From: Thomas T. Veldhouse on
SMS <scharf.steven(a)geemail.com> wrote:
> Thomas T. Veldhouse wrote:
>
> This is a good idea, though you realize that very few people are going
> to ever do something like this, it's just too much work.
>

Actually, just about anybody who purchases such a charger will do this (i.e.
the Maha Power-Ex MH-C9000, the one I bought).

> This is true, but if you don't continually completely discharge the set
> of batteries in the camera, you won't get a polarity flip in the first
> place.
>

Exactly my point! Thus, your bullet about the batteries having reduced life
and being damaged is not true or a problem [unless you discharge them
completely in devices like flashlights].

> You do point out another disadvantage of NiMH batteries that I'd
> neglected to include in the web site, the problem of polarity reversal
> of one or more cells in a pack. I've added that to the site.
>

That IS the problem you were indicating and it is NOT a problem in anything
that shuts down with low voltage [like a camera]. Flash lights might
discharge the batteries too low if one just leaves the light on until the
batteries go completely dead. But then ... we aren't talking about flash
lights here, are we?

--
Thomas T. Veldhouse

Eat drink and be merry, for tomorrow they may make it illegal.

From: Thomas T. Veldhouse on
Ron Hunter <rphunter(a)charter.net> wrote:
> Isn't a battery meter on a device using NiMH batteries rather like a
> radar detector with such a short range that it only tells you you have
> been caught? Given the discharge curve, it need only be a dot in the
> LCD display that says your battery is below the cutoff voltage. Still,
> my camera do have such a warning, and it really means what it says
> because only a couple of pictures can be taken with that warning on
> before ugly things start to happen.

If a battery is health, the capacity guage will work just fine, as long as it
is aware it has NiMH batteries rather than alkaline batteries [i.e. the Nikon
D200 with the grip ... with the camera set to NiMH]. Cell phones used to use
NiMH batteries in most models and most models didn't just go from full to
empty and shut down as the OP is implying.

--
Thomas T. Veldhouse

Eat drink and be merry, for tomorrow they may make it illegal.

From: Thomas T. Veldhouse on
SMS <scharf.steven(a)geemail.com> wrote:
>
> Yes, that's currently the case. It's too expensive for a manufacturer to
> integrate a pulse-load type of battery tester into an AA powered camera,
> especially since they couldn't charge extra for it since so few users
> would understand that it's something that's worth an extra couple of
> dollars.
>

As I indicated and you failed to read, pulse load only helps if the battery is
NOT health. Voltage is plenty sufficient for a healthy battery. When a
battery becomes unhealthy, it doesn't reach full voltage under load but will
show full voltage with no load; thus, an indicator will show a false capacity
reading that is higher than it should be. Dying LiIon batteries have issues
that are similar for similar reasons.

--
Thomas T. Veldhouse

Eat drink and be merry, for tomorrow they may make it illegal.

From: John Bean on
On Tue, 26 Jun 2007 14:10:51 -0000,
batterylogic(a)googlemail.com wrote:

>Just go straight to [some web site or other] and treat yourself...
[snip]

Just go straight to somewhere else with your commercial
spam.

Thank you for your co-operation.

--
John Bean
From: SMS on
Thomas T. Veldhouse wrote:
> SMS <scharf.steven(a)geemail.com> wrote:
>> Yes, that's currently the case. It's too expensive for a manufacturer to
>> integrate a pulse-load type of battery tester into an AA powered camera,
>> especially since they couldn't charge extra for it since so few users
>> would understand that it's something that's worth an extra couple of
>> dollars.
>>
>
> As I indicated and you failed to read, pulse load only helps if the battery is
> NOT health. Voltage is plenty sufficient for a healthy battery.

No it isn't. To show remaining capacity based on NiMH voltage, you have
to measure within 5/100ths of a volt, and the remaining capacity varies
by both temperature and discharge rate, so you need an extremely
accurate, temperature compensated voltage reference. Since the batteries
in a camera are in series, you don't know if one battery is skewing the
voltage up or down. If you only measure to 1/10th of a volt then the
error is so high that it's a worthless measurement.

There are two common ways of accurately measuring capacity on NiMH
batteries. One is the pulse load test, and one is coulomb counting. The
latter is very complex and is normally used only on very expensive
equipment, and even the former is too complex and expensive to implement
in a consumer device.

Li-Ion batteries have a fairly linear voltage discharge curve. Even
measuring to only 0.2 volts will give a good indication of remaining
capacity.

Look at the Maxim application note,
"http://www.maxim-ic.com/appnotes.cfm/an_pk/121".

Since there appears to be some confusion over the capacity versus
voltage issue I've added two graphs to the website that show remaining
capacity versus voltage, one for NiMH and one for Li-Ion.

Steve
http://batterydata.com