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Re: Charging batteries inside an appliance



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Here's a quote directly from the Panasonic web site: "Trickle charging
cannot be used with NiMh batteries."

Trickle charging NiMh cells *will* reduce their service life.  I really
do suggest that you might like to update your knowledge with a visit to
the web sites of a few battery manufacturers.

 > I know all about it already thanks.

It's hard to be clearer than the quote above, directly from one of the
most respected battery manufacturers.  Here's a link to the application
note that the quote is from:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NIMH_Precautions.pdf

Regards, Peter

Re: Charging batteries inside an appliance


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The next paragraph says:
"However, after applying a refresh charge using a rapid charge, use a
trickle charge of 0.033CmA to 0.05CmA"
It also goes on to recommend a timer just in case.
So it's actually telling you to use a trickle charge.
The quote not to use it is most likely referring to traditional NiCd
levels. The guy who wrote it probably got a bit confused.

Take a look at the Energizer application note:
http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf
Page 19:
"For charging schemes that then rely on a timed "topping' charge to
ensure complete charge, a rate of 0.1C appears to balance adequate
charge input with minimum adverse effects in overcharge.
Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is
adequate to counter self-discharge and maintain cell capacity."

and Duracell:
http://www.duracell.com/oem/Pdf/others/TECHBULL.pdf
Page 16:
"A number of applications require the use of batteries which are
maintained in a fully-charged state. This is accomplished by trickle
charging at a rate that will replace the loss in capacity due to
self-discharge. In these applications, a trickle charge at a C/300 rate
is recommended. The preferred temperature range for trickle charging is
between 10B0%C to 35B0%C (50B0%F to
95B0%F). Trickle charge may be used following any of the previously
discussed charging methods."

So Energizer and Duracell fully endorse trickle charging, just like
many other manufacturers, and just like professional charger systems
have.

So it's perfectly OK to use a trickle charge, just make sure it's very
small, smaller than for NiCd.

BTW, I'd be willing to bet big time that Panasonic brand NiMH chargers
have a trickle charge mode too.

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I have, and it's you who should update your knowledge.
You take one quote from one manufacturer that actually contradicts
itself in the next paragraph, and you take it as gospel.

Common industry knowledge is that NiMH's can be trickle charged, and
I've designed charging systems myself like this without any measurable
loss of capacity. There are many other factors which are more
detrimental to the service life of a NiMH than a high trickle charge
rate.

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Energizer and Duracell are respected manufacturers, and both of them
say I am right and you are wrong.
I'd suggest you check out a few more references next time before you go
taking one manufacturers quote as gospel.

Regards
Dave :)


Re: Charging batteries inside an appliance



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C30 to C50 is a maintenance charge, not the typical C10 trickle charge
used with NiCds.  A maintenance charge is intended to keep a cell
charged, not to charge it.  The purpose is to simply counter
self-discharge, which is about three times higher with NiMh compared to
NiCd.

In fact, that's exactly what your energizer and duracell quotes are
saying too.

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No, they are endorsing a maintenance charge, at a much lower rate than a
typical C10 NiCd trickle charge rate.  In fact, duracell is saying C300,
which will never charge a cell.

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No, read it your quotes again.  Maintenance, not trickle charge.  And at
a much lower level than a NiCd trickle charger.

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I'll take that bet.  Cash or chocolate only, please.

Maintenance, possibly.  Trickle, never.

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There is no contradiction.  Instead, you appear to be confusing trickle
charging with maintenance charging.  Your own quotes show this.

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Your own quotes do not support your statement - they are clearly talking
about maintenance, not trickle charging.  It appears that you cannot see
the difference.

 From the Duracell data sheet you quote, at the bottom of page 19:

"Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is
adequate to counter self-discharge and maintain cell capacity."

Clearly, what they're saying is that this "trickle" charge (to use the
word you like, and the word they add for people who don't understand
"maintenance" :-) is not *charging* the battery, but merely overcoming
self-discharge.  Again, they say the same thing on page 21, near the top.

