Not trying to be condescending here but at 1:50 in this video it shows how it's done...just so we can rule this out. My neighbor also has one of these on his cargo bike which can be a little tricky sometimes to get it on just right as he also has a tight squeeze to get it on there. Also Bosch has a very good customer service site you can ask questions on and they have a very good replacement warranty plan if something is not working properly. Batteries & chargers – Help Center - Bosch eBike Systems