Tearing Down Tesla Segment 4: Battery Cooling System Comparison on Tesla Model 3 vs. BMW i3

The Munro engineering team also spent some time analyzing the battery cooling systems for Tesla (coolant) and the BMW i3 (AC fluid).

Background: Outside of the battery pack, the primary cost difference seen between the Tesla Model 3 and BMW i3 is the cooling system. The Model 3 (similar to other coolant cooled battery packs, such as the Bolt) requires an auxiliary water pump to push coolant through the battery cooling circuit. Since the BMW i3, which uses AC fluid, has to move much less fluid, the compressor does not require an additional pumping mechanism, but may require a slight upsizing of the AC compressor to compensate for increased demand.

Further, an added benefit that the Tesla battery pack cooling gives to its functionality is that each battery cell in the pack has full contact along the side of the coolant tube. This differs from the BMW (and the Bolt), which have only module level contact to the coolant system (at the bottom of the battery module). This enables the Model 3’s cells to cool more evenly, as well as more efficient control of pack temperatures.

Data: Within the battery pack, the Tesla cooling system costs approx. $270 for a 75 kWh pack, which translates to $3.60/kWh in cooling cost vs. the BMW, which costs approximately $84 for a 22 kWh pack translating to $3.80/kWh. 

Methodology: All coolant system components were removed from the vehicles. Install to vehicle and battery pack were captured in Design Profit to develop assembly costs. Next, the fabrication of each part within the cooling racks in each battery pack was analyzed to develop cost for the parts. These costs are then totaled and analyzed via Design Profit to better understand the differences between the vehicles.