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'[EE]: Best rechargeable battery type for long serv'
2006\05\05@120613 by Mike Harrison

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I have an application that needs a rechargeable battery with a very long service life (5-10 years
ideally) as replacement will be difficult. Something of the order of AA size. Actual capacity not
too critical..
It will be trickle-changed very intermittently (very small wind generator), and will be used
outdoors, so must survive -20 to +50 deg.C, although impaired performance at extremes is acceptable,
as is gradual capacity loss over time as we will probably over-specify the capacity by a significant
margin.  

We've provisionally discounted using Lithium ion/polymer due to their intolerance to even
trickle-rate  overcharging, as it would be hard to keep track of charge in & out in our application.
We're looking at ni-cd and ni-mh, but I've only found one manufacturer (Varta) who quotes service
lifetime data ( as opposed to number of cycles).  

Does anyone have any comments/experience in this area..? Will hi-temp rated cells last longer? Is
Ni-Mh better than Ni-Cd? Any examples of real-world lifetime experience, good/bad makes ?


2006\05\05@124207 by Bob Axtell

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Mike Harrison wrote:
> I have an application that needs a rechargeable battery with a very long service life (5-10 years
> ideally) as replacement will be difficult. Something of the order of AA size. Actual capacity not
> too critical..
> It will be trickle-changed very intermittently (very small wind generator), and will be used
> outdoors, so must survive -20 to +50 deg.C, although impaired performance at extremes is acceptable,
> as is gradual capacity loss over time as we will probably over-specify the capacity by a significant
> margin.  
>
> We've provisionally discounted using Lithium ion/polymer due to their intolerance to even
> trickle-rate  overcharging, as it would be hard to keep track of charge in & out in our application.
> We're looking at ni-cd and ni-mh, but I've only found one manufacturer (Varta) who quotes service
> lifetime data ( as opposed to number of cycles).  
>
> Does anyone have any comments/experience in this area..? Will hi-temp rated cells last longer? Is
> Ni-Mh better than Ni-Cd? Any examples of real-world lifetime experience, good/bad makes ?
>
>
>  
The service lifetime of NiCD is very low, about 18 months. NiMH is
better but not significantly so, mavbe 3 years..

I am fascinated by LithiumVanadium Pentoxide rechargeables. They don't
deliver much current yet, but could be paralleled
by a tantalum capacitor, such as 150uF @ 6V for higher-current spikes.  
They seem like they might have a 5-years +
lifetime.

Have you tried a "GOLD CAP"? These guys have no limit on lifetime as
long as the applied voltage is not excessive.

Finally, Google for some kind of "carbon" battery; seems like something
new. I've lost the links, but saw something
on it about a year ago.

--Bob

2006\05\05@125021 by David VanHorn

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> ..? Will hi-temp rated cells last longer? Is
> Ni-Mh better than Ni-Cd? Any examples of real-world lifetime experience,
> good/bad makes ?


Although they are catching up, Nicad still outperforms NIMH in temperature
extremes.

WHATEVER ELSE YOU DO, DO NOT BUY CHEAP CELLS FROM CHINA.

Sanyo, Panasonic, Varta, any reputable mfgr will be fine.

2006\05\05@130020 by David VanHorn

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>
> The service lifetime of NiCD is very low, about 18 months. NiMH is
> better but not significantly so, mavbe 3 years..


I don't agree with that at all.  With proper charge maintainance, 5+ years
for nicad is not a problem.

5-7 years is what the McGraw Hill handbook of batteries quotes on pare 28.2

The main thing is to limit overcharging as much as possible.

--
Feel the power of the dark side!  Atmel AVR

2006\05\05@135540 by Mike Harrison

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On Fri, 05 May 2006 09:42:15 -0700, you wrote:

{Quote hidden}

Will look at these but I think cost may be an issue for the capacity we want. We'll probably be
using a reservoir cap whatever we use as we need short (~20ms)pulses of an amp or so.

