a few
days.

--
*Forget the Joneses, I keep us up with the Simpsons.

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

Huge wrote:
Ian Stirling writes:
Huge wrote:

[34 lines snipped]

Nicads also self-discharge very quickly.


No, they don't.
NiMH cells self-discharge very quickly.
NiCd cells left on the shelf at room temperature for a year will have
a significant amount of charge left.

As you wish. Not that I shall pay much attention to anything else you post.

It's got very little to do with what I wish, and much to do with the
contents of datasheets, and the performance of batteries in the
real world.
For example
http://www.gpina.com/pdf/70AAST.PDF
Specifies that their batteries will beat 20% per month charge loss in the
first 28 days.


http://www.panasonic.com/industrial/...d_Overview.pdf

Specifies that at 6 months and 20C, it'll have 75% remaining,
at 0C, 85% remaining after 6 months.
Extrapolating the graph out to 12 months, maybe 45% at 20C, or 60% at 0C.

http://www.panasonic.com/industrial/...H_Overview.pdf

Is the corresponding document for NiMH, and gives approximately similar
results - but with weeks replacing months in the time axis.

Ian Stirling wrote in message

[34 lines snipped]

Nicads also self-discharge very quickly.


No, they don't.
NiMH cells self-discharge very quickly.
NiCd cells left on the shelf at room temperature for a year will have
a significant amount of charge left.


It's got very little to do with what I wish, and much to do with the
contents of datasheets, and the performance of batteries in the
real world.

http://www.panasonic.com/industrial/...asonic_NiCd_Ov
erview.pdf

Specifies that at 6 months and 20C, it'll have 75% remaining,
at 0C, 85% remaining after 6 months.
Extrapolating the graph

To be fair you are not only quoting from arguably the best manufacture as
opposed to the sometimes-doubtful quality of some OEM batteries, but also in
NEW condition.
After a year or so of charge cycles they do self-discharge at an ever
increasing rate.
IMHO of course :-)

Huge presented the following explanation :
Yeah. Right. That'll explain why the Nicads on my 144MHz and 432MHz
handhelds, which
have been sitting on a shelf for 10 years, are as dead as doornails.

That will be due to the crystalline growth which can short circuit the
cells internally. A brief application of a high current source across a
cell will blow the short circuit away [1] and the cell can then be
charged once more.

[1} A safe way to do this is by charging up a large capacitor and
connecting it across a shorted cell.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

Mark wrote:

Ian Stirling wrote in message

[34 lines snipped]

Nicads also self-discharge very quickly.


No, they don't.
NiMH cells self-discharge very quickly.
NiCd cells left on the shelf at room temperature for a year will have
a significant amount of charge left.


It's got very little to do with what I wish, and much to do with the
contents of datasheets, and the performance of batteries in the
real world.

http://www.panasonic.com/industrial/...asonic_NiCd_Ov
erview.pdf

Specifies that at 6 months and 20C, it'll have 75% remaining,
at 0C, 85% remaining after 6 months.
Extrapolating the graph

To be fair you are not only quoting from arguably the best manufacture as
opposed to the sometimes-doubtful quality of some OEM batteries, but also in
NEW condition.
After a year or so of charge cycles they do self-discharge at an ever
increasing rate.

Not IME.

At least for AA cells, I've found that they almost always have charge in
even after a couple of years. (specifically, a radio in the attic, and
one in the garage, that I know has been up there that long still worked)
And the cells have mostly been in use since 1995 or so.

On 31 Jul 2005 16:44:31 GMT, Ian Stirling wrote:

Self discharge is one of the most damaging things for NiCds,
note that come discharged. If you know your are not going to
use the tool for a period(*) then it's best to take the charge
level down low, but then of course you need to charge it before
you use it.

What do you mean by this?
Discharging deeply harms cells, by reverse charging them.

Read what I wrote. "... take the charge level down low, ..." nothing
about a deep discharge. No lower than an average 1v/cell for the
battery. Little risk of reverse charging a cell at that level.

Sustained charging converts one of the metals in the battery to
a different form, and makes it harder to discharge rapidly.

Who mentioned sustained charging? I didn't.

Self-discharge does not harm cells.

Yeah. Right. That'll explain why the Nicads on my 144MHz and
432MHz handhelds, which have been sitting on a shelf for 10
years, are as dead as doornails.

Quite. I've got lots of dead NiCds that died on the shelf, doesn't
really tally with "Self-discharge does not harm cells." does it...

Nicads also self-discharge very quickly.

No, they don't.

Would you like to come and talk to the cells here that died within 6
months and were pretty naff after 2.

Latter you witter on about what the spec sheets say. What are the full
test conditions? I suspect the spec sheets quote a nice fresh cell
straight from the factory carefully and slowly charged in a strictly
controlled manner and then left in a controlled and stable enviroment.

Not a cell that has been bumped, charged, partially discharged, over
charged, deep discharged, partially charged, discharged, fully charged
then left on the shelf in an ordinary room. That is a real world cell
in average use in a power tool with a cheap charger.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:
On 31 Jul 2005 16:44:31 GMT, Ian Stirling wrote:

Self discharge is one of the most damaging things for NiCds,
note that come discharged. If you know your are not going to
use the tool for a period(*) then it's best to take the charge
level down low, but then of course you need to charge it before
you use it.

What do you mean by this?
Discharging deeply harms cells, by reverse charging them.

Read what I wrote. "... take the charge level down low, ..." nothing
about a deep discharge. No lower than an average 1v/cell for the
battery. Little risk of reverse charging a cell at that level.

No, you diddn't say that.

However, that paragraph made no sense to me, which is why I was trying
to get you to clarify what you meant.

Self-discharge occurs from the time the cell is made, to the time
it reaches 0V. It's the result of various parasitic electrochemical
processes inside the cell, due to compromises in the construction,
impurities, and the basic design, and you can't do anything about it.
Do you simply mean age?

And I've never seen in any manufacturers data, charger design notes, or
books about NiCd, any reference to high state of charge being detrimental
to life.

Overcharge, reverse charge, discharging and recharging, rapid charging,
rapid discharging, high ambient temperature, can all be detrimental to
cell life.

This is different to Li-ion, where high cell voltage is indeed a big factor
in aging, as it degrades the electrolyte. This doesn't happen with
NiCd.

On 31 Jul 2005 16:44:31 GMT, Ian Stirling
wrote:


No, they don't.
NiMH cells self-discharge very quickly.
NiCd cells left on the shelf at room temperature for a year will have
a significant amount of charge left.

I seem to recall reading somewhere that a car battery will loose
around 15% of its charge per month if the battery is just left
sitting.

Graham