On Wednesday, October 17, 2012 2:40:21 PM UTC+1, philo wrote:
> On 10/17/2012 05:22 AM, Whisky-dave wrote:
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> > On Wednesday, October 17, 2012 4:11:41 AM UTC+1, philo wrote:
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> >> On 10/16/2012 06:37 PM, nospam wrote:
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> >>> In article <k5koth$m5l$>, philo <>
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> >>> wrote:
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> Ok there are now two people here who have mis-interpreted what I wrote
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> so I had to re-read my posts to find out why. The fault was on my end
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> for not being clear...so here goes again:
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> The camera I used required a 6 volt battery (viz: four AA's)
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> When the battery voltage dropped to approx 4.5v the camera ceased
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> functioning.
Working in electronics and I;'m not sure how old your camera is but in electronics TTL (in photography was through the lens metering) in electronics it's Transistor-Transitor logic (now pretty much replaced)
TTL chips had a working supply voltage range of 4.75 to 5.25.
The modern equivant of TTL Is the HC series which can work from 2V to 6V
But of course others sections may required differnt voltages common today are 5V 3.3V 2.7V and some on 1.3V.
To simplify things in the trivial calculations I'll just
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> call the overall voltage 4.4v which gives a minimum volts/per cell of
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> 1.1 volts.
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> With four new alkaline batteries starting out at 6 volts (even though
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> the discharge curve is steeper than that of nicad) ...at 1.5 volts
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> /cell the camera can be used for a long time (maybe one hour of
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> continuous use) before the voltage drops to 1.1 volts / cell.
This depends on the current drawn of course.
I also ran a test a copule of years ago.
Using two AA and a white LED to draw current
at the start of teh test the voltage across the battereis was 3.1V with the LED lit. I eneded the test with the LED slighly less bright and the battery voltages being 2.45V after 2,712 hours. (I got bored watching)
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> Note: At this time the alkaline batteries are 100% discharged.
No they are not, what happened is that the resultant voltage 1.1V isn't enough to power the cirucut so it switches off.
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> To those here unfamiliar with battery terminology...100% discharge does
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> *not* mean zero voltage,
but it not 100% discharge either.
>it means the chemical reaction is fully
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> complete and the battery can no longer supply it's rated current. (A bit
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> of an oversimplification)
True it can still supply current but not at the rated amount at the rated voltage.
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> Now the nicads, starting out at 1.2 volts per cell (even though they
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> have a flatter discharge curve than alkalines) did not take too long to
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> get down to 1.1 volts per cell (perhaps 15 minutes of continuous use)
Because they have lower internal resistance, they can be discharged quicker, it's like car traveling faster uses more fuel and it might not be as efficint either traveling less distance.
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> The important thing to note is that the nicad batteries were only
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> *partially* discharged. Were it possible to have put a fifth battery in
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> series the nicads would easily have given as long a time-of-use as the
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> alkalines or probably more.
What if you put 5 alkaline battreis I'm pretty sure they'd work at 5.5V .
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> It was *not* a case that the nicads became 100% discharged sooner than
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> the alkaline batteries...it was simply that the over all voltage was
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> less. They came to the cut off point for the camera considerably sooner
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> than the alkalines even though they were not yet dead (or 100% discharged)
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> The voltage was too low to allow the batteries to be fully discharged.
But that works the same for pretty much all batteries, even car batteries.