this is a long read sorry. this description/operation listing from FCA
"The eTorque system automatically stops and starts the engine when certain conditions are met to improve fuel economy and lower Carbon Dioxide (CO2) emissions. The eTorque enable and disable selection switch is integral to the ICS.
The Battery, Starting, and Charging systems operate in conjunction with one another, and must be tested as a complete system. For correct operation of starting/charging systems, all components used in these 3 systems must perform within specifications. When attempting to diagnose any of these systems, it is important that you keep their interdependency in mind.
Certain starting system components and functions of the eTorque system are On Board Diagnostics (OBDII) monitored and will produce Diagnostic Trouble Codes (DTC). The use of the diagnostic scan tool is not only recommended, but it is necessary for proper diagnosing of the eTorque system and the components or systems that are related to eTorque system functions. Review the component and system information listed below in the operation section for diagnostic information. Otherwise, review the wiring diagram application as well as section 28 DTC diagnostics service information located in TechCONNECT.
The E-Torque system uses a high torque electric 48 Volt motor to function as a starter for Electric Start/Stop. The E-Torque system when active will shut the engine off with a signal from the PCM when the vehicle is stopped, and then start the engine when there is a demand for power. The E-Torque system on this vehicle utilizes a contained cooling system between the MGU and the Power Pack Unit (PPU), for more information on the cooling system for the E-Torque system(Refer to 07 - Cooling/Standard Procedure) .
The vehicles first engine crank event is managed by the driver acting on the ignition state and requesting an engine crank request. When this request occurs, the BCM cranking relay is opened and the PCM cranking relay is closed. When the engine is ON and the engine cranking phase has ended, the PCM cranking relay will now be opened and the BCM cranking relay will now be closed. All of the next automatic eTorque cranking events managed in the same Key-On ignition cycle are performed maintaining the BCM cranking relay closed and setting closed the PCM cranking relay. Each time an eTorque cranking event occurs which causes the engine to come on again, the PCM cranking relay is opened.
For vehicles equipped with an Automatic Transmissions (ATX), the restart procedure for the TCM is performed when the PCM requests an eTorque auto start event to occur, the PCM sends a request to start” message to the TCM. The TCM will then engage the neutral gear to avoid vehicle movement in case of a TCM module reset event during the engine cranking stage of the eTorque event. The TCM sends a signal to the PCM advising the PCM that the transmission is ready for the eTorque event to occur.
For vehicles equipped with a Manual Transmission (MTX), the PCM will initiate the eTorque start event with a short press of the clutch pedal when the MTX is in neutral. The PCM will allow an eTorque autostart event to occur while in a ranged gear if the clutch pedal travel goes past the interlock position. Otherwise the PCM will trigger an IPC display message to alert the driver to either press the clutch in or shift the transmission into neutral.
• Auto Start-Stop management
• Torque management with Torque smoothing and power assist
• Regenerative Braking
• 48V System Power Management
Monitor and report 48V battery cell voltage, current and temperature and battery pack info
Convert AC from the E-Machine (generator) to DC for storage in 48V battery
• Motor Control
• 12V System Power Management
Convert 48V DC to LV DC to provide vehicle accessory power and charge the 12V battery
• Thermal Management
Cool the E-Machine, Inverter, Battery, and DC-DC Converter
• HMI Updates
• The 48V-MGU is electrically connected to:
• The 48V power distribution network (48VB+ and 48VB-), composed of at least by a 48V Battery System
• The 12V standard boardnet for power supply (positive and ground)
• The vehicle network for information exchange via serial communication line (CAN)
The PPU is a 48V battery pack that will supply voltage for the eTorque system to start the engine during stop/start event. The high voltage battery can also supply voltage to the 12V system when needed. The PPU on the vehicle is liquid cooled on the 2.0L equipped eTorque system, for more information on the cooling system for the e-Torque system (Refer to 07 - Cooling/Description and Operation) .
The PPU has a 12V and 48V connection to it to allow for the charging of the two different voltages. The PPU contains the Battery Pack Control Module (BPCM) and is replaced as part of the PPU (Refer to 08 - Electrical/eTorque System/UNIT, Power Pack (PPU) /Removal and Installation)."
EDIT : battery price is just shy of $2600.00 in Canada. not sure what price would be south o the border.