My battery was only 3 years old, but in the morning the heater ran several times only about half an hour instead of the possible 50 minutes. On Tuesday we had -4 degrees, that also occurred again. I then drove 30 km without light (mainly highway), turned on the heater again and visited a customer for a short time (about 15 minutes). When I came back, I sat back (to prepare documents) and switched on the seat heating, the switch bli However, it was only possible and the heating stopped shortly afterwards. As I will drive almost 2500 km over Christmas/Silvester (incusiv Poland and the Czech Republic), there is also a week’s service life at frosty temperatures in the ski area, I bought a new battery from MB and installed it there in front of the door. Of course, I took the advice from the forum into account and turned on full light with fog lamps to avoid damage. Current price is 218 €, an other I didn’t want to, because I have good experience with MB batteries so far. MB tested my old battery and called me today. They could not detect any errors, however, they had only a rough test done. On their device “defect”, “charge” and “in order” (or so similar) is displayed. Today we also had -2 degrees. My own test with the new battery was successful. I ran the preheating again during a customer visit, afterwards reing esett (without engine run) and all 4 seat heaters switched on over several minutes, no failures. So the new battery has significantly more reserves. I was perhaps a little overcautious, for this I now have the good feeling that the battery will probably not let me down at an unfavorable time in the near future. lg Rüdiger:-)