>Have you tried a "GOLD CAP"? These guys have no limit on lifetime as
>long as the applied voltage is not excessive.

This is another possibility, but I think may be too expensive for the capacity we need.
By my calculations, 1 farad = 0.27mAH, so volumetric capacity is of the order of 1000x less.
I will take a look at other caps like the CAP-XX and Maxwell parts but I think cost will be
prohibitive,

2006\05\05@175230 by Nate Duehr

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David VanHorn wrote:
>> The service lifetime of NiCD is very low, about 18 months. NiMH is
>> better but not significantly so, mavbe 3 years..
>
>
> I don't agree with that at all.  With proper charge maintainance, 5+ years
> for nicad is not a problem.
>
> 5-7 years is what the McGraw Hill handbook of batteries quotes on pare 28.2
>
> The main thing is to limit overcharging as much as possible.

Have to agree with Dave here, if not - lots of dead satellites would be
circling the Earth nowadays.  Most satellites have NiCD on board.

Nate

2006\05\05@212039 by Bob Axtell

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Nate Duehr wrote:
> David VanHorn wrote:
>  
>>> The service lifetime of NiCD is very low, about 18 months. NiMH is
>>> better but not significantly so, mavbe 3 years..
>>>      
>> I don't agree with that at all.  With proper charge maintainance, 5+ years
>> for nicad is not a problem.
>>
>> 5-7 years is what the McGraw Hill handbook of batteries quotes on pare 28.2
>>
>> The main thing is to limit overcharging as much as possible.
>>    
>
> Have to agree with Dave here, if not - lots of dead satellites would be
> circling the Earth nowadays.  Most satellites have NiCD on board.
>
> Nate
>
>  
Nate, Dave, I stand in awe!.

I have a number of tools driven by NiCAD packs, and a 4-phone system
with 3-cel NiCAD packs in each
phone. Not one of these batteries lasted more than a year; the problem
was advanced memory effect. I
replaced the phones with NiMH physical replacements; after 2 years they
are still going strong. The tool packs
were all the long, round 3.6V packs from B&K (B&E?). They were wiped out
after a year; the newer "GOLD"
(NiMH) replacements are still going; has been 3 years for them.
I'd really like to know what batteries are being used in space... I'd be
truly amazed if NiCAD was used...

--Bob

2006\05\05@223013 by Herbert Graf

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On Fri, 2006-05-05 at 18:20 -0700, Bob Axtell wrote:
> Nate, Dave, I stand in awe!.
>
> I have a number of tools driven by NiCAD packs, and a 4-phone system
> with 3-cel NiCAD packs in each
> phone. Not one of these batteries lasted more than a year; the problem
> was advanced memory effect. I
> replaced the phones with NiMH physical replacements; after 2 years they
> are still going strong. The tool packs
> were all the long, round 3.6V packs from B&K (B&E?). They were wiped out
> after a year; the newer "GOLD"
> (NiMH) replacements are still going; has been 3 years for them.
> I'd really like to know what batteries are being used in space... I'd be
> truly amazed if NiCAD was used...

I don't know about satellites, but a PROPERLY cared for NiCad lasts a
LONG time.

Both the things you've choosen as "NiCads are bad" examples are HORRIBLE
to their batteries.

Tools have fast charges that charge the battery in an hour, but charging
at that rate will quickly destroy a battery.

Cordless phone chargers trickle charge forever, often overheating the
battery. Even worse they almost NEVER get deep cycled (necessary to
avoid the memory effect).

Back in my school days I regularly used a walkman while traveling
to/from school. I PROPERLY treated my NiCad batteries (mostly because,
as a student, I was poor, and $10 for 2 batteries was a HUGE incentive
to do things right). I regularly deep cycled them. I never left them
with zero charge. I NEVER overcharged them, and I never used a fast
charger. Those batteries lasted me well through my final years of high
school and most of university. I don't have an exact figure in years,
but I'd say 5 years is probably a good number. The only reason I stopped
using them was because such high capacity NiMH came on the market and
the NiCads just couldn't compete.

