Ford Focus Mk3 Battery: Specs, Fitment & Common Faults

The warning signs of a dying battery, and what size and type actually fits your specific car.

Generation covered: this guide is for the third-generation Focus, built 2011–2018 (commonly the 2014–2018 registered examples still in daily use). The newer Mk4 Focus (2018–) uses different part numbers throughout — check your V5C logbook or VIN if you're unsure which generation you have.

Illustration for editorial purposes

The Part Everyone Blames First, Not Always Correctly

A car that won't start gets blamed on the battery more often than any other component, and it's right often enough to make that assumption a reasonable first check. But it's not always the actual cause, which is worth knowing before spending money on a replacement that doesn't fix anything.

Before you buy: battery size, capacity and type (standard vs AGM/EFB for stop-start systems) vary by trim and engine. Always confirm against your VIN before ordering.

OEM Part Numbers & Sizes

Accuracy note: battery specification on the Mk3 Focus depends heavily on engine, trim, and whether the car has Ford's stop-start system — always confirm your existing battery's size and Ah rating (printed on the case) before ordering, rather than relying on part number alone.

Common OEM cross-reference	Ford 000915105DA, 13502901, 282915105 (widely used group across several petrol and diesel variants)
Typical case dimensions	Length 207–317mm, width 175mm, height 175–190mm (varies by spec — measure your existing battery)
Stop-start equipped cars	Require an AGM or EFB battery, not a standard flooded-cell replacement — fitting the wrong type can damage the stop-start system

Because Ford fitted several different battery capacities across the Mk3's production run — depending on engine, trim, and whether stop-start is fitted — the safest way to order the right one is by the Ah rating and case size printed on your current battery, cross-checked against your VIN, rather than assuming a single part number covers every car.

What It Does

The 12V battery provides the power needed to start the engine and runs electrical systems when the engine isn't turning. On cars with stop-start technology, the battery works much harder than on older designs, since the engine switches off and restarts far more frequently — which is exactly why these cars need a specific AGM or EFB battery type rather than a standard unit.

Fitment & Compatibility

Battery type and capacity differ between standard and stop-start equipped versions of the Focus Mk3, and fitting a standard battery to a stop-start car can cause premature failure since it's not designed for the frequent cycling involved. Always confirm the exact battery type and capacity for your specific trim before ordering.

Common Faults

Symptoms of Failure

Slow or laboured engine cranking — often the earliest sign, especially noticeable in cold weather.
Dashboard warning light — a battery or charging system alert shouldn't be ignored, even if the car still starts normally.
Electrical accessories behaving oddly — flickering lights or a stuttering infotainment system can point to inconsistent voltage.
Stop-start system disabling itself — many cars automatically turn off stop-start when battery health drops, a useful early warning most drivers miss.

DIY Replacement Difficulty

This is generally an easy DIY job on most versions, though modern cars increasingly require a "battery registration" step using a diagnostic tool afterward so the car's charging system recognises the new battery correctly. Skipping this step on cars that need it can lead to reduced battery lifespan even with a brand new unit. Expect 15–30 minutes for the physical swap, plus registration if your specific car requires it.

OEM vs. Aftermarket

Reputable aftermarket batteries from established brands are widely regarded as a safe, reliable alternative to OEM parts, provided the type (standard, AGM, or EFB) and capacity match your car's requirements exactly. This is one part where matching the correct specification matters far more than the brand name on the case.