So, I want to try and build a charger for alkaline batteries with an Arduino. I'll be using it to recharge 9v batteries. What I want to know is: What would the optimum charge current/voltage be? Should I pulse the charge current? How do I detect the state of charge? How can I get ~1.6v from the arduino to charge an AA? Can I use PWM 5v? And any other useful info you may want to add. I have a ton of parts/shields/etc for arduino as well as components. LCD's, IC's, LEDs, diodes, resistors, crystals, etc. Would also like to do a battery diagnostic utility to test health, resistance, charge, etc. Can anyone help? EDIT: So I made a quick circuit and sketch to charge an AA battery to 1.6v, using an LM317 adjustable voltage regulator. As os so far, it is working. Now I need to figure out how to make a voltage doubler. I'm thinking something like 40-50 mA output at 10v. I have an LM324N quad op amp chip as well as one of these. How could I make a doubler circuit?