Disconnect and Reconnect the Battery

Disconnecting the 12 V battery on a Mazda CX-5 Mk2 (KF, 2017–present) is a job most owners can do on the driveway with a single spanner. You might need to do it to renew a tired battery, to isolate the electrics before bodywork or audio work, to protect the car during long storage, or to recover after a jump-start. Done in the right order — negative off first, positive on first — the CX-5 wakes up cleanly and relearns the few settings it loses. This guide covers where the battery sits, how to take it off and put it back safely, and the handful of things you may need to reset afterwards.

Where the 12 V Battery Is

The 12 V battery is in the engine compartment, under a cover. Lift or unclip the plastic cover to reach the terminals. Mazda’s i-stop start-stop and, where fitted, the i-ELOOP capacitor system both run off this same 12 V battery — there is no separate owner battery to worry about. Identify the terminals before you touch anything: the negative (−) post carries the black earth lead, and the positive (+) post carries the red lead, usually under a red flap. If you are only isolating the electrics, you only need to lift the negative lead clear.

Getting Ready

• Make sure the ignition is fully off and the car is not left in an accessory state.
• Take the key fob well away from the car so it cannot wake the systems.
• Switch off the lights, climate and any accessories, and close the doors.
• Give the electronics a couple of minutes to power down before you loosen anything.
• Have a set of spanners, gloves and eye protection ready; the battery gives off hydrogen, so no sparks or flames nearby.

Disconnecting

1. Turn the ignition on briefly then off (Mazda’s way to settle the systems), and remove the key.
2. Loosen the negative (−, black) terminal first, ease the clamp off the post and tuck the lead well clear so it cannot spring back onto the battery.
3. If you are removing the battery, loosen the positive (+, red) next, then undo the hold-down bracket and lift the battery out level.

Airbag/pretensioner safety: if you will be working near airbags or seat-belt pretensioners, wait 1 minute after switching off (allow up to 5 minutes to fully discharge) before going near any pyrotechnic parts.

Reconnecting

1. If the battery came out, set it back level and refit the hold-down bracket first.
2. Reconnect the positive (+, red) terminal first and tighten the clamp.
3. Reconnect the negative/earth (−, black) last, tighten it, and refit the cover. Both clamps should be snug — a loose earth is the most common cause of odd electrical faults afterwards.

The CX-5 does not need the new battery coded or registered — a straight like-for-like swap is fine.

What You’ll Need to Reset Afterwards

A power cut wipes a few learned settings. On the CX-5 you may need to:

• Reset the clock and re-enter any radio presets.
• Re-initialise the one-touch power windows — auto up/down and the anti-pinch feature drop out after a power cut. See our CX-5 window guide.
• Let the i-stop system settle — it may not offer auto stop-start until the battery has recharged over a drive or two.
• Re-pair or re-check any phone/Bluetooth and personalised driver settings.

A few warning lights may glow briefly and then self-clear once the car has been driven a short distance.

If a Warning Light Stays On / Car Feels Off

• Check both clamps are properly tight — a loose earth causes flickering lights and random faults.
• Take the car for a short drive so the modules can relearn idle and stop-start behaviour.
• Re-do the window re-initialise if auto up/down still will not work.
• If a light persists, rule out a genuinely flat or worn-out battery before blaming the disconnect.
• Read any stored fault code to see what the car is actually flagging.

Frequently Asked Questions

Where is the 12 V battery on a Mazda CX-5?

It is in the engine compartment, under a plastic cover. Unclip the cover to reach the terminals. The same battery powers the i-stop and i-ELOOP systems, so there is no separate owner battery to find.

Which terminal do I disconnect first on the CX-5?

Always the negative (−) terminal first when disconnecting, and reconnect it last. On reconnection the positive goes on first. This order keeps your spanner from shorting a live post to the bodywork.

Does a new battery need registering or coding?

No — the CX-5 does not require battery coding. Fit a like-for-like battery, reconnect in the right order and re-teach the windows. There is no dealer registration step for the owner to worry about.

Will I lose my radio or clock?

The CX-5’s infotainment is not code-locked, so the radio comes straight back — you will just need to reset the clock and re-enter your presets and any personalised settings.

Will disconnecting the battery clear fault codes or the service light?

It may clear some stored trouble codes and temporary lights, but it is not a proper reset and it will not clear the service reminder. To reset the oil/service interval, use our CX-5 Mk2 service reset guide.

Can I jump-start it instead of disconnecting?

If the aim is simply to get a flat car going, a jump-start is easier and keeps all your settings. Only disconnect the battery when you actually need it isolated — for renewal, electrical work or long storage.

For any warning light that stays on after the job, look up the code on autodtcs.com, then clear the reminder with our CX-5 Mk2 service reset guide.