I can't help with your main problem, but I do have a couple of comments. The double wrench maintenance due symbol should be able to be reset just like the single wrench one. I'd sure check the 12v battery if it is original. Very few code readers work on our Smart electrics. Hopefully someone will chime in with a reader that works for you/us.
Is your car still mobile with your 40% charge?
Len
2014 EV Coupe 20,500 miles
2014 EV Cabriolet 19,500 miles
Is your car still mobile with your 40% charge?
Len
2014 EV Coupe 20,500 miles
2014 EV Cabriolet 19,500 miles