Disclaimer: This post is a question about how the van handles excess energy that is regenerated during driving, but potentially with nowhere to store the energy.
It has become clear to me during my road trips that the van is very efficient when traveling in mountain roads. The frequent curves, inclines, and declines allow me to utilize the L-gear (engine brake) for descents, physically apply the brakes, and cruise without stepping on the gas pedal. This type of driving has consistently allowed the PacHy to get good efficiency both when climbing mountains (that have some areas of descent) and especially on descents.
During a recent visit to Yosemite National Park, I rented a house that allowed 120V charging. On the day we left, the motive battery was fully charged, and we began our descent of the mountain. Although there were many short segments of uphill driving, the majority of the drive was downhill. I drove for about an hour straight, with speeds up to 50+ mph, without using gasoline.
With the recent and not-so-recent reminders of various PacHy's catching fire, I thought about heat management and how the van handles regen energy when the motive battery is effectively fully charged. When connected to a Level 2 charger, the van and the 12V battery stops accepting electricity, in theory, when full. In the case of abundant regen via mostly-downhill cruising, L-gear engine-braking, and physically braking, I wondered if I made a mistake to fully charge the motive battery before I left the rental house.
Has this been discussed before? Or how does the van handles this situation so as to not damage the hybrid components? In future scenarios like this, should I purposely avoid fully charging the motive battery before my descent?
On an unrelated or possibly related, note, the passengers in the van smelled a sweet odor, likely that of coolant. On a previous mountain trip, the sweet odor inside and outside the van during and after driving was associated with a leaking heater core, which was subsequently replaced. I'm now wondering if the odor is correlated with mountain driving and excess heat generated from frequent acceleration and deceleration (and associated charging). FYI, the coolant level in the engine coolant reservoir is 1" to 2" above the marked maximum level (filled by dealer mechanic), but each time I parked the van and looked under the hood (hot engine; both running and not running), the coolant level was not near the lid. The other two coolant reservoirs were within the normal ranges.
Thanks for your input and for reaching the end of this long post.
The following doesnt specifically answer your question, but does explain what is going on when you press the brake.
Did your guage ever regen to 100% at anytime?
You may have noticed that Driving the first 1/4mile after the vehicle is charged there is no regenerative braking. The van switches to 100% friction braking, and after some energy is skimmed then regen occurs but is limited.
Also does your coolant change level ever? or is it always 1-2” overfilled? Changing more than 1/4” is not normal..
Your technically not supposed to exceed “maximum”.. from my experience it causes higher than normal pressure in the system which can cause damage and leaks. But this isn't usually an immediate effect. You should drain this back to max.
::: Function Description of Brakes and ABS from Tech Authority. :::
DESCRIPTION AND OPERATION
The brake system is equipped with:
- Self-ventilated front disc brakes.
- Dual piston front disc brake calipers.
- Single piston rear disc brake calipers.
- An Anti-Lock Brake System (ABS) assembly that includes a hydraulic control unit, an electronic control unit, hydraulic valves that modulates braking pressure through eight solenoids (2 per wheel) and a hydraulic pump.
- Wheel speed sensors are located in the front and rear hub and bearing housings.
- Brake warning lights on the instrument cluster.
- A brake pedal sensor that sends an operating signal to the ABS control unit and also controls the brake lights.
The Electric Brake Booster Module (EBBM) provides consistent brake pedal pressure to the driver regardless if the braking is through friction, regenerative or a combination of both.
The Electronic Stability Control (ESC) receives the driver requested brake torque and the capacity of regenerative braking that can be achieved. The ESC uses this information to calculate and request the appropriate regenerative brake torque and applies the appropriate amount of friction brake torque to meet the total driver requested brake torque. The ESC can choose when to use regenerative braking, friction braking, or a blended combination of both. Regenerative braking does not affect the vehicles braking performance, pedal effort or stopping distance.
The Hybrid Control Processor (HCP), which is located within the Power Inverter Module (PIM),does not request regenerative braking power that is larger than the power boundary of the high voltage battery. The HCP does not process a regenerative braking torque request that is larger than the e-motors torque limits. The electric motor(s) capacity will be determined based upon the thermal characteristics of the motor(s) at the time of a regenerative brake request. The HCP does not send a request to the ESC a regenerative braking torque capacity that is larger than can be achieved by the electrified powertrain.
