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

Fri Jun 19, 2020 10:44 am

Ouch, wire bonded packs - those are notoriously unreliable. Every single cell has a very susceptible point of failure and even single cell failure tends to cause complete pack failure - which has a high likelihood with thousands of cells under the hood.

And you need aggressive thermal management to actually keep those many cells from drifting too far apart. Small differences in the pack tend to magnify over time, see... the Leaf battery packs!

It's doable, but only if you're Tesla. Even then, they had very bad reliability for a few years before nailing down the wire bonding and battery management issues. And for what? It's not like 18650s have a cost advantage in the automotive space these days.

(it is funny to see a bunch of 18650s on top of the original Leaf battery though)

DougWantsALeaf
Posts: 1784
Joined: Fri May 10, 2013 8:21 pm
Delivery Date: 18 May 2013
Leaf Number: 407811
Location: Chicago North Side

Re: Battery Upgrades are very possible

Fri Jun 19, 2020 10:55 am

Mux,

It does seem like GM has managed to achieve similar levels of success with the battery (density, degradation), with their pouch approach. Telsa appears (per this uninformed enthusiast) to have overall better power train efficiency (Hyundai is close). Its too soon to know how well the Hyundai batteries 64 batteries hold up.

Do you think with the newer Leaf chemistry (2018-2020 40/62 packs) that they have significantly reduced the degradation problems?

Appreciate your responses. Looking forward to your 2021 US battery upgrade shop in the states! :)
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

Oilpan4
Posts: 1491
Joined: Wed Jan 09, 2019 10:51 pm
Delivery Date: 10 May 2018
Leaf Number: 004270

Re: Battery Upgrades are very possible

Fri Jun 19, 2020 11:39 pm

So fenix never had a chance to make a viable product?

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

Sat Jun 20, 2020 12:00 am

The Leaf's battery problems are not down to the chemistry - they're fine. Even the old packs weren't bad at all, especially considering AESC was the only car manufacturer even trying to use LMO. All of the battery woes are down to not having any thermal management.

Lithium ion batteries have performance and degradation characteristics that vary WILDLY with temperature. In the Leaf 40's battery pack, it is common under almost all circumstances for the rear module stack to be easily 10 degrees C (about 20F) warmer than the frontmost stack. That by itself means the rear stack will degrade about twice as fast (on long timescales) but also that it has lower internal resistance, i.e. higher current load during both discharging and charging which also increases effective cycle load.

But probably most importantly, without a way to heat up the battery, under everything but short sleeves weather, the battery is routinely damagingly loaded. You can't expect a pack at near freezing to happily discharge at 3C (300+ amps) to accelerate, nor to accept regen braking as often and harshly as it does.

Then, when the battery has heated up, it has no way to cool down. If you fast charge at all, the battery jumps to 45C and stays hot for at least half a day after use. Batteries are actually fine being hot, consider Tesla's batteries which are actively heated up to accept a fast charge. The difference: they get cooled down to ambient as soon as you exit the car, keeping them hot and degrading for as short a time span as possible. Keep the battery hot for basically half the year and you've got a battery that degrades 4-8X as fast just because of Arrhenius' law.

------------

Oh and the 40/62 share chemistry with the 30! And the BMS as well. If you want to know how the cars/batteries last, look at historical 30kWh data and make it slightly worse for the 40 (due to higher thermal load) and slightly better for the 62 (due to higher battery mass and lower RMS C-rate, causing less heating on typical trips).

------------

On GMs batteries: It shows that even commonly derided LG E-type cells (as also used by EVBR) CAN be used and CAN last a long time without sacrificing system energy density too much. Again, the secret sauce is just an adequate BMS and some fairly aggressive power throttling when the car is threatening to exceed the datasheet performance. I think that's the ultimate dirty secret of batteries: they can be as crap as you like, if you manage them well they'll last forever.

Tesla doesn't necessarily have good drivetrain performance, they just have slightly more aerodynamic cars. Tesla's system efficiency is actually quite bad all things considered, but that has more to do with their excessive idle consumption and battery TMS overhead than their powertrain. The Ioniq is definitely in another class of car if efficiency is concerned; with no idle consumption and surprisingly little TMS overhead despite having decent battery life. Then again, the Ioniq seems to degrade about twice as fast as the Model 3 batteries, so is the overhead worth it? Probably! Again, I try to convey as much as possible that Tesla's batteries/cars/etc. aren't magic and aren't actually particularly good on any individual aspect (there are better examples all around) - they just have a really well-balanced package and know where to focus to give the best customer experience of the car. That's what makes a Tesla such a great car to recommend. You're not going to be disappointed, the best you can do is have differences of taste in certain design decisions.

jfr2006
Posts: 15
Joined: Tue Jun 19, 2018 5:56 am
Delivery Date: 19 Jun 2018

Re: Battery Upgrades are very possible

Sat Jun 20, 2020 5:30 am

mux:

What's your opinion in using the LG cells inside the Leaf cells can module (2 for each can module, as in the original situation) ? Is it safer?

