Re: 4 batteries vs. 3 batteries

On 13 Aug 2006 14:51:10 -0700, horszowski@xxxxxxxxx wrote:

May I suggest one more test and that is what is the battery voltage
when the calculator simply shuts down?

Thanks

Luis

I performed this test on the HP-50 and on an HP-49G+:

Calculator Total voltage when Per cell voltage when
calculator crashed calculator crashed

HP49G+ 3.10 1.033

HP50G 3.65 0.9125

Maybe the low batt indicator comes on so soon on the HP-50 because they
need more voltage for the RS-232? The HP-50 will continue to operate for
quite a while after the low batt indicator comes on, but how will you know
when the per cell voltage reaches about 1.0 volts per cell, which would be
a reasonable point to replace the batteries? If you don't need to use the
RS-232, you could mentally make note of how much usage you've had when the
indicator first comes on, and then use it (the HP-50) for that much again.
(As I noted in another post, the batteries are only about half discharged
when the low batt indicator first comes on.)

These measurements are for *my* calculators only, and there may be a
fairly large variance in the behavior of a large sample of units.

Perhaps a few other people could try this and give us some more data
points.

By the way, I was turning the voltage up and down a number of times and
crashed the calculator quite a few times, but I never did lose the contents
of memory. Some of the settings, such as display resolution, were reset to
the default, but I saw no memory loss.

The Phantom wrote:
On 2 Aug 2006 09:14:58 -0700, "Wes" <wjltemp-gg@xxxxxxxxx> wrote:

I verified the measurements posted in March.

I guess my original question (electric current in 50g vs. 49g+) doesn't
really depend on the variations introduced by different batteries and
meters. All we need is somebody who has both a 50g and a 49g+ to
measure the current in both machines using the same meter and same
batteries (+1) to see how the currents compare.

I'm just wanting to know if the 4 battery setup will last
proportionally longer than 3.

I ran some more tests. I used a variable bench power supply to run 3
calculators, and reduced the voltage until the low battery indicator came
on in the display. These are the results.

Calculator Total voltage when Per cell voltage when
low batt came on low batt came on

HP-48G 3.20 volts 1.067 volts
HP-49G+ 3.45 volts 1.15 volts
HP-50G 4.85 volts 1.2125 volts

If you replace your batteries when the low battery indicator first comes
on, the HP-50G will have significantly shorter run time.

See the discharge characteristic at:
http://data.energizer.com/PDFs/E92.pdf
and you will see that if you only discharge to 1.2125 volts per cell, you
will have used less than half the energy in the cell. Also, note that the
HP-48G in allowing the cell voltage to drop to 1.067 volts has used about
85% of the energy in the cell. (These are eyeball estimates)


I guess the real battery test will be testimonies from actual users in
a few weeks. How long does a set last on a 50g compared to similar use
on a 49g+. (I suspect people will be playing with their new toy^H^H^H
calculator more than usual, so the first set of batteries might not be
a fair test.)

-wes

.

Relevant Pages

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