Bad Module in Brand-New 2017 SV

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Assaf

Well-known member
Joined
Jul 21, 2013
Messages
60
A couple of weeks ago we started our 3rd consecutive Leaf lease on a 2017 SV, our first 30 kWh model.
The next day we took it to the mountains for a spin, and were dismayed to see the %SOC drop much faster than expected. Overall range performance was a good 15%-20% below expectations for the season/driving/etc., expectations I'm very familiar with from nearly 5 years of Leaf driving.

After confirming the findings a couple more times - accelerated %SOC drop seen starting around 65-70% till around 25-30% - I contacted the sales person (a very known and liked person in Leaf circles), and right now I'm sitting at the dealership waiting for service.
They just confirmed *one* bad module out of 48, and are chatting with Nissan about whether to replace the module or the entire pack.

My main question is: how likely it is that only one bad module will be responsible for 15-20% range loss? If not very likely, I will need to push back if they try a single-module fix, and demand either a full-pack replacement or a lease swap.

Please respond quickly, but only if knowledgeable about the matter. Links to authoritative info also gratefully accepted.

Thanks!

Assaf
 
One bad module does cause the behavior you state.

No one can say for certain any further than that
 
Thanks!
Do you have any reference for this, though?
Also, do bad-module swaps generally work, or is it only the start of long-term torture?

Nissan hasn't gotten back to me yet so I have some time to do my HW.

Assaf
 
One bad module is like one bad link in a chain. The cutoff voltage is based on lowest cell reading, not the average cell reading. Your module was not "very" bad cause it could have caused a much greater loss of range. I think there was someone here who reported going from 75 miles on GOM (24 kwh pack) to Turtle in a few miles.
 
The Nissan battery test at near empty yielded the following:
One "cell" (I assume module) at 3.52v, vs. the test threshold of 3.63v (I assume Fail is below threshold).

They were told by Nissan to wait for a more senior Leaf expert who perhaps works in another shop in the region(?), to come in and do more testing. The report mentions gradual discharge from 100% down to 10%. He was scheduled to come in 2 days later.

I had to pick up the car yesterday evening, though, b/c my son is scheduled to have a driving test Friday, and Leaf is what he's used to driving on, besides likely not having insurance for the loaner. It's our only car.

The report sounds much milder than their verbal description of a "bad module" or pre-test suspicions of a "shorting module". On the other hand, I still wonder how can one module with voltage ~3% below spec, cause a 15%-20% range damage.
I also wonder whether this is just a more severe case of "battery teething problems" that will resolve itself with some built-in battery management balancing over some time.

Any insight and constructive input welcome.

Thanks!

Assaf
 
Think of it as the car being limited to the capacity of just that one cell. That's essentially the case, because the way the BMS works, the car has to conform to the voltage parameters of the weakest cell, not the strongest.
 
Would you have to draw the battery down to ~5% for the LeafSpy test, or can you just do it at any charge level?
 
Assaf said:
Would you have to draw the battery down to ~5% for the LeafSpy test, or can you just do it at any charge level?
http://www.mynissanleaf.com/viewtopic.php?p=262965#p262965

It might be different for 30 kWh as it's been asserted the discharge curve is different on that battery vs. 24 kWh packs. I'd imagine a '16 or '17 service manual should specify.
 
There is an old(er) thread in this forum describing in detail the story of one bad cell in a new LEAF. Your story sounds consistent. Unfortunately, I don't remember off the top of my head if the eventual resolution was replacement of all the pack. My guess is that a cell replacement is possible if balancing is performed afterwards but I doubt a Nissan dealership is up to the task. Moreover, an ad-hoc repair is not going to be authorized and I'll be amazed if Nissan has procedures in place.
 
cwerdna said:
Assaf said:
Would you have to draw the battery down to ~5% for the LeafSpy test, or can you just do it at any charge level?
http://www.mynissanleaf.com/viewtopic.php?p=262965#p262965

It might be different for 30 kWh as it's been asserted the discharge curve is different on that battery vs. 24 kWh packs. I'd imagine a '16 or '17 service manual should specify.


This is strange to me because at that low an SOC, the voltage delta is always large. I have seen 200 mV+ differences FREQUENTLY in my pack which by all accounts has always performed well over 3 LEAFs. Keith posted a screenshot of his LEAF Spy at low SOC and the voltages are as expected, all over the place.

As far as driving it; the bad cell will degrade MUCH faster than the rest of the pack and eventually you will start to see shocking GOM readings that go from 65 miles to turtle in a few miles so tread lightly but guessing you have some time before it becomes critical.

Others have posted bad cells here as well but guessing their cells were bad a while before they noticed anything amiss.
 
Isn't this a warranty issue for Nissan to address and resolve?

(Either they replace the bad module ..replace the car..replace the entire pack..)
 
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