Jan Steinman and Frank van Lindert debated the merits of various
battery options and Jan enthused about rechargeable alkaline cells: he
really liked using them and they had good cost performance in relation to
conventional alkalines.
From an economy point of view the rechargeable alkalines are not as
good as might first appear because they have a substantially lower capacity
per cycle than the capacity of a normal alkaline. The consumer report tests
some years back showed something like a 1/4 of the capacity of a conventional
alkaline. Thus the breakeven point may be more like 12-16 charges rather than
the 4 calculated on the previous report. I seem to remember that the internal
resistance is higher especially after a few cycles so that the energy
extraction is lower too for a high current application like a flash. Also as
Jan mentioned it is quite important not to extract too much capacity per
cycle so this means rather frequent charging which may be why the
manufacturer now specifies a much large number of "cycles". Consumer reports
was not very enthusiastic about the rechargeable "Renewal" cells from a cost
per energy or an environmental point of view so it is interesting that Jan
finds them so effective.
Testing primary cells is actually quite difficult since small changes
in the exact rest between discharge cycles makes a huge difference in
performance.
Thus when using your flash with any type of alkaline you may double your
capacity if you switch off periodically to allow the cells to rest.
Temperature makes a large difference too so keep your cells under your jacket
before using them under cold conditions. Even going from 20-30C ambient can
increase capacity something like 20%.
There was also some discussion on being careful to avoid using Nicads
with the 310 flash because the lower internal battery resistance will blow
the transistors in the flash. This was common in many flashes of that era.
Normal AA alkalines will produce short circuit currents of the order of 1.5A
which translates to about 1-1.5 Ohms internal resistance. In contrast Nicads
can produce 10 times that current. If you are environmentaly conscious and
really want to use Nicads in a 310 you can just add a 5 Ohms,1.5W resistor in
series with one of the leads to the battery holder. I did that years ago with
a C*n*n flash with good results although the cycle time gets rather long if
you go back to alkalines.
Interestingly older compact flashes that included rechargeable Nicads
like the old Metz's used a different type of Nicad from the AA cells now
commonly used. These were internally dry (no electrolyte) similar to the
button style cells used internally in one of Olympus packs for the motor
drive. These have much slower self discharge rate than the more common "wet"
cells, so work much better when stored for a while between use.
Tim Hughes
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