[Closed] Extending use red eyes ?

What core cable is a red eye rear light ?

Already have 2 long cable red eyes and the cables aint long enough , want to mount one at the rear of the back as my carradice covers the seatpost and my rack obscures the stays.

Can i simply cut the wire and extend and shrink wrap easily or is it more complex than that ?

Alternatively that can i use my piggyback battery to power the red eye or does it need instruction from the smart port to go ? ( i would try this but my piggybacks in the van in the garage being moted and serviced.)