These instructions apply to the Mercedes CLA Mk2 (C118) 2019-Present. For other models, please choose your vehicle here.
Last updated:
The Mercedes-Benz CLA (C118, 2019–present) has a main 12 V battery plus a small auxiliary battery. This guide covers the main 12 V battery — the one you disconnect — and where to find it.
Where the Batteries Are
- The main 12 V battery is in the engine bay, in the rear corner on the passenger side near the bulkhead, under a rectangular plastic panel you lift off. This is the one you disconnect.
- A small auxiliary battery lives in the cabin (passenger side, under the floor carpet near the cabin filter) — a separate low-current battery you don’t normally touch.
- On the plug-in hybrid CLA 250e, keep clear of the orange high-voltage components.
Disconnecting the Main Battery
- Switch everything off, take the keyless remote out of range, and wait a minute.
- Lift the cover, then disconnect the negative (−) earth first.
- If removing the battery, disconnect the positive (+) next, then the clamp/vent.
Reconnecting & After
- Reconnect positive (+) first, then the negative (−) last; refit the cover.
- Reset the clock; MBUX reloads on its own.
- Re-initialise the windows and, if fitted, the sunroof — see our CLA window guide.
- A new battery should be registered to the power-management system with a diagnostic tool.
Frequently Asked Questions
Where is the battery on a Mercedes CLA C118?
The main 12 V battery is in the engine bay, passenger-side rear corner under a panel; a small auxiliary battery is in the cabin.
Does a new CLA battery need coding?
Yes — a new main battery should be registered with a tool; a quick disconnect/reconnect of the same battery doesn’t.
Why disconnect negative first?
It removes the earth path so a tool touching bodywork can’t short the battery.
Do I need to touch the auxiliary battery?
No — for normal disconnection you only deal with the main 12 V battery under the bonnet.
For any warning light that stays on, look up the code on autodtcs.com. To clear the service reminder, see our CLA service reset.
Disclaimer: The information on this page is provided for general guidance only. Always follow your official service manual and safety precautions when working on your vehicle. We are not responsible for errors, omissions, or any damage resulting from the use of this information.
This website is an independent resource and is not affiliated with, endorsed by, or sponsored by Mercedes. All trademarks and brand names belong to their respective owners.