Architectural Diagram for EV charging Station

There are a couple of things I would consider if this is a greenfield (brand new) development:

1. For the mobile application, go serverless and use API Gateway as your front-end and Lambda/Step Functions to take care of the API's. You can scale this solutions to millions of requests with little to no effort, plus it removes your need to manage all of those EC2 nodes.
2. For the charging station, again consider using AWS IoT services to facilitate the communication. You can easily control the stations, as well as gather metrics and report against those all within the IoT framework.

Here is a case study that is similar to what you are proposing that uses the services I mentioned above: https://aws.amazon.com/solutions/case-studies/easee-case-study/