If I had continued caring for those batteries I'm certain they would
have lasted me a few years longer.

TTYL

2006\05\06@004212 by Bob Axtell

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Herbert Graf wrote:
{Quote hidden}

This may be just my experience. I have designed some commercial products
with proper chargers
for NiMH and Li-Ion and never had any problems with lifetime.

--Bob


{Quote hidden}

2006\05\06@092910 by David VanHorn

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On 5/5/06, Bob Axtell <spam_OUTengineerTakeThisOuTspamcotse.net> wrote:
{Quote hidden}

Far more likely killed by constant overcharge. A crap charger will kill
anything.
I've induced memory effect in the lab, it takes about 20+ cycles to a
specific discharge point, and by 30 cycles it's observable as about a 50mV
droop when you pass that point in a longer discharge, and that longer
discharge erases it.



--
> Feel the power of the dark side!  Atmel AVR

2006\05\06@093458 by David VanHorn

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>
> Tools have fast charges that charge the battery in an hour, but charging
> at that rate will quickly destroy a battery.



On a cheap charger, yes, because they don't really know when to quit.
NIMH likes about a 1C charge, and all the charge termination indications are
at their clearest at this point.  In cheap cells though, things get muddy
again, and the thermal spike that should be VERY pronounced, turns into more
of a linear ramp.

On a properly designed charger, with quality cells, fast charge isn't a
problem.


--
> Feel the power of the dark side!  Atmel AVR

2006\05\06@100725 by Tony Smith

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> >
> > Tools have fast charges that charge the battery in an hour, but
> > charging at that rate will quickly destroy a battery.
>
>
> On a cheap charger, yes, because they don't really know when
> to quit. NIMH likes about a 1C charge, and all the charge
> termination indications are at their clearest at this point.  
> In cheap cells though, things get muddy again, and the
> thermal spike that should be VERY pronounced, turns into more
> of a linear ramp.
>
> On a properly designed charger, with quality cells, fast
> charge isn't a problem.


I haven't seen a decent charger for cordless tools yet.  They're all
'charge in 1 hour hour or your money back' types.  Except for the 'money
back' bit.  Battery hot = charged.

Couple that with the fact they have multiple cells, one cell will fail
early, leaving you with a dead pack.  Add on the marketing driven higher
voltage trend (more is better, right?) means more cells, means a dead
pack sooner.

This is everthing from the cheap DIY tools with Chinese NiCads sold in
supermarkets, to Japanese tradesman tools.

FWIW, I've a set of NiCads that are about 15 years old.  Only 500mAh, so
I don't use them much.  I haven't tested them to check the capacity, but
they seen to hold a decent charge.

Tony

2006\05\06@102939 by David VanHorn

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>
> I haven't seen a decent charger for cordless tools yet.  They're all
> 'charge in 1 hour hour or your money back' types.  Except for the 'money
> back' bit.  Battery hot = charged.


Dewalt, Makita, they make good chargers.  I've had my Makita since '92, and
gone through three batteries, but with pretty brutal service.

Couple that with the fact they have multiple cells, one cell will fail
> early, leaving you with a dead pack.  Add on the marketing driven higher
> voltage trend (more is better, right?) means more cells, means a dead
> pack sooner.


Yeah, marketing drives the bus when it shouldn't at times.
Six cells is a "sweet spot" in nicad/nimh pack design. Not enough reverse
charge to damage the weak cell in a deep discharge, and individual cell
differences tend to average out over time.


This is everthing from the cheap DIY tools with Chinese NiCads sold in
> supermarkets, to Japanese tradesman tools.


When I see those NIMH powered scooters, I can't help thinking "Thermal
Grenade"

FWIW, I've a set of NiCads that are about 15 years old.  Only 500mAh, so
> I don't use them much.  I haven't tested them to check the capacity, but
> they seen to hold a decent charge.


