Vicki Powys wrote:
>
> Hi Walt and All,
>
> Well I got busy with my (very fine) hacksaw and sliced open the plastic
> casing of my defunct Sony D10 DAT battery (NP-22H 6 volt 1800 mAh
> rechargeable ni-cad). There were three cells inside, two long and one
> short, linked by 2 short wires to a mysterious silvery connector 2cm long
> (which is marked IP305AF 80C ISUZU 0A3.)
The silvery connector is probably a thermal sensor. If they get too hot
in recharging it will either open some contacts or change resistance to
fix the problem. Try not to damage it.
> The two long cells look for all the world like "tuppeny bungers"
> (firecrackers), but are yellow instead of red. The batteries are about 2.25
> cm diameter, is that about the thickness of C cells?
Are you sure the long ones are not two cells linked together? We more or
less worked out that there should be 5 cells total.
> I now have to decide what I would use for the replacement cells, assuming
> that I go with NIMH rechargables. Should I use 4 or 5 AA cells, or should I
> go for C cells? What are the dimensions of C cells?
Use 5 cells, which would give you the 6 volt rating. Note that there are
also rechargables in half length and it's possible that's what you are
dealing with. Any 5 rechargable cells that will fit in the case will
work, but of course there are variations in capacity.
I just happen to have a C cell here, a dead Duracell Alkaline, let's
see... About 24mm diameter, 45mm long plus a couple mm for the positive
contact. How does that compare to what you found? AA's are something
like 13mm or so dia and more like 50mm long.
> Rechargeable cells often run at a lower voltage than disposable long-life
> cells, would this make a difference in the number of cells I used?
If you use disposables you would only need 4. Disposables typically are
1.5 volts or so, rechargables are nominally 1.2 volts, thus the need for
5 cells.
> What is the voltage of a freshly charged rechargeable C cell?
Same as any other single cell, rated 1.2 volts, though the actual
unloaded voltage is slightly higher just like it was for the AA's.
> The original Sony battery pack, when new and freshly charged, put out up to
> 7 volts I think (the battery pack is marked 6 volt), and the tape stops
> turning at 5.9 volts (5.5v under load).
That comes out right for 5 nicad cells.
Walt
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