These instructions apply to the MG MG3 Mk2 2024-present.
For other models, please choose your vehicle here.
When the remote on your MG3 (2024–present), including the Hybrid+, only works up close — or the cluster shows “Remote Key Low Battery, Please Replace” — the coin cell in the smart key needs renewing. The MG3 key takes a single CR2032 3 V lithium coin cell, and swapping it is a five-minute job that keeps the key paired to your car.
The Battery You Need
The MG3 smart key uses a CR2032 3 V lithium coin cell — the most common fob battery there is. Buy a branded cell; cheap multipack cells can sag under the transmitter’s current draw and give poor range even when new. Match the code on the old cell to confirm it reads CR2032.
How to Replace the MG3 Key Battery
- Take out the backup key. Press the release button (or catch) on the fob and slide out the emergency mechanical key blade — on some keys you first press a button to eject a decorative trim panel.
- Open the case. Insert a small flat-bladed tool into the seam on the side of the key and gently prise the two halves apart. Some keys have a waterproof pad under the cover — note it.
- Note the orientation, then lift out the old CR2032 — see which way up it sits (the printed + face normally points up) before removing it.
- Fit the new CR2032 the same way up, handling it by the edges, and press it fully home so it makes firm contact.
- Reassemble. Refit any waterproof pad, clip the cover back until the seam closes evenly, slide the mechanical key back in, then start the car once to let the key resynchronise. Test lock and unlock.
⚠️ Get the polarity right. A cell fitted upside down makes no contact and can slowly discharge against the terminals, leaving the key dead even with a “new” battery. Always match the way the old cell sat.
If a Fresh Cell Doesn’t Fix It
- Re-check polarity and seating — positive up, flat under its clip against clean contacts.
- Wipe the contacts inside the fob with a dry cloth to clear any film.
- Start the car once to resynchronise; if range is still poor the fob itself may be at fault.
- Caught out with a dead fob? You can still start the car — see our start the MG3 with a dead key fob guide.
New Key or Spare — Why It’s a Dealer Job
Changing the coin cell keeps the key’s coding, so it works the moment the case clicks shut. A brand-new or replacement smart key must be programmed to your MG3 by an MG Authorised Repairer, so adding a spare or replacing a lost key is a dealer job. Keep the battery in your spare fresh too.
Frequently Asked Questions
What battery does the new MG3 key fob take?
A single CR2032 3 V lithium coin cell — the code is printed on the cell you remove.
Do I need to reprogram the key after changing the battery?
No. A battery swap doesn’t affect pairing; the key works straight away. Only a brand-new or replacement key needs coding by the dealer.
Is the Hybrid+ key the same?
Yes — the petrol and Hybrid+ MG3 share the same smart key and CR2032 cell.
Which way up does the cell go?
Match the orientation of the cell you removed — the printed + face normally sits upward.
Can I still drive if the fob battery is completely dead?
Yes. Use the mechanical blade to unlock, then hold the smart key in the standby-start position and press Start — see our dead key fob start guide.
Independent guide — not affiliated with MG. Always follow your official service manual and safety precautions. Read our full disclaimer.