Is There Anything to Do Before My 2020 Subaru WRX Battery

Before changing your 2020 Subaru WRX battery, you need to know a few key steps to avoid electrical issues, data loss, and CVT transmission quirks. This guide covers preparation, safety, terminal cleaning, ECU reset, and post-installation checks. Follow these tips to make your battery replacement smooth, safe, and stress-free.

So you need to swap out the battery on your 2020 Subaru WRX. Maybe it won’t turn over in the morning. Maybe you left the lights on. Either way, you are here, and that is great. But before you grab a wrench and rip into the engine bay, there are a few things you should know.

Changing a car battery seems simple on the surface. Pop the hood. Disconnect the old one. Connect the new one. Done, right? Well, not exactly. The 2020 Subaru WRX is a bit special. It has a CVT transmission, a sensitive ECU, and a battery setup that demands a little extra care. Skip a step, and you could end up with error codes, reset settings, or even electrical gremlins that are a real headache.

This guide walks you through everything you need to do before changing your 2020 Subaru WRX battery. We cover prep work, safety steps, terminal cleaning, ECU memory, and post-installation tips. By the end, you will feel confident and ready to get the job done right. Let’s dive in.

Key Takeaways

• Safety first: Always disconnect the negative terminal first to prevent short circuits.
• Resetting matters: Your 2020 Subaru WRX may need a few resets after a new battery goes in.
• Check your battery tray: Corrosion or damage on the tray can affect battery life.
• Use the right battery: Match the cold cranking amps and group size for your WRX.
• Protect your CVT: The CVT transmission relies on stable voltage from the battery.
• Keep a memory saver: This small device preserves your settings during the swap.
• Test before you toss: Confirm the old battery is actually dead before replacing it.

Why Preparing Before a Battery Change Matters

Some people treat a battery swap like it is no big deal. But your 2020 Subaru WRX is not just any car. The battery powers more than just the starter motor. It keeps the ECU happy, supports the CVT transmission logic, and holds memory for your radio, clock, and power windows. When you cut power without preparing, all of that can reset or glitch.

Here is why preparation matters so much:

• It prevents data loss. Your ECU stores learned driving data. A sudden power drop can erase that.
• It protects the CVT transmission. The CVT relies on stable voltage for smooth shifts.
• It saves your settings. No one wants to re-enter their radio presets and Bluetooth pairings.
• It avoids electrical shorts. Disconnecting in the wrong order can spark and damage components.

Taking ten minutes to prepare can save you hours of frustration later. Trust me on this one.

Step-by-Step Prep Before You Touch the Battery

Before you even open the hood of your 2020 Subaru WRX, there are a few things to do. Think of this as your pre-work checklist. It keeps you organized and safe.

Gather Your Tools and Supplies

You do not need a garage full of tools. But you do need a few essentials. Here is what I recommend having ready before you start:

• A 10mm wrench for the battery terminal bolts
• A wire brush or battery terminal cleaner
• A new battery that matches your WRX’s group size and CCA rating
• A memory saver device (more on this below)
• Safety glasses and gloves
• A clean rag or paper towels
• Anti-corrosion spray or dielectric grease

Having everything lined up before you start makes the whole process smoother. You do not want to be halfway through and realize you are missing a tool.

Use a Memory Saver Device

A memory saver is a small gadget that plugs into your car’s OBD-II port or cigarette lighter. It keeps power flowing to your ECU and other modules while the battery is disconnected. This is a game-changer for your 2020 Subaru WRX.

Without a memory saver, your car may forget learned shift points in the CVT transmission. It might also reset your adaptive cruise control, infotation preferences, and throttle response settings. A memory saver costs around twenty to forty dollars and is well worth it. If you do not have one, you can ask a friend with a running car to jump your WRX while you work. But a memory saver is the cleaner option.

Confirm the Battery Is Actually Dead

Before you replace the battery, test it. A dead battery might actually be a charging problem. Your 2020 Subaru WRX uses an alternator to keep the battery charged while driving. If the alternator is failing, a new battery will die quickly too.

Use a multimeter to check the voltage. A healthy battery should read around 12.6 volts when the car is off. When the engine is running, it should read between 13.7 and 14.7 volts. If the voltage is low in both cases, you likely have a battery issue. If the voltage is good with the engine running but low when off, the alternator might be the culprit. Fix that first before spending money on a new battery.

Safety Steps for Disconnecting the Old Battery

Now that you are prepared, it is time to disconnect the old battery. Safety comes first here. Car batteries contain sulfuric acid and can produce hydrogen gas. A spark near the battery can be dangerous. Follow these steps carefully.

Disconnect the Negative Terminal First

This is the golden rule of battery work. Always disconnect the negative terminal first. On your 2020 Subaru WRX, the negative terminal is marked with a minus sign and usually has a black cable. The positive terminal is marked with a plus sign and has a red cable.

