It is recommended to use a storage battery charger like a Victron Smart IP65 4A, it can be left on the battery during these 4 weeks. a Nice feature of the charger is that is has Bluetooth built in so you can use your smart phone to monitor the status of the battery using VictronConnect, a free app used for Bluetooth enabled Victron products.
Disconnecting could be a solution but you might have a tracker that needs to report.
A battery will self discharge if left connected, if disconnected it will have to be looked after by means of charging, here you need a charger with a storage mode as described above.