I built up a rig to test these things, a measurement computing USB data
aquisition pod, some relays, some constant current dumps, and an AVR doing
the charging, doing everything including the 500kHz buck regulation from
it's 64 MHz driven timer.

Very interesting.  A VB front end plots current, voltage, and temperature on
the pack.  I can tell a cheap pack now just from the shape of the thermal
curve.

The cheap packs normally do ok, it's just that a few of them in any lot will
fail catastrophically at some point, without any provocation.  Lack of rare
earth catalyst material, too much electrolyte (by a small fraction of a mL)
not having enough excess positive plate capacity (from trying to get that
last few mAH)



--
Feel the power of the dark side!  Atmel AVR

2006\05\06@121242 by Tony Smith

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> >
> > I haven't seen a decent charger for cordless tools yet.  
> They're all
> > 'charge in 1 hour hour or your money back' types.  Except for the
> > 'money back' bit.  Battery hot = charged.
>
> Dewalt, Makita, they make good chargers.  I've had my Makita
> since '92, and gone through three batteries, but with pretty
> brutal service.


Dunno about DeWalt, but Makita are on par with everyone else.  Charge it
until it gets hot.

Still, shoving 15 cells (18v, Makita does it too) in a pack and charging
them as fast as possible is asking for trouble.

Tony

2006\05\06@130107 by David VanHorn

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>
>
> Dunno about DeWalt, but Makita are on par with everyone else.  Charge it
> until it gets hot.


The only one I have is an older makita with 6 cell pack.
The getting hot IS part of a normal high rate termination. That heat spike
is when the energy transitions from mostly recharging, to mostly making
hydrogen and oxygen. At that point the battery is "fully charged". A good
charger detects this event at about 1-2 degrees C per minute.



> Still, shoving 15 cells (18v, Makita does it too) in a pack and charging
> them as fast as possible is asking for trouble.


Yes, you can't really see a single cell problem that way.  But marketing
says the other guys are 12V, so we have to be 15V!


Kind of like vaccuum cleaners, where they brag about how many amps they
pull.  NO relationship to air handling ability expressed or implied.  By
that measure, a dead short would be the world's best vaccuum cleaner.


--
Feel the power of the dark side!  Atmel AVR

2006\05\06@180843 by Howard Winter

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Dave,

On Sat, 6 May 2006 10:29:39 -0400, David VanHorn wrote:

> Dewalt, Makita, they make good chargers.  I've had my Makita since '92, and
> gone through three batteries, but with pretty brutal service.

I've got quite a bit of DeWalt 18V stuff.  Because of the high price of their batteries, I bought one (NiMH)
from eBay - it was said to be 3Ah.  After about a dozen cycles (maybe a few less) two different DeWalt
chargers say it's dead, and won't charge it!  This happens within about a minute of plugging it in.  I'm
wondering about taking it apart to see what cells they used - is this likely to reveal anything interesting,
do you think?

If they're an easily-obtainable form factor, I may have a go at replacing them myself.  At least I can get
more use from the money I wasted buying it!

Cheers,



Howard Winter
St.Albans, England


2006\05\06@184447 by David VanHorn

picon face
>
>   After about a dozen cycles (maybe a few less) two different DeWalt
> chargers say it's dead, and won't charge it!  This happens within about a
> minute of plugging it in.  I'm wondering about taking it apart to see what
> cells they used - is this likely to reveal anything interesting, do you
> think?


There's so much counterfeit stuff out there, it wouldn't surprise me at all
if the cells were.
Replacing with a good Sanyo or Panasonic cell would probably make a big
difference.

Or, bad charger, or some other problem.



