Disconnect and Reconnect the Battery

Renewing a flat battery or disconnecting for other work on your Volvo XC40 (536, 2017–present)? You might be fitting a fresh battery, waking the car after it’s stood for a while, isolating the electrics for electrical or bodywork jobs, or recovering from a drain that’s flattened it. It’s a job most owners can do at home. On the petrol and mild-hybrid XC40 the electrical system is a conventional 12 V setup with no high-voltage hazard. On the Recharge plug-in hybrid there is an additional high-voltage battery, but the 12 V battery is still the one you service — never touch the orange high-voltage cabling, which is strictly a workshop task. The fully electric XC40 Recharge is not covered here. Provided you work in the correct order, the car powers up, relearns its settings and drives normally.

Where the 12 V Battery Is

Open the bonnet — on the XC40 the 12 V battery sits in the engine bay, usually under a cover that lifts or unclips away. Clear that first so you can reach both posts cleanly. Identify the terminals before you loosen anything: the negative (−) post normally wears a black cap and earths to the body, while the positive (+) post is usually under a red flap and carries the main supply. On the petrol and mild-hybrid XC40 there is no high-voltage traction system to worry about. On the Recharge plug-in hybrid the 12 V battery is still the owner-serviceable one, but the orange high-voltage cabling is off-limits — leave anything orange to a qualified workshop.

This is a common job that needs little more than a spanner and a few minutes.

Before You Begin

• Make sure the car is fully off — not in READY — with all lights and electrical loads switched off.
• Take the key well away from the car so it can’t wake the electronics or bring the car back to READY.
• If your infotainment or radio uses a security code, have it ready in case it’s requested when power returns.
• Wait a couple of minutes after switching off so the control modules power down and sleep.
• Have the correct spanner ready, plus gloves and eye protection — and on the Recharge, keep well clear of any orange cabling.

Disconnecting the Battery

1. Switch everything off, take the key away and wait a couple of minutes for the modules to settle.
2. Slacken the clamp on the negative (−, black) terminal first, lift it off the post and secure it clear so it can’t spring back onto metal.
3. Only if you’re removing or replacing the battery, release the positive (+, red) clamp next; for most jobs isolating the negative is enough.
4. If you’re lifting the battery out, undo the hold-down bracket and remove it keeping it upright.

Reconnecting the Battery

1. Refit the battery and hold-down bracket if it was removed, making sure it sits square.
2. Fit the positive (+, red) terminal first and tighten the clamp.
3. Fit the negative (−, black) terminal last and tighten it firmly — a loose earth is the usual cause of odd electrical faults afterwards.
4. Switch the ignition on, wait a few seconds for the systems to boot, then start the car.

What You’ll Need to Reset Afterwards

Losing power clears a few short-term settings, so plan to redo a handful of small things:

• Reset the clock and re-enter any radio presets or security code.
• Re-store the tyre-pressure baseline — see our guide to re-store your tyre pressures once they’re set correctly.
• Re-initialise the electric windows so one-touch and anti-pinch work again — follow our steps to re-initialise the windows.
• Let the car sit a minute before driving, then drive gently so the systems re-initialise; any warning lights that appear usually self-clear after a short drive.

If a Warning Light Stays On or the Car Feels Off

• Re-check that both clamps are properly tight — a loose or corroded terminal mimics real faults.
• Give the car a short, steady drive so the systems can relearn and settle.
• If the windows won’t auto-close or anti-pinch trips, re-do the window initialisation; if the tyre light stays on, re-run the TPMS reset.
• If the battery was deeply flat or is old, confirm it’s holding charge before chasing electrical gremlins.
• If a light refuses to clear, read the stored fault code to see what the car is actually reporting.

Frequently Asked Questions

Where is the battery on a Volvo XC40?

It’s in the engine bay under a cover — a standard 12 V battery. Lift the bonnet, remove the cover, and identify the black negative (−) and red positive (+) terminals before you start.

Which terminal comes off first?

Disconnect the negative (−) terminal first, then fit the positive (+) first and the negative last when reconnecting. Working in that order prevents an accidental short against the bodywork.

Is the Recharge PHEV safe to work on?

The 12 V battery is fine for an owner to disconnect — it’s the same job as on the petrol car. Never touch the orange high-voltage cables, though; leave anything to do with the high-voltage system to a qualified workshop.

What resets when I disconnect the battery?

Typically the clock, radio presets, the tyre-pressure baseline and the one-touch/anti-pinch window function. Most of these are quick to redo, and any warning lights that appear usually clear after a short drive.

Do I need to code a new battery on an XC40?

Volvo recommends registering a new battery so the charging matches it; the car runs without it, but registering preserves battery life. A like-for-like swap will still start and drive normally either way.

Can I jump-start it instead of disconnecting?

Yes — if the 12 V battery is simply flat you can jump-start from a healthy 12 V source rather than removing anything. Only disconnect when you’re renewing the battery or need the electrics fully isolated for other work.

Take your time, keep the order right, and the XC40 relearns cleanly. If a warning light stays on afterwards, check the code on autodtcs.com.