Hi,
I recently added a new battery to my ebike. My old battery has 17 Ah and the new one has 15,5 Ah (both 36V). I connected them in parallel with the following diode in between: https://www.aliexpress.com/item/33043341733.html?spm=a2g0s.9042311.0.0.357a4c4d18na71
Everything works fine, but...