Cold climate EV range is determined by a number of factors.
First of all though, let’s look at the range results as conducted by Motor.no in their winter range tests.
An impressive test with 29 different electric vehicles.
Read the full description of the tests on the Motor page and there you can see some of the details around some vehicles.
However, here we want to just show the spread in range results. WLTP standard numbers versus those acquired on the road in temperatures that ranged from -5°C to -19°C.
There are a number of factors that will impact the vehicle range and it is not totally due the battery as this is a two axis problem with the vehicle energy consumption also playing it’s part. Hence, let us break this into battery energy and vehicle energy consumption at the highest level and then list the factors under each.
- Vehicle energy consumption
- Inverter efficiency – this should be better as it wants to run cold and it should require less cooling in cold ambient conditions.
- Motor efficiency – again, this should require less cooling, however, the bearing oil/grease will be more viscous and the bearing lip seals will be stiffer and hence have more drag.
- Gearbox oil – more viscous and hence more drag.
- Cabin heating will be required and will be a significant drain on energy.
- Heating losses in pipes.
- Battery energy
- Cell capacity decreases with temperature.
- Cell internal resistance increases as temperature decreases, increasing resistive losses.
- Pack heating requires electrical energy.
- Cooling fluids become more viscous and so higher pumping power.
- Heat lost from battery pack.
The curves show the voltage versus capacity for a 12V LFP battery pack being discharged at C/2.
The highest capacity is at 50°C which would be the highest operating temperature for this type of pack.
As the temperature decreases the voltage decreases due to increasing internal resistance.
The voltage and capacity of this pack show a significant decrease at -10°C.
When designing a battery pack is it really important to consider it’s performance at all temperatures. Also, don’t be afraid to ask questions about the complete system.