Cell Voltages mostly RED in LEAF Spy Pro (?)

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

MartinChico

Well-known member
Joined
Oct 22, 2014
Messages
85
Location
Chico, California, USA
A few weeks ago, after an overnight L-1 charge, I noticed that (almost) all of the cell voltages in the LEAF Spy Pro app were red:



Should I be worried? (What does this mean?)

Thanks for tolerating my ignorance.

I have (unintentionally) double or triple-posted this. (I'm an idiot.) Can a moderator delete these posts from Range/Efficiency/Carwings?
 
A few weeks ago, after an overnight L-1 charge, I noticed that (almost) all of the cell voltages in the LEAF Spy Pro app were red:



The only information I've been able to find indicates "The red bars represent those cell pairs that have the shunt active to bleed off some of the stored energy and balance the battery pack". It doesn't sound like a problem, but it is a bit unnerving to see all of those red lines. Should I be worried?

Thanks for tolerating my ignorance.

I have (unintentionally) double or triple-posted this. (I'm an idiot.) Can a moderator delete these posts from Range/Efficiency/Carwings?
 
MartinChico said:
A few weeks ago, after an overnight L-1 charge, I noticed that (almost) all of the cell voltages in the LEAF Spy Pro app were red:



The only information I've been able to find indicates "The red bars represent those cell pairs that have the shunt active to bleed off some of the stored energy and balance the battery pack". It doesn't sound like a problem, but it is a bit unnerving to see all of those red lines. Should I be worried?

Thanks for tolerating my ignorance.


No, you shouldn't be worried.
 
One person already told me not to worry, but I can't resist asking:

I looked at three 2013 SVs yesterday and today. One had about 50% red cells yesterday at 76.6% SOC and 88% SOH. Neither of the others had any red cells. I went back today and that car still had mostly red cells and lots of variation in cell voltage. SOC now 75.5%, I suppose just from sitting overnight and being moved across the lot before I drove it, since before that it was parked in the same place as yesterday. Still has > 50% red bars. After driving 23 miles, still has similar bars and high cell-to-cell variation. Calculated battery capacity from test drive was 20.6 kWh.

Car with all blue bars (before and after test drive), low cell-to-cell variation and 86% SOH over same test drive course had calculated capacity of 20.4 kWh. Rounded to the nearest hundred, both cars have 2500 L1/L2 charges (no QC in either). Why do cars with such seemingly similar conditions vary so much in this department?
 
BuckMkII said:
Why do cars with such seemingly similar conditions vary so much in this department?
Good question!

There can be quite a few reasons for larger amounts of cell imbalance. Here are a few:

Reasons for high cell imbalance which have nothing to do with the condition of the battery in question (these don't indicate any permanent issues):
1) The battery may not have been charged to full in a long time. I think the MY2013s still had the 80% charge setting. If that car with the red bars is set to charge only to 80%, then the cells in its battery will tend to get more out-of-balance as time goes on. Cars that charge to 100% regularly will tend keep their cells well-balanced.
2) It could be very cold, which increases the resistance of all the cells, particularly the ones on the ends of the stacks, causing rapid unbalancing during driving. (Obviously this does not apply to this situation, since it is warm and all the cars are in the same environment.)
3) The car with the more-unbalanced battery may have been driven particularly hard in its last test drive while the other two cars were driven gently during their last drives. The BMS has more difficulty keeping the cells in balance under high-power operation since that accentuates the differences between the cells.
4) I don't know if this is still true, but I have heard that there is a setting in LeafSpy that causes it to change how it interprets the shunts in the battery. Perhaps that one car needs that setting to be changed to read properly. (I doubt this is the issue, since you said the variation *is* higher with that car.)

Reasons for high cell imbalance which are due to some (permanent) condition of the battery.
5) As the battery ages, the resistance of the cells increase significantly. Some cells will have a larger increase in resistance than others as the battery ages. The result is that the BMS has more-and-more difficulty keeping the pack balanced.
6) There could be one or more cells which have lost more capacity than the rest in the stack. As a result, the BMS will have difficulty keeping the pack balanced.
7) One or more modules in the battery could have been replaced. In the case of a replaced module, there will be a pair of adjacent cells with MORE capacity than all of their neighbors. This also causes the BMS to have difficulty keeping the pack balanced.

So, how do you tell which one has the best pack? You need to get the batteries FULLY charged and balanced. The 2013s are decent at this, but it might require keeping them connected for a couple of hours after the battery gets full. Then you can to drive in similar conditions down to below *at least* very low battery warning (VLBW). That's not the first warning, but the second one. That will allow you to see if any have significantly more or less capacity than the others. It will also give the BMS a chance to "read" the battery in case it has been sitting for many months. Between your mileage numbers and the LeafSpy Ah readings, you should have a good idea what is going on.

Unfortunately, I doubt any dealership would let you do all of this! Good luck with your decision.

Finally, you should find out where these cars have spent their lives. If they all lived in Seattle, then they shouldn't be too bad, but you cannot assume they are local cars.
 
Wow, that is truly an awesome response! Thanks!!!

RegGuheert said:
Unfortunately, I doubt any dealership would let you do all of this!
Yeah, that would be asking a lot! This dealer is "no haggle" and a bit pricey, so they probably style themselves as being special, but that seems like a big project.

Finally, you should find out where these cars have spent their lives. If they all lived in Seattle, then they shouldn't be too bad, but you cannot assume they are local cars.
Both are from California. The one without red bars seems to have been on the peninsula (most Carfax points from Sunnyvale or nearby), while the weird one may have been in the Central Valley. I think I will plunk down for with the one with slightly fewer miles and the calmer battery, unless someone swooped in this afternoon and bought it!
 
Back
Top