Will the Shimano BT-E8036 battery fit the Merida e-OneSixty 10K 2020 model which is fitted with the E8035? Ie do they share the same dimensions and mountings?
The BT-E8036 has the same dimensions as the BT-E8035-L (note the *L* suffix at the end). The original BT-E8035 is smaller so the bigger battery won't fit. So the short answer is no, but you have a second battery in the 2020 model that you didn't get in the 2021 version, which comes with a BT-E8036.