L-mode drives like D?

Chevy Spark EV Forum

Help Support Chevy Spark EV Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Oceanbreeze

Member
Joined
Apr 2, 2021
Messages
23
Location
SF bay area (Berkeley)
I almost always drive in L mode in town.

This morning I turned on the car after charging fully (and also remote recond.), and immediately noticed that while I was in L it behaved exactly like D. Thinking it might be some issue with the shifter switch, I stopped and shifted to P and back down to L, and still it drove like in L.

I kept it in L, and after driving for a bit (maybe 1 mile?) it started behaving like normal, i.e., with more aggressive regen. It was fine for the next 6 miles.

Anyone else had that happen?

Any suggestions as to what to look for? (I'll check the AGM battery voltage later today.)
 
Oceanbreeze said:
I almost always drive in L mode in town.

This morning I turned on the car after charging fully (and also remote recond.), and immediately noticed that while I was in L it behaved exactly like D. Thinking it might be some issue with the shifter switch, I stopped and shifted to P and back down to L, and still it drove like in L.

I kept it in L, and after driving for a bit (maybe 1 mile?) it started behaving like normal, i.e., with more aggressive regen. It was fine for the next 6 miles.

Anyone else had that happen?

Any suggestions as to what to look for? (I'll check the AGM battery voltage later today.)
I used to drive in L all of the time. I suspect what you are seeing is protection for a fully charged battery. I think when the battery is fully charged, the regen activity is reduced to protect the battery. Then after the battery has room to accept a higher charge rate, you will feel the regen kick in as the car quickly decelerates. Also, when driving in L, the brake lights will come on if you take your foot off of the accelerator pedal and let the car decelerate quickly. You need to test this at night to verify. This is great when driving in stop and go traffic like you find in town.
 
I'd like to add that the car should allow some regen at 100% SOC if you use 100% heater / HVAC power + rear defrost.

To my understanding, the power management scheme limits net regen at 100% SOC, so by increasing power consumption in the vehicle, the regen power will be diverted to those ~7kW loads, and the instrument cluster will seem to indicate net 0 kW during regen braking.

The energy management system will switch from battery charging to sending power to what we can functionally describe as a dump load in order to keep the electric motor loaded down as a generator.

You'll be able to regen better on that first mile without wasting any energy at the brakes as the regen power will go towards climatizing your cabin and defrosting the windows while the battery protection severely limits charging.

As far as specifics go, the Heater core uses about 7kW, the cabin blower about 0.15kW, Rear defroster, 0.2kW. In total, HVAC should use around 7.4kW. This should show up on the instrument cluster as a +7KW power consumption.
Further, 12V Sockets allow up to 0.2kW, and halogen headlights use about 0.2kW.

If there was a way to toggle the battery heater core, you could add another 2.4kW of 100% SoC regen, bringing your dump load to over 10kW.

I live on a hill, so there have been instances where this has come in handy for the first 5 minutes of a fully charged drive.
 
When you press the Defrost button doesn't it use the heater element and the AC compressor at the same time for dehumidification?
It may depend on the humidity sensor, if the Spark EV has one....
The Bolt has an auto defog function that can be turned off. I forget if the Spark EV also has Defog (heat and AC at the same time).
 
NORTON said:
When you press the Defrost button doesn't it use the heater element and the AC compressor at the same time for dehumidification?
It may depend on the humidity sensor, if the Spark EV has one....
The Bolt has an auto defog function that can be turned off. I forget if the Spark EV also has Defog (heat and AC at the same time).

You're absolutely right, I checked and there is a humidity sensor at the top middle of the front windshield for defogging.

Service manual further supports compressor use with auto defog:

Windshield Temperature and Inside Moisture Sensor
The relative humidity sensor measures the relative humidity of the compartment side of the windshield. It also detects the temperature of the windshield surface on the passenger compartment side. Both values are used as control inputs for the HVAC control module application to calculate the fog risk on windshield compartment side and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield. The humidity sensor element temperature sensor supplies the temperature of the humidity sensor element.

