hi andy 2 small points no 1 never leave a battery charging on your car with the batt conected subarus dont have over load protection, you could fry your alternator as well as some control units no2 AS A RULE NEVER JUMP START A MODERN CAR UNLESS YOUR JUMP LEADS ARE VOLTAGE PROTECTED ///////SURGE PROTECTED better go by this method for safety recharge battery or change battery, make sure you have all things switched off in car to prevent voltage surge damaging alternator ,lights, again control units .i see damage every day in my job with mercedes you cant be too careful . remember to check that polarity is correct if charging out or in car if you charge it with wrong pol/ when you conect it up BANG fried every thing. seen this done before it costs loads of money to repair lastly get battery tested m8 hope this helps geo