At sub-zero temperatures, the capacity of Li-ion batteries decreases, the voltage drops, the resistance increases, the current output decreases, and the self-discharge rate increases. Thus, the initial reserve capacity is sufficient for shorter distances compared to travel in warmer months.

Factors in winter range reduction

In addition to low temperatures, driving range is negatively affected by snow, headwinds and other factors that create additional drag while driving. Unlike a car whose battery is heated by a running engine while it’s on the move, e-bikes and other types of light-duty electric vehicles don’t have this effect. On the contrary – during the journey, the battery was cooled by another 3-5°C due to the cold oncoming air.
Although the effects of negative temperatures on lithium-ion batteries are temporary, prolonged exposure to cold environments is not desirable for them. Rapid self-discharge usually results in deep battery discharge, battery degradation and irreversible capacity loss. Therefore, insulation of traction batteries on EVs in winter is considered a good idea.

Creating a thermocase for a battery

You can make a thermowell for the battery from the following materials:

Foam – polyethylene foam with a reflective surface and a thermal conductivity coefficient of 0.04 W/(m – °C);
Foam plastic – its thermal conductivity coefficient depends on the brand and is in the range of 0.037 – 0.043 W / (m – ° C)
foil-is on foam plastic – a material with a coefficient of thermal conductivity of 0.038- 0.043 W / (m – ° C);
Felt – its coefficient of thermal conductivity is 0.036 W/(m – ° C).
The main thing is to avoid using flammable materials. From the selected insulation material, a cut is made according to the size and shape of the battery. Several layers of material are used to enhance the protective properties of the thermal cover. The battery is insulated on all sides. The insulation is fixed with scotch tape. Sometimes Velcro fasteners are adapted for ease of use. Technological holes are made for the withdrawal of wires and pins.