Check "EV battery replacement" post there is lots of info. I bought the car and the dealer said he bought a Charging cable from Ebay and it did not charge the car. I looked at EQpassion for info. I dropped the Traction battery and removed the 12Volt battery. Both where dead. 12 Volt battery needed a healthy charge and the 3 banks in the traction battery where down at 10 Volts. I made a charger out of an adjustable transformer, rectifier capacitors and some gauges. I charged the traction battery carefully with low current to 3.2 volt a cell. it took week or more charging let it settle checking the individual cells . Now the gauge in the car showed a charge but it did not drive. I bought an AUTEL MaxiDiag MD806 Pro OBD2 reader from Amazon and it reads the Smart car electrical error code and cell voltages. I put the error code here in the forum and on the EQpasssion forum. I had the dreaded P15081C bricked battery code. I paid $500 on EQpassion for reprogramming and an extra $50 so the code does not come back. Moritz told me where to send the BMS. Then I bought for another $500 the current sensor. As I had been told, when the 12 volt battery goes low, a DC/DC converter in the BMS cannot regulate the output voltage and destroys the current sensor. Moritz had some in Germany and sold me one. After I got everything back together the car drove again. But still displayed the error on the dash. I bought an OPENPORT 2.0 OBD2 to USB and Jochen logged into my laptop and deleted the error on my dash. Now the car runs. It is my weekend car. When it was fixed in spring it showed 70 miles on a charge, now I am down to 40miles per charge. I think it the cold weather and my driving style. I have a friend she live 25 miles away and I make it back with 20% left on the charge. I am happy with the car.