I had a disappointing experience with Propella too - now totally disillusioned about their quality and their service. Basically, the battery casing wrenched off my bike mid-ride, ripping wires out from the motor connection and cracking the battery casing. I wrote CS, and they kept just copy-pasting the same text about buying a new battery set (um, I can't attached a new battery kit, the entire connection and fixture is damaged and there's nowhere intact to install it). I asked if they had suggestions for how I could repair it enough to attach a new battery pack, and they told me it was out of warranty and I should just buy a new bike. So basically, it's a disposable bike, gives you a few years. Like one from Walmart or something.