These instructions apply to the Smart Forfour Mk2 (W453) 2014-2021.
For other models, please choose your vehicle here.
Disconnecting the 12 V battery on your Smart Forfour (W453, 2014–2021) — the four-seat city car built alongside the Fortwo and sharing its Renault-developed platform — is a job you will meet for a new battery, winter storage, an electrical repair, or before working near the airbags. It is a straightforward task once you know where the battery lives, and taking the terminals off and refitting them in the correct order lets the car power back up and relearn its settings cleanly. Like the Fortwo, the Forfour is rear-engined, so the 12 V battery is at the front of the car.
Where the 12 V Battery Is
The engine sits in the rear, so the 12 V battery is at the front, under the bonnet/front service flap behind the front trim. Open that panel and the battery will be under a cover or clamp. Identify the posts before you touch anything: the negative (−) terminal is the earth, usually with a black cap or lead, and the positive (+) terminal is the live post, marked red and normally hidden under an insulating cover.
Electric drive (EQ) models: these have a separate high-voltage system — never touch the orange high-voltage cabling. The 12 V battery is still the one you disconnect for normal work, just as on the petrol car; the high-voltage side is not an owner job.
Before You Begin
- Make sure the car is fully off — ignition off, and on an EQ not in READY — with the key out and away from the car.
- Switch everything off: lights, climate, heated screen, radio.
- Note your radio code if the head unit uses one, along with your presets.
- Give the electronics a couple of minutes to power down after switching off before you loosen a terminal.
- Have the correct spanner ready and wear gloves and eye protection.
Disconnecting Safely
- Switch everything off, key to OFF, and remove it.
- Close all the doors and wait until the daytime running lights go out, so the car has gone to sleep.
- Disconnect the negative (−) terminal first, then move the lead clear of the post.
- Now disconnect the positive (+) terminal and cover or move it clear.
- Working near airbags or pretensioners? Wait a few minutes after disconnecting before you start.
Reconnecting
Refit in the reverse order — live post first, earth last.
- Refit the positive (+) terminal first and snug the clamp.
- Refit the negative (−) terminal last and tighten it.
- Check both clamps are firm, refit any cover, and give the car a minute before switching on so the modules boot in sequence.
What You’ll Need to Reset Afterwards
Cutting the power clears a few short-term memories. On the Forfour that typically means:
- Clock and radio — re-enter the time, your presets, and the security code if the head unit asks.
- Power windows — re-initialise the one-touch function by holding the switch fully up at the limit, then fully down and back.
- Service and TPMS — these displays settle after a short drive once the sensors have reported in.
- Warning lights — a passing ABS or stability light usually clears itself once you have driven a short way.
If Something Isn’t Right Afterwards
- Recheck that both clamps are tight and squarely seated.
- Take a short, steady drive so the electronics can relearn and self-clear.
- Re-do the window one-touch setup if auto-up or auto-down has stopped working.
- Rule out a genuinely flat or worn-out battery that will not hold charge.
- A persistent light stores a code — look it up on autodtcs.com.
Frequently Asked Questions
Where is the battery on a Smart Forfour W453?
At the front of the car, under the bonnet/front service flap behind the front trim — the engine sits in the rear, so the battery is up front.
Which terminal do I take off first?
The negative (−) terminal comes off first and goes back on last; the positive (+) goes on first when reconnecting. That order avoids shorting the live post to the body.
Is the electric Forfour different?
The EQ has a separate high-voltage system — don’t touch the orange cabling. You still service the same 12 V battery, in the same way and the same order, for normal work.
What will I need to reset afterwards?
The clock and radio presets (and any code), the one-touch window function, and the service and TPMS displays, which settle on a short drive. Any passing warning light usually self-clears too.
Do I need to recode a new battery?
A like-for-like 12 V battery of the correct size and rating normally just fits with no coding. Match the type the car was built for and let it settle a few minutes before starting.
Can I jump-start it instead of disconnecting?
If you only need to get a flat car going, a jump-start keeps your settings and is fine. Disconnect properly only when the battery genuinely needs isolating — for renewal, storage, or airbag work.
If a warning light stays on after reconnecting, look up the code on autodtcs.com.
Independent guide — not affiliated with Smart. Always follow your official service manual and safety precautions. Read our full disclaimer.