2018 Pacifica Gas models with ESS have a small auxiliary battery right next to the main battery.
My question is: When at a stop and the engine is shut down, which battery is running the AC, Entertainment, Lights, wipers, etc? Is the small auxiliary battery used to run that stuff, or is it isolated and saved for restarting the gas engine?
It doesn't matter, as long as it all works, but I'm curious.
The small battery powers the majority of the electrical needs of the van when the engine shuts off, which reserves the larger cranking battery for engine starting. This is from the factory shop manual:
How does the ESS system function - simple overview:
- ESS shuts the engine off when the vehicle stops
- The vehicle has to be stopped for a pre-set time before the engine is switched off
- Then, it restarts when the driver releases the brake to move the vehicle
- The system senses brake pedal position and vehicle speed to determine that the vehicle is moving
- Powertrain calibration makes the decision when to shut off the engine and when to restart the engine again
- The ESS function is transparent to the driver
- When the engine stops, a smaller secondary battery keeps accessory features powered, like the fan, wipers, headlights, audio system, etc.
- A Dual Battery Control and Power Relay Control are used to smooth out voltage dips when the starter cranks the engine