HP41, N battery (N Cell), charging of HR1

[Erik-M]

(10-12-2020 07:16 PM)Dave Frederickson Wrote:  I must say the SkyRC MC3000 is the fanciest charger I've ever seen (Bluetooth, really?) and also the most expensive.

Yes it has bluetooth but I never used it because it has a USB connector and its supported by data explorer trough USB, http://www.nongnu.org/dataexplorer/.
Nice thing is that it runs on 12V so you can power it also from a solarpanel or car battery if needed.
It supports almost all rechargeable batteries except for 9V block so its used for all kind of batteries here.
Charging with 50 mA is a bit tricky because you don't see the voltage drop indicating the call is full, but I set the timer to 16 hours as indicated on the cell and that worked fine.
Made a few aluminium adapters on the lathe because the small cels just fit and I want the temp sensor to work (see topicstart )
They are in the calculator for 3 months now and still no low batt

[Dave Frederickson]

(10-12-2020 08:34 PM)Erik-M Wrote:  Charging with 50 mA is a bit tricky because you don't see the voltage drop indicating the call is full, but I set the timer to 16 hours as indicated on the cell and that worked fine.

One, at 50mA charging current (0.1C) I wouldn't expect the -deltaV circuitry to detect end-of-charge. The recommended minimum charging rate is 0.3C.
Two, the MC3000 has a Break-In Mode built in, so why are you manually timing charging???

Dave

[GVHOVE]

(10-11-2020 10:56 PM)Dave Frederickson Wrote:  Your charger appears to charge the 4 cells in series. Is that correct?

Yes ... 6V over the 4 batteries in series (have not measured the charging current yet).

(10-12-2020 03:56 AM)Wes Loewer Wrote:  "Replace" or "recharge" every year?

The whole reason I got rechargeable N's is so that I would never need to worry about leakage damaging my 41. I don't know that I have ever seen rechargeable batteries leak. I've got rechargeable batteries that are 12 years old in my class set of calculators at school.

Leak is not the correct word.
On 1 occasion I have seen a bit of greenish, foamy 'rash' on the + side of 1 of the batteries after what must be 50+ recharge cycles in the HP-41 I use with the card reader and IR-printer at home. My HP-41 at work never had any issues and usually will run on the same charge for weeks/months.
I now have 3 battery sets I rotate between the 2 machines, keeping 1 charged at all time, replacing the entire set if needed (better safe than sorry).

[Erik-M]

(10-12-2020 09:45 PM)Dave Frederickson Wrote:  Two, the MC3000 has a Break-In Mode built in, so why are you manually timing charging???

Could have done that but I didn't want to discharge/charge/discharge/charge * 16 hours. Just a slow charge the first time.