Pandora's Battery [Creation]

Ok, so,I reada few tutorials. Theres only one thing they NEVER made clear. It stated tha you need an (old) battery and NOT a new one. Ok. so.

What I want to know: Can I go out and buy an old battery and create a pandora's battery out of it using a psp slim?

(Also, my psp slim has version 4.00, not homebrew, if it was brewed, why would i want to make this?)

Also, can i update to homebrew v4.01 from non homebrew 4.00? If so, whats the chances it bricks? (I don't want a very high, 1 in 3? Or a % rate)

Thank you.

Don't mind that. Any battery will do.

Use your current battery if you want.

OFWs(Official firmwares) can't run homebrew. Pandoras flash a CFW(Custom Firmware).

0% chance of a brick, As an OFW(Higher than 1.50) won't even read the installer.