Battery Replacement — Start-Stop and eTorque Systems

The 2018+ Wrangler JL ships with an AGM H7 (BCI group 94R) main battery — typically 80 Ah and 850 CCA. eTorque trims (2.0L turbo and 3.6L with the 48V mild hybrid) add a small 12V AUX14 auxiliary AGM battery rated around 200 CCA, plus the separate 48V lithium-ion pack that handles the mild hybrid functions. The 48V pack carries an 8-year warranty and is not a DIY part. The auxiliary 12V AGM and the main H7, however, are both owner-serviceable.

Use AGM only. The JL's body control module is configured for AGM charging voltage and current profiles. Drop in a flooded lead-acid battery and the BCM will overcharge it on highway runs and undercharge it during ESS stop events, which kills the battery in months and throws "Service Stop/Start System" warnings. Quality H7 AGM options include Mopar OEM (Interstate MTX-94R/H7), Odyssey AGM94R, Optima YELLOWTOP DH7, and the OEM eTorque part 56029720AA. Expect to pay $250–$350 for a quality H7 AGM.

The auxiliary battery on start-stop and eTorque trims lives on the passenger side firewall under a small cover. It powers electronics during the ESS engine-off pause so cabin power, infotainment, and HVAC don't drop out. When it fails, ESS stops working and you'll see a service message — but the truck still runs fine on the main battery alone. Replacement AUX14 batteries run $90–$140.

After replacing either battery, the BCM needs to register the new battery so it can manage charging correctly. On non-eTorque JLs the system usually self-relearns within a few drive cycles. On eTorque trims, a Mopar dealer or aftermarket scan tool (Topdon, Autel, wiTECH) is recommended to perform a battery registration. Without registration, the alternator may not properly charge the new battery, shortening its life by half.

Steps

1. Park on level ground and turn off all accessories. Open the driver door so the BCM stays awake briefly.
2. Optional: plug a memory saver into the OBD-II port to preserve radio presets and adaptive transmission learning.
3. Open the hood. Loosen the 10mm negative (black) terminal clamp on the main battery first. Tuck the cable aside.
4. Loosen the 10mm positive (red) terminal clamp and remove the plastic cover. Tuck the cable aside.
5. Remove the 13mm battery hold-down bracket bolt at the front base of the battery.
6. Lift the battery straight up — it weighs roughly 50 pounds.
7. Clean the tray and terminals with a battery brush. Inspect for corrosion or moisture damage.
8. Set the new AGM battery in place with terminals matching the original orientation.
9. Reinstall the hold-down bracket and torque the 13mm bolt snug — do not overtighten.
10. Connect the positive terminal first, then the negative. Tighten the 10mm clamps until snug.
11. For eTorque or start-stop trims, perform a battery registration with a scan tool that supports BCM coding.
12. For the auxiliary battery: open the passenger-side firewall cover, disconnect the small terminals (10mm), remove the strap, and swap. Reverse to install.

Why it works

• 30–60 minute job in the driveway
• $250 DIY vs. $500+ at the dealer
• Restores start-stop function and clears service messages
• AGM batteries handle deep-cycle abuse better than flooded

Trade-offs

• Battery registration may require a scan tool on eTorque trims
• AGM costs roughly 2x a flooded H7
• The 48V lithium pack on eTorque is dealer-only
• AUX14 auxiliary battery is buried behind a firewall cover

Tools required

• 10mm socket
• 13mm socket
• ratchet
• battery terminal brush
• memory saver (optional)

Parts

Sources

• JL Wrangler Forums — Main and Aux Battery Size
• 2021 3.6 eTorque OEM Battery Specs
• Wrangler Forum — Auxiliary Battery AGM Discussion

Related

• All Jeep Wrangler JL guides & tools
• Browse the full DIY database

Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.