From: ASAAR on
On Tue, 12 Jun 2007 09:35:17 -0700, SMS wrote:

> My son has an old A60, similar to the original poster's A70, and the
> Energizer lithium non-rechargeables work well considering that he uses
> the camera infrequently. Next time I see the eneloops on sale I might
> buy four of them.

Considering that your son uses the camera infrequently and that
the A60 and A70 had extremely good battery life, capable of over 850
shots per charge* using DPReview's old tests that included a mix of
flash and non-flash shots, splurge. Your son doesn't need
rechargeable batteries. A couple dollars worth of cheap alkaline AA
batteries will probably keep his A60 going for years. Get him a new
A640 instead. And unless he decides to turn a new leaf and start
taking lots of pictures, he probably won't need anything more than
cheap alkaline AA batteries in the A640 too. :)

* 850 shots is based on the A60/A70 getting 515 shots per charge
using 1,600mAh NiMH batteries. If 2,700mAh batteries are used
instead, the works out to 515 * 2,700 / 1,600, or 869 shots per
charge. The A640 should do even better.

From: SMS on
Thomas T. Veldhouse wrote:

> You can get reasonably accurate capacity readings based on voltage alone,

Not on NiMH batteries. The majority of the discharge cycle is in an
extremely narrow voltage range of about 0.1V (between 1.1 and 1.2
volts), see "http://www.girr.org/girr/tips/tips7/nimh_tests.gif" for a
good graph of it. That's why you have to use another method, such as
used by that battery tester.

> but
> it doesn't work well when the battery becomes damaged [or nears end-of-life].
> The MB-D200 grip for the Nikon D200 takes any AA battery and of course the
> standard LiIon batteries. The D200 can be configured to know that it is using
> NiMH batteries and does a good job with it.

On my Canon 20D, when I use the battery grip with AA cells, the charge
indicator doesn't show full, since 6 x 1.2V is less than the 7.4V put
out by the Li-Ion packs. It works fine, but the charge indicator never
changes until the NiMH cells go through their fast drop-off at the end.

> I simply stated it is possible, not that it is practical for in camera field
> use on cheap consumer point-and-shoots.

Fair enough.

From: ASAAR on
On Tue, 12 Jun 2007 18:54:19 GMT, Thomas T. Veldhouse wrote:

>> I should have said that it's not possible inside the camera. Or perhaps
>> more accurately, it's too expensive to implement the pulse load test
>> inside the camera, especially considering the manufacturers are cutting
>> every possible expense on the AA powered cameras in the first place.
>>
>> It's an inherent characteristic of NiMH batteries that the voltage
>> discharge curve is so flat. This isn't necessarily a bad thing, but it
>> does mean that it's non-trivial to measure remaining capacity, and it
>> results in the lack of accurate battery level indicator in-camera for AA
>> powered cameras.
>
> You can get reasonably accurate capacity readings based on voltage alone, but
> it doesn't work well when the battery becomes damaged [or nears end-of-life].
> The MB-D200 grip for the Nikon D200 takes any AA battery and of course the
> standard LiIon batteries. The D200 can be configured to know that it is using
> NiMH batteries and does a good job with it.

It's strange that so many smart chargers are available, often for
under $15, yet they manage to have the complex pulse/delta v charge
circuitry, yet cameras that cost hundreds of dollars can't also
incorporate similar inexpensive, albeit moderately complex circuits.
And again, my PDAs and radios didn't need anything more
sophisticated than a fairly accurate voltmeter to track the battery
charge state. This even with the relatively flat discharge curve of
NiCd and NiMH batteries. Why? Because while the voltage curve is
relatively flat, it's not horizontal. It has a fairly uniform slope
and battery capacity tracks very well with voltage at a given load.
NiMH batteries are flat and need to be recharged when the voltage
drops to a little above 1.00 volts per cell. When fully charged,
the voltage will be up around 1.25 volts, and it drops pretty
uniformly and is easily monitored by the simplest camera CPU. As
usual, SMS is spreading his misinformation/disinformation about what
is and what isn't possible. He's been doing it for years.

From: ASAAR on
On Tue, 12 Jun 2007 18:04:53 GMT, Thomas T. Veldhouse wrote:

>> I've already given an example of a very accurate battery
>> meter used with NiMH batteries, but your Li-Ion zealotry may have
>> something to do with your repeating this nonsense.
>
> It is VERY possible. Simply applying the load and checking the volage will do
> it. Consider this fine piece of equipment.
>
> http://www.thomasdistributing.com/zts-mini-mbt-battery-tester.htm

That's an interesting tester, and quite reasonably priced for what
it claims to do. My example, a nice Sangean radio was not even
close in sophistication, and probably didn't rely on a CPU (although
it probably contained a few). Its LCD display had a 14 or 15
segment battery meter, that was extremely accurate in reporting the
status of the radio's 4 AA batteries. It seemed to have been
perfectly calibrated for NiCD or NiMH batteries, since all but one
or two of the segments would be displayed for fully charged
batteries. For the volume I used, the segments would wink out at
the rate of about one for every 2 hours of playing time. No matter
what capacity batteries were used or what condition they were in,
after all of the segments were no longer visible, the radio would
play a little bit longer, maybe 10 or 15 minutes before powering
off. It appeared to be very linear too, with the playing time per
segment virtually the same, from top to bottom of the display. If
only my cameras had a meter half as accurate, I'd be quite happy.

Also extremely accurate are the hacks that ran on my Palm IIIx,
TRGPro, HandEra and other PDAs. These used either 2 or 4 AAA
batteries and the hacks displayed the battery voltage to much
greater accuracy than needed, 0.01 volts, and the voltage also
provided a very accurate estimate of the remaining operating time.

There's nothing inherent in the batteries that limits charge
reporting to Li-Ion technology. It's better to put some of the
electronics to do this within the battery, so the camera, laptop,
whatever, won't get confused when batteries are swapped. All this
requires are batteries expensive enough to easily absorb the cost of
the added electronics. This can be done with any type of
proprietary battery pack, including not only Li-Ion but NiMH as
well. And as my radio and the battery meter you found indicates,
even that isn't necessary to get a good indication of the battery's
charge state. But SMS will continue to rave on. It's kind of odd
that after all these years his kid is still conveniently using that
same old outdated 2mp Canon A60. <g>

From: SMS on
Thomas T. Veldhouse wrote:

> That is because you bought a Canon ;-) They always leave features off for the
> more expensive cameras. The Nikon D200 allows you to indicate which batteries
> are installed and it will then properly show the indicator accordingly. It
> has options for NiMH, Alkaline, Lithim (1.5) and of course the LiIon batteries
> for the camera.

Uh-oh, is this turning into a Canon vs. Nikon thread?!

At least with the Canon there are after-market Li-Ion packs available so
you don't have to resort to AA's. Up until the D100, Nikon had
after-market packs available too.

I don't know if the 30D from Canon has the battery type feature.