charged battery- now no crank
 

I recently thought my battery was bad, so I took the battery out of the 04 mini to charge..after charging, reinstalled..now no crank..just a humming noise from engine bay..after 2 days of same issues..towed to mechanic..mechanic calls and says mini started right up..no problems..he does diagnostic..starter good- battery good..I get the mini back next day, drive 20 miles to play golf..after golf same issues..no crank , same hummining noise..towed to mechanic again..right off the tow truck, mini starts up normally..is this issue with car computer ?

Is he hundred percent it's not the starter it could be an intermittent fault and when he had the car the starter was performing OK so it would show as fine? When it doesn't start try bump starting it (get someone to push it have ignition on, car in 2nd gear with foot on clutch then as the person pushing gets some speed let your foot off the clutch and if it starts you know its either starter/solenoid or wiring fault (most common thing would be starter solenoid sticking or a bad earth)

04 Mini Cooper S
 

the fix for this problem was almost idiotic in nature...it was the battery in my key that was low in power...thus not sending a signal to the starter to start the car..the mechanic thought the same as you and I..they swapped out starter motor and same problem..so they put my starter back in..we checked relays..ignition switch..they had my car for a total of 10 days befor they figured it was the FOB key battery..