Active battery cooling on the Cheap

As discussed, one of the issues with the 2018 Nissan Leaf is lack of active battery cooling. Thus, driving more than 500 km in a day, becomes somewhat painful, as rapid charges slow to a glacial 20 kW maximum speed as you do your third rapid charge. Recently I wound up buying a portable fan, so I figured, why not put it under the car during a fast charge? I was somewhat surprised by the effectiveness of this simple trick, it seems to have saved a heat-bar, perhaps 5C worth of heating was avoided. That in turn means a slightly faster charge at the next charge stop.

I had a few North Bary runs this summer (see this post), so I figured Id run an experiment, using the fan on one trip, but not the other, to see if this simple fan trick helped heating in any way. In both cases, I charged up at the same Ivy station in Gravenhurst. Weather was similar on both days, and conditions (traffic, winds etc.) were close.

I was quite surprised to see a difference. After all, the fan was fairly haphazardly placed to blow a little air underneath the car from the front. Follow up testing showed slightly better results if I tip the fan on its side and blow more air underneath the car instead of leaving it upright where some air blows onto the idle radiator. Its certainly a simpler operation than say, shifting AC air from the cabin down the “transmission tunnel” (see this video).

I have done this a few times now (on a Toronto to North Bay run), and I feel this is a real effect. Its not large, in both cases battery temperature started out close to 25 C, and wound up around 45 C. Perhaps a 20 C heat increase without the fan and a 15 C increase with the fan? You might also notice a difference in ambient temperature in the figure above, which also played a role. Also, repeatability of rapid charging sessions is challenging, for example if a car plugs into the station next to you, your charging rate might slow to accommodate the newcomer, that impacts heating as well. There is also the placement of the fan, and I certainly could 3D print some ducts to further target the airflow for maximum effect.

The real test will come once ski season gets underway, on the Mt. Tremblant run. Does the fan allow me to do better than the current 10 hrs and 30 minutes (see this post)?