Re: Dpreview selector: AA batteries?

On Sun, 19 Aug 2007 07:12:52 GMT, David J Taylor wrote:

Thomas T. Veldhouse wrote:
SMS <scharf.steven@xxxxxxxxxxx> wrote:
. . .
7. Faster shot to shot times, especially when using flash

Same issue. Unless LiIon can supply more current than NiMH, then
this doesn't make a whole lot of sense. If a given camera has a
current draw that both battery types can supply, then there would be
no advantage to either in this area.

If the internal resistance is different, or if the cut-off voltage below
which the camera or flash will operate is different (as a fraction of the
full-charged voltage), that will create a situation where the same WH
provide a different field life.

Field life is a different matter. As for faster shot to shot
times, that is sometimes true for small cameras using low power
flashes, probably due to Li-Ion batteries supplying a higher
voltage, especially when compared with cameras that only use 2 AA
NiMH cells. But lithium batteries (and I'm talking about AA now)
tend to get very hot when supplying high currents, so for safety
they are current limited. The result of this is that in higher
power external speedlights such as Nikon's SB-600 and SB-800,
lithium AA cells can actually have a slightly longer recycling time
than alkaline AA cells, and NiMH cells (and low capacity 1,000mAh
NiCd cells) recycle in about 1/2 the time that lithium cells take.
Although I don't know for sure, I suspect that Li-Ion cells are
similarly protected by internal current limiting. I don't think
that this would be part of the Li-Ion battery pack's protective
circuitry, but would be incorporated into the Li-Ion cells, as is
the case with lithium AA cells. As camera's internal flashes are
relatively weak, this probably wouldn't affect most of them.
Exceptions might be very small cameras that use very small Li-Ion
batteries.


8. More convenient to swap and charge (no fumbling with multiple
cells, and keeping track of which battery is in which set)


Huh? It is easier to put in a backup LiIon than it is NiMH? Or are
you simply referring to in-device charging. In that case, in device
charging is available for NiMH batteries as well ... just depends
upon the device. Or perhaps you are specifically referring to AA
NiMH. In that case, you aiming at intended usage. AA NiMH batteries
are a general solution where you are comparing to proprietary LiIon
solutions. Not apples to oranges there. There are proprietary NiMH
solutions as well (i.e. portable home phones like the
5.8GHz uniden and v-tech models currently available).

His point is quite valid. One of the reasons I prefer Li-ion is that I
prefer handling a single battery than multiple individual cells,
especially when those cells are an awkward shape (i.e. cylindrical).
Particularly true if you need to change cells in the field - during a
critical event or where you have no table to hand (on top of a mountain or
in the middle of a pyramid in Egypt).

How soon you forget. That might have been valid years ago, but it
really isn't any longer. Only the most hopelessly clumsy
individuals could possibly have any problems holding two AA cells in
one hand, even if it's the same hand holding the camera. Moderately
clumsy individuals might have a slightly greater problem dealing
with four AA cells, but it shouldn't be a real problem for two
reasons. One, many cameras that use 4 AA cells can take from 1,000
to 1,600 shots per charge. To need to change batteries on the top
of a mountain, etc., indicates that we're dealing with a fool that
started the day with nearly depleted batteries in the camera.
Smarter photographers that start the day with four fresh batteries
will probably never have to change them until the day is over and
they're getting ready to hop into bed or a sleeping bag. The other
reason is that even years ago when the terminally clumsy might have
had to change batteries in the middle of the day, they didn't have
to pick the most foolish way to do it (recalling echoes of 'juggling
8 AA cells' in past messages). Cameras don't lose their settings if
the batteries aren't swapped within 10 seconds. With most you can
take hours or months to change them. It's not very difficult even
on a mountain top to remove the batteries and store them in a pack,
and then, after that's done, get the fresh batteries and insert them
into the camera.

It's one thing to have a preference for Li-Ion batteries, and I
don't fault you for that. But it's another thing to raise the false
spectre of possible calamity, when you say it's "Particularly true"
when changing batteries in the field. With the long life of many
cameras that use AA batteries these days, most of the photographers
that will have to worry about changing batteries in the field at all
are probably those that use Li-Ion batteries in their cameras. :)


16. Li-Ion batteries do not suffer from the "dud" cell problem

What the hell are you talking about?

He means the problem which hit many of us - buy 12 NiMH cells and get 10
good ones. Even from reputable suppliers. Maybe they are better now - I
wouldn't know as I stopped using them.

I question your use of "hit many of us". I've bought many NiMH
cells, probably far more than most in this newsgroup, and I've never
had a dud cell. I did get two duds in a large box of alkalines
about 10 years ago, but they were part of a bargain bin sale, and
were clearly marked as being repackaged. On the other hand, of the
first two Li-Ion battery packs I bought, one was able to be charged
only once, and after that would be rejected by the battery charger
within 5 to 10 seconds. B&H cheerfully replaced it. If when you
used NiMH batteries you got more than one dud, you were probably
buying them from a dud dealer. :)


17. No need to "Battery Match" cells of similar capacity

There is really no need to do that for NiMH either. It is just a
method for geeks like me to maximize the life of their AA cells by
grouping them together to maximize available capacity.

So you would put a set of four cells with 2 x 1500mAh and 2 x 2500mAh in
the camera? I rather hope not.

This isn't what battery matching has been about. It's not just
foolish, it's quite stupid to use mismatched batteries like that.
What battery matching has long been about was when battery packs
were put together using large numbers of cells (such as 8 to 12 or
more), whether using NiMH or NiCd or other types, to eliminate or
minimize the chance of batteries being ruined due to cell reversal
when the pack is nearly depleted, individual cells would be hand or
machine tested, and battery packs would be made using cells having
very close to the same capacity. I knew some people years ago that
did this as part of their job.


You blow a lot of propaganda buddy.

but some of his points which you dispute are quite valid.

Less than you realize, and many of SMS's points not mentioned are
quite invalid. I've already commented on most of these in past
replies, but if you didn't see them and have doubts, just let me
know and I'll be happy to point out SMS's other bogus claims, and
why he's mistaken, although at this point it's quite obvious that
his mistakes aren't really unintentional mistakes.

.

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