How to Replace the Battery on a 2018 Honda Accord

The quick overview: use a compatible Group 51R 12-volt battery (AGM or flooded per your trim’s spec), disconnect the negative cable first, then the positive, swap the battery, reconnect positive first then negative, secure the hold-down, and finish with a battery-management reset and window re-initialization. Below is a step-by-step guide, fitment notes, required tools, safety tips, and what to do after installing the battery to ensure all systems work correctly.

Which Battery Fits a 2018 Honda Accord

Before you buy, confirm the exact battery specification for your trim. You can verify the size and type in the owner’s manual, on the existing battery label, or via a reputable parts lookup using your VIN. The notes below reflect what most 2018 Accords use in North America.

• Most gasoline trims (1.5T and 2.0T): Group 51R, top post, reverse polarity; typically 410–500+ CCA. Standard flooded batteries are common; AGM is an upgrade that tolerates heat and short-trip use better.
• Hybrid: uses a conventional 12V auxiliary battery as well; many trims also use Group 51R and typically AGM. The 12V battery location may differ (often in the trunk area). Do not touch orange high-voltage cables.
• If your Accord has Idle Stop/Start (market- and trim-dependent), follow Honda’s recommendation for AGM/EFB chemistry to support frequent restarts.
• Dimensions must match Group 51R so the hold-down and cables fit correctly; match terminal orientation (R = reverse polarity).

When in doubt, match what came out: same group size, polarity, and chemistry. If upgrading chemistry (e.g., to AGM), ensure your parts source specifies compatibility with your trim.

Safety, Tools, and Preparation

Battery work is straightforward but demands care. The steps and tools below help you complete the job safely and avoid damage to electronics or injury.

• Safety glasses and gloves
• 10 mm wrench or socket (terminals), 12 mm socket (hold-down on many trims)
• Battery terminal brush or small wire brush
• Dielectric grease or battery protectant spray
• Baking soda/water mix and a rag (to neutralize corrosion)
• Memory saver (OBD-II or 12V accessory port), optional but helpful
• Multimeter (optional, to check resting and charging voltage)

Work on a cool engine, park on level ground, set the parking brake, and keep metal tools away from both terminals at once to avoid short circuits.

Step-by-Step: Replacing the Battery

This procedure covers the common under-hood installation on gasoline trims. Hybrid models follow a similar process, but location and covers differ; consult your owner’s manual for access panels and exact placement.

1. Preserve settings (optional): Connect a memory saver to retain radio presets and window/mirror positions. The 2018 Accord typically won’t need a radio anti-theft code, but presets and clock can reset without a memory saver.
2. Shut down: Turn the engine off, remove the key or turn the vehicle fully off, and open the hood. Identify the battery: the positive terminal usually has a red cover; the negative often has a small sensor on the cable.
3. PPE: Put on safety glasses and gloves.
4. Disconnect negative first: Use a 10 mm wrench to loosen the negative (-) clamp. Wiggle it free and secure the cable away from the battery so it can’t spring back.
5. Disconnect positive: Flip up the red terminal cover, loosen the 10 mm nut, and remove the positive (+) clamp.
6. Remove hold-down: Loosen and remove the hold-down bolts/bracket (often 10–12 mm). Note any shims or spacers so you can reinstall them in the same orientation.
7. Lift out the battery: It’s heavy; use proper lifting technique. Watch for any vent tubes and keep acid upright.
8. Prepare the tray and cables: Clean corrosion with a baking soda/water mix, rinse and dry. Brush the inside of the terminal clamps to bare metal.
9. Compare batteries: Confirm the new battery’s group size (51R), height, terminal layout, and that any shipping caps/vent plugs are removed as directed.
10. Install the new battery: Place it in the tray with the same orientation as the old one. Ensure cables and the negative battery sensor are not stressed or pinched.
11. Reinstall hold-down: Tighten evenly until snug so the battery cannot move. Typical hold-down torque is about 15–20 lb-ft (20–27 N·m); do not overtighten.
12. Reconnect positive first: Install the positive (+) clamp and tighten until the clamp does not rotate by hand. Typical terminal clamp torque is around 45–55 in-lb (5–6 N·m).
13. Reconnect negative last: Install the negative (-) clamp onto the post and tighten similarly. Ensure the battery sensor (if equipped) remains aligned on the negative cable.
14. Protect terminals: Lightly coat with dielectric grease or apply protectant spray to reduce future corrosion. Close the red terminal cover.
15. Verify operation: Start the engine. A healthy charging system typically reads about 13.5–14.8 V across the battery with the engine running.
16. Battery Management System (BMS) reset: If your Accord has a battery sensor (most do), use a scan tool with Honda’s BMS/battery reset function after replacement. If a tool isn’t available, the system usually relearns within a few drive cycles; you can help by idling with no accessories for ~10 minutes, then taking a steady-speed drive (10–20 minutes) with minimal loads.
17. Re-initialize auto windows and roof (if equipped): Ignition ON. For each window, fully lower, then fully raise and hold the switch up for ~2 seconds. Repeat per window. Similar procedure applies to the moonroof (consult the manual).
18. Restore settings: Reset the clock and re-enter any preferences if you didn’t use a memory saver.

