gary65536
Posts: 3
Joined: Thu Sep 21, 2017 9:59 pm

Leaf range after battery module replacement

Mon Oct 07, 2019 8:26 pm

Hello all,

I recently had some battery cells replaced on my 2018 Leaf with 7000 miles under warranty. This was due to internal battery leaks in some of the cells.

Since I received the car back after the repair I believe my range is lower. Before the repair I found I was consistently getting the rated mileage of 150 miles / charge. After the repair I'm getting around 100 miles / charge even though the distance remaining shows 150 miles after a full charge. I have used the Leafspy app and have linked to a screenshot.

https://ibb.co/RzpxSYB

From this screenshot I can see some of the cells have a lower voltage difference than the others. Maybe these were the cells that were replaced. Does anyone know if this difference could be causing the issue I have? If yes, this will help me make a stronger claim to the dealership when I have them look at this new issue.

Thanks

LeftieBiker
Moderator
Posts: 13206
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

Re: Leaf range after battery module replacement

Mon Oct 07, 2019 8:43 pm

The answer is "probably." Give it a few full charges, running it down to maybe 20% after each charge (don't let it sit for more than a couple of hours fully charged), and then take another LeafSpy reading. The new cells may equalize with no extra effort.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

Dala
Posts: 101
Joined: Sun Oct 28, 2018 11:24 am
Delivery Date: 01 Jan 2015
Leaf Number: 316851

Re: Leaf range after battery module replacement

Tue Oct 08, 2019 5:32 am

Looks like inexperienced technicians did the replacement.

When you do a module replacement, you need to do it at the extreme sides of the SoC. Either at 100% or at close to 0%. If you do it in the middle SoC range, you will often find yourself in this scenario.

Another thing I've noticed is that some places don't even balance the cells before installing them.

60mV diff at that high SoC is unacceptable. It will take months or even years for the puny battery balancing shunts inside the BMS to take care of that imbalance.

I'd take this piece of info and talk to the place that did the replacement. You are in a bad spot, since this will not trigger any check EV system lights, but it will cause range loss. Let us know if you can get them to re-do it.

nlspace
Posts: 48
Joined: Mon Jun 05, 2017 10:21 pm
Delivery Date: 06 Jun 2017

Re: Leaf range after battery module replacement

Tue Oct 08, 2019 6:47 am

Yes, the 60mV difference in cells will affect your range. The low cells hit the bottom first and you can't access the energy in the higher cells. On charging the higher cells hit the top first and limit charging of the low cells. Balancing happens all the time according to Wolftronix, so if you can drive and chargge it for a few days or a week, and capture the cell chart at the end of charging, you will be able to see the progress.

If you take it back in, they will likely just put it thru numerous cycles in the shop to affect the balance before doing anything, so you may as well drive it and cycle it as you use it. They might keep it a month to balance it in the shop, if cycling works then there is no reason for them to re-open the pack. It would be a complicated procedure to open the pack and selectively chargge and balance individual cells, plus the hazard of exposed HV in a working service area...i'm guessing that won't happen.

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Leaf range after battery module replacement

Tue Oct 08, 2019 7:05 am

It would be interesting to see the the cell SoC delta at the VLB warning
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

GerryAZ
Gold Member
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Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Leaf range after battery module replacement

Wed Oct 09, 2019 8:22 pm

Try to discharge the battery as deeply as you can between charges. Deep discharge will get the other cell voltages closer to the low ones and also extend the charging time so it should help the balancing process.
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL+ purchased 8/10/2019

nlspace
Posts: 48
Joined: Mon Jun 05, 2017 10:21 pm
Delivery Date: 06 Jun 2017

Re: Leaf range after battery module replacement

Thu Oct 10, 2019 6:16 am

GerryAZ wrote:
Wed Oct 09, 2019 8:22 pm
Try to discharge the battery as deeply as you can between charges. Deep discharge will get the other cell voltages closer to the low ones and also extend the charging time so it should help the balancing process.
How do you figure they get closer? That theory doesn't make sense with the data.

If you monitor the cell voltages with the phone app you will see that the difference gets greater as the SOC decreases--the lower cells drop quicker, they fall off the linear slope first and the voltage heads toward the bottom end at a faster rate, whereas the remaining cells are still up on the flat linear slope. So the difference grows greater, not lesser.

If you monitor the cells with the phone app with the car READY but not driving, you will see the balancers cycling on and off. It might be quicker to reach balance by charging and then just turning the car ON and let it sit and balance. Don't know if it balances when the car is OFF like Tesla does.

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Leaf range after battery module replacement

Thu Oct 10, 2019 7:08 am

nlspace wrote:
Thu Oct 10, 2019 6:16 am
GerryAZ wrote:
Wed Oct 09, 2019 8:22 pm
Try to discharge the battery as deeply as you can between charges. Deep discharge will get the other cell voltages closer to the low ones and also extend the charging time so it should help the balancing process.
How do you figure they get closer? That theory doesn't make sense with the data.

If you monitor the cell voltages with the phone app you will see that the difference gets greater as the SOC decreases--the lower cells drop quicker, they fall off the linear slope first and the voltage heads toward the bottom end at a faster rate, whereas the remaining cells are still up on the flat linear slope. So the difference grows greater, not lesser.

If you monitor the cells with the phone app with the car READY but not driving, you will see the balancers cycling on and off. It might be quicker to reach balance by charging and then just turning the car ON and let it sit and balance. Don't know if it balances when the car is OFF like Tesla does.
I think he meant that the deeper the discharge, more energy is added to the unbalanced cells on the subsequent charge.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

nlspace
Posts: 48
Joined: Mon Jun 05, 2017 10:21 pm
Delivery Date: 06 Jun 2017

Re: Leaf range after battery module replacement

Thu Oct 10, 2019 9:20 am

SageBrush wrote:
Thu Oct 10, 2019 7:08 am
...
I think he meant that the deeper the discharge, more energy is added to the unbalanced cells on the subsequent charge.
Huh? How does this explanation even make sense either? The cells are in series and all have the same current--where or how would this extra energy originate?

SageBrush
Posts: 4907
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: NM

Re: Leaf range after battery module replacement

Thu Oct 10, 2019 9:34 am

nlspace wrote:
Thu Oct 10, 2019 9:20 am
SageBrush wrote:
Thu Oct 10, 2019 7:08 am
...
I think he meant that the deeper the discharge, more energy is added to the unbalanced cells on the subsequent charge.
Huh? How does this explanation even make sense either? The cells are in series and all have the same current--where or how would this extra energy originate?
It is not difficult to understand if you set aside your attitude and think for moment: Charging is limited by the first cell to reach 'full,', just as discharging is limited by the first cell to reach 'empty.'
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

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