Feel the power of the dark side!  Atmel AVR

2006\05\06@213735 by Dave Lag

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Howard Winter wrote:

> If they're an easily-obtainable form factor, I may have a go at replacing them myself.  At least I can get
> more use from the money I wasted buying it!
>
> Cheers,
>

I haven't seen any that weren't sub-c size (so far).
D

2006\05\06@225324 by Tony Smith

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> >   After about a dozen cycles (maybe a few less) two
> different DeWalt
> > chargers say it's dead, and won't charge it!  This happens within
> > about a minute of plugging it in.  I'm wondering about
> taking it apart
> > to see what cells they used - is this likely to reveal anything
> > interesting, do you think?
>
>
> There's so much counterfeit stuff out there, it wouldn't
> surprise me at all if the cells were. Replacing with a good
> Sanyo or Panasonic cell would probably make a big difference.
>
> Or, bad charger, or some other problem.


Put in the pack in the drill (or whatever) and run it until it goes
flat.  Shouldn't take long!  Dismantle the pack, and test each cell
(voltage under a small load).  You'll find all bar one will read 1.2v.
Replace that one.  I've only ever seen sub-c size cells.  They're not
that hard to find.

Downside is the brand-name tools, say Festool, Makita, DeWalt etc always
use the latest & greatest cells, 3000mAh last time I looked.  You wind
up paying a premium for these, as opposed to the next capacity or 2
down.  This makes repacking it yourself not worth the effort, and you
already know you can buy a new tool for the cost of the genuine
replacement pack.

They don't call it the bleeding edge for nothing.

Buy Japanese made ones if you can, then Tiawanese, then Chinese (like
the eBay ones).  I don't think India make all that many NiCads yet, but
best to steer clear if they do.

Last time I did this I had 2 dead packs (yes, Makita).  I made one pack
out of 2, used some for my bike light, the rest in a box as spares.  I
figure I'll be needing them soon.

Tony

2006\05\06@230436 by David VanHorn

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>
>
> Buy Japanese made ones if you can, then Tiawanese,


Hmm..

then Chinese (like the eBay ones).


AKA thermal grenades.

 I don't think India make all that many NiCads yet, but
> best to steer clear if they do.


I can only imagine.

--
Feel the power of the dark side!  Atmel AVR

2006\05\07@124303 by Philip Pemberton

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In message <.....25b178740605050950g3b6a571bhe74ee169e3358744KILLspamspam@spam@mail.gmail.com>>          "David VanHorn" <dvanhornspamKILLspammicrobrix.com> wrote:

> WHATEVER ELSE YOU DO, DO NOT BUY CHEAP CELLS FROM CHINA.

I take it that includes the stuff GP Batteries and Uniross sell then?

I've got a few sets of Kodak NiMHs (need to build a decent charger for them,
my last one blew up and caught fire). No idea who really made them, but
they're marked up at 1600mAh, "Made in Japan for Eastman Kodak company" which
(I guess) would probably make them Sanyo, Sony or Panasonic.

One of these days, I'll build a programmable charger and a programmable
battery analyser. One PIC (probably a 10F or 12F) monitoring each battery,
and a 16F or 18F running the charge control algorithms and controlling the
display and data logging. Watchdog timers active on everything - if a chip
crashes, I want it reset post-haste, preferably before any damage can occur.
I'd probably make a WDT reset throw the thing into an error state rather than
have it try and recover. Maybe add a relay to allow the master controller PIC
to kill everything if a power transistor fries and sticks on.

Thing is, for stuff like Li-Ion you need to control current and voltage. I'm
trying to figure out how you'd do that with a switch mode system. Monitor I
and V and tweak the drive waveform's duty cycle to make sure one (or the
other) doesn't go outside the limits?
Is average V/I the killer, or is it instantaneous V/I? Aagh...


Also, if it's that easy to judge cell quality based on charge curves, would
you mind posting a few examples somewhere?

Thanks.
--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
.....philpemKILLspamspam.....dsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

2006\05\07@124722 by Peter

picon face


On Sun, 7 May 2006, Tony Smith wrote:

> I haven't seen a decent charger for cordless tools yet.  They're all
> 'charge in 1 hour hour or your money back' types.  Except for the 'money
> back' bit.  Battery hot = charged.

Try Makita ?

