Auxiliary systems power consumption in electric vehicles

Auxiliary systems power consumption in a vehicle especially an electric vehicle have a big effect on the vehicle range. The Range is decided by the battery capacity in kWh. Battery capacity is primarily used to provide traction power through AC or DC motor. Efficiency of motor, drivetrain and battery can tell you how much power is available out of the total for propulsion. But there are also many auxiliary systems in an electric vehicle which consume kW power which in term reduces the power available for traction. In this article, I will try to list the different auxiliaries and their power consumption’s. My aim is to understand roughly for an average EV how much power should be deducted for auxiliary system power consumption but at the same time also to understand better the auxiliary system components in a vehicle especially an electric vehicle.

This is just a starting point as I have been researching this topic for the last few days. I need to get more data on many points to reconfirm or correct the assumptions and conclusions.

Total gross battery output kWh = Power output required for traction kWh + Auxiliary load peak kWh.

Thermal management system

In traditional ICE vehicles, the biggest auxiliary power consumption was or is the AC climate control system. Depending on the weather but especially in the hot and humid climate conditions ICE AC climate control systems can consume roughly up to 25-30% of fuel consumption.

Source: https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2360&context=iracc

In EVs, along with the traditional cabin climate control, there are other heat-producing sources such as motors, HV power electronics, and the big one “the battery”. Cooling the cabin and the heat-producing components requires 5-6kW of power. In winter, at very low temperatures (-10 C or below) the vehicle requires heating the cabin with a PTC heater if no heat pump is available.

Batteries perform better ideally between 20-25 degree Celsius. Source: https://www.engie-vianeo.com/en/heatwaves-and-your-cars-range/.

Other Sources claim somewhere between 20 to 35 degrees. Source: https://www.nrel.gov/docs/fy08osti/42716.pdf.

A Study by Alaska Center for Energy and power says the Ideal range is 10 to 20 degree Celsius.

Source: Alaska Center for Energy and Power and Batterypowertips blog

Below study by Geotab showed the ideal range was obtained between 20 to 25 degree Celsius:

“Geotab looked at anonymised data from 5.2 million trips taken by 4,200 EVs representing 102 different make/model/year combinations, and analysed average vehicle trip efficiency by temperature.”

https://www.geotab.com/ie/blog/ev-range/

Study by Rivus Group over their fleet of EV showed the data below.

https://www.rivusgroup.co.uk/effects-of-temperature-on-ev-performance/

We can therefore say the ideal range for optimal Battery performance in EV’s is somewhere between 20 to 30 degrees. Above and below this temperature the performance of batteries starts to decreases especially in Cold conditions. Cold temperature below -20 degree Celsius can reduce range by ~20 to 40% but also temperatures above 35 degree Celsius can steeply drop the range by 10 to 20%.

Batteries therefore require battery Thermal management system (BTMS) especially.

There are different BTMS Types.

Detailed classification sources:

Hybrid Battery Thermal Management System in Electrical Vehicles: A Review Chunyu Zhao , Beile Zhang, Yuanming Zheng, Shunyuan Huang, Tongtong Yan and Xiufang Liu.

Lets see power consumption by power components in a thermal management system
HOT Temperature (Kuwait) country study of EV efficiency and range with temperature.

As much as winter and low temperatures affect power consumption by thermal management system, Hot temperatures especially temperatures above 30 degree Celsius also lead to higher power consumption by AC system.

Below study shows effects of high temperature on EV Efficiency and Range. Study is done using Chevy Bolt 2019.

Hamwi, H.; Rushby, T.; Mahdy, M.; Bahaj, A.S. Effects of High Ambient Temperature on Electric Vehicle Efficiency and Range: Case Study of Kuwait. Energies 202215, 3178. https://doi.org/10.3390/en15093178

This confirms that the ideal temperature range for batteries is between 20-25 Degree Celsius. As you go higher or lower than that the auxiliary power consumption which is mainly thermal management system increases. Human beings or Drivers like to have a temperature of 20 degrees.