On your "techbull.pdf" file (what a great filename, lol), Duracell are
saying exactly the same thing (top of page 17), but they are using your
term "trickle charge", when it's really just overcoming self-discharge.
  They even say these exact words.  C300 will never *charge* a cell, so
saying that this is trickle charging the cell is just plain silly.

A typical NiCd C10 trickle charger will fully charge a NiCd cell in
about 12-14 hours.  Connect this same C10 charger to a NiMh cell for the
same time, and you'll probably not cause any problems.

*HOWEVER*, a typical NiCd C10 trickle charger does not have a timer, and
is often left on (by the user) for longer than 14 hours.  At the C10
rate, you can virtually charge a NiCd cell forever without causing any
problems.  Not so with NiMh cells.  As you'll read in the data sheets
you quote, C10 for more than about 12 hours *will* overcharge a NiMh
cell, and NiMh cells *will* suffer a reduction in capacity because of
this overcharging.  Measurable, and definite.  *AND* is says so in the
data sheets.

Peter

Re: Charging batteries inside an appliance


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So this "maintenance" charge value is such a precisely engineered value
that it *just* counteracts the self discharge?
What if you go 0.01C over the quoted maintenance rate, are you going to
eventually damage the cell? The answer of course is no.

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I was not implying you use those exact figures to trickle charge the
cell.

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Now this is just playing around with words and specific numbers.

Yes, a NiMH cell may have its service life reduced by a normal 0.1C
charger, due to overcharge, but you are talking specific values now.

It is possible to "trickle charge" a NiMH cell (at some rate between
0.1C and the "maintenance" charge rate for arguments sake) to
eventually fully charge a NiMH cell and not damage it. That's what I've
been saying all along.

You can dick around with exact C numbers all you like, the fact is in
practice you can do it sucessfully. I know, I've done it myself.
If you get too high a trickle charge rate you might shorten the life of
the cell, but even then it's not a big deal in many applications, you
can still get a good service life for your money.

Not everything is black and white as per the data sheet you know, not
all cells are the same either, nor are any two systems alike.
Build some real systems, test some real batteries, you'll find out.

Dave :)


Re: Charging batteries inside an appliance



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No it's not - the figures are from your data sheets.

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Yes, specific because C10 is the typical rate used to trickle charge NiCd.

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Surely now *you're* just "playing with words and specific numbers" :-)

Your original statement was this:

  > There is essentially no difference between the two chargers.
  > You can use a Nicd charger to charge NiMH's.

Patently, that's untrue.  And now you appear to even be agreeing that
you need to charge at a specific rate.

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The fact is, unless you "dick around with exact C numbers", you're in
danger of overcharging NiMh cells, and therefore reducing their service
life.  Which is exactly what your data sheets all say, many times over.

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I've probably built more that you can imagine, Dave.

Peter

Re: Charging batteries inside an appliance


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See my comment below.

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So you finally admit that a charge rate somewhere between that of a
suggested "maintenance" rate and a typical 0.1C rate will be able to
(eventually) charge a NiMH safely?

Even the maintenance charge rate suggested by the manufacurers is above
the actual self discharge rate of the battery, so the battery is
receiving charge. It's just that rate of charge is so low that the
battery does not damage itself through pressure or temperature
increase. They say that 0.1C is slightly too high and may cause some
damage. It doesn't take a genious to then realise realise that a rate
somewhere between this is a good compromise. Real practical testing
shows this to be true.

Even if you do "damage" a cell and reduce it's service life, it's often
not a big deal, you still get very effectice service use for your
money. You can abuse them a little and get away with it, it's done all
the time with the cheap timer based chargers.

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It's not a "specific rate", in practice, anything under 0.1C is fairly
safe and will work just fine.
You do realise that a 0.1C NiCd rate is *not* a 0.1C rate for NiMH
don't you?
A typical old NiCD charger has a timed charge at maybe 0.2C and then a
trickle charge rate of 0.1C, but that is for a typical 600mAh NiCd. An
NiMH cell is now 2500mAh, so that equates to 0.05C and 0.025C for the
NiMH. That should be perfectly safe for the OP's application - heaven
forbid we actually get back onto the OP's original topic to which you
haven't actually contributed anything directly.

