charge rate affects battery degradation?

This post poses questions about battery degradation/replacement, and
offers a warning to other users of the Leaf 30KWH battery, about charging
strategy. Battery degradation in the Leaf I own appears to be charging-
related:

Sep 2019 Purchased a used 2016 Leaf with 29K miles and a 30KWH
10-bar battery. It was previously owned by a woman, from
which I have assumed that the vehicle was likely charged
only with a 120V charger at ~15A (1.8KW).

Mar 2020 Purchased a 240V 10A/16A/32A charger for faster turnaround.
Set charger to 16A, which provides an indicated charge rate
of 3.5KW. Assumed this would be OK, as Nissan's manual says
3KW is OK for frequent charging, and 6KW should be used
only occasionally.

Jun 2020 My mechanic noted that the battery had dropped to 9 bars.

Oct 2020 I noted the battery had dropped to 8 bars. Switched
charging down to 10A (indicated charge rate 2.1KW).

Nov 2020 The vehicle is now at 35K miles. I figure I got about 3000
miles out of it, before battery degradation began.

This vehicle has been babied, otherwise. Garaged 95% of the time. Never
driven when ambient temperature is over 90F (yes, I knew when I bought it
that the battery is air cooled). I don't floor it except when being crowded
upon entry to a parkway/freeway. The battery temp gauge has been watched;
it has gone up to 4 bars within the normal range only a few times, and has
been at 2 or 3 bars within the normal range, most of the time. I also noted
that the drop from 10 to 9 points, occurred in late winter/spring, when I
began charging at 3.5KW, but ambient temperatures in Colorado were still
pretty low at that time.

I checked the web about this and immediately noticed a couple things. The
primary factors affecting Leaf battery life are (1) the conditions under
which it is driven, esp. temperature, and (2) how it is charged. I also
noted articles claiming that the 30KWH battery has faster degradation,
than the 24KWH battery.

My questions are:

1. Has anyone correlated 30KWH battery degradation with ~3KW charging?
2. Does anyone know if the later Nissan batteries (40KWH and 62KWH) are
engineered for better heat transfer, and have lower degradation rates,
than the 24KWH or 30KWH batteries?
3. Does the configuration/physical size of the 40KWH battery, allow it to
be installed in 2011-2017 Leafs?
4. Has anyone out there dealt directly with Nissan on the issue of battery
degradation, and received any satisfaction, for batteries degraded less
than 4 bars?
5. Has anyone found any business, other than Nissan dealers, which does
battery replacement? I checked NissanLeafBatteryReplacement.com, but
the only shop in Colorado on their list, still isn't doing replacement.

Others will chime in with more, but the bullet points are:

* There is a known issue with the 30kwh packs. Nissan claimed at first that it is just a software issue, and has a Battery Management System (BMS) update for the cars with 30kwh packs.

* It is NOT just a software issue. Many of the affected packs are suffering from real accelerated degradation. The only real way to find out is to get the update, which will temporarily raise the capacity display to 12 bars in all cases, and then see how many bars go away again.

* The cars are still under their 8 year, 100,000 mile battery warranty, and Nissan is installing 40kwh packs as warranty replacements. You must first get the BMS update to qualify for a warranty replacement.

My 2015 was charged at the maximum L2 (240-volt) rate of about 6 kW for the entire time I owned it and my 2019 is charged the same way. In my opinion, the degradation you see is not related to L2 charging. Since it is down to 8 capacity bars, you should see your dealer about a battery replacement under warranty.

OP, cut to the chase:

1. Get the BMS update through a Nissan dealership. It is free
2. The car capacity bars will increase due to a reset that is part of the update and then settle down to its real capacity when calibration is complete.
3. When the capacity drops to 8 bars from ongoing or already present degradation, if you are still within the battery degradation warranty period and miles you are likely to get a 40 kWh battery replacement
4. Be happy

3/6 kW charging has nothing to do with battery degradation
If your garage is hot and unventilated, it is cooking your LEAF battery

It seems you are located in Colorado, which is surprising given the apparent 8 remaining capacity bars shown on the dash. A drop of 2 bars over a year (Sep 2019 to Oct 2020) is abysmal, as that represents at least a 15% drop in the SOH. Even if you L2 charge to 100% every night, or do frequent L3 charging, degradation shouldn't be that bad in your climate.

For sure, you should go to a Nissan dealership and have the BMS update done as some of this apparent loss is likely due to the BMS software bug. After the BMS update, I would hope that your real SOH will be closer to 80% - only one way to find out...

You should also purchase an OBD2 dongle and install LeafSpy on your cell phone. More details here:

https://www.youtube.com/watch?v=6yS-5HMYUHc

Without it, you really don't have any insights into the state of the battery pack.

SageBrush said:

OP, cut to the chase:

1. Get the BMS update through a Nissan dealership. It is free
2. The car capacity bars will increase due to a reset that is part of the update and then settle down to its real capacity when calibration is complete.
3. When the capacity drops to 8 bars from ongoing or already present degradation, if you are still within the battery degradation warranty period and miles you are likely to get a 40 kWh battery replacement
4. Be happy

3/6 kW charging has nothing to do with battery degradation
If your garage is hot and unventilated, it is cooking your LEAF battery

Click to expand...