Why negative first? Disconnecting the negative side breaks the ground connection. This means the car’s chassis is no longer connected to the battery. If your wrench slips and touches metal, there is no spark risk. If you disconnect positive first, a wrench touching the chassis could create a short circuit. That is a real danger.

Then Disconnect the Positive Terminal

Once the negative is off and safely tucked away, go to the positive terminal. Use your 10mm wrench to loosen the bolt. Pull the terminal clamp straight up and off the post. Set it aside where it cannot accidentally touch any metal.

Remove the Battery Hold-Down

Your 2020 Subaru WRX has a battery hold-down clamp or tray to keep the battery from shifting. Before lifting the battery out, remove this hold-down. On some WRX models, it is a top-mount bracket. On others, it is a side clamp. Check your owner’s manual if you are unsure. Once the hold-down is loose, carefully lift the battery straight up. Batteries are heavy, so use both hands and lift with your legs, not your back.

Cleaning and Inspecting the Battery Area

With the old battery out, take a moment to look around. This is a great time to inspect the battery tray, terminals, and cables. A clean setup helps your new battery last longer.

Check for Corrosion

Look at the battery terminals and cable ends. White, blue, or greenish crusty buildup is corrosion. Corrosion forms when battery acid reacts with metal. It creates resistance and can prevent a good electrical connection.

If you see corrosion, clean it with a wire brush or a battery terminal cleaner. You can also make a paste of baking soda and water, apply it to the terminals, and scrub gently. Wipe everything clean and dry with a rag before moving on.

Inspect the Battery Tray

Hold the old battery up to the tray and look for cracks, rust, or damage. A damaged tray can cause the battery to vibrate, which shortens its lifespan. If the tray is corroded or broken, consider replacing or repairing it before installing the new battery. A sturdy, clean tray keeps your new battery secure and performing well.

Examine the Cables

Run your fingers along the battery cables. Feel for any spots that are brittle, cracked, or swollen. Damaged cables can cause intermittent electrical issues. If a cable looks worn, replace it before installing the new battery. It is a small cost that prevents big headaches down the road.

Choosing the Right Replacement Battery

Not all batteries are the same. Your 2020 Subaru WRX needs a battery that fits the tray, matches the electrical demands, and delivers enough power to start the engine and run the CVT system smoothly.

Match the Group Size

Check your owner’s manual for the correct battery group size. The 2020 WRX typically uses a group size 35 battery. This refers to the physical dimensions and terminal placement. A battery that is too small or too big will not fit properly. It might also not connect securely to the terminals.

Check the Cold Cranking Amps

Cold cranking amps, or CCA, measure how much power a battery can deliver in cold weather. The 2020 Subaru WRX needs a battery with at least 330 to 400 CCA, depending on the specific model and trim. If you live in a cold climate, go with a higher CCA rating. It gives you extra starting power when temperatures drop.

Consider Battery Type

Most 2020 WRX owners use a standard lead-acid battery. However, you may also see AGM (absorbent glass mat) batteries available. AGM batteries are more durable, handle vibration better, and last longer. They are also more expensive. If you drive in rough conditions or want maximum longevity, an AGM battery is a solid choice.

Battery Feature	Standard Lead-Acid	AGM
Price	Lower cost	Higher cost
Durability	Good	Excellent
Vibration Resistance	Moderate	High
Lifespan	3-5 years	4-6 years
Maintenance	Sometimes needs water top-off	Sealed, maintenance-free

Pick the battery that fits your budget and driving needs. Either type will work well in your 2020 Subaru WRX as long as it matches the group size and CCA requirements.

Installing the New Battery Correctly

Now comes the fun part. You have your new battery, a clean tray, and prepped cables. Let us get it installed the right way.

Place the New Battery in the Tray

Lift the new battery carefully and set it into the tray. Make sure the positive and negative terminals are on the correct sides. On most 2020 WRX models, the positive terminal is on the left side when facing the battery from the front of the car. Double-check this before tightening anything down.

Secure the Hold-Down

Reinstall the battery hold-down clamp or bracket. Tighten it snugly, but do not over-torque. You want the battery secure without stressing the tray or the battery case. A loose battery can vibrate and damage the terminals. An over-tightened hold-down can crack the case.

Connect the Positive Terminal First

Here is the reverse order from when you disconnected. Connect the positive terminal first. Place the red clamp over the positive post and tighten the bolt with your 10mm wrench. Make sure it is tight and does not wobble.

Then Connect the Negative Terminal

Now connect the negative terminal. Place the black clamp over the negative post and tighten the bolt. Give both terminals a gentle tug to confirm they are secure.

Apply Anti-Corrosion Protection

Once both terminals are connected, spray a thin layer of anti-corrosion spray or apply dielectric grease to each terminal. This helps prevent future buildup and keeps the connection clean. It is a small step that pays off over the life of your new battery.

Post-Installation Checks and Resets

Your new battery is in, and everything is connected. But before you close the hood and drive away, there are a few final steps for your 2020 Subaru WRX.

