Blog - Winston

The example of a technical solution that shows   an improper handling of the LFP cells in the battery pack.   The issue here is not the performance of the cells (which themselves are excellent), but   the deficient thermal handling of the whole solution.

1) The first photo shows the design of a battery pack that is placed in the frame of an electric motor-bike (large size scooter). This is a pack that consists of 20 cells of WB-LYP60AHA cells. This pack is placed inside a steel box that is mounted inside the motorbike skeleton.  There is no additional thermal insulation and thermal handling of the pack.   The cells are “left as they are.”

2) The second photo shows the thermal condition of the cells when driving in cold weather. The air flow cools the cells very significantly.   The cells in the front are constantly cooled by the flowing air.   As this is a high power-rate engine, the current draw may be up to 3C (120A to 180A). That is why the cells inside the pack heat up. These cells on the other hand are not cooled at all.    In this situation the performance of the battery pack is poor.   This is a situation that cannot be handled by BMS and some electronics.  

3) The solution is following, as seen in the third photo:    A) install thermal insulation   that will prevent the cool air to flow around the base with the cells. You need to insulate the cells from the outside cold wind. B) Allow some spacing between the cells, or   install a thermal conductive separation   between the cells. Allow some cooling air (in a limited volume) to pass through the cells from bottom to the top to take away the heat caused by the high current discharges. 

4) One possible solution is by means of the   poly-carbonate chamber insulation boards.

For development and improvement reasons, it would be recommended to install multiple thermal sensors in different places of the pack and see the actual thermal conditions and modify the design accordingly.

GWL/EU team   is helping customers to find the right solution to their issues. We will be happy to help you as well.   Get in touch with us.