These instructions apply to the Ford Puma Mk2 (J2K) 2020-Present. For other models, please choose your vehicle here.
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Disconnecting a battery on the Ford Puma (2020–present) is mostly a normal 12 V job — but the popular EcoBoost mHEV versions add a twist: they carry a 48 V mild-hybrid battery as well, in a different place, and that one isn’t an owner part. This guide keeps the two clearly apart so you work on the right battery safely, and covers the BMS reset a new 12 V needs.
Two Batteries on the mHEV — Know Which Is Which
- 12 V starter battery (every Puma) — in the engine bay, under a cover. This is the one you disconnect or replace for normal electrical work, jump-starts and flat-battery problems.
- 48 V lithium battery (mHEV only) — located under the front passenger seat, under a carpet flap. It feeds the belt-driven starter-generator. Leave it alone: the 48 V system must be properly deactivated first, which is workshop territory, not a driveway job.
For the rest of this guide, “the battery” means the 12 V in the engine bay.
Disconnecting the 12V Battery
- Apply the parking brake, switch the ignition off, and make sure all electrical consumers (lights, climate, radio) are off.
- Wait 2 minutes for the modules to power down.
- Open the bonnet and disconnect the earth/negative (−) cable first, then the positive (+) if you’re removing the battery.
Working near airbags or pretensioners as well? Keep the ignition off and leave the system to discharge before going near pyrotechnic parts.
Reconnecting and What to Re-set
- Reconnect positive (+) first, then earth/negative (−) last; tighten and refit the cover.
- Reset the clock and date, and re-enter radio presets and personal settings.
- Re-initialise the power windows — one-touch drops out after a power cut. See our Puma window initialise guide.
Fitted a New Battery? Reset the BMS
The Puma uses a Battery Monitoring System (BMS) for smart charging and to manage start/stop. When you fit a new 12 V battery, the BMS should be told, so it charges the fresh battery correctly and re-enables Auto Start-Stop. On the Puma this is done with Ford’s diagnostic software (a dealer or an independent with FDRS/Forscan) — a like-for-like swap will run without it, but start/stop and charging behave better once it’s reset. A simple disconnect/reconnect of the same battery doesn’t need it.
Frequently Asked Questions
Is the Ford Puma a 48V mild hybrid?
The EcoBoost mHEV versions are — they have a genuine 48 V system and a 48 V battery under the passenger seat. Plain (non-mHEV) EcoBoost and the diesel use only the 12 V battery.
Where is the 12V battery on the Puma?
In the engine bay under a cover — the same place on every Puma, mHEV or not. The under-seat battery is the separate 48 V unit.
Can I touch the 48V battery myself?
No — the 48 V system has to be deactivated properly before anyone works on it. Treat it as a workshop item; only the engine-bay 12 V is owner-serviceable.
Why won’t Auto Start-Stop work after a new battery?
The BMS needs resetting so it trusts the new battery’s charge state; until then (or until the battery is fully charged) start/stop may stay off.
For any warning light that stays on, look up the code on autodtcs.com. To clear the oil-service reminder afterwards, see our Puma service reset guide.
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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