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As I've said from the start, if you keep it under 0.1C you shouldn't
have any problems.
There are many other variables that effect the service life of a NiMH,
a slight overcharge due to trickle charging, even at 0.1C rate simply
isn't a big deal, get over it!

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None at under 0.1C obviously!

Dave :)


Re: Charging batteries inside an appliance



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Now you're frightening me, Dave.  0.1C is 0.1C is 0.1C for whatever it's
referring to.  C is the rated capacity of the cell, it doesn't mean
anything else, and it has nothing to do with the chemistry.

0.1C for one cell is the same as 0.1C for another cell of the same
capacity, and it's different to 0.1C for another cell of a different
capacity.

Do you have this same problem with understanding decibels?

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I think you're demonstrating here that you don't understand what C
means, Dave.

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No, what you said from the start was that NiCd and NiMh chargers were
the same, and that it was fine to use one for the other.  And that's
wrong.  The 0.1C business came into it much later, as you started to try
to qualify your ill-informed original statement.

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Dave, there's a right way to do things, and a wrong way.  If you're
happy with your "she'll be right mate" way of doing things, then that's
something that the facts are unlikely to change.

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At least I understand what 0.1C *means* - the quote from you at the top
of this message shows that you don't.

Peter



Re: Charging batteries inside an appliance


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You have made yourself look like a complete and utter goose Peter. See
below.

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Rubbish. My post stands correct. A 0.1C 600mAh NiCd charger can be used
on a 2500mAh NiMH with no problems.

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You sniped the explaining paragraph in my post to screw things around
completely. What the hell are you trying to prove?
I know perfectly well what C means, you know it, and my posts show
this.

Here is my full post AGAIN just in case you didn't understand it the
first time:
"You do realise that a 0.1C NiCd rate is *not* a 0.1C rate for NiMH
don't you?
A typical old NiCD charger has a timed charge at maybe 0.2C and then a
trickle charge rate of 0.1C, but that is for a typical 600mAh NiCd. An
NiMH cell is now 2500mAh, so that equates to 0.05C and 0.025C for the
NiMH. That should be perfectly safe for the OP's application "

Do you see and comprehend that second paragragh? I was qualifying the
first paragraph.

*of course* 0.1C is the same for both NiCd and NiMH or any other, I did
not say or imply that it was not (unless you stupidly take my post out
of context). My following paragraph which you deliberatly snipped out
shows that.

This is a *real* NiCd charger we are talking about here that charges at
0.1C rate *for a NiCd cell*. For a 600mA NiCd cell that is a 60mA
charge current. If you connect this *same charger* to a 2500mAh NiMH
cell it is no longer a 0.1C charge rate, it becomes 0.024C *for the
NiMH cell*. You know, basic math, 60mA/2500mAh, it's not that hard, try
it.
The charger doesn't magically know it's got a NiMH cell in there with a
greater capacity and adjust the current to 0.1C for the NiMH.
This is what the OP wants to know, can an old NiCd charger be used on a
new NiMH cell, the answer is yes. But of course you aren't contributing
to the actual thread and helping the OP, you are just being silly.

Stop these stupid context and misquote games, you really are making
yourself look like a total goose.

You admit that you have no experience with NiMH chargers working at
less than 0.1C, so why don't you just bow out?

Dave :)


Re: Charging batteries inside an appliance



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Except that that's *not* what you said - you gave no figures, and made
the general statement that any NiCd charger could be used on any NiMh cell.

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A 0.1C NiCd rate *IS* a 0.1C NiMh rate, Dave.  How can it not be?

If what you really meant to say is that 0.1C for a 600mA cell is not the
same as 0.1C for a 2500mH cell, then that would be correct.  But the
chemistry itself has no bearing on what 0.1C means, so your statement is
just plain silly.

