LeftieBiker
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Re: Battery Upgrades are very possible

Mon Jun 22, 2020 5:35 am

Yes, pre-Lizard packs fared horribly in hot weather. And cold weather for that matter, they were shit packs.
There are actually two pre-Lizard packs: the aforementioned "Canary" pack, made until April of 2013 (and thus overlapping with the 2013 refresh by three months) and the later 2013 - 2014 "Wolf" pack. The latter is much , much better than the first gen, and is mainly noticeably worse than the Lizard pack in hot climates. In normal weather it's about as good as a Lizard pack. I assume that it was Nissan's first attempt at making a heat-resistant, degradation-resistant pack, with the Lizard pack being the second.

The above applies to North American packs. We have never established whether or not there was a Wolf pack in Europe, or if they went from Canary to Lizard - and if so, when.
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mux
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Re: Battery Upgrades are very possible

Mon Jun 22, 2020 10:51 am

Ah, that's news to me - I'm not very well-versed in the US Leaf (even though I started out with the canmsgs reverse engineering document of course, I very quickly just reverse engineered everything about my own car myself).

There's a fair possibility there has been this distinction in Europe as well, because we can clearly see 3 different rates of degradation in early packs. The very first packs, up to about March 2012 or so (in the Netherlands very easy to identify by the registrations 49-RX[letter-number]) have horribly quick degradation - near 60kmi you'd have a 75% SOH pack, and it'd be pretty much unusable by 100kmi. Then we see slightly newer packs, all the way through Gen. 1, that fare quite a bit better, but not up to Lizard standard. Then the Lizard packs are phenomenal by comparison. Today I serviced a customer who has a Gen. 2 Leaf with 222 000km and still 76% SOH - about twice as little degradation as my old Canary pack had. Another customer with 90 000km still had 85ish %.

However, the actual crossover from canary to wolf, or at least A crossover between packs, seems to be much earlier here. We don't see any 'bad' Gen. 2 packs, aside from packs tha thave been obviously QCed a lot (and even then, usually much better than early Gen. 1 still). So I don't *think* we had a wolf-lizard crossover during gen2. Maybe we did immediately go from canary to lizard?

All of this is REALLY hard to say with data on less than 100 batteries on our hands. Incomplete data at that.

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Marktm
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Re: Battery Upgrades are very possible

Mon Jun 22, 2020 1:01 pm

To throw in some highly anecdotal comparison of my leaf (since the subject has morphed a bit):
Original date of service - 9/17/2012
My purchase 1/7/2016
New replacement "Lizard" battery 11/3/2016 - mileage 25,520, amphours estimated at 43-44 (no LeafSpy :cry: ).
Current mileage approx 48,500
Attached graph is used to calculate the overall degradation of amphours per month:
Original battery about 50 months with 66-43 = 23 amphour loss => 0.46 amphours/month loss
"Lizard" battery about 42 months with 66- 53 = 13 amphour loss => 0.31 amphours/month loss
Mileage per month about the same, all miles in hot, humid South Texas.

I realize this is highly unscientific analysis as the battery data "cycles" so much during the seasons, however, it does seem that the Lizard battery is holding up significantly better.
battery log 5.3.20.jpg
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2012 Leaf SL; 46,000 miles. Battery replaced November 1st, 2016.

DougWantsALeaf
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Re: Battery Upgrades are very possible

Mon Jun 22, 2020 1:11 pm

mux,

Do you get to look at battery states for any other types of vehicles? you often see in the media...0% degradation for Bolts or Teslas. We know that is often misunderstood as GOM readings which look to have new mileage, not actual battery capacity.

Just curious to see in your opinion the gap the newer Nissan batteries (either Lizard or 2018-2020 chemistry) have vs. competition.
2019 S Plus (98.6% SOH) & 2019 SV Plus (94.6% SOH) Both Silver
2013 Leaf SV sold 2019
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Max Miles on 13 Leaf: 120 miles
Max Miles on 19 SV Leaf: 242 Highway 4.5 miles/kWh

mux
Posts: 297
Joined: Sat Jan 13, 2018 3:52 am
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Re: Battery Upgrades are very possible

Mon Jun 22, 2020 11:22 pm

Nothing beats the Leaf in speed of degradation. As far as we know, they're the worst, not because of chemistry (see the last paragraph) but because of the BMS/thermals.

There are some interesting findings about Tesla and how they 'hide' degradation. Honestly, a lot of this is conjecture but I'm fairly sure I'm at least in the right direction.

