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From uwm.edu!spool.mu.edu!agate!stanford.edu!leland.Stanford.EDU!news Fri Nov 13 14:26:07 CST 1992
Article: 8049 of comp.sys.laptops
Newsgroups: comp.sys.laptops
Path: uwm.edu!spool.mu.edu!agate!stanford.edu!leland.Stanford.EDU!news
From: avery@scruffy.neuroinformatik.ruhr-uni-bochum.de (Avery Wang)
Subject: Re: NiCad batteries again -- useful hints
Message-ID: <1992Nov13.092439.11529@leland.Stanford.EDU>
Sender: news@leland.Stanford.EDU (Mr News)
Organization: DSO, Stanford University
References: <1992Nov11.030643.21030@schaefer.math.wisc.edu>
Date: Fri, 13 Nov 92 09:24:39 GMT
Lines: 111
Here's something I pulled off the net over 4 years ago -- hope it's useful!
-Avery
-------------------
" NICAD BATTERIES - FACTS AND FALLACIES " Published on Radio Communication
May 1988, TT.
Richargable nickel cadmium batteries, have, with reasons, become a popular
source of power for portable and handportable equipment. They can provide
reliable service over many years if due account is taken of their
peculiarities. Yet it remain true that many amateurs are failing to appreciate
not only the full capabilities but also the limitations of nicad cells used in
battery packs.
J.Fielding,ZS5JF,in "Nickel cadmium batteries for amateur radio equipment"
(Radio ZS september 1987,pp4-5) provides a useful survey of the facts and
foibles of nicads.The following extracts from his article attack some of the
common myths and also provide some safety hints.
1) "Rapid charging causes a decline in cell capacity".
NOT TRUE provided that the charge is always terminated at a safe point.
2) "You should not charge only partially discharged cells as this causes a
loss in capacity."
NOT TRUE. It is not necessary to discharge fully nicad batteries before
charging. In fact, THE OPPOSITE is true. Repeated partial charging gives an
increase in the number of charge/discharge cycles compared with
full-discharged cells.
3) "White crystals growing on the tops of nicad cells mean that the seal is
faulty and the cell should be scrapped."
NOT TRUE. The electrolyte (potassium hydroxide) is extremely searching and can
penetrate the seals used in minute quantities. These crystals are potassium
carbonate, which is harmless and can be removed with soap and water. The
action of the carbon dioxide in the atmosphere reacts with the electrolyte to
form the crystals. After removing the crystals, it is recommended that a smear
of silicon grease is applied to slow down the growth of new crystals. The
amount of electrolyte lost in this way is insignificant.
4) " I have a cell which appears to take a charge, but after the normal
charging period the open circuit voltage is very low. I have been told I
should throw it away."
NOT TRUE. The reason the cell won't take a charge is usually due to minute
crystalline growth across the internal electrodes, caused by prolonged
storage. A cure that nearly always works is to pass a very high current for
very short time through the affected cell. This fuses the internal "whisker".
Discharging a large electrolytic capacitor is one method of doing this. But
note that in a battery the faulty cell MUST be isolated from the other cells
since zapping the complete battery will not usually result in a cure. Charge
the capacitor to about 30v and then discharge it through the faulty cell.
Several attemps may be required to clear a stubborn cell.
5) "A battery contains a cell with reversed polarity. The only cure is to
replace it".
NOT TRUE. The reversed cell ca usually be corrected by a similar technique as
that given for 4). After re-polarising the cell, the complete battery can be
recharged in the normal way. Full capacity can be regained after about five
cycles.
6) "A nicad battery should be stored only in a discharged state".
NOT TRUE. It can be stored in any state of charge. Due to its inherent
self-discharging characteristics it will eventually become fully discharged
after a sufficiently long period of storage. To recharge the battery before
returning it to service, a "conditioning" charge of 20h at the normal charging
rate is recommended. Afterwards charge normally; full capacity can again be
expected after about five cycles.
7) "It is not advisable to keep a nicad battery on permanent trickle charge as
this causes permanent degradation of the cells".
NOT TRUE. So long as the trickle charge current is adjusted correctly, the
charge can continue indefinitely without loss in cell capacity. The safe
current can usually be obtained from the manufacturer's data, but 0.025C is a
reasonable guide (ie. about 100mA for a 4Ah cell and PRO-RATA). This enables
the battery to remain fully charged.
