The battle mechanics are much like Gyms and Raids and have a four minute timer. Here, you tap to use your Fast Move which also charges up your Charge Moves. When the Charge Moves are charged up, you can then select to use the Charge Attack. When this is selected, in a change to the Raid & Gym system, the battle stops and the player attacking can tap repeatedly to do more damage with the Charge Attack. Meanwhile, the Defending Player can choose to use a Protect Shield which prevents any damage done to it from the attack. However, each player only has a finite amount of Protect Shields that they can use each battle.
As always, players also have a choice to switch out in the middle of battle, to bring in a more suitable Pokémon.
When all three of either player's Pokémon is knocked out, or the match timer ends, then the winner is declared based on remaining Pokémon and remaining HP.
Weather boosts do not impact Trainer Battles and all Pokémon are fully healed after battle.