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Then why did you ask me (and I quote) "You do realise that a 0.1C NiCd
rate is *not* a 0.1C rate for NiMH don't you?"

Dave, you appear to be trying to prove something.  I just wish I
understood what it was.

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At last - you're making sense!  However, to do so, you've had to start
quoting numbers rather than making silly generalisations.  But when I
quote numbers, you accuse me of all sorts of things.

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The original poster said nothing about "old", that's something you
added.  The original poster, as I recall, asked a general question,
without specifying anything about the charger other than that it was a
NiCd changer.

You then gave a general answer, without knowing *any* of the details of
the charger.  That general answer was wrong, *because* you didn't know
any of the details.

Now you're saying that a *specific* NiCd charger in a *specific*
situation, will work.  I agree.

However, we've taken a bloody long time to get here, and there's been an
awful lot of waffle, and some *bad* information that some people may
take as fact because of the way it was presented, *without* any detail.

The devil's in the detail, Dave - you can't generalise.

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Your contribution started with a bad generalisation, then progressed to
a few more bad generalisations, some strange advice that 0.1C for NiCd
chemistry was different to 0.1C for NiMh chemistry, and other similarly
silly generalisations.

Finally, though, *because* I took you to task on that generalisation,
we've finally arrived at good advice.  And that's that a specific charge
rate for a specific NiCd charger probably wouldn't damage a NiMh cell.

That's *vastly* different to your original claim that any NiCd charger
is suitable to charge NiMh cell.

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Every quote I've made has been your exact words, or the words from data
sheets of battery manufacturers.

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And *I* misquote?  I said no such thing.

Peter

Re: Charging batteries inside an appliance


Hi

The NiCd changer I have is about 15 years old and I think it takes
about 16 hours to charge up the batteries. However it warns on the
label that it is only suitable fror NiCd rechargeable batteries.

Could it still be ok for NmH batteries?

Your help is appreciated,
Regards Richard.


Re: Charging batteries inside an appliance


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15 yeas ago NiMh wasn't commonly available.  I think the label was to
stop people from putting carbon-zinc, and alkaline cells in it.

If you figure the charge rate at 600mAh in 16 hours a 2400mAh cell is going
to take 4 times longer, so if you start it monday morning about wednesay
evening the it'll be done.

Bye.
   Jasen

Re: Charging batteries inside an appliance


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The whole thread is the context!
I was implying that the NiCd charger the OP had could be used just
fine.

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*rolling eyes*
Of course it is, I never said it wasn't!
Can't you take anything in context?
I'm sorry I didn't spell it out absolutely clearly for the lowest
common denominator.

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Geeze you are quick... That's why I put the second paragraph clearly
explaining what I meant. You knew exactly what I was talking about but
you wanted to play silly buggers and prove something. It made you looke
like a goose it what it did.
Just for you, I'll spell things out nice and slowly next time and try
not to rely on context.

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It is not when it is taken in context and read with the paragraph after
it.

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I should have rephrased that better, obviously you didn't understand...

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I'm just countering your silly picky waffle and defending my original
post that the OPs NiCD charger will work just fine.

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Rubbish. The OP said in his very first post:
"I do have some Nickel Cadmium battery chargers that charge slowly over
about 16 hours"
That is quite clearly a 0.1C charger for a 600mAh NiCD, and as I have
said (and you now agree), that will work just fine for a 2500mAh NiMH.

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See above.


There was perfectly good detail in my posts, it was your snipping that
removed it.
But I will try better next time to spell things out nice and clearly
without context, just for you!

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See above.


As I have said, only someone who takes it completely out of context
could take it the wrong way.

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Fancy that, I was right all along!

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Context dear Peter, context.

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My exact words taken out of context by you.
Oh, and I loved your attempt at posting a datasheet. It didn't even
have anything in it about maintenance charging, and it had confusing
info about trickle charging. No wonder I assumed your claim meant that
NiMH's can't be trickle charged in any way shape or form.