Peter

2006\05\07@140325 by Gerhard Fiedler

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Philip Pemberton wrote:

> Thing is, for stuff like Li-Ion you need to control current and voltage. I'm
> trying to figure out how you'd do that with a switch mode system.

That sounds interesting... :)

Seriously, how does that work? How would you control current (supposedly
into the battery) /and/ voltage (supposedly at the battery)? If I'm not
completely mistaken, both are tied together through the battery
characteristics. You wiggle one, the other follows, according to those
characteristics (which of course depend on the battery, charge state,
possibly charge history, temperature, ...).

Gerhard

2006\05\07@141322 by David VanHorn

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Current limited, voltage regulated.  It's actually pretty easy.






--
Feel the power of the dark side!  Atmel AVR

2006\05\07@142850 by Micah Stevens

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Gerhard Fiedler wrote:
> Philip Pemberton wrote:
>
>  
>> Thing is, for stuff like Li-Ion you need to control current and voltage. I'm
>> trying to figure out how you'd do that with a switch mode system.
>>    
>
> That sounds interesting... :)
>
> Seriously, how does that work? How would you control current (supposedly
> into the battery) /and/ voltage (supposedly at the battery)? If I'm not
> completely mistaken, both are tied together through the battery
> characteristics. You wiggle one, the other follows, according to those
> characteristics (which of course depend on the battery, charge state,
> possibly charge history, temperature, ...).
>
> Gerhard
>
>  
I've done it with a PWM switch on the power feed. Monitor the voltage
and current, and if you want to maintain a current, jiggle the duty
cycle to keep the current at a specific place, this will throw the
voltage all around. If you want a constant voltage, just pay attention
to the voltage, which will throw the current all around. It's fairly
straightforward.

-Micah



!DSPAM:445e3c60115611072050172!

2006\05\07@144703 by Philip Pemberton

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In message <1h4h2outol6j8.1kitjvxdsbg40$EraseME.dlgspam_OUTspamTakeThisOuT40tude.net>
         Gerhard Fiedler <listsspamspam_OUTconnectionbrazil.com> wrote:

> Seriously, how does that work? How would you control current (supposedly
> into the battery) /and/ voltage (supposedly at the battery)? If I'm not
> completely mistaken, both are tied together through the battery
> characteristics. You wiggle one, the other follows, according to those
> characteristics (which of course depend on the battery, charge state,
> possibly charge history, temperature, ...).

You provide it with a fixed 4.2V (actually most manufacturers seem to
reccomend 4.1V if you can live with a reduction in battery life) and limit
the current to 0.5C (or something like that).

Hmm, actually, if you had control of current but not voltage, you could
provide just enough current to get the 1-second average voltage up to 4.1V or
so, then ramp down the current as the cell voltage goes up...

I dunno, maybe I should just make a Nicad/NiMH charger, then I don't have to
deal with voltage regulation at all. What I really need is a battery
simulator of some description. Something I can plug in in place of the
battery and use to test the charge algorithms...

--
Phil.                         | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
@spam@philpemKILLspamspamdsl.pipex.com         | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/     | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

2006\05\07@150542 by David VanHorn

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>
>
> I dunno, maybe I should just make a Nicad/NiMH charger, then I don't have
> to
> deal with voltage regulation at all. What I really need is a battery
> simulator of some description. Something I can plug in in place of the
> battery and use to test the charge algorithms...


Having done that, I think that NIMH is the most complicated of the consumer
battery types to charge.

Have a look through the panasonic and sanyo data sheets, and through McGraw
Hill's handbook of batteries, and through the material on the Cadex site,
and see what it takes to meet all those conditions.

--
> Feel the power of the dark side!  Atmel AVR

2006\05\08@065517 by Gerhard Fiedler

picon face
Micah Stevens wrote:

>>> Thing is, for stuff like Li-Ion you need to control current and
>>> voltage. I'm trying to figure out how you'd do that with a switch mode
>>> system.
>>
>> That sounds interesting... :)
>>
>> Seriously, how does that work? How would you control current (supposedly
>> into the battery) /and/ voltage (supposedly at the battery)?
>>  
> It's fairly straightforward.

