I have a question to the electric experts.
I have read several times, that when reconnecting a battery cable and it sparks, that shows there is a problem with power drain or ground cables.

Here something I copied from a Chevy board:

"If there is a spark there is current draw. Use a test light, you can make one or buy one. Use a side marker of tail light with the connector. Disconnect the + battery cable and hook the two wires from the the light between the battery terminal and the cable. Start pulling fuses and disconnecting wires until the light goes out. When the light goes out you found the short."

Maybe some others can comment on this.
When I connect the battery on my grey 750 I have no sparks, but on the Highline it sparks a bit.
The grey one is my daily driver, no problem at all with power drain, the Highline is still under reconstruction and I can't say of any battery problems at the moment as the battery is always on a trickle charger.