ZS5JF also lists seven safety points that should be considered by users:
1) DO NOT short circuit a fully-charged battery. This if prolonged, can cause
excessive gas production with the danger of possible rupturing of the sealed
case.
2) Nicads contain a caustic electrolyte: this is perfectly safe as long as
common sense is used in use and handling of the cells.
3) A nicad can supply a very high current for a short period (a 4Ah cell can
supply over 500A for a few seconds). Sufficient thought should be given when
selecting a fuse between the battery and the equipment. The connecting wire
should be capable of passing enough current to ensure the fuse blows quickly
in the event of a short circuit.
4) DO NOT use partially-discharged cells with fully-charged ones to assemble a
battery. Assemble the battery with all the cells discharged and then charge
them as a battery.
5) DO NOT carry a fully- or partially-charged battery on an aircraft without
taking proper safety precautions. A short-circuited battery pack ca be a time
bomb in such situations. Consult the relevant IATA regulations or ask at the
airline check-in.
6) DO NOT subject battery packs to very high or low temperatures. Never
dispose of a battery pack in a fire or throw it out with domestic waste.
If it cannot be disposed of properly it is probably best to bury it in the
garden in a safe spot.
7) DO NOT discharge battery packs below about 1V per cell, otherwise there is
a possibility of cell reversal.
ZS5JF provides a good deal of other information on charging nicad batteries,
and gives as a reference a Varta publication of 1982 "Sealed Nickel Cadmium
Batteries" from which some of his notes may have been derived. (G3VA)
----=====***=====----
From uwm.edu!wupost!decwrl!csus.edu!netcomsv!mork!brunette Mon Aug 10 23:18:11 CDT 1992
Article: 9997 of rec.models.rc
Xref: uwm.edu rec.models.rc:9997 sci.electronics:38540
Newsgroups: rec.models.rc,sci.electronics
Path: uwm.edu!wupost!decwrl!csus.edu!netcomsv!mork!brunette
From: brunette@netcom.com (Hal Brunette)
Subject: Re: How to dispose of NiCads?
Message-ID: <p5mmrwq.brunette@netcom.com>
Date: Tue, 28 Jul 92 20:10:45 GMT
Organization: Netcom - Online Communication Services (408 241-9760 guest)
References: <1992Jul27.161240.4905@nynexst.com> <k6lmatq.brunette@netcom.com> <1992Jul28.140405.28429@gdunix.gd.chalmers.se>
Lines: 88
>|> D.C. Myers, "Zap New Life into Dead Ni-Cd Batteries," Popular Electronics,
>|> July 1977, pp. 60-61.
>|>
>|> The article explains internal shorts and how to clear them.
>If it`s possible, try to rewrite the article in a message here in rec.models.
>rc and sci.electronics.
>
>I`m sure many readers here has many NiCd cells they want to restore.
The failures the article talks about occur in mutli-cell Ni-Cd battery packs,
and are due to the voltage differences between cells. Say you have four 1.25 V
cells in a pack connected to a 200 ohm load. The load "sees" 5 volts and draws
25 mA. Since each cell must pass the entire 25 mA and each cell's potential is
1.25 volts, Ohm's Law tells us that each cell sees the equivalent load of 50
ohms.
But in practice, no four cells in a battery ever exhibit exactly the same output
voltage. Assume that one cell is delivering only 1.2 V, and the others are at
1.25 volts. Now, the 200 ohm load sees 4.95 volts and draws 24.75 mA. Since
all four cells must pass the entire 24.75 mA, each of the strong cells at 1.25
volts sees an equivalent load of 50.5 ohms; the weak cell sees only 48.5 ohms.
The weak cell works into the heaviest load and as a result will discharge more
rapidly than the other cells. If the pack is charged for only a short period
of time, the weak cell, which has been working the hardest, is also the one
that receives the least charging power.
This usually doesn't matter if you trickle charge after each day of flying.
The inequality is small for any given charge or discharge cycle, due to the
relatively flat output voltage NiCd cells exhibit over most of their range.
But a combination of incomplete charges and deep discharges will exaggerate
the energy difference between a weak cell and the other cells. Operated
continually in this manner, the weak cell invariably reaches its "knee," the
point at which its voltage decreases sharply, long before the other cells
reach the same point.
