camera cutoff voltages ?

Archived from groups: rec.photo.digital (More info?)

Adam. Seychell wrote:
> I own two digital cameras and I have measured their battery cutoff
> voltages to find if full capacity being used from NiMH battery. Cutoff
> voltage is the voltage the camera automatically turns off due to under
> voltage.
>
> Camera cutoff @ current cells type
> -----------------------------------------------
> Pentax 330GS 2.43V 836mA 2 AA
> Canon S1 IS 4.45V 510mA 4 AA
>
> The high cutoff (1.22V/cell) of the Pentax renders it almost useless for
> NiMH batteries. I get about 20 minutes continuous usage on 2300mAh NiMH
> batteries. It seems Pentax expect you to buy the 3V expensive disposable
> lithium batteries for this camera.
>
> My Cannon is better (1.11V/cell) since looking at discharge curve data
> for NiMH from the Panasonic web site, 1.11V looks fairly close to the
> end. 1.11 volts is probably a good compromise between useful capacity
> and over discharging.
>
> Cutoff voltage strongly influences the useful capacity from NiMH
> batteries. So why is there no mention of cutoff voltage in camera reviews ?
>
> Adam

I've noticed that too, and it kind of pisses me off.
I get almost as many shots from 2 AA Alkalines (1.5V each)as I do from
my 2300AH NiMH batteries (1.2V each).
I can't believe that Pentax couldn't have reduced the Cutoff Voltage a
few more tenths of a Volt which would have greatly improved the useful
life of the NiMHs
Bob Williams

Archived from groups: rec.photo.digital (More info?)

Malcolm Stewart wrote:

> "Adam. Seychell" <invald@invalid.com> wrote in message
> news:421fa0bb$0$1022$afc38c87@news.optusnet.com.au...
>
>>I own two digital cameras and I have measured their battery cutoff
>>voltages to find if full capacity being used from NiMH battery. Cutoff
>>voltage is the voltage the camera automatically turns off due to under
>>voltage.
>
> snip
>
>>Cutoff voltage strongly influences the useful capacity from NiMH
>>batteries. So why is there no mention of cutoff voltage in camera reviews
>
> ?
>
>>Adam
>
>
> How do you get at the terminals for making the measurements? I assume
> you're measuring the voltage under load. Pseudo battery mock-up ?
> I tried doing this when my EOS3 was eating 2CR5s like there was no tomorrow,
> and I found it was quite difficult.

Your right. I use a variable power supply and two multimeter. I also had
to make two probes from lengths of 2mm diameter solid copper wire. At
one end of the solid wire I soldered leads to the power supply (via a
current meter) and at the other end I soldered wires to a voltmeter. The
voltmeter connected side of the probes is poked into the camera battery
compartment and pressed firmly on the + and - terminals. That way I
should measure voltage directly at the terminals. Yes, the voltage
measurements were made under load at the currents listed.

I emailed Pentax regarding the improper cutoff voltage and got no response.

Archived from groups: rec.photo.digital (More info?)

"Adam. Seychell" <invald@invalid.com> wrote in message
news:421fdd9b$0$6167$afc38c87@news.optusnet.com.au...

> That way I
> should measure voltage directly at the terminals. Yes, the voltage
> measurements were made under load at the currents listed.
>
> I emailed Pentax regarding the improper cutoff voltage and got no
response.

Well done.
I set up something a bit similar when trying to establish why my (new) EOS3
was eating batteries. Unfortunately, even my limited but technically
accurate methods and results were not understood by the "man in a suit" in
Reception at my local national agency, and request for Warranty Repair was
refused. When I did eventually get the camera corrected, it was a totally
different animal.

--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm

Archived from groups: rec.photo.digital,sci.chem.electrochem.battery (More info?)

Ron Hunter <rphunter@charter.net> wrote in message news:<Bd0Ud.22158$yv.12159@fe03.lga>...
> DaveC wrote:

> >
> > The high cutoff (1.22V/cell) of the Pentax renders it almost useless for
> > NiMH batteries. I get about 20 minutes continuous usage on 2300mAh NiMH
> > batteries. It seems Pentax expect you to buy the 3V expensive disposable
> > lithium batteries for this camera.

Save some money - info..

Did you know you can sell your used non-rechargeable Lithium batteries online?

FW: LINKs to Used lithium (not Li-Ion) camera batteries wanted, and available

LINK to Non-rechargeable photo lithium batteries wanted for recycling
http://tinyurl.com/5e9pe

Archived from groups: rec.photo.digital (More info?)

On Sat, 26 Feb 2005 09:03:39 +1100, "Adam. Seychell" <invald@invalid.com>
wrote:

>I own two digital cameras and I have measured their battery cutoff
>voltages to find if full capacity being used from NiMH battery. Cutoff
>voltage is the voltage the camera automatically turns off due to under
>voltage.
>
>Camera cutoff @ current cells type
>-----------------------------------------------
>Pentax 330GS 2.43V 836mA 2 AA
>Canon S1 IS 4.45V 510mA 4 AA
>
>The high cutoff (1.22V/cell) of the Pentax renders it almost useless for
>NiMH batteries. I get about 20 minutes continuous usage on 2300mAh NiMH
>batteries. It seems Pentax expect you to buy the 3V expensive disposable
>lithium batteries for this camera.
>
>My Cannon is better (1.11V/cell) since looking at discharge curve data
>for NiMH from the Panasonic web site, 1.11V looks fairly close to the
>end. 1.11 volts is probably a good compromise between useful capacity
>and over discharging.
>
>Cutoff voltage strongly influences the useful capacity from NiMH
>batteries. So why is there no mention of cutoff voltage in camera reviews ?
>
>Adam

I've probably not thought this through completely, but off the top of my
head, I would guess it's more to do with current drain than voltage. Both
cameras draw about the same power (2W vs. 2.2W), but because the Pentax
only has two batteries, it's drawing a much higher current from them than
the Canon does from its four. Drawing a higher current means (because of
the batteries' internal resistance) that the voltage will drop quicker
under load with the Pentax, and so it probably needs to set the cut-off
voltage higher.

Also, the (apparently) lower-voltage chips in the Pentax might have less
leeway for their "absolute minimum operating voltage" than the circuits in
the Canon.

In other words, I doubt that Pentax has "chosen" to set a higher cut-off;
it's been imposed on them by their choice of only two batteries.

Regards,
Graham Holden (g-holden AT dircon DOT co DOT uk)
--
There are 10 types of people in the world;
those that understand binary and those that don't.