Communication between two Bluetooth devices
I mean, you could use something like a BT 4.0 beacon mode to broadcast information, but really: shouldn't you be pairing?

From an application point if view, wouldn't it be pretty bad if just anyone in the vicinity of your bike could update the battery calibration? They could essentially reduce the usable battery to nearly nothing, I.e. brick your bike, without even touching it, if you don't build in some constraints on who and when can interact with the battery controller via Bluetooth.

A Bluetooth pairing is exactly that: making sure you're talking to the right partner.

I imagine this would work like the following:

Since the service guy would need to have an electrical connection to the bike for measurements, anyway, normal Bluetooth pairing happens, initiated by bike firmware. The secret pin exchange necessary for that happens through a one wire (twi) bus or similar when plugged into the measurement device.

That way, an attacker would at least have to have physical access to your bike to brick it