I read this above to mean "control current and voltage /at the same
time/"... which probably wouldn't be straightforward. Control either
current or voltage at different times obviously /is/ straightforward :)

Gerhard

2006\05\08@091411 by Tony Smith

picon face
> On Sun, 7 May 2006, Tony Smith wrote:
>
> > I haven't seen a decent charger for cordless tools yet.  
> They're all
> > 'charge in 1 hour hour or your money back' types.  Except for the
> > 'money back' bit.  Battery hot = charged.
>
> Try Makita ?
>
> Peter


I have indeed.  Give me long enough and I'll find the empty pack plus a
few cells, the rest went to repair another pack, bike lights etc.  18v
3Ah (NiMh obviously) if you're curious.

I've also tried Hitachi, Bosch, Panasonic, Ryobi, Black & Decker, Arlec,
Festool, HappyFunDrillCo, etc.  I've yet to try DeWalt & the
ExtraHappyFunDrillCo.

I'll probably re-pack the empty one with 2Ah NiCads, at least they're
cheap.  2/3 capacity for 1/3 the price, from memory.  Charging the cells
individually would be an interesting challenge.  Or a very interesting
connector.  Which then fails instead.

The tools are fine, the problem is you can't string 12-15 cells together
and then charge them as fast as possible without something going
backwards (like the voltage on one of the cells!).  None of the chargers
even offer to charge slowly, say overnight.

And now they're going to 24v.  Sigh.  And Lithium-Ion, to add some
excitement.

Tony

2006\05\08@094341 by David VanHorn

picon face
>
>
> The tools are fine, the problem is you can't string 12-15 cells together
> and then charge them as fast as possible without something going
> backwards (like the voltage on one of the cells!).  None of the chargers
> even offer to charge slowly, say overnight.


I agree. When you study the problem, it becomes apparent that beyond six
cells, you can't see what's happening with enough certanity.  It would be
interesting to see a design that used six beefier cells, and a
SEPIC converter, which would also double as the speed control.

--
> Feel the power of the dark side!  Atmel AVR

2006\05\08@103514 by Peter

picon face
Tony Smith <ajsmith <at> rivernet.com.au> writes:

> And now they're going to 24v.  Sigh.  And Lithium-Ion, to add some
> excitement.

Imho this means that the chrgers will get better. Because they can't afford to
sell cordless drills that can be used to cash in on fire insurance in any kind
of quantity.

Peter

2006\05\09@074015 by Tony Smith

picon face
> > And now they're going to 24v.  Sigh.  And Lithium-Ion, to add some
> > excitement.
>
> Imho this means that the chrgers will get better. Because
> they can't afford to sell cordless drills that can be used to
> cash in on fire insurance in any kind of quantity.
>
> Peter


Good point, I hadn't thought of that.

Probably won't happen because they'd lose the '15 minute charge' selling
point.

Maybe when James figures out how to recharge his pushbike, we can use
that instead.  I still reckon coiled springs.  Really big ones.
Clockwork cordless drills...

Tony

2006\05\09@135634 by Peter

picon face


On Tue, 9 May 2006, Tony Smith wrote:

> Maybe when James figures out how to recharge his pushbike, we can use
> that instead.  I still reckon coiled springs.  Really big ones.
> Clockwork cordless drills...

There was a windup spring powered car in the 18th ? century, made by a
clockmaker (how else). As usual, someone will feel he was born too late:

www.halfbakery.com/idea/Regenerative_20Brake_20Bike
www15.homepage.villanova.edu/rebecca.vernot/Senior%20Design.htm
http://www.cybersaa.org/newsletter/praise.html

http://www.aircaraccess.com/history.htm

Note Hardie design and Porter! The 'German' locomotive is interesting
(note pun on Prius vs. patents). Terry Miller's contribution!

Peter

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