Well ..... Misjudged a yump in the road which compressed the rear wheel so far that the tyre tore out the under tray which is where the battery was living, it then somehow found its way to the road under the back wheel and exploded into many pieces
Had to push the bike 3 or 4 miles home... was quicker than waiting for recovery
Anyhow battery didn't work after that hence the 1 failure
Is the short answer