Turn the Key and Listen

Turn the ignition to the “ON” position without starting the engine. Listen for any warning lights on the dashboard. If the check engine light, battery light, or any other warning stays on, do not panic. This can happen after a battery swap. Turn the key off, wait a few seconds, and try again. If the light persists, you may need to clear a fault code.

Start the Engine

Start the engine and let it idle. The 2020 Subaru WRX with a CVT transmission may need a few moments to relearn idle settings. You might notice the idle is slightly higher than normal for the first few minutes. This is normal. The ECU is recalibrating after the power interruption.

Reset Your Settings

Even with a memory saver, some settings may need a quick reset. Check your radio presets, clock, power window auto-up/down, and any personal preferences. Re-enter your data if needed. It only takes a couple of minutes.

Take a Short Test Drive

Go for a short drive around the block. Pay attention to how the CVT transmission shifts. It should feel smooth and responsive. If you notice any hesitation, harsh shifts, or warning lights, give it a few more minutes of driving. The transmission control module often relearns its values during normal driving. If the issue persists, check the battery voltage or consult a Subaru technician.

Dispose of the Old Battery Properly

Do not just toss your old battery in the trash. Car batteries contain lead and sulfuric acid, which are harmful to the environment. Most auto parts stores, including Subaru dealerships, will recycle your old battery for free. Some even offer a core charge refund when you buy your new battery. Always recycle responsibly.

Common Mistakes to Avoid When Changing Your WRX Battery

Even experienced DIYers can make mistakes during a battery change. Here are a few common ones to watch out for with your 2020 Subaru WRX.

• Forgetting the memory saver. This leads to lost ECU data and annoying resets.
• Disconnecting positive first. This creates a spark risk and can damage fuses or electronics.
• Using the wrong battery size. A mismatched battery will not fit or perform correctly.
• Skipping terminal cleaning. Corrosion on the new terminals shortens battery life.
• Over-tightening the hold-down. This can crack the battery case or damage the tray.
• Ignoring the alternator. If the alternator is weak, the new battery will die fast too.

Avoiding these simple mistakes saves time, money, and frustration. Keep this list handy the next time you work on your WRX.

How Often Should You Replace Your 2020 Subaru WRX Battery

Most car batteries last between three and five years. But several factors can shorten or extend that lifespan. Climate is a big one. Extreme heat causes battery fluid to evaporate. Extreme cold reduces starting power. If you live in a place with harsh winters or scorching summers, your battery may wear out faster.

Driving habits matter too. Short trips that do not give the alternator enough time to fully recharge the battery can lead to premature failure. If you mostly drive short distances around town, consider using a battery maintainer or trickle charger during periods of inactivity.

Watch for warning signs. A slow cranking engine, dim headlights, a bloated battery case, or a battery warning light on the dashboard all point to a failing battery. Catching these signs early gives you time to replace the battery on your schedule instead of being stranded with a dead one.

Final Thoughts

Changing the battery on your 2020 Subaru WRX does not have to be intimidating. With the right preparation, tools, and knowledge, you can do it yourself in under an hour. The key is to take it step by step. Prepare first, disconnect safely, clean the connections, choose the right replacement battery, and install it correctly. Do not skip the post-installation checks either. A little extra care goes a long way in keeping your WRX running strong.

Remember, your 2020 Subaru WRX is a well-engineered machine with a CVT transmission and sensitive electronics. Treat the battery change with the respect it deserves, and your car will reward you with reliable starts and smooth performance for years to come. Now go get it done, and enjoy the satisfaction of a job well done.

Frequently Asked Questions

Do I need a memory saver for my 2020 Subaru WRX battery change?

A memory saver is not strictly required, but it is highly recommended. It preserves your ECU settings, radio presets, and CVT learned values. Without one, you may experience temporary glitches or reset preferences after the swap.

What size battery does the 2020 Subaru WRX use?

The 2020 Subaru WRX typically uses a group size 35 battery. Always check your owner’s manual to confirm the exact group size and CCA rating for your specific trim and model year.

Can I change the battery myself or should I go to a dealer?

You can absolutely change the battery yourself if you are comfortable with basic car maintenance. The process is straightforward and requires only common tools. However, if you are unsure or do not have the right equipment, a Subaru dealer or certified mechanic can handle it quickly.

How long does a 2020 Subaru WRX battery last?

Most batteries in a 2020 Subaru WRX last between three and five years. Factors like climate, driving habits, and maintenance can influence how long your battery performs well.

Will changing the battery reset my Subaru WRX’s ECU?

Disconnecting the battery will reset some ECU learned values. This can cause the idle to be slightly higher for the first few minutes after installation. The CVT transmission may also need a short drive to relearn shift points. These temporary changes are normal and not a cause for concern.

What should I do with my old car battery?

Never throw a car battery in the regular trash. Take it to an auto parts store, a Subaru dealership, or a recycling center. Most locations accept old batteries for free and recycle them properly to protect the environment.