Saturday, February 25, 2017

Shocking Prelim Data On 30 KWH LEAF Pack Temperature Management...Maybe

As mentioned MANY times in the 3 months I have had my S30, I have noticed the pack does not seem to retain the heat as much as my previous 24kwh LEAFs.  Now, it was a very warm Veteran's Day when I picked up the S30 but the weather has been pretty cold ever since. In fact, this Winter ranks as one of the coldest of this Century!

Anyway, me being cheap me (as usual) was avoiding home charging if I was even remotely going to be going by a free fast charger and the other day was no different.  But free was not to be! For one thing, it was very cold in the morning and I had a detour and defrost issues (I forgot my wiper. Took it inside to set over a heat register to dry it and forgot it!) so I basically had to stop at a Blink to gather enough juice before making it to the Tumwater AV so that was 44 cents down the drain!

So to put it mildly, I was in need when I got there. Unfortunately there was already someone there who was at 75% when I arrived but took another 28 mins before finishing.

So I plugged in and did random nothings and after 20 mins, I checked LEAF Spy to see how I was doing and pleased to see I was still over 40 KW charging (Ok, so I caught a temporary dip...)

**NOTE** GIDs = 77.5 wh


Either way, I only had about 30 miles or so for the day planned so decided at this point I would unplug when someone else arrived or when I dropped below 20 KW. 

I then noticed I was at 7 TBs for the first time ever in this car.  The Sun was out so some solar radiation would be contributing but I was only in the 102Âșish range so not too bad. A coolish Spring day in Phoenix really... :) 

But the unthinkable happened.  The temperature started dropping! This was completely alien to everything I thought I knew about charging and TMSless LEAF battery packs! I was still charging over 20KW so how was this happening??

The Sun was still out so that wasn't it. I was so engrossed with what was happening I got a near full charge from the Chademo not unplugging until I was at 15 KW charging rate. The temps were still dropping now down to the mid 90's.  So I took off from the charger and about a minute later... I dropped to 6 TBs!

Final Stats (from LEAF Spy Log) GIDs 352,  charging speed; 14.7 KW.  SOC on dash would have been about 97%. I have to say, I am fairly confident I have never seen charging that fast at that high of an SOC!



So again, very preliminary and despite a sunny day, the air temps were still in the mid 40's that day but still VERY interesting observations. 

FYI; Tire rotation #1 in the books which means my new LEAF is "officially" no longer new... 

**EDIT**
To clear up some confusion, I am in no way whatsoever implying that my LEAF has TMS. Notice the the title says "Temperature Management?"  TMS is used when manufacturers can't solve the problem.  Nissan chose to tackle the root cause instead. Have they found the answer?  Doubtful, but if the above can be repeated it would be obvious they are on the right path. 

4 comments:

  1. Very interesting.
    I don't do a lot of fast charging but took one long trip and found that between fast charging and highway driving, I got to 10 temperature bars and stayed there. I was surprised that driving at 60 mph didn't for an hour or so didn't cool my 24 kWh pack, but that is what seemed to happen.
    I'll have to set up Leaf spy some time.

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    1. in my 2 previous 24 kwh packs, I saw what you saw. Generally it took over 24-36 hours for pack temps to normalize if I did not fast charge during that time. Now I am seeing temps back to ambient in a much shorter time including one as low as 10 hours, and a few just over 12 hours. Excited to see how the pack does when Summer comes!

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  2. My 30kWh LEAF is typically on 5 TBs. The first fast charge of 50% overall will put it on 7TBs. The next will take it to 9TBs. If I'm driving at more than 55mph the TB level will typically not go down. If I slow Doreen to 50mph it may drop a bar. But almost inevitably after the 3rd fast charge I'll be on at least 9 or 10 TBS and the 4th FC will pouch me to 11TBs.....For 5-10 mins. It always drops back to 10TBs very quickly rive to how slowly it drops any OTHER bar. I should note it's summer time in Auckland and the ambient temp during the day is around 25C-30C.

    I have found I can AC charge at 16 or 32amp and it has no effect on battery temperature. It may even cool down. On one long journey I deliberately charged for two hours at 30amp after 3 FCs at 50kw took me to 10TBs. After 2.5 good of AC charging I was back to 8 TBs.

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    1. In your case Steve, its the ambient temps you need to worry about most. I have not had a Summer yet so that is the real test. I have been collecting data for a while now but only posted this because I had never seen a temperature drop during a fast charge especially when the charge rate was no lower than 15 KW! I have seen the temps rise a few degrees AFTER unplugging though! Can't wait to see what happens when it is hot out!

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