3-4-5 Bar Drop Analysis

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Joined
Sep 2, 2016
Messages
6
Hi everyone,

I live in Vancouver, Canada and just bought a used 2012 Leaf that someone else had imported from California. It is currently displaying 9 bars and has 78,800 km (48,800 miles) on it. Since I would looooove to have the battery replaced under warranty I have become very curious about whether or not it's likely to drop the 4th bar while it's still under the battery degradation warranty.

Being an analytical guy, I went through the Real World Battery Capacity Loss on the Wiki and made a spreadsheet to try and figure out what factors (miles, months, Ahr, SOH, Hx, GIDs) correlated best with dropping of the 3rd, 4th and 5th bar. The sample size isn't huge since many vehicles didn't report the technical details, but I think it gives a relatively good picture. Since the information from this forum and the wiki has been so valuable I wanted to share the spreadsheet with everyone in the hopes that some people would find it useful for their own predictions.

You can view or download the excel spreadsheet through Google Drive. (Click the words "Google Drive")

There are two tabs on the spreadsheet, "Generic" and "4 Bar Analysis."
The "Generic" tab shows all the info in a table as well as a bunch of histograms (bar charts) showing how many vehicles dropped their 3rd, 4th and 5th bar at various points in relation to miles driven, months of ownership, Ahr, SOH, Hx and GIDs. One tip on reading the histograms: each number on the x-axis (bottom) means "not more than." For example, you can see that 16 vehicles lost the 4th bar after 50,000 miles and before 60,000 miles.
The "4 Bar Analysis" tab goes into more detail about the loss of the 4th bar and also has charts showing what % of vehicles dropped the 4th bar based on Ahr, SOH, Hx and GIDs. Please keep in mind that this is only based on the population of vehicles that reported these stats!! For example, only 10 vehicles (out of 58) reported the GIDs when the fourth bar dropped, so please take it all with a grain of salt.

Given the data (and probably not surprisingly) it looks like miles, months and Hx are poor predictors of bar drop while Ahr and GIDs are better predictors. The confusing thing right now is that there doesn't seem to be a clear correlation between Ahr and GIDs when the bar drops happen. I can only speculate that the capacity bars are based on some other parameter, or some average value over a period of time. It would be great if someone had additional information on what exact parameter the capacity bars represent.

The Leaf I purchased has the following stats: 48,802 miles, 44 months since first registration, 42.90 Ahr, 65% SOH, 44.29Hx and 184 GIDs. Based on Ahr I figure there is about a 50% chance that I'll drop the bar any day now. Based on GIDs I figure there is a 10% chance I'll drop the bar any day now. Using the Surfingslovak model from the Battery Capacity Loss Wiki I figure that being in Vancouver I'll drop 5 GIDs per year which would put me around the 70% chance of dropping the 4th bar by this time next year based on GIDs.

Anyway, I hope that some people can find the information useful!
 
Your location may very well slow the rate at which you will lose the next bar, especially if your chart is populated with cars from Arizona and California


Off topic:
I've always said that becoming an aware Leaf own makes you a statistician.
 
Agreed, your location makes it MUCH more difficult to lose that 4th bar. TayorSFGuy, near Seattle, went about 70,000 mi before losing his first bar (135 mi RT commute). He did note that the bars dropped much faster after having to DCQC charge twice per day (mid-commute), after he had lost two bars. So, bottom line: DCQC charge to 100% as much as possible and keep that battery warm. I see essentially ZERO decrease in the AHr value from October to April (temps drop below 60 F average).
 
Reddy said:
Agreed, your location makes it MUCH more difficult to lose that 4th bar. TayorSFGuy, near Seattle, went about 70,000 mi before losing his first bar (135 mi RT commute). He did note that the bars dropped much faster after having to DCQC charge twice per day (mid-commute), after he had lost two bars. So, bottom line: DCQC charge to 100% as much as possible and keep that battery warm. I see essentially ZERO decrease in the AHr value from October to April (temps drop below 60 F average).

Thanks for the tip on the DCQC!! I'm going to check it with Leaf Spy weekly to see if I can get a sense of any degradation through the fall and spring (Vancouver doesn't get winter). From anecdotal evidence and the Battery Capacity Loss Wiki I figure that if I can knock off that fourth bar and get the battery replaced then the Vancouver climate will do so little damage I'll be able to pass the battery on to my unborn grandkids for their spaceships.
 