This study shows that the range starts decreasing with 30 degree Celsius at 6% (8Wh/km) to 32% at 50 degree Celsius (60Wh/km).

Winter and range loss studies

Main reason for EV to have range loss in winter as compared to ICE cars is because EV have to generate heat energy either by PTC heater or Heat Pump as opposed to ICE cars where the waste energy from the engine is pumped into the cabin. Also the batteries do require preconditioning in cold winter conditions and some active cooling to keep the operating temperatures in the 20-25 degree celsius range.

Below is a research study done by Recurrent Auto on EV range 10,000+cars in winter and cold Weather. Recurrent is new company whose mission is to help people buy and sell EV’s and thus help in its adoption. They also have a lot of data collection.

https://www.recurrentauto.com/research/winter-ev-range-loss

Above analysis shows range loss in 12 popular EV Models at freezing 0 degree Celsius to Ideal at 25 degree Celsius.

Hyundai
  • Kia EV6 – 5-8% Range loss at 32F.
    • Comes with Heat Pump on AWD models. Same platform as Ioniq. E-GMP.
  • Kona – 15% at 32F but these are on 2020-21 Models with no Heat pump. The Range loss becomes worse with colder temperature. From 2023 onwards all Kona will get Heat Pumps.
  • Ioniq 5 (2022) – 3-5% Range Loss
    • Comes with Heat Pump on AWD models. The Range loss is very less thus showing the importance of Heat pump vs PTC Heater.

Fords:
  • Ford F-150 Lighting – 26% Range loss at freezing.
    • No Heat Pump so the range loss is big with PTC Heater at 20F its about 45%.
  • Ford Mustang Mach -E – 34% Range Loss
    • No Heat Pump so the range loss is significant with PTC Heater. At 20F the range loss observed is 45%
Tesla’s:
  • Tesla Model Y – 24% Range loss below freezing.
  • Tesla Model 3 – 24% Range loss
  • Tesla Model X -24% Range loss
  • Tesla Model S- 28% Range loss

Tesla’s dashboard and EPA range is way off the mark as compared to other vehicles. Almost 40% short for most of the models. The range loss in winter is 25-30% on average. Most of the Tesla’s starting first with Model Y and now Model 3 etc are now coming equipped with Heat Pumps. This has reduced the impact on range loss. Model X comes with a variety of heated seats etc options which help reduce energy consumption from heat pump to increase cabin temperature.

Nissan Leafs
  • Leaf 2019 Plus – 40% Range loss at 32F
  • Leaf 2015 – 42% Range loss at 32F
    • Nissan Leaf doesn’t come with active battery cooling. This seems to be main cause of losing range.

Another Study: Al-Wreikat Y, Serrano C, Sodré JR, Effects of ambient temperature and trip characteristics on the energy consumption of an electric vehicle, Energy, https://doi.org/10.1016/j.energy.2021.122028.

This study was done on Nissan Leaf. This shows in Wh/km Nissan can consume additional 100Wh/km at 0 degree Celsius as compared to 15-20 degree ideal range for auxiliary systems. Also at 35 range it can go higher up to 80Wh/km.

VW family
  • Audi E-Tron – 16% Range loss (comes with Heat Pump)
  • ID 4 – 46% Range loss
Chevrolet
  • Volt 2017-2022 – 32% Range loss
  • Bolt 2017 – Similar 32% range loss

EPA

Summary thermal management system including AC system power consumption

AC system part of the thermal management system of EV are responsible for the biggest auxiliary power consumption. Battery management system especially in winter conditions also uses a lot of power but with preconditioning during charging this can be reduced. Nevertheless active temperature control systems will use power to maintain the battery temperature in the ideal 20 degree range.

