I bought a 2014 or 2015 Kalkhoff (with impulse 1 motor) and I bought two new batteries (one for home, one for workplace) before I realized that the motor has a problem. So now I have 2 impulse batteries for sale. I am not sure if I should give up on repairing the bike, so I am selling one of the batteries now . Asking 400 for the 11 Ah. I also have a 17 Ah battery but I will sell it later. (feel free to offer for the 17 Ah, in which case I will keep the 11 Ah until I decided to sell all the parts).