The ESC does not request regenerative braking when any of the following conditions are true:
ABS is active
ESC is active
Traction Control (TC) or Anti Spin Regulation (ASR) is active
Neutral gear is selected
Instability conditions are detected
ESC fault that prevents regenerative braking
The HCP does not enable regenerative braking when any of the following conditions are true:
Vehicle speed is greater than the maximum regenerative speed
Vehicle speed is less than the minimum regenerative speed
Cyclic Redundancy Check (CRC)/Message Counter (MC) failure
Vehicle shift lever position is in reverse
The EBBM shall provide a calibrated rate of change, determined during development, in the control of the transitions between regenerative and friction brake torque in a dynamic environment.
The ESC achieves the driver total braking input torque request through either regeneration, friction or a combination of both. The ESC controls the transitional and steady-state conditions between regenerative and friction braking torques under all use applications. The ESC allocates the brake torque blending between regeneration and friction. The ESC does not request a regenerative braking torque request that is greater than the regenerative brake torque capacity. The ESC receives signals from the EBBM to determine the driver intended braking torque. The ESC receives signals from the HCP to determine the available regeneration torque.
When the EBBM detects a CRC/MC error then the EBBM will not enable regenerative braking and will set the appropriate DTC and send a signal to the Instrument Cluster (IC) to illuminate the warning light.
When the ESC detects a CRC/MC error then the ECS will not enable regenerative braking and will set the appropriate DTC and send a signal to the IC to illuminate the warning light.
The standard Electronic Stability Control (ESC) system is a four-channel independent control to all four corners of the vehicle, with a active handling system that links the vehicle’s dynamic control systems to assist the driver in maintaining control under demanding or adverse conditions. ESC primarily integrates the ABS and Traction Control Systems (TCS) to control all 4 corners of the vehicle in response to yaw and in relation to steering input. The system’s algorithm determines when to activate the system based on data from the vehicle’s sensors: wheel speed, yaw rate, lateral acceleration, master cylinder pressure, steering wheel angle and vehicle velocity.
The Electronic Brake Distribution (EBD) function regulates the rear wheel slip independently during braking to keep the wheels stable and optimize the braking distribution between axles.)
The EBD manages the distribution of the braking torque between the two axles limiting braking pressure to the rear axle to prevent overslip and to avoid vehicle instability.
During turning phase the EBD intervention level will be defined also with the target to reduce possible vehicle drift in straight maneuvers. A correct EBD intervention level shall minimize vehicle drift.
EBD is available during braking maneuvers. EBD is activate when the rear axle slip exceeds the target value.
If EBD is active it shall be switched off in case of ABS intervention on the rear axle. The ESC shall calculate target rear slip for both wheels for electronic brake distribution function.
The ESC shall estimate the rear brake pressure for both the wheels for electronic brake distribution function.
The ESC shall regulate rear slip for electronic brake distribution function.
The system also features:
Brake/Lock Differential regulates braking pressure side-to-side on the driven axle to optimize stopping distances and vehicle sway control under all vehicle-loading conditions.
Traction Control System (TC) is integrated with the ABS, also an all-speed, four-channel system. It combines both torque and brake control to regulate wheel spin at all driving speeds and conditions. The system can be turned off via a button located on the center console.
Brake Assist (BA) senses emergency braking by detecting the speed or force the driver applies to the brake pedal and boosts the power as needed.
Engine Drag Control (EDC) senses if there is a difference in speed between the free rolling wheels and the driven wheels. Under these conditions the EDC sends more torque to the driven wheels to ensure all 4 wheels are spinning at similar speeds, resulting in enhanced stability and vehicle dynamics.
Trailer Sway Control detects the trailer moving in one direction, then applies selective brake pressure on the tow vehicle’s opposite side (called asymmetric braking). This creates counter-moments to the forces applied on the vehicle from the trailer, dampens the motion and helps to reduce the sway.
Hill Start Assist (HSA) prevents the vehicle from rolling on an up or down gradient. The system engages automatically when a gradient of five-percent or more is detected. It then acts to hold the truck stationary for two seconds after the brake is released, giving the driver time to apply the throttle.
Rollover Mitigation determines when a vehicle is experiencing extreme lateral tire force and activates (selected braking forces at the corners of the vehicle) to reduce these forces and reduce the chance of rollover events.
Automatic Brake Lamp Actuation senses emergency brake situations earlier than humanly possible (via brake pedal sensing and steering angle positioning) and actuates/flashes the tail lamps.