A question about alternative power supply for hp41 series

[Dieter]

(02-27-2016 08:31 AM)wojtek Wrote:  ...10 year old Energizer with nominal capacity of 1800 mah and real probably less than 1000mah (I was afraid of damaging any of my eneloops).

You can avoid deep discharge by simply testing flag 49 in your program. If this flag is set, the 41's BAT annunciator comes on. You may check the voltage of your NiMH battery at this point to get the exact threshold. I once determined 4 V for a regular HP41 four cell battery pack.

Now imagine what you can do with a time module or a CX: store the current time at program start, check flag 49 at the end of each loop and if set exit, calculate the elapsed time and finally turn the device OFF.

Edit: A nice idea, but I just realized that this probably will not work here: If your DC-DC converter really provides 5,5 V even from an input voltage as low as 0,8 V this will not protect the battery from discharging to a level that is not recommended. But you may still find out at which input (!) voltage the 41 turns on its BAT annunciator. In other words: which input voltage of your DC-DC converter produces an output as low as, say, 4 Volts.

(02-27-2016 08:31 AM)wojtek Wrote:  Certainly if someone would like to apply such a converter to power the 41c it would be worth to invest in the newest eneloop of 2500mah capacity

These are the Eneloop XX/Pro with an extended capacily of typically 2550 mAh, but also with somewhat more self-discharge and a reduced number of charge/discharge cycles: 500 instead of 2000 (well, under perfect conditions in a smart charger). OTOH 500 cycles should be more than enough. ;-)

Dieter