These instructions apply to the Smart Fortwo Mk2 (W451) 2007-2015. For other models, please choose your vehicle here.
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Disconnecting the 12 V battery on your Smart Fortwo (W451, 2007–2015) — for a new battery, winter storage, or work near the airbags — is a straightforward job once you know where it lives. On the rear-engined Fortwo the 12 V battery is at the front of the car.
Find the Battery First
Because the engine is in the rear, the 12 V battery sits at the front, under the front service flap behind the front trim. Note your radio code and presets before you start.
Some mhd (micro-hybrid) Start/Stop versions also have an additional small battery — the main 12 V starter battery is the one you disconnect for normal work.
Disconnecting Safely
- Switch everything off, key to OFF, and remove it.
- Close all the doors and wait until the running lights go out.
- Disconnect the negative (−) terminal first, then the positive.
- Working near airbags or pretensioners? Wait a few minutes after disconnecting.
Reconnecting and Re-initialising
Reconnect positive first, then negative. The Fortwo then relearns a few items:
- Power windows — re-initialise one-touch (hold the switch at the limits).
- Re-enter the clock and radio presets.
- The service display settles after a short drive.
If Something Isn’t Right Afterwards
- Warning lights often clear after a short drive.
- A persistent light stores a code — look it up on autodtcs.com.
- Fit a like-for-like battery of the correct size and rating.
Frequently Asked Questions
Where is the battery on a Smart Fortwo W451?
At the front of the car, under the front service flap — the engine is in the rear.
Which terminal first?
Negative (−) off first, reconnect it last.
Does the Start/Stop version have two batteries?
The mhd micro-hybrid has an additional small battery, but you disconnect the main 12 V starter battery for normal work.
Do I need to recode anything?
Windows may need a one-touch relearn, and you’ll re-enter the clock and presets.
If a warning light stays on after reconnecting, look up the code on autodtcs.com.
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.
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