After all, you did say "Trickle charging cannot be used with NiMh
batteries." Trickle charging NiMh cells *will* reduce their service
life." - that's what started all this.
What you really meant was that a 0.1C charging rate will do damage, and
I have never said it won't. Who's not expressing things clearly now?

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You implied it by brushing it off and saying "At least I understand
what 0.1C *means*"
I'll ask again then, do you have any experience with NiMH chargers
below 0.1C?

But I've had enough, this is silly. I'll go back to helping the OP now.

Regards
Dave :)


Re: Charging batteries inside an appliance



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But that's not what you said - you said that there is essentially no
difference between NiCd chargers and NiMh chargers, in your original
"answer".  Go back and check.

Your back-pedalling and attempted justification and re-phrasing of what
you actually said have now finally arrived at the truth of the matter in
a certain specific circumstance, and that's what the original poster wanted.

I'm  tired of correcting the errors and generalisations in what you
posted, and I give in - clearly you're right, and I'm wrong.  Everyone
can see that, Dave.  You win.  Congratulations.

For the record, I've done a lot of work with battery powered equipment.
  I've designed a number of battery chargers for a variety of
chemistries, worked with and repaired many more, and even "re-designed"
a few battery chargers in some imported equipment so that they actually
worked properly.  I've seen some excellent designs, and some very poor
stuff, the poorest stuff invariably intended for NiMh cells.  However,
I'm clearly out-classed in this subject by you, Dave.  Good work.

Peter

Re: Charging batteries inside an appliance


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This might help:
http://dictionary.reference.com/browse/context

Also, note the word "essentially" in my sentence:
This might help too:
http://dictionary.reference.com/browse/essentially

My use of the word "essentially" means that there is more to it than
that.
Then of course there are all the other posts which explain stuff in
more detail, but you have to harp on about one particular sentence. Get
a life, really.

I could take you to task exactly the same way over your statement:
 ""Trickle charging cannot be used with NiMh batteries." Trickle
charging NiMh cells *will* reduce their service life."
but I won't.
You are just as guilty as me, so let it be.

Like I said, next time I'll try and rephrase things a bit clearer, just
for you!

This is my last post on the subject.

Dave :)


Re: Charging batteries inside an appliance



Hi

I am not sure if everyone saw my last post that may clarify things. It
is below together with another question.

The NiCd changer I have is about 15 years old and I think it takes
about 16 hours to charge up the batteries. However it warns on the
label that it is only suitable for NiCd rechargeable batteries.

Could it still be ok for NmH batteries?

If not, do you know of any NmH chargers that would be slow enough to
charge batteries inside an appliance like a camera?

Alternatively could one be made up economically?

Bear in mind the charger could be connected to a common electric timer
to turn it off frequently to prevent to fast a charge or overheating.

Your help is appreciated,
Regards Richard.


Re: Charging batteries inside an appliance


Hi Dave, I think you lost that one. If we have to revert to the dictionary
to determine that in some obscure circumstances your wording may have had
the meaning you now say you meant it to have then I believe you are behind
the 8 ball. Next, we will be looking at the legal definition of words and
court determinations on word phrasing to win our discussions.



Re: Charging batteries inside an appliance


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OMG I'm guilty of generalising! Anyone know a good priest I can confess
to? :->
Is there some way I can install a "spell stopper" program to stop me
typing words like "essentially", that could be useful on here!
It's all quite good fun actually, was getting a bit dull on here :->

BTW, is it just me, or do others think the OP might be a bot of some
sort?...

Dave :)


Re: Charging batteries inside an appliance



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I was just about to suggest the same thing - no matter what you
suggest, he/it will always find some way to say that your suggestion
is impractical and then go on to ask for more !

He/it did the same with a request for a wireless data link a short
while ago until aonther poster lost patience with him.

Yet another Dave



Re: Charging batteries inside an appliance


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la784110> have.
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C/20 (Energiser) is larger than the standard (14 hour) charge rate for
a similarly (physically) sized nicad.

--

Bye.
   Jasen

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