A question about alternative power supply for hp41 series

[Artur - Brasil]

Just converting your words (I really would like to use HP50G solver):
t - time of continuous work [hours]: what we want to know
Cbat - battery capacity [mA.h]: let's say 2000mAh
Eff - converter efficiency [%]: 90%
Vbat - battery voltage [V]: 1.2V
Vcalc - operating calculator voltage: 6V
Icalc - operating calculator current [mA]: 10mA

So, using the solver for hp50g...

t[h] = Cbat*Eff.Vbat/(Vcalc.Icalc.100)

t = 36h of continue work;

Not bad, as I won't use it for so long time at once. Let's say, 1 hour daily -> easily 30 days.
Being less confident in numbers, I would say recharging battery once a week. Not bat, at all....

This if we don't put two AA batteries inside the battery holder - my mistake: really forgot to measure it yet.
And remember, we have stronger cell phone batteries available too.
   
Beyond calculations, what I really would like to express is this simple point: N cells here are difficult to find; I have some rechargeable, but thery are always depleted when I need them - and the charger is hard to find too... AA battery is easy to find (ready to use 1.5 alkaline or 1.2 NiMH, also easily chargeable).
so, its a question of hard x easy and also a new project to keep my mind occupied with something positive.