Strange: Different timekeeping behaviour of 2 WP34S calculators

[rkf]

Hi, dear other WP34S owners out there!

I have two of this nice calculators in my collection; both having the clock crystal, and one of them also with IR output e.g. for printing.

Whereas the clock-crystal-only WP34S keeps the time nicely, the other one (with IR) "looses" it's time and date a while after setting, and after switching on defaults to Monday, 1.012007, and a time of 0.0000. "BATT" on this bad behaving WP34S says 2.7V - maybe that's not enough to keep the time? Unfortunately, I don't have the good one with respect to time WP34S at hands for now to check its BATT level.

Any comment on this is very appreciated!

Kind regards, Ralf.

[burkhard]

(05-22-2019 11:16 AM)rkf Wrote:  "BATT" on this bad behaving WP34S says 2.7V - maybe that's not enough to keep the time? Unfortunately, I don't have the good one with respect to time WP34S at hands for now to check its BATT level.

I think maybe that is the problem. If it says 2.7V under low load, it might drop down further during some extended operation. And maybe that is enough to cause troubles.
My WP34S is likewise reporting 2.7V on BATT as well, but as I key something in, I can see the "low battery" light flashing on... It still has correct time and date (I also have a crystal), but maybe trouble soon?

What does BATT report on the "good" calculator?
Why not try swapping the batteries between them?

[rkf]

(05-22-2019 05:34 PM)burkhard Wrote:  ...
My WP34S is likewise reporting 2.7V on BATT as well, but as I key something in, I can see the "low battery" light flashing on... It still has correct time and date (I also have a crystal), but maybe trouble soon?

What does BATT report on the "good" calculator?
Why not try swapping the batteries between them?

The "good one" reports 2.8V, that's not really much more. I'll give a try to the suggestion of swapping batteries.

[burkhard]

(05-23-2019 04:00 AM)rkf Wrote:  The "good one" reports 2.8V, that's not really much more. I'll give a try to the suggestion of swapping batteries.

Hah, I looked at mine again this morning and the time and date had reset! You jinxed me!
Maybe *I* need to change my batteries...

[rkf]

(05-23-2019 02:17 PM)burkhard Wrote:  Hah, I looked at mine again this morning and the time and date had reset! You jinxed me!
Maybe *I* need to change my batteries...

Now I took the 2.8V one home from work, and although today in the morning both DATE and TIME were still correct, until now both also became 1.012007, and zero. BATT still at 2.8V, but no more need now to swap them between calcs.

Time to buy four CR2032 now! :-(

[grsbanks]

(05-23-2019 02:49 PM)rkf Wrote:  Time to buy four CR2032 now! :-(

Make sure they're good quality batteries from a known brand. No-name Chinese el-cheapo batteries cause no end of problems with their usually high internal resistance.

[rkf]

Now I installed new sets of batteries (@grsbanks: by Varta, a renowned brand), both calcs show now a BATT value of 3.2V. And now both keep the time as expected!

What do we learn from that? When BATT level nears about 2.8V, the calculator ceases timekeeping. Calculators with IR diode drain batteries quicker than those without (I bought the one without from Eric Rechlin‘s site in Dec, 2013, thats 5.5 years from now, whereas the other one with IR is half a year younger, and ceased keeping time already in 2018).

Thanks to all who replied, and have a nice weekend for now!