Disconnect and Reconnect the 12V Battery

Disconnecting the 12 V battery on your Seres 3 (2021–2024) — the electric SUV — is a job you might do before winter storage, ahead of bodywork or electrical repairs, or when you need to work near the airbags. It is also the first step in reviving a car that has been left standing with a drained low-voltage battery. On the Seres 3 this task involves the 12 V low-voltage battery only. The high-voltage drive battery that powers the motor is sealed, managed by its own system, and must never be touched. Done in the right order — negative off first, positive on first — the car wakes back up and relearns its settings cleanly.

Where the 12 V Battery Is

On the Seres 3 the 12 V battery sits in the engine compartment, under the bonnet. Because this is a fully electric SUV, that space houses the low-voltage electrics and the battery rather than a combustion engine, and the battery may sit under a plastic cover or trim panel that lifts away. Once you can see it, identify the two terminals: the negative (−), marked with a minus symbol and normally a black lead, and the positive (+), marked with a plus and often protected by a red or coloured cap. Confirm which is which before loosening anything — the order you work in is what keeps the job safe.

High voltage warning: the bright orange cabling and connectors belong to the high-voltage drive system. Never touch, cut, or unbolt anything orange. This whole procedure concerns the 12 V battery and nothing else.

Before You Begin

• Make sure the car is fully powered off — not in READY mode — with the doors closed so the electrics settle.
• Take the key fob well away from the car so it cannot wake the systems.
• Switch off the lights, climate, and any accessories, and unplug anything from the 12 V or USB sockets.
• Note down your radio security code (if the car uses one) and the clock setting so you can restore them afterwards.
• Wait a couple of minutes after shutting down so the control modules power down before you disconnect.
• Wear gloves and eye protection, and have the correct spanner ready for the terminal clamp nut.

Disconnecting Safely

1. Power the car fully off and wait a couple of minutes for the modules to sleep.
2. Open the bonnet and remove any cover so you can reach both terminals.
3. Slacken and lift off the negative (−) terminal first, then tuck the lead aside so it cannot spring back onto the post.
4. Next slacken and remove the positive (+) terminal, and cover the exposed post so it cannot short against bodywork.
5. Working near the airbags? Wait a few minutes more after disconnecting before you begin, so any stored charge in the restraint system has bled away.

Reconnecting

1. Refit the positive (+) terminal first and tighten its clamp until it is secure.
2. Refit the negative (−) terminal last and tighten it the same way.
3. Check both clamps are firm — a loose terminal causes flickering warnings and a car that will not wake properly.
4. Allow the car a minute to wake fully before you power it up and drive.

What You’ll Need to Reset Afterwards

Cutting the 12 V supply clears the short-term memory in several systems. On the Seres 3 you may need to sort out:

• Clock and date — reset the time, and re-enter the radio security code if the audio system asks for it.
• One-touch windows — if a window loses its auto function, hold the switch fully up at the top limit to relearn it, then repeat at the bottom.
• Driver settings — some display or comfort preferences may return to default and need setting again.
• Warning messages — a few dashboard alerts appear on first power-up and self-clear once the car has been driven a short distance.

A straightforward like-for-like 12 V battery of the correct type and rating does not normally need any coding on this car.

If a Warning Light Stays On or the Car Feels Off

• Re-check that both terminal clamps are tight and clean — a poor connection mimics an electrical fault.
• Take the car for a short, gentle drive to let the systems relearn and clear first-power-up messages.
• Re-do the window relearn if one-touch or anti-pinch is still not working.
• Rule out a genuinely flat or worn-out 12 V battery — if it will not hold charge, disconnection was not the real problem.
• If an alert persists, it has stored a fault code — look it up on autodtcs.com.

Frequently Asked Questions

Where is the 12 V battery on a Seres 3?

In the engine compartment, under the bonnet. As the Seres 3 is fully electric, the low-voltage battery lives in that space instead of an engine, and it is completely separate from the high-voltage drive battery.

Is it safe to disconnect the battery on an EV?

Yes. The 12 V battery is low voltage and safe for an owner to handle, just like the battery in any petrol car. The only thing you must never touch is the bright orange high-voltage cabling, which belongs to the sealed drive system.

Which terminal do I disconnect first?

Always take off the negative (−) terminal first and refit it last. Reconnect the positive (+) first when you put things back. That order avoids any risk of a short across the terminals while you work.

What will I need to reset afterwards?

Expect to reset the clock and date, re-enter the radio code if prompted, and possibly relearn the one-touch windows. A few dashboard messages may show on first power-up and clear themselves after a short drive.

Does a new 12 V battery need coding on the Seres 3?

A like-for-like replacement of the correct type and rating does not normally require any coding for an owner. Fit the same specification the car came with, make sure the terminals are tight, and let the car settle before driving.

Can I jump-start the 12 V system instead of disconnecting?

If the 12 V battery is simply flat, a careful jump or boost from another 12 V source can wake the car so you can then charge it properly. Never connect anything to the high-voltage system — only the 12 V battery’s own terminals.

If a warning message stays on after reconnecting, look up the code on autodtcs.com.