So, what we see with older Tesla packs is:
1) they do degrade, much more than Tesla says in the car.
2) Internal resistance measurements show this quite clearly
3) actual cell capacity is maintained a bit better than SOH would make you believe there is because they're eating into their buffers ever so slightly more as the cells age. BOL they get charged to e.g. 4.08V, by EOL they're near 4.15V/cell.
4) performance is maintained by increasing pack temperature a bit it seems. This is a well-known aging effect: you can counteract the increase in internal resistance by increasing temperature, and you don't even need to do that much.

As far as we know, but again - very small sample sizes of only a few types of car batteries - Tesla is the most sophisticated in their battery management this way. Other car manufacturers don't strategically change battery management as the pack ages, they just limit performance. One exception seems to be the old Ioniq 28kWh, where we see significant degradation (like 15%+ after 130 000km or so) in taxis, but the car doesn't seem to reflect this anywhere in decreased range. This is by far the most high performance battery pack in the field, so no wonder they degrade quickly.

I guess e-golf is the only car that comes close to the rate of degradation of the Leaf. Even then, less than half the degradation in well-used e-golf packs. And also: with all of these cars we don't actually know this for sure-sure, because their CAN engineering data hasn't been reverse engineered fully. All we can do is do IR and capacity measurements.

Now, AESC cells aren't bad AT ALL. They are competent, good even. How do we know? e-NV200. It's got thermal management - well, thermal management while the car is stationary and charging. Not while driving. But even then, we've had a number of vans visit us and all of them have just excellent batteries. A taxi with almost 140 000km on the clock and nothing but QC sessions had 91% SOH. A Leaf battery with the same QC stats would be low-80s. This is comparable to e-golf, Zoe, etc. Just a good battery overall. Add to that the fact that these batteries are capable of really good performance - the 24kWh cells are rated for 2C continuous charge and 3C continuous discharge at pretty low temperatures. We have less data for the 40kWh packs, but I'm sure judging by the degradation characteristics of customer cars that they'd be excellent vehicle batteries if you add some thermal management. They're 3C charge/5C discharge cells, really stable, well-designed chassis... just a shit BMS/TMS.

LeftieBiker
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Re: Battery Upgrades are very possible

Tue Jun 23, 2020 12:29 am

I guess e-Golf is the only car that comes close to the rate of degradation of the Leaf.
The batteries in the first generation Kia Soul EV have experienced quite a lot of degradation. From what I have read it's more than that of the Leaf's Lizard pack, and probably more than the Wolf pack as well. It seems to be less than the Canary pack anyway!
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2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
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PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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Marktm
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Re: Battery Upgrades are very possible

Tue Jun 23, 2020 6:27 am

mux wrote:
Mon Jun 22, 2020 11:22 pm

3) actual cell capacity is maintained a bit better than SOH would make you believe there is because they're eating into their buffers ever so slightly more as the cells age. BOL they get charged to e.g. 4.08V, by EOL they're near 4.15V/cell.
4) performance is maintained by increasing pack temperature a bit it seems. This is a well-known aging effect: you can counteract the increase in internal resistance by increasing temperature, and you don't even need to do that much.

mux;
My "Lizard" pack data plots show a marked "cycle" (in Houston, TX) of amphour capabilities during winter to summer months. I do have some pack temperature data, but basically the pack ranges from in the 60-70 degree Fahrenheit at the end of winter to in the 90s at the end of summer. I never QC, so charging is 3.3kw max. I don't rag the car very often (it is a little go cart!) and I keep in a garage and out of the hot sun mostly. Does this corroborate your observation of keeping battery temps (Tesla) at some optimum between life expectancy and range?

I have SOH, Hx, GIDs and pack voltage data at same points as this Ah graph, would that data be of any help in establishing Leaf's "buffer" analysis for the Lizard chemistry.

BTW, have you seen any pragmatic pack temperature modulator systems (likely during charge sessions - in my garage) that could be installed on my 2012 Leaf? (Other than a window a/c with a heater strip blowing under the battery :mrgreen: )

Again, great posts - very interesting info!
battery log 5.3.20.jpg
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2012 Leaf SL; 46,000 miles. Battery replaced November 1st, 2016.

DougWantsALeaf
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Re: Battery Upgrades are very possible

Tue Jun 23, 2020 8:12 am

Mux,

To follow on MarkKtm's comments, for those of us in northern climates, who don't go on long trips or QC, battery temps may never exceed the low 90's which would suggest we should see a similar cycle to what a Bolt or Tesla might see. Especially since Tesla will bring cells up to close to 60C at times.