Following this sequence—negative off first, on last—prevents accidental short circuits. The post-install resets ensure the electrical system charges correctly and convenience features operate normally.

Notes for Hybrid Models

The 2018 Accord Hybrid also uses a 12V auxiliary battery for starting the control systems; replacement is similar to gasoline models but access may differ and the battery is often located in the trunk area behind a panel on the right side. The high-voltage system is separate—never touch orange high-voltage cables or service plugs. If you are unsure, have a qualified technician perform the replacement.

Troubleshooting After Installation

If something doesn’t seem right after the swap, the checks below resolve most issues quickly.

• No crank or intermittent power: Ensure both terminal clamps are fully seated and tight; verify the hold-down isn’t contacting terminals.
• Warning lights or charging message: Confirm the negative battery sensor is properly positioned and its connector is secure; perform a BMS reset with a scan tool if available.
• Auto up/down windows inoperative: Re-initialize each window as described above.
• Low voltage reading: Fully charge the new battery with a smart charger and recheck. New batteries can ship partially charged.
• Corrosion returns quickly: Clean thoroughly and use protectant; check for overcharging issues if corrosion is severe.

If problems persist, test the battery and charging system. Most parts retailers will load-test a battery and check alternator output at no cost.

Disposal and Core Return

Lead-acid batteries are recyclable and typically carry a core charge that you get back when returning the old unit. Handle and dispose of them responsibly.

• Keep the old battery upright to avoid acid spills.
• Return it to the retailer for a core refund or take it to a local recycling center or hazardous waste facility.
• Never discard a battery in household trash or leave it outdoors.

Recycling recovers lead and plastic safely and helps you recoup the core charge from your purchase.

AGM vs. Flooded: Which Should You Choose?

Choosing the right chemistry can improve reliability based on your driving patterns and climate.

• AGM: Better for frequent short trips, high accessory loads, hot/cold extremes, and trims with Idle Stop/Start. More expensive but more resilient.
• Flooded: Lower cost and adequate for typical commuting in moderate climates if your trim doesn’t require AGM/EFB.
• Always follow Honda’s recommendation for your specific trim and market; mixing types without confirmation isn’t advised.

When upgrading to AGM, verify compatibility in a trusted parts catalog for your VIN and consider using a scan tool to reset the BMS for accurate charging.

Summary

Replacing the battery on a 2018 Honda Accord is a manageable DIY job: confirm a Group 51R battery that matches your trim, disconnect negative then positive, swap and secure the new unit, reconnect positive then negative, and perform post-install resets (BMS and window initialization). Use proper safety gear, avoid short circuits, and recycle the old battery. If your Accord is a Hybrid or equipped with a battery sensor, follow the noted precautions and consider a scan-tool BMS reset to ensure optimal charging and system behavior.

How to replace a 2018 Honda Accord battery?

And has three 10 mm nuts that need to be loosened to remove the battery. Start the battery removal by removing the negative terminal first loosen and then wiggle the battery terminal clamp to free it.

What kind of battery do I need for a 2018 Honda Accord?

The Honda Accord 2018 battery type depends on the engine, with the 1.5L engine typically using a Group Size H5 (or 47) AGM battery, and the 2.0L and Hybrid models using a Group Size H6 (or 48) AGM battery. You should confirm the exact battery group size by checking the sticker on your current battery or referring to your car’s owner’s manual.
 
Key Details

• 1.5L Engine: Generally uses a Group Size H5 (or 47) AGM battery. 
• 2.0L & Hybrid Engines: Typically use a Group Size H6 (or 48) AGM battery. 
• AGM vs. Standard: The 2018 Accord often comes with an Absorbed Glass Mat (AGM) battery for better performance, and you should not replace an AGM with a standard flooded battery. 

How to Confirm Your Battery Type

1. Check the sticker on your current battery: The group size (e.g., H5, H6) and type (AGM) should be listed on the label. 
2. Consult your owner’s manual: This will provide the exact specifications for your specific vehicle. 
3. Use an auto parts store locator tool: Websites like Firestone Complete Auto Care, Advance Auto Parts, or AutoZone.com have tools to help you find the correct battery for your year and engine. 

How do I reset the battery on a Honda Accord?

Honda Battery Reset

1. Turn the ignition switch to LOCK and remove the key.
2. Disconnect the battery negative cable first, then disconnect the positive cable.
3. Short the battery cables together with a jumper wire.
4. Turn the ignition switch to ON and wait 10 minutes.
5. Turn the ignition switch to LOCK and remove the key.

How much does it cost to replace the battery in a Honda Accord 2018?

The average cost for a Honda Accord Battery Replacement is between $223 and $244. Labor costs are estimated between $45 and $66 while parts are typically priced around $178. This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.