When I took this car to a Nissan dealer, they examined it and told me the BMS update had already been done. Of course, they could be lying. If I get an OBD device and LeafSpy, will I be able to see the software version number and, if so, do you know what the current software version number is? When I said "8 bars", I made the mistake of counting only white bars, I did not include the two red bars at the bottom. So this is a 2+8=10-bar car, and I'm not going to get a 40kwh battery out of Nissan until I lose two more bars.

There is no doubt in my mind that the problem is related to charging. The car is always charged in the garage overnight, which means there is no air circulating around the car, or being blown into the radiator in front of the battery pack. On the other hand, the garage was not noticeably hot at night. The reasons I have no doubt:

1. My experience with the car as described. Have not lost more bars since dropping from 3.5kw to 2.1kw.
2. A youtube EV-er I encountered who flat-out stated that trickle charge is the only truly safe charging method for Leaf.
3. The fact that air movement thru the little radiator that sits behind the lower front grille, and in front of the battery pack, is required for significant cooling. (I am assuming the battery is properly designed to conduct heat to the casing, so air flow can remove heat from the case.)
4. There are accounts out there about Leafs experiencing charge throttling, which must be due to warm ambient temp and/or inadequate conduction inside the pack combined with inadequate air flow over the pack casing.
5. Nissan has more-or-less confessed that ambient air cooling is inadequate, by changing their NV vans so that cooled air from the A/C chiller is directed over the battery. Tesla does the same thing, only with liquid.

I'm not totally UNhappy with the situation! At least I learned something, i.e. ambient air-cooling sucks (which I learned WRT motorcycles years ago, but forgot). The only thing I'm unhappy about, is that I cannot use this car to goto Denver International without having to charge it at the airport, so I can get home.

If your garage isn't hot while the car is charging, then charging isn't heating the battery - not unless you have a 50+KW DC Fast Charger in there. What is tripping you up is the rapidity with which a 30kwh pack can degrade even at normal temps.

Also, take what you see on YouTube with a grain of salt. It's true that L-1 charging puts virtually no stress on the battery. The same, however, is also true of L-2 charging. It's DC Fast Charging that heats the batteries.

OP:
Leafspy cannot ID the software update.

----
Your reasoning that slightly lower power home charging is mitigating battery degradation is flawed because you presume that heat removal is the important variable in charging but it is not. Heat generation is the core problem. DCFC generates ~ 50 - 200 times the heat for the same energy put into the battery compared to home charging. That is why the stories of charge throttling are always related to fast charging. While it is true that heat removal is impaired in the LEAF, home charging does not generate enough heat to matter. Specifically, heat generation is proportional to the square of the current.

It is not difficult to estimate the amount of heat generated, or you can simply rely on others who have used LeafSpy to monitor the increase in temperature in the battery pack from home charging. It is in the range of 1.0 degree F.

SageBrush said:

OP:
Leafspy cannot ID the software update.

Click to expand...

It might be able to. See page 7 of https://static.nhtsa.gov/odi/tsbs/2018/MC-10143483-9999.pdf for the "part" numbers BEFORE the update.

One can read ECU versions with Leaf Spy Pro: https://mynissanleaf.com/viewtopic.php?p=526563#p526563. I alluded to this at https://www.mynissanleaf.com/viewtopic.php?p=584829#p584829.

L2 charging at ~6 kW barely heats the battery, at least the 24 kWh packs). It doesn't rise by more than a few degrees. 1 to 3 F sounds about right.

I've been looking for more information on how charge rate affects battery life. I came across this paper on cathode degradation. Very interesting but I'm struggling to apply it to my 62kwh leaf.

Is fast charging ok as long as the battery stays with the blue heat bars?
Is 3.3 better for the battery vs a 6.6 charger?

Does it all not matter if heat is controlled?

https://engineering.purdue.edu/kjzhao/papers/37.pdf

Feasible said:

I've been looking for more information on how charge rate affects battery life. I came across this paper on cathode degradation. Very interesting but I'm struggling to apply it to my 62kwh leaf.

Is fast charging ok as long as the battery stays with the blue heat bars?
Is 3.3 better for the battery vs a 6.6 charger?

Click to expand...

Saying what has already been said (by @cwerdna) in another way: L3 (DC) charging bad, L1/L2 charging good.
There are additional factors (like heat)...but in response to your question, generally speaking--that's the deal. That is one reason why I never added the CHAdeMO option to my Gen1 Leaf (although I wish I had the faster L2 option).

Ironically, I use DCFC now, more than ever before, as it makes the LEAF more capable as the pack ages (and available range drops as a result).

At this time of year, any trip over 80km usually means I need to pick up a quick charge en route. Having to do that with L2 charging would definitely change my attitude about the usability of the car.

Pack life be damned, I need a car that gets me from A to B in a reasonable amount of time.

Stanton said:

Saying what has already been said (by @cwerdna) in another way: L3 (DC) charging bad, L1/L2 charging good.

Click to expand...

alozzy said:

Ironically, I find I using DCFC now, more than ever before, makes the LEAF more capable as the pack ages and available range drops as a result.

At this time of year, any trip over 80km usually means I need to pick up a quick charge en route. Having to do that with L2 charging would definitely changed my attitude about the usability of the car.

Pack life be damned, I need a car that gets me from A to B in a reasonable amount of time.

Click to expand...

Agree with you from a practical use aspect, but stand by my direct answer to the OP's question.