Arlington wrote:... and I have heard good things happened to battery tech as 2013 production ramped up in the USA, so I'm hoping that my battery is from after some sort of generational change (for the better). ...
The tooth fairy was a wonderful thing to believe in for a while too.
I hope you are right, but there has not been much hard data to back up that claim.
Nissan said the heat resistant battery arrived with USA model year 2015.
They would not even sell replacements till it was available.
Why does everyone want to not believe them and start assuming they started using it a year and a half earlier.
I'm going to keep digging, not just waiving off well-documented changes as tooth fairy.
This is the first clue: in 2013, the casing on battery modules went from 2011/2012 "solid box":
to a new casing with a split all the way around:
(see this 2014 article on the battery replacement program
that shows a split-casing module, and this pair of "2013" battery pack teardown articles from April
and September 2015
Again, we're looking for generational changes of the sort that go with "continuous improvement" that Japan is famous for, especially when confronted with rapidly-emerging tech (like batteries) and vociferous feedback (heater-off switch)
Some 1.x to 1.x++ changes will be small (like number of sensors and mounting bracket positions) and some will be large (like lizard's leap in heat-resistance) and some will be true generational changes (I'd call 30kWh the first "2.0" )
A small "continuous improvement" change in battery CONSTRUCTION in 2013 is a now a proven fact, and that 2013's changes might have been a small continuous improvement in battery DURABILITY isn't ruled out by the fact that there is said to have been a big change in chemistry for 2015 (big enough to hold up production) and a discontinuous "2.0" kind of change in internal wiring to support 30kWh.
I think a change in battery modules in 2013 (small enough to *not* hold up production), is particularly of the kind that you might introduce in the course of setting up the Smyrna TN battery production assembly line and organizing a new supply chain.
So far, my guess is that the switch from a solid to a split module casing in 2013 was a "winner" improvement, which is why it is part of acknowledged 2014/2015 "Lizard" production of "Gen 1.5" replacements for failed Gen 1.0/1.1 batteries and is why 2013 owners seem happier with battery durability. Maybe they also knew that a split casing would move heat around differently and so changed the sensor setup.
91040 wrote:If memory serves…
2011MY 24kWh battery.
Later 2011MY 24kWh battery with heater (part of the cold package).
2013MY 24kWh battery with minor chemical composition change.
2015MY 24kWh battery with a more heat resistant chemistry. Dubbed the lizard battery for that reason.
There are 4 temperature sensors on the batteries for MY2011& 2012. Three temperature sensors starting with MY2013.
In the spirit of continuous improvement, I'm re-working my generations list as follows:
Gen YearMY What's New
1.0 2011MY (Launch 25kWh battery)
1.1 2011MY battery with heater (part of the cold package).
1.3 2013MY USA-assembled battery changes*
1.5 2015MY battery with a more heat resistant chemistry. Dubbed the lizard battery for that reason.
1.x (possible further improvements in Lizard / 2016 S / Future Gen 1.x replacement supplies)
2.0 2016MY 30kWh Batteries
* Known generational changes during switch to Smyrna battery production in Spring 2013
that would appear in 2013MY production by July or August:
1) Known reduction in number of temp sensors from "1,2,3,4" to "1,2,4" (perhaps the 2013's only "ask" for 3, even if the pack has 4)
2) 2nd HV Connection on the front of the pack that goes to the cabin heater
3) Exterior casing changes: fewer simpler bolts & seal change (see this teardown
4) Change in battery module casing & venting (allowing greater airflow?) (see this teardown
So I look at the list, above, of known changes for USA 2013MY and confidently declare gen 1.3 for MY13. (there may never be a 1.2 or 1.4 "released" so let's go with 1.3 = '13 cause it is an easy mnemonic
Is Gen 1.3 really "better" or "more durable"? That seems like a better hypothesis than to just assume they were cost cutting or accommodating equal-or-worse US domestic suppliers in their changes.
Sure, some of those 2013 changes may be purely "cosmetic" and driven by what kind of deal Nissan could cut with USA parts suppliers (maybe USA bolts are expensive and seals are cheap), but all speak to a Nissan engineer, somewhere, having been given a list of redesign items. Equal-or-better seems like the more "normal" set of design and sourcing changes you'd make.
I find the case that 2013 saw better venting & convective temperature management within/between the battery modules to be very compelling because we see a change (to a split case) and have a good hypothesis as to why it was made (to allow heat to move/moderate better). It may be that 2013 didn't see a chemistry change at all, but rather just this change to better manage heat making it *look* like the chemistry changed.
Frankly, Given all the known/visible changes for 2013 (see #1, 2, 3, 4, above) it seems at least a 50% chance that they tweaked the actual chemistry, or 50% that the left chemistry unchanged in 2013 but knew that a new 4-cell casing could better dissipate heat.