If the iPhone XS can only be charged to 97% but not fully charged, this reason is most likely because the health of the battery has declined to a certain extent, leading to dissatisfaction with charging. There are several reasons for this situation, possibly because the activity of the lithium battery is decreased due to overheating during charging. It is also possible that frequent power loss leads to reduced activity of lithium batteries. These two situations are relatively harmful to lithium batteries, which will lead to a decline in battery health and dissatisfaction with charging.