Tools you need for battery on a 2016-2021 Honda Civic

Swapping the battery on a 10th-gen Civic is one of the easiest jobs on the car. Everything sits in the front driver's-side corner: two terminal clamps (usually 8 mm nuts) and one long 10 mm hold-down bolt that threads into a J-hook rod down the outboard side of the tray. That bolt is the only awkward part, so grab a 6 to 10 inch extension instead of trying to reach it with a stubby ratchet.

Both the 2.0 K20C2 and the 1.5 turbo L15B7 use the same Group 51R battery and the same fasteners, so nothing changes by engine. The thing people get wrong is over-tightening the hold-down bolt and cracking the case or bending the tray, and skipping the memory saver then wondering why the power windows no longer auto-up and the idle hunts for a few minutes. Both are avoidable in about 30 seconds each.

Complete tool and parts list

Differences within the 2016-2021 generation

No difference between the 2.0 K20C2 and the 1.5 turbo L15B7: same Group 51R battery, same 8 mm terminal nuts and 10 mm hold-down bolt. Si and Type R use the same tray and fasteners, though Type R often gets a lighter-duty battery from the factory.

Torque specs

How the job goes

1. Park on level ground, turn the ignition fully off, remove the key/fob from the car and let it sit a minute so modules go to sleep.
2. Open the hood and locate the battery in the front driver's-side corner. Lift off the plastic terminal cover and the black insulating jacket if fitted.
3. If you want to keep presets and learned values, plug a memory saver into the OBD-II port under the driver's dash before disconnecting anything.
4. Loosen the negative (black, -) terminal nut with an 8 mm socket (10 mm on some clamps), spread the clamp and lift it off. Tuck the cable aside so it can't touch the post.
5. Loosen and remove the positive (red, +) terminal clamp the same way, then set the cable clear of the battery.
6. With a 10 mm socket on a long extension, unscrew the hold-down bolt at the outboard edge of the battery and remove the bracket and its J-hook rod. Keep the rod; you need it for the new battery.
7. Lift the battery straight up and out with a carry strap, keeping it level. Watch the fender lip and the surrounding plastic.
8. Inspect the tray. If there is white/green corrosion, scrub it with baking soda and water, rinse lightly and dry fully.
9. Clean both cable clamps inside and out with the terminal brush.
10. Set the new Group 51R in the tray with the positive post in the same corner as the old one (the cables will only reach one way).
11. Refit the J-hook rod and hold-down bracket and tighten the 10 mm bolt until the battery is firm and cannot rock. Do not over-tighten or you will distort the case and tray.
12. Connect the positive clamp first and tighten the nut snug (about 9 Nm). Then connect the negative clamp and tighten it.
13. Spray both terminals with protectant, refit the insulating jacket and the plastic terminal cover, and remove the memory saver.
14. Turn the ignition on. Reset the clock and radio presets if needed, and re-cycle each power window fully down then fully up and hold to relearn auto-up.
15. Start the engine and let it idle 5-10 minutes with the A/C off so the ECU relearns idle. Drive normally; a faint stumble on the first couple of starts is normal.

Watch out

Terminal clamp nuts on this generation are usually 8 mm with some 10 mm variants, and the hold-down bolt is 10 mm; check yours with both sizes before forcing anything, and confirm torque values in the factory service manual.

Other jobs on the 2016-2021 Honda Civic

Battery Replacement on other vehicles