Adapting cell battery to HP 41

[Artur - Brasil]

Hi, guys!

Last week I concluded my plans to adapt a cell phone battery to my HP-41.

Using just a small 850mAh battery, one small charger board, another small step-up board and it's done!!!

The circuits themselves use only 85nA;
The HP in standby mode I think something around 1mA.

So, I believe 850mAh/1.085mA --> 780 h --> 30 days in standby mode!

Red - charging
Blue - charged.