Hi everyone. Summer is here in full swing in south FL and my Leaf's battery temps are holding around 90 - 100F around the clock. Seeing how I lost about 3% of my battery capacity last summer, and winter loss was basically flat, I could not let my battery rot in the heat again this year. So I decided to explore ways to help keep it cool.
First, I cleaned out my garage to make space for parking my Leaf there overnight at around 78F indoor ambient temp and keep it out of the afternoon sun (I depart to work at 4pm). Doing that made little to no improvement in battery temps, but made much more comfortable experience of starting the drive in pre-cooled car. I was still arriving at work with highest temp sensor reporting ~100F.
I decided to use flex air duct to channel my house central AC air directly under the Leaf. That did not make a difference, due to Leaf's plastic battery under belly cover blocking cold air stream from reaching the battery. So then I tried channeling that air into open battery disconnect plug hatch inside the cabin. It worked, and i could feel cold air escaping underneath the car. Next day the highest battery temp was 85F and was 90F after driving to work.
Next I tried adding a booster fan to my air duct with fan speed adjusted using a variac. This about doubled the air flow and allowed for cool air to keep flowing around the battery when AC was off. Next day the battery temps were 80F, 75F and 73F. After the drive to work they were 87F, 85F and 84F. So it appears that I managed to lower average temp from around 95F down to 85F by doing this. I think average temp will get down by another 5 degrees once I let the battery sit one more day unused while being cooled.
I should mention that the weather was the same these 3 days, with ambient temp in 89 - 92F range and sunny. My drive is 60 miles round trip, I charge from 20% SOC to 70% from 2am - 5am, then finish to 90% SOC in last hour and a half before departure. I arrive at work at ~50% SOC and the car sits there for about ~7 hours.
I plant to add further improvements to this cooling method and make this setup a bit more user friendly. Here are pictures of my contraption: https://imgur.com/a/pD8FP