Disconnect and Reconnect the Battery

Last updated: June 6, 2026

On the BMW 2 Series (G42, 2021–present) the 12 V battery isn’t under the bonnet — it lives in the boot, under the luggage floor. Disconnect it in the right order and your settings come back cleanly.

Where the Battery Is

Open the boot and lift the luggage-compartment floor panel. The 12 V battery sits beneath it on the right-hand side. There is a remote jump-start positive post in the engine bay (marked +) for boosting, but the battery itself is in the boot.

Disconnecting

1. Switch everything off, remove the key and wait a couple of minutes.
2. Lift the boot floor, fold back the cover and slacken the negative (−) terminal first; move it clear.
3. Release the positive (+) clamp only if you’re removing the battery.

Reconnecting

1. Fit positive first, then negative, and tighten both firmly.
2. Switch the ignition on, correct the clock, then start.

A Note on Mild-Hybrid Models

The 220d mild-hybrid has a separate 48 V system — leave that to a workshop. The owner-serviceable 12 V battery in the boot is what’s covered here; never touch the 48 V components or their cabling.

Afterwards

Reset the clock, re-store your tyre pressures, and note the CBS clock needs to be right before any service reset.

Frequently Asked Questions

Where is the battery on a BMW 2 Series (G42)?

In the boot, under the luggage-area floor on the right; a jump-start + post is in the engine bay.

Which terminal first?

Negative (−) off first; positive (+) on first when reconnecting.

Does a new battery need coding?

BMW recommends battery registration so charging matches the new battery — the car runs without it, but registering preserves battery life.

Is it safe on the mild-hybrid?

The 12 V job is fine; never work on the orange 48 V cabling — that’s a workshop task.

This is a common job. If a fault light stays on afterwards, check the code on autodtcs.com.