HHC 2014

Richard J. Nelson rjnelsoncf at cox.net
Sun Jul 13 08:18:21 MDT 2014


Hello RichardS & Roger et cl.,

The usual procedure is to charge a capacitor and discharge it into the cell.
This provides an energy controlled pulse.  Check the Internet for UF values
and voltages.

X < > Y,

Richard

-----Original Message-----
From: hhc-bounces at lists.brouhaha.com [mailto:hhc-bounces at lists.brouhaha.com]
On Behalf Of Roger Hill
Sent: Saturday, July 12, 2014 5:14 PM
To: Handheld Computing Conference discussion list
Subject: Re: HHC 2014

Hi Richard S and all,

I don't know about probabilities outside of [0,1], but I do remember
rejuvinating NiCad cells from my HP-41 printer.  Seems that the cells
developed internal conducting filaments and gradually shorted themselves
out.  The battery pack had to be taken apart enough so that one could get at
each individual cell (I believe each cell was about 1.5V).  I used a model
train power supply that would supply 12V DC at around 3A (didn't have a
circult breaker but it did have a current limiter) and **momentarily**
touched wires from the terminals to the ailing cell (+ to + and - to -, as
if you were trying to charge the cell).  The idea was that the zappings
would "burn out"
the filaments.  After a few zappings I would measure the voltage of the cell
and see if it it stayed steady or slowly dropped to zero; if the latter I
would repeat the zappings.  If the cell held its voltage I would put
everything back together and charge the pack normally.

(WARNING: Usual warning and disclaimer; wearing glasses at least would be a
good idea...  I would also be wary of using fancy modern solid-state model
train power supplies.  My power supply was an old toy train transformer with
selenium rectifier, in series with an auto headlamp bulb for a current
limiter.)  

There was a period of some years where I only used the printer about once a
year, and each time I found one or more cells that needed zapping.  I was
always able to get the cells going again, at least for the time I needed to
use the printer.

I don't think I ever tried it with HP-67 cells, but I would imagine it ought
to work -- but I don't know after how many years of disuse....

-- Roger

------------ On richard nineteenfortyone's message ------------
 
> Is 100% the best you could do?   I heard that there is some kind of 
> meaning associated with probabilities outside of [0, 1], but I am not 
> advanced enough to know about stuff like that.   I certainly plan to 
> be there.
> 
> Another matter: does anybody remember the procedure for restoring 
> NiCad cells from the HP-67 days?  This is an ongoing problem with old 
> ham radios, and a bit of technology transfer is in order.

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