Thanks, yes I see what you mean.
I'm stuck with this one bike, but I have a pretty good idea that it will work at low speed / low cadence if I just use it as a manual bike with the motor turned off entirely, which I should be able to do if I get the lighter battery.
That way I can keep the motor for when I am on the longer roads that aren't all stop-start.
I'm hoping to get to the bike shop later in the week and I think they will let me test the smaller battery there. I think that should help a lot.
I will report back when I have tried that. Thank you for your help and for listening to me thinking out loud about all this. It is really helping.
Just one last thing: Since you're stuck with this bike now, I
strongly recommend working on that cadence — preferably with the feedback of a cadence meter. Even 60 rpm would be much better than 40 rpm, and in the long run, you might find it better for your legs as well — especially your knees.
If your Gazelle's display can't be set up to show cadence, maybe the Flow app can. There are also plenty of inexpensive alternatives. The bike shop can help. On my hub-drive, I use a $20 IGSport Bluetooth cadence sensor from Amazon. It straps to one crank. Readout is via the RideWithGPS app runing on my handlebar-mounted phone.
You might find RideWithGPS useful for many other things, including ride recording and navigation. It'll even record your cadence to help you track your progress. The free version will probably suffice for your cadence training, but I find the premium version worth every penny.
Just take your time and push your cadence by a few rpm at a time, briefly every day. Try pedaling as smoothly as you can with each attempt to improve the muscle coordination. As you practice, visualize the success — you cruising around Cambridge on your beautiful Gazelle with a big smile on your face and none of the fuss you've experienced so far.
You might be surprised at your progress.