How to Replace the 12V Battery on a 2018 Subaru Legacy (Group 35)
Step-by-step DIY instructions with required tools/parts, safety tips, and torque specs for 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019
How to Replace the 12V Battery on a 2018 Subaru Legacy (Group 35)
Step-by-step DIY instructions with required tools/parts, safety tips, and torque specs for 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019
🔧 Legacy - Battery Replacement
You’ll remove the old 12V battery from the engine bay and install a new one of the correct size. This restores reliable starting and prevents random electrical issues caused by a weak battery.
Difficulty Level: Beginner | Estimated Time: 0.5-1.0 hours
⚠️ Safety & Precautions
- ⚠️ Wear safety glasses and gloves—battery acid is corrosive.
- ⚠️ Keep sparks/flames away; batteries can vent explosive gas.
- ⚠️ Remove the negative (-) cable first and install it last to reduce short-circuit risk.
- ⚠️ Don’t let a tool bridge the positive terminal to metal—this can arc and damage electronics.
- ⚠️ Battery disconnect is required for replacement; you may lose clock/radio presets.
🔧 Required Tools
You'll need the following tools for this repair:
- 10mm socket
- 1/4" ratchet
- 3" socket extension
- 10mm combination wrench
- Battery terminal puller (specialty)
- Battery post/terminal cleaning brush
- Torque wrench (inch-pound or low-range)
- Nitrile gloves
- Safety glasses
🔩 Required Parts
HowToo sells all the parts you need for this repair:
- 12V battery (Group 35, 550+ CCA) - Qty: 1
- Battery terminal anti-corrosion spray - Qty: 1
- Battery terminal felt washers (red/green) - Qty: 1 set
- Baking soda (for corrosion neutralizing) - Qty: 1
📋 Before You Begin
- 🅿️ Park on level ground, shift to Park, set the parking brake, and turn the ignition OFF.
- 🔑 Remove the key/fob from the vehicle and keep it a few feet away.
- 🧠 If you want to preserve radio presets, use a memory saver. (A memory saver is a small device that powers the car through the OBD port while the battery is out.)
- 🧼 If you see crusty buildup on the terminals, mix a little baking soda with water and have it ready.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Open the hood and locate the battery
- The battery is at the front of the engine bay with a hold-down bracket across the top.
- Put on safety glasses and nitrile gloves.
Step 2: Disconnect the negative (-) battery cable
- Use a 10mm socket with a 1/4" ratchet to loosen the negative terminal clamp nut.
- Wiggle the clamp up and off the negative post. If it’s stuck, use a battery terminal puller (specialty). (A terminal puller presses the clamp off without prying.)
- Tuck the negative cable to the side so it cannot spring back and touch the battery.
- Torque to 5 N·m (44 in-lb / 3.7 ft-lb) when reinstalling.
Step 3: Disconnect the positive (+) battery cable
- Use a 10mm socket to loosen the positive terminal clamp nut and remove the clamp from the positive post.
- Move the positive cable aside without letting it touch any metal parts.
- Torque to 5 N·m (44 in-lb / 3.7 ft-lb) when reinstalling.
Step 4: Remove the battery hold-down bracket
- Use a 10mm socket, ratchet, and 3" extension to remove the two hold-down nuts.
- Lift off the hold-down bracket and set it aside.
- Torque to 7.5 N·m (66 in-lb / 5.5 ft-lb) when reinstalling.
Step 5: Remove the old battery
- Lift the battery straight up and out carefully. Batteries are heavy—use your legs, not your back.
- Keep it level to avoid spills.
Step 6: Clean the battery tray and terminals (if needed)
- If you see corrosion (white/blue crust), lightly scrub using a battery post/terminal cleaning brush.
- If needed, apply a small amount of baking soda + water to neutralize corrosion, then wipe dry.
- Make sure everything is dry before installing the new battery.
Step 7: Install the new battery
- Place the new Group 35 battery into the tray in the same orientation as the old one.
- Reinstall the hold-down bracket and tighten with a 10mm socket.
- Torque to 7.5 N·m (66 in-lb / 5.5 ft-lb).
Step 8: Reconnect cables (positive first, negative last)
- Install the positive (+) clamp first and tighten using a 10mm socket.
- Torque to 5 N·m (44 in-lb / 3.7 ft-lb).
- Install the negative (-) clamp last and tighten using a 10mm socket.
- Torque to 5 N·m (44 in-lb / 3.7 ft-lb).
- If you have them, install felt washers and apply anti-corrosion spray after everything is tight.
Step 9: Final checks
- Gently try to rotate each terminal by hand—if it twists, tighten slightly with the 10mm socket.
- Confirm the battery is secure and cannot move in the tray.
✅ After Repair
- 🚗 Start the engine and confirm normal cranking speed and no warning lights related to low voltage.
- 🕒 Reset the clock and radio presets if they were lost.
- 🪟 If the auto-up/down window doesn’t work, relearn it: fully lower the window, then fully raise it and keep holding the switch up for 2-3 seconds.
- 🔍 Check that the terminals stay cool after a short drive—hot terminals can mean they’re loose.
💰 DIY vs Shop Cost
Shop Cost: $220-$380 (parts + labor)
DIY Cost: $140-$240 (parts only)
You Save: $80-$140 by doing it yourself!
Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hours.
🎯 Ready to get started?
HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.


















