🚀 go-pugleaf

In article <1991Feb11.005844.1630@julius.cs.uiuc.edu>, totty@flute.cs.uiuc.edu (Brian Totty) writes:
> 
> 	I just bought a set of rechargable batteries and a charger for them.
> 	To my surprise, I found out that the 9v batteries were actually only
> 	7.2v in a "nine-volt size".  I was wondering why they couldn't make
> 	NiCd batteries in the same size that could store 9v.  Other brands on
> 	rechargeables also seem to be 7.2v.  This seems to be a pretty serious
> 	degradation from 9v, and I am surprised that these batteries would
> 	even work in some applications.


One person has already mentioned Varta as a source of 9V "9V" batteries,
and Everready also sells (or did sell?) one.  This may be a re-labled
Varta.

There are two basic types of "9V" NiCd batteries: The 7.2V ones are
made of 6 cylindrical cells.  At 1.2V per cell, this gives 7.2 Volts.
Varta (and others?) make a 7-cell model, made of stacked oval "button"
cells, yielding 8.4 Volts.  From what I've seen, the button cells also
have a higher Amp-hour capacity; about 100 mAh, as opposed to about
65 mAh for the cylindrical cells, making the 7-cell battery an all-
around winner.

Actually, the lower Voltage of the 6-cell (and 7-cell) batteries isn't
really much of a loss, compared to the Carbon-Zinc or Alkaline 9V batteries.
The NiCd discharge curve is *much* flatter that the non-rechargables.
The non-rechargables spend as much time *below* 7.2V as above it, during
discharge.

Your battery charger will probably charge the 7-cell NiCd batteries just
fine.  They are typically a constant-current charger, with some taper as
the battery Voltage reaches overcharge.  A charger for 6-cells should
work, but the time to full-charge may be increased a bit.  You can measure
the charging current to verify this, or measure the open-circuit output
Voltage of the charger to get a clue.
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