Well, MG Motor ZS EV hasn't completed even a single year since it has been launched neither we have been reported such issue yet. Also, we too do not expect such problems with it. However, you may claim its warranty if you face such issue.
The battery of MG Motor ZS EV is not portable and can't be removed from the case to charge it separately. One has to park the car near to charing station or socket to get the battery charged.
Most manufacturers have a five to eight-year warranty on their battery. However, the current prediction is that an electric car battery will last from 10 – 20 years before they need to be replaced.