A question about alternative power supply for hp41 series

[wojtek]

(02-24-2016 05:26 PM)Artur - Brasil Wrote:  Wow! 5.5V from 1.5V is great!
About the ripple, I believe you should try a bigger capacitor - 10uF is too low.
If at calculators power off state the converter doesn't work, what to put a resistance that keeps the current around 100uA? Do you believe this would dry out the battery?

In fact it gives 5.5V out of 0.8V, enough to use badly dried nimh accu. It is from a telephone backup power source.
As for a resistor to keep a small load in case the converter won't start it certainly would dry the battery sooner. But just count, on average 1800 mAh for a single nimh accu would give 1mA for some 500 hours till the voltage drops to some 1V from 1.2V. With 100uA the accu would last for 5000 hours or 200 days. So perhaps it would not be so bad.
But, this quick calculation does not allow for the self discharging of the accu and efficiency of the converter. So the real values certainly would be much smaller (with the efficiency of some 25%, what seems to be reasonable, we would get 50 days instead of 200 what still would be good enough to consider).