Biohazard famicom repro, help needed

Hello!, first, sorry for the bad english, i want to do a Biohazard repro, is a bootleg game for the famiclone, my questions are:
_Its posible to change a mapper for another?, i have two roms, one in 015 mapper and another in 227, the only posible donor i found is the Contra 100 in 1 multicart, but the pcb has not battery.

_How i can add a battery on the pcb?

Thank you for your time

Mapper hacks are possible in theory, but you have to go through the whole program and change every place it writes to the mapper.

And that's obviously assuming that the target mapper is equivalent or superior to the original mapper.

Bio Hazard on mapper 15 will not work. BioHazard should not be assigned mapper 15 as it hangs on it, due to difference in banking. There is fixed version on mapper 227 (there difference is NOT only assigning other mapper number). If you want PCB for mapper 227, contact me on PM.