Same bike, different years so different battery. The problem bike is a 2018 Radmini. It first shut down last year when going up a steep, nasty road called Lone Frank Pass. We turned around and went back down the road. The second time was on a just about as bad road and also a pass. We again turned around. It happened this year on another, smoother grade. About a half mile up, the bike quit. She called Rad and they sent a new controller. We installed that, then returned to the last road and the bike quit again, at the same place. Rad sent a new rear wheel with motor. We put that on and tried it on our now a test road. It conked out at the same spot. This time we stopped for a couple of minutes, the bike turned on and we went on up. The rest of the road we rode on was not as steep.
I have a 2017 mini with a different style battery. It just chugs right along up the hills.
Oh, and we both were pedaling in second gear on the third and fourth power levels. Today was cooler than the previous days we tried the hill. The controller did not feel hot today. We have no idea but suspect they'll want to replace the battery next. The new motor is noisier than the original motor.
That is the conundrum. Her bike is now called, Lemonny.