Vintage Synth Repair

Hi,

I own a Roland Tb303. Analogue Solution make a mod :

    * Lithium battery for at least ten years battery backup, so there is no
need to install C-cell batteries.

Does anybody know how to make this mod? I will be very happy to know how to
make this mod... It would be heaven if my Bass Line could save the presets
when I switch it off...

Let me know.....

Best Regards !

@lexandre