The standard, OEM battery for the 2020 Subaru WRX is a 12-volt Group 35 battery. Replacements commonly use the same Group 35 size, though climate and electrical load may justify an upgraded option such as an AGM variant with higher cranking amps.
OEM battery size and specifications
To help shoppers and owners understand what to look for when replacing the battery, here are the core specifications typically associated with the 2020 WRX. These figures can vary by market and trim, so always verify against your vehicle’s label or owners manual.
- Group size: 35 (12V lead-acid design; standard orientation with top-post terminals).
- Nominal capacity: typically in the 35–40 Ah range (depends on brand and model).
- Cold-cranking amps (CCA): commonly about 350–600 A, with higher numbers available from premium brands or AGM variants, especially in colder climates.
- Reserve capacity (RC): roughly 90–100 minutes, depending on the exact battery model.
- Fit/clearance: must fit the WRX battery tray and hold-down bracket; terminal placement should align with factory connections.
In practice, many owners replace with a conventional Group 35 battery that matches or exceeds the original CCA and RC ratings. If you live in a region with harsh winters or run a high electrical load (aftermarket audio, additional lighting, etc.), an AGM version of Group 35 with higher CCA is a common upgrade choice.
Choosing the right replacement
Before buying a new battery, use these criteria to guide your choice and ensure long-term reliability in your WRX.
- Group size compatibility: ensure the replacement is Group 35 so it fits the tray, hold-down, and terminal layout.
- Battery type: decide between conventional flooded lead-acid and AGM. AGM offers better resistance to vibration, slower discharge, and higher CCA, but at a higher price.
- CCA and RC targets: aim for at least the original spec; in colder climates, consider a higher CCA (roughly 450–700 A from premium AGM options) and a solid RC.
- Brand and warranty: choose a reputable brand with a warranty that matches your expectations (3–5 years is common for modern batteries).
- Installation compatibility: verify terminal polarity and post type matches the vehicle’s harness and clamps, and confirm the battery fits under the hood without interfering with under-hood components.
Choosing a Group 35 battery that meets or exceeds the original specifications will help ensure reliable starts and consistent performance in a WRX, especially in winter or with added electrical loads.
Installation and maintenance tips
For a smooth replacement and longer battery life, follow these practical steps. Disconnect the negative terminal first, then the positive, and reconnect in reverse order. Clean corrosion from terminals and clamps, apply protectant grease, and secure the battery with the factory hold-down bracket. After installation, measure the resting voltage (12.6–12.8 V is typical for a healthy battery) and perform a quick load test if you have the equipment. Periodically check for parasitic drain and ensure the alternator is charging the battery properly to avoid sulfation.
Summary
In short, the 2020 Subaru WRX uses a Group 35 12-volt battery, with typical capacity in the mid-30s to low-40s Ah and respectable CCA ratings. For upgrades or climates with harsh winters, an AGM Group 35 battery with higher CCA and RC is a common, reliable option. Always verify the exact fit and specs on your battery label or in the owner’s manual, and ensure proper installation to maximize performance and longevity.
Bottom line: when replacing, aim for a Group 35 battery that meets or exceeds the original CCA/RC specs, decide on flooded vs AGM based on climate and load, and check fitment to keep your 2020 WRX starting reliably year-round.