Disconnect and Reconnect the Battery

Disconnecting the 12 V battery on your Infiniti QX30 (H15, 2016–2019) is a job most owners can do on the driveway with a single spanner. You’ll want to do it when you’re fitting a new battery, laying the car up for winter, working near the airbags or seat-belt pretensioners, or recovering from a flat after a jump-start. The QX30 shares its platform and much of its electrical architecture with the Mercedes A-class of the period, so the routine is the same as any modern German-engineered hatchback: switch everything off, take the negative terminal off first, and the car will relearn its settings cleanly once power is restored in the right order.

Where the 12 V Battery Is

On the QX30 the 12 V battery sits in the engine compartment, usually under a plastic cover you lift or unclip to reach the terminals. Once the cover is off, identify the two posts before you touch anything: the negative (−) terminal wears a black cap or clamp and connects to the body/earth, while the positive (+) terminal is red and normally hidden under a hinged plastic guard. Knowing which is which up front stops you slipping and bridging the two with a spanner, which is what causes the alarming spark.

First, a Few Checks

• Turn the ignition fully off, take the key well away from the car, and shut the doors so nothing wakes the electronics.
• Switch off every consumer — lights, climate, heated seats, wipers — so there’s no load on the terminals as you break the connection.
• Note your radio and infotainment settings, including any security code the head unit asks for, plus your clock and paired-phone details.
• Wait a couple of minutes after switching off for the control modules to power down before you loosen anything.
• Have the right spanner ready (the QX30’s clamps are typically 10 mm) along with gloves and eye protection.

Disconnecting

1. Confirm the ignition is off and every electrical consumer is switched off.
2. Lift the cover and loosen the clamp on the negative (−) terminal first. Ease the clamp off the post and tuck the lead aside so it can’t spring back onto the battery.
3. Only then loosen and remove the positive (+) lead if you actually need the battery fully out; for most electrical work, taking the negative off is enough to isolate the system.
4. If you’re working near the airbags or pretensioners, wait a few minutes after disconnecting before you start.

Reconnecting

1. Refit the positive (+) terminal first, seating the clamp fully before you tighten it.
2. Reconnect the negative (−) terminal last and nip both clamps up snug — firm, not over-torqued.
3. Refit the cover, then get in, switch on and let the car settle for a moment before you start it.

What You’ll Need to Reset Afterwards

• Clock and radio — re-enter the time, your presets and any radio security code.
• Power windows — the one-touch/anti-pinch function needs re-initialising; follow our QX30 power-window guide.
• Tyre pressure monitor — re-store the current pressures from the driver menu or let it relearn over a short drive.
• Seat and mirror memory — some presets may need re-saving if the car is so equipped.
• A few warning lights may glow briefly and then self-clear once the systems see steady voltage and a little driving.

If a Warning Light Stays On or the Car Feels Off

• Re-check that both clamps are tight and fully seated on their posts — a loose earth causes all sorts of odd behaviour.
• Drive gently for ten minutes so the systems can relearn idle, throttle and the tyre pressures.
• Redo the window re-initialisation if the auto-up has stopped working.
• If the battery was deeply flat or is simply old, suspect the battery itself rather than your work — a tired battery can’t hold the modules stable.
• Any light that won’t clear has logged a code — look it up on autodtcs.com.

Frequently Asked Questions

Where is the battery on an Infiniti QX30?

In the engine compartment, under a plastic cover. The QX30 shares its layout with the Mercedes A-class of the era, so it’s a conventional under-bonnet battery rather than one hidden in the boot.

Which terminal do I disconnect first?

Always take the negative (−) terminal off first, and reconnect it last. Working positive-first risks earthing the live lead through your spanner. On reassembly the order reverses: positive on first, negative last.

What needs resetting after I reconnect?

Expect to redo the clock and radio presets, re-initialise the one-touch windows, and re-store the tyre pressures. Seat and mirror memory may also need re-saving. Most items either come back with a menu step or relearn themselves after a short drive.

Does a new battery need coding on the QX30?

A like-for-like replacement of the same type and rating generally doesn’t need coding to drive away. Because the QX30 uses stop/start, fit the correct AGM or EFB battery; some cars benefit from a battery-management reset so the charging system treats the new unit as fresh.

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

Temporary, self-clearing lights often disappear once voltage is restored, but a genuine stored fault will return because the underlying condition is still present. The service interval reminder is stored separately and isn’t reset simply by pulling power.

Can I jump-start it instead of removing the battery?

If the aim is just to get going after a flat, a jump-start is quicker. Remove the battery only when you’re renewing it, storing the car long-term, or working somewhere that needs the electrics fully isolated.

To relearn the windows after reconnecting, see our QX30 power-window guide. If a warning light stays on, decode it on autodtcs.com.