I think I’m about to buy a Velotric T1 ST Plus which would be my first ebike.
The manual says to store it indoors at a temperature of 50°F to 77°F (10°C to 25°C). However the location I actually have to store it in is in an uninsulated shed that will probably reach 120ºF (50ºC) in the summer in baking sun, and below freezing in the winter.
Is this going to kill the bike or its battery?
Don’t charge your battery at extreme temperatures (freezing or roasting) and consult your manual about safe operating temperatures.
I can tell you when it is freezing, your battery will definitely suffer depleted range. If you operate it in extreme temperatures, bring the battery back inside and allow it to return to a safe temperature before you attempt to recharge.
These are partly why I ended up ditching my ebike in favor of a regular bike most of the time: It’s just less to manage and stress about. My legs work at any temperature and won’t burst into flames (though sometimes when I am tired or too beat up, I wimp out and take something that has its own power).