Disconnect and Reconnect the Battery

Last updated: June 12, 2026

Disconnecting the 12 V battery on a Hyundai Bayon (2021–present) is a simple engine-bay job. This guide covers safe disconnection and what the car needs re-taught afterwards.

Where the Battery Is

The 12 V battery sits in the engine bay, behind a cover. The petrol and 48V mild-hybrid Bayon keep the 12 V battery here — only the small 48V unit on the mild-hybrid is a specialist item.

Disconnecting

1. Switch the ignition off, remove the smart key and wait a minute for the electronics to sleep.
2. Disconnect the negative (−) terminal first and tuck the lead aside.
3. If removing the battery, disconnect the positive (+) next, then the clamp.

Reconnecting & Re-teaching

1. Reconnect positive (+) first, then negative (−) last.
2. Reset the clock; the radio usually reloads on its own.
3. Re-initialise the one-touch windows — see our Bayon window guide.
4. If your car has a sunroof, it may also need re-initialising.

The Bayon doesn’t need the battery coded.

Frequently Asked Questions

Which terminal first on the Bayon?

The negative (−) first, and reconnect it last.

Does the Hyundai Bayon battery need coding?

No — just fit it and re-teach the windows (and sunroof if fitted).

Will I lose my radio?

No code is normally needed — just reset the clock.

Why won’t my windows auto-close now?

The power cut cleared their learned position. Run the quick re-initialise.

For any warning light that stays on, look up the code on autodtcs.com. To clear the service reminder, see our Bayon service reset.