It's been requested so here it is, the electronics behind my Seele Schneider.

The LED string comes from a Master Replicas Lightsaber.
I bought 2 of them from a website that does Lightsaber conversions and so had surplus stock.

The top left picture shows how the LED string came, with all the wires cut.
The next step was to use a multimeter to check the resistance across different the different wires, this took a while.
I found that all the LED sections had a common + positive terminal, which actually had two wires, one on the back (dark blue) and one on the front (purple) with the rest of the wires. So I cut off the spare one on the back.
As I don't have the electronic board to be able to light the LEDs in sequence to make the blade seem to grow from the hilt I deceided to combine all the - negative terminals.

I soldered a switch across the + positive wires and combined the two battery blocks in series. See top right picture.
You can also see from the picture that I wired in connectors so the LEDs could be disconnected and reconnected, but when it came to construction that there wasn't enough space in the hilt so I later cut this off.

The bottom picture shows the electronic setup with a foam difuser over the LED string, which they came with.