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Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 3:25 pm
by Vaggeto
Hi,

I started a longer than normal commute home today. I'm a comfortable LeafSpy pro user and have a good feel for what miles/kwh I can get. I decided to try to make it home by driving very conservatively but half way into the drive things were not going as planned.

I started with (per the dashboard) 46% SOC on my 2015 Nissan Leaf.
I needed to go 40 miles. It was about 100* outside and the leaf was parked out in the sun. (it normally isn't)
I pulled up Leafspy Pro and it determined I needed to do 4.7miles/kwh before hitting VLBW.
As I had 22/40 miles left in my drive, LeafSpy was now saying I needed well over 5m/kwh to get evne 20 miles but the dashboard efficency which I reset at the start of the drive said I was at 4.6m/kwh.

I decided I would need to stop to charge and got to a Nissan dealership. By the time I got there it said 10% left on the dashboard. Shortly after working with the dealership to get to a charging port, I started the car again and it was only 6%!
As I stopped I was at 6% dashboard SOC (dashes), 29.1 miles driven at 4.6m/kwh economy.



According to my math, I shouldn't have run out of power so quickly. I seem to have some inbalance in my cells and also have a large difference between %SOC and % GIDS at 6.3% GIDs and 21% SOC as you can see in these screenshots of Leafspy Pro. http://imgur.com/a/xgVBK

Is there anything else I can provide to help understand if there is an issue?

Thanks in advance for any advice/help!

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 3:29 pm
by Vaggeto
After charging for 75 minutes at ~5200 watts I'm now at 46.7% GIDS and 52.7% SOC and up from 1.4 kWh to 10.4kWh. This doesn't seem possible based on the math of 5200 watts for 1.25 hours - 100watt aux usage while charging.

Cell balance looks a bit better as well although not perfect, but I'm not familiar with what it should look like. Updated screenshots attached:
http://imgur.com/a/xgVBK

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 3:41 pm
by DNAinaGoodWay
Wow! You have a lot of weak cells! 139 mV is a lot of variance. Charge up to 100% asap and see if it improves.

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 3:43 pm
by DNAinaGoodWay
Should be more like this:
image.jpeg

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 5:09 pm
by Valdemar
My new pack had a couple of weak(er) cells from day 1, while at lower SOC they are clearly outliers, hopefully the situation will not get progressively worse at those cells and the whole pack will degrade more or less uniformly, but the fact they are located in the hottest spot (literally) is somewhat disconcerting.

Image

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 7:38 pm
by keydiver
Vaggeto wrote: I seem to have some inbalance in my cells and also have a large difference between %SOC and % GIDS at 6.3% GIDs and 21% SOC as you can see in these screenshots of Leafspy Pro. http://imgur.com/a/xgVBK
Do you ever charge to 100% to let the BMS equalize the cells? IMO, you should try that a few days in a row and see if that improves those weak cells. Even one weak cell will really hurt your range, because the BMS will not allow that weak cell to drop below some preset voltage, even if the rest are fine.

Re: Gid Vs SOC and Cell Balance Issue

Posted: Fri Jul 22, 2016 10:18 pm
by Vaggeto
Interesting, thanks for the feedback!

I charge to 100% every night via an L2 charger at home. I typically end up around 25-40% left each day, sometimes in the teens when I go somewhere after work.

I'll take another look after it's at 100%.

Before today I have been very confident to use LeafSpy Pro along with my guess at m/kWh economy but this has me second guessing that.

Re: Gid Vs SOC and Cell Balance Issue

Posted: Sat Jul 23, 2016 12:26 am
by jkline
I find that my 2012 Leaf gives much rosier efficiency than LSPro. Let's say I take a 30 mile drive, the car will say I went an avg of 4.6m/kwh; but with LS, it will give an efficiency of 3.2.

I don't understand the discrepency. I suggest people compare the LS readings and the car's readings, then use your judgement on how far you can go.

Re: Gid Vs SOC and Cell Balance Issue

Posted: Sat Jul 23, 2016 7:59 am
by DaveinOlyWA
Vaggeto wrote:Interesting, thanks for the feedback!

I charge to 100% every night via an L2 charger at home. I typically end up around 25-40% left each day, sometimes in the teens when I go somewhere after work.

I'll take another look after it's at 100%.

Before today I have been very confident to use LeafSpy Pro along with my guess at m/kWh economy but this has me second guessing that.
your charging profile is near perfect to maintain a balanced pack. it looks like you have bad cells. the voltage delta increases as the SOC drops. mine are typically under 10 mV at full charge but no more than 15 mV at 70% SOC. I am guessing yours is probably a lot higher.

the erratic changes in your estimated ranges are due to the very low voltages that will cause an early pack shutdown. problem with weak cells is while under very low load (like sitting at a red light) the voltage delta is likely to be small but when load applies, the weak cells drop much farther than the rest of the pack meaning that weak cells take on the greatest amount of the load so will wear out faster and discharge faster

Re: Gid Vs SOC and Cell Balance Issue

Posted: Sat Jul 23, 2016 2:15 pm
by DNAinaGoodWay
You need to see a dealer and request a CVLI test, Which you can read about here: http://www.mynissanleaf.com/viewtopic.p ... 10#p411119

But there are other similar threads. They may only replace the bad cells, not the whole pack, but you want to stress that they're causing loss of range. As Dave suggested, they'll only get worse. Save your LeafSpy shots to show them, but they won't go by that, they have to do the official test.