Mine is more preventative, my wife does lots of short trips so I hooked my charger to it and it read 25%
so I left it for a while and it only came up to 50%
I left the charger on but I had to go out of own for work so I will have to ask my wife what % it showed in the morning.
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X5M, Eisenmann exhaust, 22" HRE wheels, catless down pipes, Stage II tune/X5 Diesel, Lowered & Tuned