Normally chargers exchange between 30 and 100 MB of data per month. Amount of exchanged data depends on charger configuration and operator manipulations.
* if charger is configured to send measurements during charging very often, then this will reflect on higher traffic (specially if charger will be often occupied),
* if operator is often requesting detail diagnostics, then charger transfers a large amount of data (depends on log details) in a form of files to the central system. Depends on log level and time span, log files size can be up to couple MB.
* if operator often triggers firmware update, then charger has to download firmware file from central system. Depends on vendor, firmware file size could be from 1MB to 40MB. Firmware update is normally executed less than once per month.
Min. recommended bandwidth is 50kb/s. Most critical is firmware update. With this speed firmware update file with size 30MB would be downloaded 600 seconds.
Most of the modern chargers are using OCPP 1.6 JSON protocol. This protocol is based on websockets. Websockets are keeping TCP connection alive. Therefore another important parameter is stability/persistence of the connection.