I'm running the V2 server (API v3) on a VM and I noticed that I no longer have access to the 12V battery history that used to be shown when I used the official public server. Is there an existing way to add this functionality to the self-hosted server or is it something that needs development (or just isn't possible)?
Which public server were you using? The api.openvehicles.com server just uses the standard v3 server code. Are you sure you have setup the database correctly? Historical data should be stored in the OVMS historical data table.