My battery is flat on my quattroporte. Happened before last year. Couldn’t start it from engine and AA came and used the points in the boot to charge it. Everything I see on YouTube and in manual says to use engine but aa guy said it wasn’t powerful enough. Problem is (as in the engine where there seems to be no negative point) it’s not clear where to attach the +ve and -ve cables. Can anyone help ? Thanks. I’ll attach pic of batttery in boot