I have followed Lemon Tea and find him quite informative. I have charged my Leaf
at battery temperatures from below 20 C to a max of 35 C. Today in Hope my battery temp
as reported by Leaf Spy was 35 C when I started charging and 37 almost 38 when
I finished. The starting amps were 93 Amps. I finished charging at 95% and the charge rate
was still over 20 Kw and I think it said 59 amps. I have never regardless of battery temp
gotten more than 99 amps from a BC Hydro charge station. I have never rapid charged
below 35% so that may have something to do with it, the battery resistance may drop enough
to get the full 50 Kw.
I have found that driving from Chilliwack to Vancouver numerous times that my battery
temperature does not rise more than 3 to 4 degrees above ambient. So I am not having
troubles with the battery temperature management.
A good friend of mine is at the NRC doing battery research. Talking with him the charge
strategy that Nissan is using he thinks is very good, All batteries have the charge rate back
off as the SOC rises, unavoidable. Charging at temperatures in the 40s is not good at high
rates, so the charging is pulled back. He says if the battery does not remain at temperatures
in the high 40s for long, no damage should occur, Battery temps in the 50s is BAD.
One thing on the TMS system that Chevy and Tesla use that I have not been able to determine
is if the AC system is used in the cooling of the battery. If it is not then the TMS can not cool
below ambient. The water system will help when charging at high rates to keep the temperature
down and even across the pack. BMW does use a refrigerant to cool their battery, so cooling below
ambient is possible for them.
When I worked at Ballard Power Systems on the Fuel Cell Bus we had troubles with temperature
regulation in the Southern US as summer air temperatures above roadways often reached 115 F
or higher. When we needed to keep the FC temp below 60 C this resulted in enormous radiators.
Keeping batteries cool in these climates is a problem for every manufacturer with and without
water cooling. The PEM Fuel Cell industry is looking for higher temperature membranes to allow
higher operating temperatures, I am certain that the battery people are looking at higher operating
temperatures for batteries as a way to reduce weight and improve reliability.