Now comes the problem! Suddenly, the weakest cell sees an increasingly heavy
load, which causes its voltage to drop even faster. This avalanche continues
until the cell is completely discharged, even as the other cells continue to
force current to flow. The inevitable result is that the weak cell begins to
charge in reverse, which eventually causes an internal short. Once an
internal short develops, recharging the cell at the normal rate is
futile. The short simply bypasses current around the cells active materials.
(Even though the cell is apparently dead, most of its plate material is still
intact.) If the small amount of material that forms the short could be removed,
the cell would be restored to virtually its original capacity once again.
300 ohm Charge
5W / Switch
20-40 + O---/\/\/\----o------o o------------o-------------------------o
VDC | | |
| Zap | |
| Switch | +|
| ___|___ | -----------
o------o o---------o -----
| | + Shorted |
6000 micro- | + ------- Cell |
Farad, 40V _________ | | |
Capacitor --------- |_____| Volt |
| | meter |
| | |
- O-------------o----------------------o-------------------------o
Using the circuit shown, the internal short can be burned away in a few seconds.
In operation, energy stored in the capacitor is rapidly discharged through the
dead cell to produce the high current necessary to clear the short. Current is
then limited by the resistor to a safe charge rate for a small A cell.
Several applications of discharge current are usually necessary to clear a cell.
During the "zapping" process, it is a good idea to connect a voltmeter across
the cell to monitor results. Momentarily close the normally open pushbutton
switch several times to successively zap the cell, allowing sufficient time
for the capacitor to charge up between zaps, until the voltage begins to rise.
Then, with the toggle switch closed, watch as the potential across the cell
climbs to 1.25 volts. If the potential stops before full voltage is reached,
some residual short remains and another series of zaps is in order. If you
observe no effect whatsoever after several zaps and shorting out the cell and
taking an ohmmeter measurement indicates a dead short, the cell is beyond
redemption and should be replaced.
Once full cell potential is achieved, remove the charging current and monitor
battery voltage. If the cell retains its charge, it can be returned to charge
and eventually returned to service. But if the cell slowly discharges with no
appreciable load, the residual slight short should be cleared. To do this,
short circuit the cell for a few minutes to discharge it, zap again, and
recharge it to full capacity.
Good luck.
From uwm.edu!cs.utexas.edu!sun-barr!olivea!uunet!infonode!ingr!b11!naomi!lester Mon Aug 10 23:19:34 CDT 1992
Article: 10011 of rec.models.rc
Xref: uwm.edu rec.models.rc:10011 sci.electronics:38596
Path: uwm.edu!cs.utexas.edu!sun-barr!olivea!uunet!infonode!ingr!b11!naomi!lester
From: lester@naomi.NoSubdomain.NoDomain (Les Bartel)
Newsgroups: rec.models.rc,sci.electronics
Subject: Re: How to dispose of NiCads?
Message-ID: <1992Jul29.124224.26312@b11.b11.ingr.com>
Date: 29 Jul 92 12:42:24 GMT
References: <1992Jul27.161240.4905@nynexst.com> <k6lmatq.brunette@netcom.com> <1992Jul28.140405.28429@gdunix.gd.chalmers.se> <p5mmrwq.brunette@netcom.com> <1992Jul29.084514@ufps9.unifr.ch>
Sender: usenet@b11.b11.ingr.com (Usenet Network)
Reply-To: lester@naomi.b23b.ingr.com
Organization: Dazix, An Intergraph Company
Lines: 56
In article <1992Jul29.084514@ufps9.unifr.ch>, waeber@ufps9.unifr.ch (Bernard Waeber SIUF) writes:
|> In article <p5mmrwq.brunette@netcom.com>, brunette@netcom.com (Hal Brunette) writes:
[Text of 'zapper' deleted]
|> Please correct me if i get this wrong, i guess the above circuit requires
|> to remove the dead cell from the multi-cell pack, right ?
Maybe not, see below.
|>
|> Which means, one has to take the Ni-Cd pack appart, and get the dead cell out.
|> The cells are usually connected with a point welded metal plate, which requires
|> you to rip the metal plate off the cell.
|> Now, once you fixed your shorted cell ( you hope ),with the above circuit ,you will have to
|> solder the cell back in place, which isn't that abvious, if you apply to much
|> heat when soldering you may damage the cell, if you don't apply enough heat you get
|> a cold solder spot, in which case it may brake loose, due to vibrations.
|>
|> The point is : You better know what you're doing, when trying to recover a
|> dead Ni-Cd cell.