Are the NV200 cells different than the Leaf? I had they they just used the same 24/30/40 pack and added some forced air over the pack, which would suggest degradation would be similar to a lightly used cold weather pack, no?
2019 S Plus (98.6% SOH) & 2019 SV Plus (94.6% SOH) Both Silver
2013 Leaf SV sold 2019
100 Mile Club Member (Number 87)
Max Miles on 13 Leaf: 120 miles
Max Miles on 19 SV Leaf: 242 Highway 4.5 miles/kWh

LeftieBiker
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Re: Battery Upgrades are very possible

Tue Jun 23, 2020 12:50 pm

BTW, have you seen any pragmatic pack temperature modulator systems (likely during charge sessions - in my garage) that could be installed on my 2012 Leaf? (Other than a window a/c with a heater strip blowing under the battery :mrgreen: )
A portable A/C unit with a hose to blow the air where you want it would be worth trying.
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.

mux
Posts: 297
Joined: Sat Jan 13, 2018 3:52 am
Delivery Date: 13 Oct 2011
Leaf Number: 6177

Re: Battery Upgrades are very possible

Wed Jun 24, 2020 12:04 am

Marktm wrote:
Tue Jun 23, 2020 6:27 am

mux;
My "Lizard" pack data plots show a marked "cycle" (in Houston, TX) of amphour capabilities during winter to summer months. I do have some pack temperature data, but basically the pack ranges from in the 60-70 degree Fahrenheit at the end of winter to in the 90s at the end of summer. I never QC, so charging is 3.3kw max. I don't rag the car very often (it is a little go cart!) and I keep in a garage and out of the hot sun mostly. Does this corroborate your observation of keeping battery temps (Tesla) at some optimum between life expectancy and range?
First of all, the temperature dependence of those values is more an artefact of the BMSes ability to accurately gauge capacity, internal resistance and thus come to an SOH value. It seems like the SOH value we're reading out (0x7BB group 61 byte line 10 byte 6-7) is some sort of 'effective capacity' (i.e. usable capacity) value, not the actual SOH as AESC defines it in the datasheet. This obviously varies with average temperature; at higher temperatures, li-ion cells naturally have a slightly higher voltage so you gain a little bit of capacity at the bottom of the discharge curve. Likewise, lower internal resistance will make the pack seem better. There are some nonlinear temperature effects that will make all batteries seem better in most respects at higher temperatures.

Keep in mind that Leaf Spy calls these things SOH, Hx, GIDs, but all of that is names we gave to just a very few data values in the pack's engineering data. Well, okay, GIDs are correct, we know that from Nissan's documentation now, but Hx is just one of at least 8 different health-related values in that response group.
I have SOH, Hx, GIDs and pack voltage data at same points as this Ah graph, would that data be of any help in establishing Leaf's "buffer" analysis for the Lizard chemistry.
I'm not at present doing anything with this data and won't be for a while. Obviously more data is more better, and an effort to centralize this kind of data will yield interesting results. It's not going to be my research though.
BTW, have you seen any pragmatic pack temperature modulator systems (likely during charge sessions - in my garage) that could be installed on my 2012 Leaf? (Other than a window a/c with a heater strip blowing under the battery :mrgreen: )
Any kind of external thermal management of the Leaf battery is going to be hampered by the piss-poor thermal conductivity of the shell. You have to establish very large temperature gradients to transfer enough heat into or out of the battery that way, and it's going to be distributed anisotropically within - possibly exaggerating the thermal issues these batteries have already. Obviously I'd love to engineer and sell something that you can just slap on and it works, but - pending internal design efforts being done right now - I don't think that will be worth it.
DougWantsALeaf wrote: <span>To follow on MarkKtm's comments, for those of us in northern climates, who don't go on long trips or QC, battery temps may never exceed the low 90's which would suggest we should see a similar cycle to what a Bolt or Tesla might see. Especially since Tesla will bring cells up to close to 60C at times. </span>
But there's a big difference between the Leaf battery heating up to near 50C and a Tesla pack going to 55C - Tesla's doing it isotropically (i.e. evenly throughout the entire pack) and thermostatically (i.e. they keep it at a fixed temperature on purpose). Leaf packs can be 50C at the rear module stack and 40C in front, which is actually really bad for degradation. Additionally, the Bolt and Leaf cool down the pack right after driving, reducing thermal load where the Leaf stays hot for hours and hours.
Are the NV200 cells different than the Leaf? I had they they just used the same 24/30/40 pack and added some forced air over the pack, which would suggest degradation would be similar to a lightly used cold weather pack, no?
Exact same cells. Degradation is better than any Leaf battery, without fail. Consider how simple and cheap it would have been for Nissan to improve their battery longevity (and reputation) on these cars. The e-NV200 shows the absolute stupidity of their battery strategy.

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