Be careful, your FL2 will have a lower signal voltage to its components as well as the main 12v supply.

As well as the 12v earth system, you may need to check that the various earthing points for the controllers signalling system have been damaged, some are under the carpets.




Some Useful Battery questions and answers.

https://www.quora.com/Why-are-there-12-vol...n-voltages FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)