A/C Compressor

The AC compressor function is to provide refrigerant flow in the AC refrigerant loop to help cool down the cabin, help dehumidify the air in a defrost mode and help maintain the battery temperature. Rather than a more-typical pulley, the A/C compressor uses a 3-phase alternating current, high voltage electric motor to operate. It has an on-board inverter that takes high voltage direct current from the vehicle's high voltage battery and inverts it to alternating current for the motor. The AC compressor shall be activated when any of the three following events occur:

- The customer pushes the AC button or

- The HVAC control, in ECO climate or Comfort Climate Settings, requests the electric AC compressor on to help in cooling the cabin or removing moisture in conditions where the windows may fog or

- The hybrid/EV powertrain control module 2 requests the AC compressor on to help maintain the battery temperature

The hybrid/EV powertrain control module 2 uses values from the A/C refrigerant pressure sensor, A/C refrigerant thermistor, duct temperature sensors, ambient air temperature sensor , passenger compartment temperature sensor, evaporator temperature sensor, battery cell temperature sensors, battery coolant temperature sensors and battery coolant pumps to determine the speed at which the compressor will operate. This message is sent from the hybrid/EV powertrain control module 2 to the A/C compressor control module via serial data message.



Air Delivery

The HVAC control module controls the distribution of air within the passenger compartment by the use of the mode actuator. The modes that may be selected are:

- Defrost
- Defog
- Panel
- Floor
- BiLevel

In auto mode, the air delivery mode is controlled automatically based on cooling/warming needs of the compartment. The desired air distribution mode can be selected with the air distribution buttons at the HVAC faceplate control. The HVAC control delivers the values to the HVAC control module via serial data. The HVAC control module controls the mode actuator so that it drives the flap to the calculated position. Depending on the position of the flap, air is distributed through various ducts leading to the outlets in the dash. Turning the mode flap to the defrost position, the HVAC control module will move the recirculation actuator to outside air, reducing window fogging. When defrost is selected, the blower motor will be activated. The HVAC control module enables a high volume of air delivered to the front defrost vents. A/C is available in all modes.


Recirculation Operation


The recirculation button is part of the HVAC faceplate control. The selected recirculation button position is sent to the HVAC control module via serial data. The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes and opens the recirculation flap in order to circulate the air within the vehicle, or route outside air into the vehicle.

Inside air recirculation is prevented if the defrost mode is not active. When the defrost mode is active, the recirculation actuator opens the recirculation flap and outside air is circulated to the windshield to reduce fogging.

In automatic recirculation mode the values of the windshield temperature and inside moisture sensor are used as control inputs for the HVAC control module application to calculate the fog risk on the passenger compartment side of the windshield. The A/C compressor and the defrost mode are activated to prevent or remove fog on the passenger compartment side of the windshield.

Automatic Operation

The user can select to operate the Blower, Recirculation and Air Delivery operations in auto per auto operation mode.

To put the HVAC system in full automatic mode, the following is required:

The auto button must be pressed.
The system indicates that all 3 functions are being operated automatically by lighting the auto button LED.

When the auto button is pressed, the system responds by putting the blower, air delivery and recirculation into auto mode. If any of these functions are adjusted then the auto button indication shall go off and the function will leave auto operation and follow the user requested setting: auto, blower, air delivery and recirculation. In this setting the blower request is adjusted to quickly heat the cabin initially. After comfort is reached, the blower is mimized to reduce noise and temperature drifts.

Under cold ambient temperatures, the automatic HVAC system provides heat in the most efficient manner. The operator can select an extreme temperature setting but the system will not warm the vehicle any faster. Under warm ambient temperatures, the automatic HVAC system also provides air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

In automatic mode the values of the windshield temperature and inside moisture sensor are used as control inputs for the HVAC control module application to calculate the fog risk on the passenger compartment side of the windshield and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The A/C compressor and the defrost mode may be activated to prevent or remove fog on the passenger compartment side of the windshield. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield.

Quite a lot of info ... So it seems like you're right about compressor function if you have automatic recirculation mode on. Otherwise, the other strategy to defrost is to evaluate fog risk and use the blower and heater with recirculation (partially if cold) disabled, bringing in outside air. I haven't seen the power go higher than 7kW but I should addend from your feedback that that power isn't strictly the heater core, coolant pump, and blower, Fantastic!

Now I'm wondering what sort of power consumption differences the different settings have.
 
Back
Top