Some help please: Personal Power plant

Hi i'm new to these forums and i have a few doubts to clear.

I want to make this project which was up in instructables,

personal powerPlant

I want to make a few modifications to it and i want to know if it's plausible

1) Attach a spring coil to the crank so that i need not keep cranking all the time.

2) Place a 8~9v zener diode in parallel with the battery to prevent over voltage.

Also can i use five 1.5V batteries in series instead of a single 7.2V battery; Will it affect the performance?

Thanks!