60 miles with a kit bike is a lot easier than with a store-bought bike, because you have the freedom to add more battery. You don't have to do it with one big battery, but can do it with two. That allows you to carry just one for shorter trips, and not have an extra 5-6 pounds to store on the bike.
Here's two 48V batteries I own, rated at 14AH and 15AH. Those are marketing ratings based on running very light loads. In real life, I would derate with the heavier draw of an ebike motor, to about 12AH each. That's still around 550 watt-hour, and I estimate most riders could get 40 miles out of each on flat ground, with wind, because I have. For hills, I don't know. Put one on the frame of the bike, and carry the second on top of the rear rack when needed.
How far you go depends on your speed too. I'm basing my estimates at 12-14 mph with some rider effort on the pedals. COld weather hurts too. Probably lose 15-25% of capacity when it's freezing,
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