Where Is 2018 Jeep Compass ESS Battery Located?
2018 Jeep Compass ESS Battery Location: The auxiliary battery for the Engine Start-Stop (ESS) system in the 2018 Jeep Compass is typically located in the rear cargo area, beneath the floor panel on the driver’s side. This 12V lithium-ion or AGM battery powers the ESS functions independently of the primary starting battery, which resides under the hood near the firewall. Access requires removing the cargo floor trim and protective cover. Pro Tip: Disconnect the negative terminal of the main battery before servicing the ESS unit to prevent electrical faults.
Why does the Jeep Compass have two batteries?
The ESS system requires a dedicated auxiliary battery to maintain power to critical electronics (e.g., infotainment, sensors) during engine restarts. This prevents voltage drops that could reset systems or strain the primary battery. Unlike conventional setups, the ESS battery handles short-duration, high-frequency cycling, while the main battery focuses on cold-cranking amps (CCA) for ignition.
In the 2018 Compass, the primary battery (Group 48 H6) delivers 700–800 CCA and sits in the engine bay. The ESS unit, however, uses a smaller 12V lithium-ion or absorbed glass mat (AGM) battery rated 20–30Ah. This separation ensures the ESS doesn’t drain the starter battery during traffic stops. For example, if the ESS battery fails, the vehicle may display “Service Stop/Start System” warnings or fail to auto-restart. Pro Tip: Test ESS battery health every 15,000 miles using a load tester—voltages below 12.4V indicate replacement urgency.
How do I access the ESS battery in a 2018 Jeep Compass?
Accessing the ESS battery requires removing trim panels in the cargo area. Follow these steps:
1. Disconnect the primary battery to deactivate the 48V system.
2. Lift the cargo floor mat and unscrew the plastic fasteners securing the side trim.
3. Pull the trim panel outward to reveal the ESS battery compartment.
4. Unbolt the metal retention bracket and disconnect terminals (negative first).
You’ll need a T20 Torx bit and 10mm socket for this task. The process takes 15–20 minutes, but rushing risks breaking trim clips or pinching wiring harnesses. Practically speaking, this design prioritizes space efficiency over serviceability—a trade-off common in modern SUVs. For instance, Mercedes-Benz C-Class hybrids use similar rear-mounted ESS layouts but include service flaps for easier access.
| Component | Primary Battery | ESS Battery |
|---|---|---|
| Location | Engine bay | Rear cargo area |
| Function | Ignition, lighting | Auto stop-start, sensors |
| Testing Interval | Every 12 months | Every 15k miles |
Battery Expert Insight
FAQs
Yes, but it requires aftermarket modules or persistent button presses. Disabling ESS voids no warranties but reduces fuel efficiency by 5–7% in city driving.
What happens if the ESS battery dies?
The vehicle defaults to primary battery operation, disabling auto stop-start and triggering dashboard alerts. Immediate replacement is advised to prevent CAN bus communication failures.