Absolutely.
|>
|> Guess your plane or heli is worth more, opposed to the 20 bucks
|> for a new Ni-Cd pack.
|>
|> So, if you aren't too confident of fixing your Ni-Cd pack, return them to the place
|> where you bourght them.
|>
|> --
|> ben
You don't have to remove the cell from the pack (unless it is in parallel
with another cell). Just clip the zapper leads to the terminals of the
cell. In fact, it seems to me that it may even work without isolating
the cell if there is a cell in parallel. The shorted cell should take
most of the current, and the non-shorted cell some current as well.
Bad cell
|
v
___ ___ ___
--|___|----|___|----|___|--
| |
| |
| |
| |
zapper leads
- Les
--
Les Bartel lester@naomi.b23b.ingr.com
Dazix, An Intergraph Company uunet!ingr!b23b!naomi!lester
From uwm.edu!wupost!cs.utexas.edu!sun-barr!ames!data.nas.nasa.gov!splatter.nas.nasa.gov!bross Mon Nov 16 22:36:07 CST 1992
Article: 8084 of comp.sys.laptops
Newsgroups: comp.sys.laptops
Path: uwm.edu!wupost!cs.utexas.edu!sun-barr!ames!data.nas.nasa.gov!splatter.nas.nasa.gov!bross
From: bross@splatter.nas.nasa.gov (Wilson S. Ross)
Subject: Re: NiCad batteries again
Keywords: Storage, interrupted charging
References: <1992Nov10.062202.14404@schaefer.math.wisc.edu> <1992Nov10.084031.5374@jarvis.csri.toronto.edu> <1992Nov11.030643.21030@schaefer.math.wisc.edu> <1992Nov11.174659.2467@odin.corp.sgi.com>
Sender: news@nas.nasa.gov (News Administrator)
Organization: NAS Program, NASA Ames Research Center, Moffett Field, CA
Date: Tue, 17 Nov 92 03:55:52 GMT
Message-ID: <1992Nov17.035552.16083@nas.nasa.gov>
Lines: 9
My Toshiba battery was force-charged by a friend who has some sort
of generic charging equipment. It had reached a point where the machine
would not operate at all with the battery - even plugged in. Now it has
remained plugged & working for months, i.e, I have overcome the problem
of always shuffling batteries for home use. My other battery (still
good, I hope) sits on the shelf for when I travel. The 'dead' battery
isn't good without the power supply.
Bill Ross
From uwm.edu!cs.utexas.edu!zaphod.mps.ohio-state.edu!darwin.sura.net!uvaarpa!murdoch!holmes.acc.Virginia.EDU!lch3e Sun Nov 22 15:10:20 CST 1992
Article: 8155 of comp.sys.laptops
Newsgroups: rec.video,rec.video.releases,comp.sys.laptops
Path: uwm.edu!cs.utexas.edu!zaphod.mps.ohio-state.edu!darwin.sura.net!uvaarpa!murdoch!holmes.acc.Virginia.EDU!lch3e
From: lch3e@holmes.acc.Virginia.EDU (Lauren C. Howard)
Subject: An easy fix for nicads that REALLY works!
Message-ID: <1992Nov22.143820.13596@murdoch.acc.Virginia.EDU>
Originator: lch3e@holmes.acc.Virginia.EDU
Sender: usenet@murdoch.acc.Virginia.EDU
Organization: University of Virginia
Date: Sun, 22 Nov 1992 14:38:20 GMT
Lines: 47
Xref: uwm.edu rec.video:41091 rec.video.releases:3862 comp.sys.laptops:8155
Easy FIX for NICADS that REALLY works!
It's simple, it's easy, and it really works well!
First reinforce the battery pack (if in one) with clear cellophane tape.
Then drop the battery, onto it's side, on the floor from about 6
ft. up. You want it to be a really HARD drop: but don't break the
battery. Do this seven or more times for each battery.
If it's in a pack, drop the pack so each battery hits the floor seven
times.
I know this seems crazy, but it DOES work, and well. If it doesn't
work the first time, try again; harder! You have nothing to lose,
since you'd have to replace the battery anyway.
An example: the batteries in my portable printer are 8 years old.