MapleLeafAndrew said:
Thanks for the tip on the DCQC!! I'm going to check it with Leaf Spy weekly to see if I can get a sense of any degradation through the fall and spring (Vancouver doesn't get winter). From anecdotal evidence and the Battery Capacity Loss Wiki I figure that if I can knock off that fourth bar and get the battery replaced then the Vancouver climate will do so little damage I'll be able to pass the battery on to my unborn grandkids for their spaceships.
While DCQC will definitely heat the battery and speed degradation, it does have a cost (well, I assume you don't get free charging up there). Another, perhaps better option, is to drive UP and DOWN some very steep hills. Remember, that you can consume 80 KW with the accelerator. Some very spirited driving, jack rabbit starts/stops, can also add some additional battery degradation. Definitely, charge to 100% and discharge to "turtle" as much as possible. Good luck. EDIT: Perhaps read this thread:
http://mynissanleaf.com/viewtopic.php?f=9&t=22134#p463591
 
Reddy said:
While DCQC will definitely heat the battery and speed degradation, it does have a cost (well, I assume you don't get free charging up there). Another, perhaps better option, is to drive UP and DOWN some very steep hills. Remember, that you can consume 80 KW with the accelerator. Some very spirited driving, jack rabbit starts/stops, can also add some additional battery degradation. Definitely, charge to 100% and discharge to "turtle" as much as possible. Good luck. EDIT: Perhaps read this thread:
http://mynissanleaf.com/viewtopic.php?f=9&t=22134#p463591

Actually there's a DCQC on my way to work that's completely free so I've been stopping in the mornings and trying to top up to 100% although it's definitely taking a lot longer than I expected to get close to a full charge. I'll look for some hills and start trying to run the battery down as much as possible between charges.

Is the take home point that whatever I'm doing should be getting the battery temperature up?
 
After learning a bit more about the information presented in Leaf Spy I realized that GIDs people reported will depend on the maximum state of charge (SOC) that their car is achieving with whatever charging method they're using. There were basically three data points that gave the GIDs and a believable SOC (I didn't count reports that said "full charge" or "100% charge"):

176 GIDs at 91.2% SOC = 193 GIDs at theoretical max
180 GIDs at 94.0% SOC = 191.5 GIDs at theoretical max
177 GIDs at 91.8% SOC = 192.9 GIDs at theoretical max

While three is a very small number of data points, I was surprised at how well they line up. It makes me wonder if the 192-193 "maximum" GIDs is the point where the 4th bar will drop. I believe this ends up being 15.4 kW (192.5 x 80W) which is below the theoretical rating of 15.9 kW (24kW x 66.25%). Does anyone have any GID and true SOC number at the 4th bar drop that are out of line with this??
 
MapleLeafAndrew said:
Is the take home point that whatever I'm doing should be getting the battery temperature up?

Yes, heat your garage to 30 *C and leave the battery at 100%. Better yet, take the car to pheonix and loan it to a friend for 6 month.s Afterall, this is a $6000 USD question. Do whatever you can to make it happen.
 
MapleLeafAndrew said:
... Does anyone have any GID and true SOC number at the 4th bar drop that are out of line with this??
Mine were lower when bar nine dropped.
More like 14.9 to 15.1 kWh remaining and SOH at 64% when fully charged.

I think quite a few people were more like 64% or 65% capacity instead of the 66.25% that Nissan stated.

Of course my numbers were also before P3327 which may have also made them lower.
 
vwDavid said:
... Yes, heat your garage to 30 *C and leave the battery at 100%. Better yet, take the car to pheonix and loan it to a friend for 6 month.s Afterall, this is a $6000 USD question. Do whatever you can to make it happen.
30C is too low for quick capacity loss.
Need more like 43C to 46C (110F to 115F) or higher like the temperatures packs see in Phoenix in summer.

It can be above 90F for six months in Phoenix.
Driving can easily raise pack 15F or more above ambient.
So that is what is necessary for relatively fast capacity loss.
 
MapleLeafAndrew said:
Actually there's a DCQC on my way to work that's completely free so I've been stopping in the mornings and trying to top up to 100% although it's definitely taking a lot longer than I expected to get close to a full charge. I'll look for some hills and start trying to run the battery down as much as possible between charges.