Overall winter temperatures as they go below 0 degree Celsius causes a range loss of 40% or 70 Wh/km (with PTC Heater) or 25% or 40 Wh/km with Heat Pump. Summer temperatures especially in high temperature regions will also cause a loss of range through higher power consumption by AC system. The Losses can be as high as 32% or 60Wh/km.

For this article purpose I am going to assume following:

Average speed city – 40 km/hr

Average highway speed – 70 km/hr

Weekdays commute – 2 hours/day

Weekend commute – 1.5 hours/day

Trips outside city 10 hours/Trip, 1.5 trip per month

Total Hours Summer/Autumn/Spring – 62 Hours Commute + 15 Hours Trips = 62 Hours

Type of Car – Tesla Model 3 Standard

Battery – 57.5 kWh, Range WLTP 513 km. 112 Wh/km. This is based on WLTP and average speed is 60 km/hr.

Read in Benchmarking about Tesla Models and their specifications.

  • LED Headlights: Long and short (mostly in the night)
  • LED Tail Lights.
  • LED Daytime Running Lights (DRL)
  • Brake Light
  • Indicators : Front and Rear
  • Boot light
  • Interior light
  • Number plate illumination light
  • Other additional lights depending on vehicle model.

Source: https://www.researchgate.net/publication/320917775_Energy_consumption_of_auxiliary_systems_of_electric_cars

https://www.stockwiseauto.com/hella-9005-daytime-running-light-bulb?Year=2017&Make=Tesla&Model=S

B. Schoettle, M. Sivak, Y. Fujiyama. Leds and power consumption of exterior automotive lighting: implications for gasoline and electric vehicles. Report No. UMTRI-2008-48, 18 (2008)

M. Vražić, O. Barić, P. Virtič. Auxiliary systems consumption in electric vehicle. Przegląd elektrotechniczny, 12, 172-175 (2014)

Audio systems

Tesla entry level model 3 comes with 325 W of Audio power and can go up to 605 W. Other models have 200 to 960 W.

For this article purposes I will assume 500 W of Audio system power consumption.

Sources:

Windshield Wiper system

Windscreen wiper system has motor for wipers and water pump. Both of them are about 50W.

Windscreen can be heated too. But mostly used in winter months. They are about 600W. Used barely for 15 mins to 30 mins. The Max watts will be 300. Used 15 times a month lets say. 4500 watts/month. 2wh/km.

Miscellaneous Systems: Power Steering, Windows Open and close, Passive & Active Safety System, Autopilot, Heated seats.

Conclusion

Total average power consumption per hour depends on various conditions. Time: Day or Night. Weather: Summer, Winter or Rainy Season.

There are number of traditional power consumption components like audio System, lights, window wiper etc but the amount of energy they consume is very small. Regenerative energy gain through braking is suffice to overcome that power loss.

AC system part of the thermal management system of EV are responsible for the biggest auxiliary power consumption. Battery management system especially in winter conditions also uses a lot of power but with preconditioning during charging this can be reduced. Nevertheless active temperature control systems will use power to maintain the battery temperature in the ideal 20 degree range.

Overall winter temperatures as they go below 0 degree Celsius causes a range loss of 40% or 70 Wh/km (with PTC Heater) or 25% or 40 Wh/km with Heat Pump. Summer temperatures especially in high temperature regions will also cause a loss of range through higher power consumption by AC system. The Losses can be as high as 32% or 60Wh/km.

Tesla European Union Energy label data

Source: Tesla Website Page

Checking forums and online data, Tesla Model 3 performs like 120Wh/km to 140 Wh/km in summers to 200-220Wh/km in winters. Average it loses like 80-100 Wh/km.

There are a lot of variants for average Wh/km, type of tires, average driving speed, weather conditions, traffic and location (City or highway),type of vehicle model/battery type.

Research Papers and Blogs

I will add more sources as I update this article more, I have given credit to the papers and blogs as I have used the data or images above. If I have missed something or needs to be added please drop us a not in comments.

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