They were at the point where even after 24 hours charge, and still
plugged into the charger, the printer wouldn't operate. After
dropping, I now get three weeks of printing from one charge.
So far, it's never failed. What have you got to lose? Post your
results so others can benefit, and spread the word!
From uwm.edu!zaphod.mps.ohio-state.edu!darwin.sura.net!gatech!destroyer!news.iastate.edu!sknapp Sat Nov 28 14:31:51 CST 1992
Article: 8219 of comp.sys.laptops
Newsgroups: comp.sys.laptops
Path: uwm.edu!zaphod.mps.ohio-state.edu!darwin.sura.net!gatech!destroyer!news.iastate.edu!sknapp
From: sknapp@iastate.edu (Steven M. Knapp)
Subject: Re: T1000SE battery replacement (INSTRUCTIONS!)
Message-ID: <ByF3yp.6Ir@news.iastate.edu>
Sender: news@news.iastate.edu (USENET News System)
Organization: Iowa State University, Ames, IA
References: <41667@sdcc12.ucsd.edu>
Date: Sat, 28 Nov 1992 08:37:36 GMT
Lines: 76
In article <41667@sdcc12.ucsd.edu> ma90fau@imath1.ucsd.edu (ma90fau) writes:
>Sorry if this has been discussed before. On the recent thread,
>people has been talking about the Radio Shack's replacement nicad
>cell. For people who has done the replacement for T1000SE, can you
>give me the detail instructions(what type of cell to use?..etc) to
>revitalize my old battery? .... just trying to find a cheap method
>to power my cheap notebook...
>Thanks!
Read me now, or save me for later. (in that imfamous Hans `n' Frans tone) :-)
Ok, so you have a T1000SE, and you have found how it does not work if you do
not have a good battery on the back. You called Toshiba, and suddenly felt
woozy. Aftermarket? Shure! $60 for the T1200XE pack (extended life, the only
way to go), but there still has to be a better way, the "college student
method"!
You call a battery store, and discover that the pack is 'sealed' and can not
be rebuilt. Then again, you never did listen to the 'no user serviceable parts
inside' lables.
The plan? Open it, replace the cells, and close it up.
Opening:
It is sealed, ultrasound welded actually. All you need to do is break
this thin joint. Take the pack off of the computer (back up that hardRAM!) and
place it so that the metal contact squares are faceing you and up. The part
faceing up, or the bottom of the pack, was physically seprate from the rest of
the shell. Note that all 4 metal contact squares are attached to this piece.
Now get 2 THIN screwdrivers or knives(jewlers screwdrivers work GREAT). Pick a
point that is faceing you (so it will not show when the battery is
reinstalled) and push a screwdriver in the small crack/seam between the two
pieces. Continue to CAREFULLY pry apart the rest of the seam, and remember,
the contact squares are comming all together. After having it all opened, make
shure to keep the latch and spring (trust me!).
Replacement:
Call you local battery distrubitor, or Mr. Nicad, or TNR-The battery
store (#'s should be in the 1-800 directory), tell them you got it open. Give
them the measurements of one of the cells. I believe they are 4/3A 1700mah,
and should be about $5 a shot. Mr NiCad does know them as T1000SE cells last I
checked. Get 6 of them. Looking at the old pack, replicate it using the new
cells, wire, tape, whatever! DO NOT FORGET THE TEMPRATURE SENSOR! The little
black thing attached to one of the cells in the original pack is VERY
important! After haveing everything hooked up, you are just about done.
Close it up:
Check that the contact squares do have voltage around what you would
expect (5-7.2V). Reassemble the case, and hold it shut however you see fit.
Since I use only one pack, having it on the computer holds it together, and
makes it easy to show others my hack. If you have 2 or more, scotch tape
should help, or even super-glue. But be warned, you might want to open the
pack again some time, and super-glue will make that VERY difficult.
There ya go! Good luck!
Any questions to sknapp@iastate.edu
Flames or insults to /dev/null!
I hereby declare this to be advice, use at own risk! I am not responsible for
your actions!