Is the take home point that whatever I'm doing should be getting the battery temperature up?
Yes, warm it up and keep it warm by charging as fast as possible, drive hard, drain it below VLBW, then recharge to 100%, rinse & Repeat. Hmmm, that sounds like fun driving, just like it should.
Is this the charger that you're talking about: 140 1st St E North Vancouver
If so, then how about this 900 m hill: Cypress Mountain, 6000 Cypress Bowl Rd?
Alternatively, you could drive fast up to Squamish (no elevation gain), DCQC and return. Another weekend project might be driving to Osoyoos using 5 or 6 stations! That'll warm it up.
 
Reddy said:
Is this the charger that you're talking about: 140 1st St E North Vancouver

I'm using the term "Vancouver" very loosely - I actually live in Surrey (a very flat suburb south-east of Vancouver) and the DCQC I've been using is on my way to work at 17710 56A Ave. Surrey. Cypress road and the North Vancouver DCQC is definitely a good idea. If I haven't made much progress by next summer I'll pick a few hot days and really put the hammer down.

An interesting point I learned about the charging stations in BC: our government-owned power supplier has a monopoly and is the only entity legally allowed to sell power which is why all charging stations in the province are free. Not a bad situation for EV drivers!
 
MapleLeafAndrew said:
Reddy said:
Is this the charger that you're talking about: 140 1st St E North Vancouver

I'm using the term "Vancouver" very loosely - I actually live in Surrey (a very flat suburb south-east of Vancouver) and the DCQC I've been using is on my way to work at 17710 56A Ave. Surrey. Cypress road and the North Vancouver DCQC is definitely a good idea. If I haven't made much progress by next summer I'll pick a few hot days and really put the hammer down.

An interesting point I learned about the charging stations in BC: our government-owned power supplier has a monopoly and is the only entity legally allowed to sell power which is why all charging stations in the province are free. Not a bad situation for EV drivers!
Free L2 only, DCFC @0.35 per kWh.
 
Reddy said:
Agreed, your location makes it MUCH more difficult to lose that 4th bar. TayorSFGuy, near Seattle, went about 70,000 mi before losing his first bar (135 mi RT commute). He did note that the bars dropped much faster after having to DCQC charge twice per day (mid-commute), after he had lost two bars. So, bottom line: DCQC charge to 100% as much as possible and keep that battery warm. I see essentially ZERO decrease in the AHr value from October to April (temps drop below 60 F average).

just to add to this; Its my generalized estimation that time plays the greatest factor for degradation for us here in a probably 3 to 2 ratio against cycling. I think TaylorSF lost his first bar at 73,000 miles but more importantly in roughly 27 months. Now cycling can vary a ton and lots of factors apply including how deeply the car is discharged and how long the car sits at very low SOC or very high SOC.

The primary reason TaylorSF noticed a steeper degradation curve is because he was now driving until a very low SOC due to range loss. The first 73,000 miles happened because he was getting to work with 15-20% SOC left. He was only charging at home and then at work.

Then he lost his first bar and was making it to work with less than 10% SOC (sometimes much less) in Summer but having to stop to grab a quick charge boost in Winter. after losing his 2nd bar he was having to stop for a quick charge in the afternoon in addition to the boost in the morning.

Now his LEAF is well over 150,000 miles and no longer able to make his 68 mile one way commute so he is driving the 2014 now.


For reference; my 2013 has just over 43,000 miles in 33 months of service and degradation is probably in the 8-10% range. Hard to pinpoint because it bounces around quite a bit dropping pretty low if not driven much
 
100% DC charge is not easy to do and doesn't really add to degradation speed.
Maximum heat generation happens when pack is very empty (below LBW). Discharge efficiency goes down,
especially with heavy acceleration. And charging at 20+kW rate also helps heating up the pack.

Nothing interesting happens when topping up at DCQC slowly.
Also do not charge when you run out of juice at home and pack is hot (and car will not be used).
 
arnis said:
100% DC charge is not easy to do and doesn't really add to degradation speed.
Maximum heat generation happens when pack is very empty (below LBW). Discharge efficiency goes down,
especially with heavy acceleration. And charging at 20+kW rate also helps heating up the pack.

Nothing interesting happens when topping up at DCQC slowly.
Also do not charge when you run out of juice at home and pack is hot (and car will not be used).

cell resistance increases with the increase in voltage
 
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