The Magnuson–Moss Warranty Act of 1975 ensures that’s not the case in the US. I suspect something similar is true in EU.
For the manufacturer to avoid a warranty claim due to a modification or aftermarket part, they must show that the defect was linked to the part or modification.
They might have to show that it was caused by, but in any case, if your paint fails prematurely, they can’t say your warranty is void because you disabled the cell connection.