________________________________________________________________________
Steven M. Knapp Computer Engineering Student
sknapp@iastate.edu President Cyclone Amateur Radio Club
Iowa State University; Ames, IA; USA Durham Center Operations Staff
--
________________________________________________________________________
Steven M. Knapp Computer Engineering Student
sknapp@iastate.edu President Cyclone Amateur Radio Club
Iowa State University; Ames, IA Durham Center Operations Staff
From uwm.edu!cs.utexas.edu!uunet!noc.near.net!news.bbn.com!news.bbn.com!wbe Wed Dec 16 12:28:08 CST 1992
Article: 8462 of comp.sys.laptops
Path: uwm.edu!cs.utexas.edu!uunet!noc.near.net!news.bbn.com!news.bbn.com!wbe
From: wbe@bbn.com (Winston Edmond)
Newsgroups: comp.sys.laptops
Subject: Very dead T1000SE battery revived
Date: 16 Dec 92 03:01:31
Organization: Bolt Beranek and Newman, Inc., Cambridge, MA
Lines: 87
Distribution: world
Message-ID: <WBE.92Dec16030131@crystal.bbn.com>
NNTP-Posting-Host: crystal.bbn.com
Thanks to suggestions from this newsgroup, and after some experimenting, I
seem to have managed to revive a completely dead T1000SE battery pack. The
message rambles a bit so that others that have experienced the same problem
may compare the solution I found with others that have been discussed in this
newsgroup.
Completely dead battery = 0V output, 0 Ohms resistance, regardless of how
long it was "charged" on a T1000SE.
Current state = 7.2V output, and it just powered my T1000SE for 75 minutes
from full charge (green light) to first low charge beep, while
running the screen at medium brightness and using the 2400 bps modem.
Yes, 75 minutes isn't as good as new, but this is the first full
charge/discharge cycle after revival, so I don't yet know if it will get
better with proper use, or get worse again.
BACKGROUND (how I got into this mess and what didn't work):
My problem started when the battery pack began running out of power much
sooner than it "should have". I tried deep discharging, dropping the battery
pack from a moderately high distance (and other forms of physical bashing
that some people thought might help), and various other tricks over the
course of time. At first, these seemed to help slightly, but the
improvements were only temporary.
Eventually, while using an auto light bulb to discharge the battery pack,
I forgot the advice to not go below 1 Volt and let the pack discharge
completely. After trying to recharge it, I could get the green light to come
on, but the system would INSTANTLY shut down if the wall-plug power unit was
unplugged. A Voltmeter showed that the battery was only putting out 4.8V.
(NOTE: the green light doesn't mean the battery pack is fully charged -- it
means the battery pack isn't likely to accept any more charge, and that only
means "fully charged" if all the cells are working.)
Continued attempts to revive the battery pack eventually left me with a
battery pack in which all cells were "dead" (in "cell reversal" mode, I
think, but I don't understand NiCads well enough to be sure) -- 0V, 0 Ohms
resistance, immune to all the simple attempts I tried to charge it.
WHAT DID WORK:
Someone on this newsgroup suggested using a large electrolytic capacitor
charged to 8V and discharged through a completely discharged battery pack. I
didn't have a big enough electrolytic capacitor to do the job, so I tried two
alternatives: (1) another battery pack, and (2) an industrial power supply
capable of supplying 10 Volts at 10 Amps.
Partial success was obtained by connecting a working, fully charged
battery pack's + to the now-completely-dead battery pack's +, and - to -,
with just wires, for a few seconds. This produces a modestly bright spark.
Using a second battery pack was good enough to revive 4 of the 6 NiCad cells
in the pack, but wasn't enough to bring back the last two. It might have
been enough if I'd put some regular batteries in series (and in parallel) to
get the voltage and current capacity up a bit.
The first industrial power supply I tried could only provide up to 5A at
up to 10V. This wasn't enough.
The second power supply I tried could supply 10A at up to 20V, and 10A at
just 10-12V was enough. The power supply was a high grade unit with
adjustable current and voltage limits. I connected + to +, - to -, and let
10A at 12V flow through the battery for a few seconds. That brought the
battery pack back up to a full 7.2V! The rest of the charging I did on the
T1000SE, because I think feeding 120W into a few NiCad batteries for more
than a few seconds at a time is unwise. :-)
DISCLAIMER:
This message provides history and opinions, not advice. If you elect to
try to duplicate this success, you do so at your own risk. I did find
that a Voltmeter for measuring the battery pack voltage (which was always
N * 1.2V) was indispensible.
COMMENTS ON OTHER SOLUTIONS (given what worked for me):