And is it easy to get 62kWh pack to place on a older leaf?

brunohill
Posts: 23
Joined: Thu Jan 03, 2019 10:36 pm
Delivery Date: 05 Oct 2017
Location: VK3

Re: Battery Upgrades are very possible

Sat Jun 20, 2020 5:50 am

Perhaps it can be done similar to a Renault ZOE ZE 40 battery. It uses the same LG chem batteries and the same number of them.

User avatar
Marktm
Gold Member
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Leaf Number: 022737
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Re: Battery Upgrades are very possible

Sat Jun 20, 2020 5:55 am

Have to compliment all poster on this subject - some good challenging conversations and better answers! IMO, this is one of the most interesting/informative posts on this forum! Please keep it non-personal and keep the information flowing.
Thanks!
2012 Leaf SL; 46,000 miles. Battery replaced November 1st, 2016.

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

Sat Jun 20, 2020 6:45 am

jfr2006 wrote:
Sat Jun 20, 2020 5:30 am
mux:

What's your opinion in using the LG cells inside the Leaf cells can module (2 for each can module, as in the original situation) ? Is it safer?

And is it easy to get 62kWh pack to place on a older leaf?
Safety... in which respect? If you're talking about the LG E63 cells (the ones used by at least three companies doing rebuilds now), they're the just as non-intrinsically safe as Leaf cells. I wouldn't call either cell type safer as a blanket statement. But the way battery rebuilds are being done now, there is some opportunity for unsafe battery management:

The LG cells are high density cells, not high performance cells - so they have relatively high internal resistance (about twice that of the Leaf cells), lower allowable charge current and lower (burst/continuous) discharge current. They also have significantly higher allowable capacity tolerance. Altogether this means the original BMS cannot be used with these cells. Without thermal management, you'd almost certainly need completely new hardware with much higher balancing current capability. With thermal management, I think you should be able to manage with the original hardware and just do some external management. Without thermal management, you're not going to have a safe battery system long-term with the original BMS.

The higher internal resistance and similar thermal properties to the original Leaf cells (in particular the 30/40/62 cells) means you'll get hot spots a bit quicker in an LG pack. You'd most likely need to throttle or limit QC sessions a bit more aggressively with a pack like that to avoid thermal runaway.

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Yes, we offer a kit to battery-swap a 62kWh battery under any Leaf. It's $1490 and comes with replacement rear springs+adapter brackets.

coleafrado
Posts: 279
Joined: Fri Oct 11, 2019 11:58 pm

Re: Battery Upgrades are very possible

Sat Jun 20, 2020 7:44 am

mux wrote:
Fri Jun 19, 2020 10:44 am
Ouch, wire bonded packs - those are notoriously unreliable. Every single cell has a very susceptible point of failure and even single cell failure tends to cause complete pack failure - which has a high likelihood with thousands of cells under the hood.
So you're not going to back this up with anything?

knightmb
Posts: 472
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Delivery Date: 15 Sep 2013
Leaf Number: 414897
Location: Franklin, TN

Re: Battery Upgrades are very possible

Sat Jun 20, 2020 9:35 am

coleafrado wrote:
Sat Jun 20, 2020 7:44 am
mux wrote:
Fri Jun 19, 2020 10:44 am
Ouch, wire bonded packs - those are notoriously unreliable. Every single cell has a very susceptible point of failure and even single cell failure tends to cause complete pack failure - which has a high likelihood with thousands of cells under the hood.
So you're not going to back this up with anything?
I think for the sake of this topic and keeping the conversation going and keeping in mind that for a lot of people at this forum, English is their *second* language and a lot of what we take for granted as native speakers, innuendo does not always translate. So maybe we could all qualify anything that we do say if it isn't so much of a text book reference as much as an experience reference, then that experience could be what is qualified for the statements. Such as the statement that Mux made or any statements I make here for example. :D :mrgreen:

Experience always trumps logic. 8-)
2013 Leaf SV

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