Recharge the calculator ??? No CR2032?

Discussion around the Swiss Micros DM42 calculator.
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mcc
Posts: 211
Joined: Fri Jun 23, 2017 3:10 am

Recharge the calculator ??? No CR2032?

Post by mcc » Thu Dec 21, 2017 5:06 pm

Hi,

Logan West put a video online:
https://www.youtube.com/watch?v=D5D7CcLP4kM
. In this video he talks about "recharging the calculator via the USB port".
I am a little confused...I thought a CR2032 is the powerhouse of the gem?!?

Please give me a deconfusion pill... :)

Cheers
Meino
DM 42 - SN: 00373, Firmware v.:3.14. / 3.14. as compiled by SwissMicros

grsbanks
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Location: Preston, Lancs, UK
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Re: Recharge the calculator ??? No CR2032?

Post by grsbanks » Thu Dec 21, 2017 6:09 pm

Now that depends on the calculator. Many high-end graphing calculators nowadays have a 3.7V rechargeable Li-ion battery inside them (HP Prime, TI-NSpire CX for example) and the USB port is indeed used for recharging that battery as well as transferring data.

The DM42 has no such rechargeable elements. It is powered by a bog standard 3V LiMn cell. If, however, you power the DM42 from the USB port then no power is taken from the CR2032 battery during that time. Nor is the CR2032 recharged. It is not a rechargeable battery and "bad things" would happen if you tried to recharge it.
Not SwissMicros staff, just an enthusiast.

elulis
Posts: 5
Joined: Mon Nov 27, 2017 8:53 pm

Re: Recharge the calculator ??? No CR2032?

Post by elulis » Thu Dec 21, 2017 6:10 pm

CR2032 is not rechargeable, Maxell datasheet says “Never charge”. So I believe the circle board has such a certain design to prevent the cell battery from being charged.

There is a rechargeable version of same voltage and size, its ML2032, with 65mAh capacity and a maximum 2mA charge and discharge current(up to 4mA is tested on the datasheet). When apply a 10% depth(6.5mAh) charge/discharge, it can circle 1000 times(or 30 fully depth circle). I dont think any one would like to charge their calculator 3 hours each day :D

mcc
Posts: 211
Joined: Fri Jun 23, 2017 3:10 am

Re: Recharge the calculator ??? No CR2032?

Post by mcc » Thu Dec 21, 2017 6:21 pm

Hi,

thanks for the informations and clearifications!!!

The video says "recharging the calculator" ...
Must be something like a "spoken typo" ;)

I am really happy that the DM42 is powered by a CR2032.
LiPos wear out over time and most of them are really
difficult to get as a replecement.

Cheers
Meino
DM 42 - SN: 00373, Firmware v.:3.14. / 3.14. as compiled by SwissMicros

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4ster
Posts: 6
Joined: Wed Dec 20, 2017 2:08 am

Re: Recharge the calculator ??? No CR2032?

Post by 4ster » Thu Dec 21, 2017 6:41 pm

elulis wrote:
Thu Dec 21, 2017 6:10 pm
CR2032 is not rechargeable, Maxell datasheet says “Never charge”. So I believe the circle board has such a certain design to prevent the cell battery from being charged.

There is a rechargeable version of same voltage and size, its ML2032, with 65mAh capacity and a maximum 2mA charge and discharge current(up to 4mA is tested on the datasheet). When apply a 10% depth(6.5mAh) charge/discharge, it can circle 1000 times(or 30 fully depth circle). I dont think any one would like to charge their calculator 3 hours each day :D
Does the DM42's memory remain in tact when changing the battery? I was thinking rechargeable batteries and a charger would be worth looking into. I use a smart charger and N cells for my 41 calculators, which works pretty well. But.....The reviews for ML2032 batteries are all over the place. I suspect that people are discharging them fully and getting poor life because of their relatively low charge rate and capacity. (CR2032 batteries are in the neighborhood of 240mAh to 2 volts as a comparison to the specs above.)

The CR2032 batteries are pretty inexpensive from good online retailers, with some shopping. It's not worth the hassle of recharging, except of course the added volume of electronics waste.
Steve
Acquired in order: HP 41CV, CMT MC-GPS, HP 41CX, DM41, DM42!

grsbanks
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Re: Recharge the calculator ??? No CR2032?

Post by grsbanks » Thu Dec 21, 2017 6:46 pm

4ster wrote:
Thu Dec 21, 2017 6:41 pm
Does the DM42's memory remain in tact when changing the battery?
Not for very long but you can do either of two things:
  • Plug the DM42 into a USB port while you remove the battery and insert the new one
  • Save the DM42's machine state before you remove the battery and then if the memory was cleared, you just have to re-load that machine state file
Not SwissMicros staff, just an enthusiast.

elulis
Posts: 5
Joined: Mon Nov 27, 2017 8:53 pm

Re: Recharge the calculator ??? No CR2032?

Post by elulis » Thu Dec 21, 2017 7:14 pm

4ster wrote:
Thu Dec 21, 2017 6:41 pm
But.....The reviews for ML2032 batteries are all over the place. I suspect that people are discharging them fully and getting poor life because of their relatively low charge rate and capacity. (CR2032 batteries are in the neighborhood of 240mAh to 2 volts as a comparison to the specs above.)

The CR2032 batteries are pretty inexpensive from good online retailers, with some shopping. It's not worth the hassle of recharging, except of course the added volume of electronics waste.
You are right, ML2032 is very “hard” to maintains.
ML2032 chargers on market usually has a exceed charging current about 10mA or more, maybe the factorys making them are thinking customers wont accept a 30 hours charge waiting time(with 2mA charging current), and datasheet says “Large surges of current could degrade the battery’s characteristics”.
Even with hand fine tuned charge circuit which can achieve 30x recycling discharges, a ML2032 cell only provides 10 times capability of CR2032 cell(30 * 65mAh compare to 220mAh) with ~5 times price. It might only be environment friendly or useful in the very heavy usage situation or ~2000mAh capacity could provide a lifetime support(like solar charged watches) :D

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