The Focus ST uses a 12-volt automotive battery. In most 2018 Focus ST models, you’ll find a standard 12V lead-acid battery, but if the car is equipped with Auto Start-Stop, Ford typically specifies an AGM (Absorbent Glass Mat) battery to handle the frequent start–stop cycles without degrading performance.
Battery types used in the 2018 Ford Focus ST
There are two common battery configurations you might encounter with this model, depending on equipment and market.
- Conventional flooded lead-acid battery
- Absorbent Glass Mat (AGM) battery for vehicles with Auto Start-Stop or heavier electrical load
In short, if your Focus ST has Start-Stop, you’re more likely to have an AGM battery; otherwise a traditional flooded lead-acid battery is common. Always verify with the battery label or the owner’s manual to be sure.
How to tell which battery your Focus ST uses
To determine the exact type in your car, use these checks or references.
- Look for an “AGM” marking on the battery case or label. If present, it’s an AGM battery.
- Check whether your vehicle is equipped with Auto Start-Stop. If so, your battery is often AGM by design.
- Consult the owner’s manual or Ford’s official specs for your VIN to confirm the original battery type and replacement requirements.
If you’re replacing the battery, match the original type and ensure the replacement meets or exceeds Ford’s recommended CCA (cold cranking amps) and capacity. Using an incorrect type (for example, a non-AGM battery in a Start-Stop system) can lead to electrical issues or reduced performance.
What size and capacity should you buy?
Battery size and capacity vary by the car’s equipment and climate. For a typical 2018 Ford Focus ST, you’ll want a 12-volt battery with a capacity in the roughly mid-range for modern vehicles and an appropriate CCA rating for your climate and driving needs. Always confirm the exact specification from the owner’s manual or the original battery label, and aim to choose an OEM-equivalent or a reputable aftermarket battery that meets or exceeds those ratings.
Note on Start-Stop compatibility
If your vehicle has Auto Start-Stop, do not substitute a conventional flooded battery for an AGM one, as the AGM design is required to handle frequent stopping and restarting without shortening battery life.
Summary
The 2018 Ford Focus ST generally uses a 12-volt battery. If Start-Stop is present, an AGM battery is typically specified; otherwise a conventional flooded lead-acid battery is common. To be sure, check the battery label, the owner’s manual, or your dealer based on your VIN. When replacing, match the original type and choose a battery with at least the original or better CCA and capacity to ensure reliability and performance.