Disconnect and Reconnect the Battery

The 12 V battery on the Mercedes-Benz GLA (H247, 2020–present) isn’t under the bonnet, which catches a lot of owners out. Here’s where it actually is, how to disconnect it safely, and what the car needs re-taught afterwards.

Owners disconnect the 12 V battery for the usual reasons: fitting a fresh battery, carrying out electrical work that needs a dead circuit, laying the car up for a long spell, or recovering after a flat. Done in the correct order, the H247 comes back cleanly — expect little more than a reset clock and a couple of comfort features that need re-teaching.

Where the Battery Is

On the H247 GLA the 12 V battery is inside the car — Mercedes locates it in the centre-console / front floor area, under a cover (check your handbook for the exact panel for your build). The engine bay has a remote jump-start terminal for jump-starting, but the battery itself is in the cabin. On the plug-in hybrid GLA, the 12 V battery is the only one you handle here; keep clear of the orange high-voltage components, which are not owner-serviceable.

With the cover off you’ll find the two posts: the negative (−) earth, usually black, and the positive (+), usually red under a protective cap. Identify both before you start loosening anything.

First, a Few Checks

• Make sure the car is fully off and not in READY on the plug-in hybrid.
• Take the keyless remote out of range so the car can’t wake and re-power circuits mid-job.
• Switch off lights, climate and wipers, and shut the doors you’re not using.
• Wait a couple of minutes for the modules to power down before touching the terminals.
• Have the correct spanner, gloves and eye protection ready; MBUX reloads on its own, so there’s no separate radio code to note.

Disconnecting

1. Switch everything off, take the keyless remote out of range, and wait a minute.
2. Remove the cover to reach the battery, then disconnect the negative (−) earth first and tuck the lead aside.
3. If removing the battery, disconnect the positive (+) next, then release the hold-down clamp and the vent hose.

Reconnecting & After

1. Reconnect positive (+) first, then the negative (−) last; tighten both clamps and refit the cover.
2. Reset the clock; MBUX reloads on its own, but the time and date want checking.
3. Re-initialise the windows and, if fitted, the sunroof — see our GLA window guide.
4. A new battery should be registered to the power-management system with a diagnostic tool; the same battery reconnected does not need coding.

When a Warning Persists

• Check both clamps are tight — a loose earth is the usual cause of odd behaviour afterwards.
• Let the car relearn over a short drive; assistance and stop-start lights often clear after a few normal cycles.
• Re-do the window/sunroof initialise if one-touch or anti-pinch isn’t working.
• Rule out a weak or aged battery — a tired 12 V keeps a modern Mercedes throwing faults.
• If a light stays lit, read the stored code before changing parts.

Frequently Asked Questions

Where is the battery on a Mercedes GLA H247?

Inside the car (centre-console / floor area under a cover) — not under the bonnet. Use the engine-bay jump terminal for jump-starting; the battery itself lives in the cabin.

Which terminal comes off first?

The negative (−) earth first, then positive if you’re lifting the battery out. On refit, positive first and negative last, so a slipped spanner can’t short to the body.

What needs resetting afterwards?

Mainly the clock, and the one-touch windows and sunroof, which lose their learned travel. MBUX profiles and radio presets usually survive. A short drive settles the self-learning systems.

Does a new GLA battery need coding?

Yes — a new battery should be registered with a tool so the power-management system charges it correctly. A quick disconnect and reconnect of the same battery doesn’t.

Will disconnecting reset the service light or clear codes?

It may drop transient codes but won’t reset the service reminder, which is a separate procedure. Genuine faults return once detected, so cure the cause rather than relying on a power cut.

Can I jump-start it under the bonnet instead?

Yes — use the marked jump-start terminal under the bonnet and a good earth point. That’s the intended recovery method when the battery is simply flat, and it saves lifting the cabin cover.

For any warning light that stays on, look up the code on autodtcs.com. To clear the service reminder, see our GLA service reset.