Friday, August 10, 2018
Casual Observational Differences in the 40 Kwh Battery Pack
Have had to address a lot of speculation over the 40 kwh battery pack with many automatically assuming (VERY applicable word here) that the new pack is the same old cells in a somewhat fatter configuration. This I have found to be far from the truth. In fact, other than the nameplate, nothing seems to be the same.
GOM Part 1
After all this time, people still take the GOM (Estimated remaining range on the dash) as some sort of "official" word on range. That is far from the truth and the 2018 strays even farther from it. The GOM estimates the remaining range by using your performance over the recent past to extrapolate that performance to the remaining charge in the pack. Unless you live "on the freeway", you can't use the estimated range for a mostly freeway trip as it will bring you well short. Same thing if the last few miles to your home is at a lower elevation which results in a very high GOM estimate or if your trip is uphill to home with its resulting low estimate. In previous LEAFs you could monitor the GOM while it was still blinking and make a mental note of the odometer so you had an idea of how far you could go with a margin of safety. The 2018 removed that option as well (see below) IOW, ignore it!
GOM part 2
Another common complaint is the GOM loses 20% of its full range as the car is driven to low SOC. That isn't completely true either. For one thing (see above) because most people live in areas where the speed limit is low and LEAF effieciency is high, the GOM will always overestimate the range slightly anyway. So how does those 20% claims come about?
Apparently Nissan has decided to do what it can to encourage us to plug in at 20% so much so that they have realigned their low SOC alerts and even added another one. But despite the car implying its now running on static electricity, LEAF Spy tells a completely different story. Lets compare alerts from the 2018 LEAF to previous models.
LBW (Low Battery Alert; GOM estimate starts blinking SOC 9%) So this is the first alert so Nissan has done what every car manufacturer has done and that is provided the first alert well before action is needed. I give them a pass here.
2011-2017 LEAFs--------- 2018 LEAF
--------48 GID -----------------87 GID
VLB (Very Low Battery; GOM goes to "_ _ _" SOC 4%) No more passes here. The range estimate is now gone so no way to even guess at how far you can go unless you notate odometer readings and knew what the GOM said before it started this...
2011-2017 LEAFs--------------2018 LEAF
------24 GID-----------------------62 GID---
Below we have to make up stuff in order to have easier references to them in the future. Granted they will likely only be valid on this blog unless for some crazy reason, people decide to adopt them. All these ONLY apply to 2018 LEAFs with the exception of Turtle since nothing from nothing still equals nothing.
SLB (Super Low Battery?? GOM "_ _ _" SOC 1%) This happens "around" 50 GID. **See LBW reference above** I only mention this because it is the MOST robust 1% of the entire pack.
SEW (Static Electricity Warning GOM "_ _ _" SOC "_ _ _" ) This happens around 40 GID (See VLB reference above. I posted this info several months ago and had someone say that Turtle happened MUCH sooner. I retested "only" to prove him wrong. Key takeaway here is that 24 GIDs is roughly 2 kwh with as much as 1.5 kwh useable.
TP ( "Trashed Pack" AKA "Turtle Power" mode) GID level varies. On the energy screen of the 2018, we have segments; 32 power segments, 16 regen segments. These provide the same function the power/regen circles did on earlier LEAFs. As they disappear, they become unavailable. Unlike the above warnings, Turtle is "voltage controlled." Turtle should be avoided at all costs.
Lithium cells can be permanently damaged if they drop below a voltage threshold. A "single" bad cell will take the ENTIRE pack down to its level which WILL result in a huge loss of functionality. For this reason, cell balance is VERY important and your cells are balancing ALL the time. This voltage protection is job #1 for the BMS.
Now we have all had flashlights with weak batteries where the light slowly fades but we can turn the flashlight off a minute or two and turn it back on and the light is bright!!... for 10 seconds anyway.
Your LEAF battery pack works the same way. If you feel like you are in danger of being stranded, then DON'T KEEP GOING! Driving until the car stops is VERY bad and will almost always cause "some" permanent damage to one or more cells. If you feel like you have no choice but to keep going, then slow down... A LOT. Take breaks to let your pack balance. I know all this sounds inconvenient (as if sitting on the side of road waiting for a tow isn't!) but too many times I read about people who were 500 feet short of a charger. There is no doubt in my mind that if they had stopped 10 minutes before that point. Turned the car off, took a 10 minute walk and returned to the car, they would have made it.
So back to the GOM (since that is what we are talking about) The GOM on a full charge is actually relatively accurate minus the recent driving history issues discussed above. It does not lose 20% simply because most of that range is transferred to the reserve. Not that I recommend doing this to your LEAF but getting LEAF Spy will allow you do this.
Turtle Mode. 14 power segments. FYI; I shut off car with only 6 power
segments to talk with someone interested in my car. It popped up to 14
in about 4-5 minutes.
Turtle Mode. 12 (of 32) power segments. FYI; I shut off car with only 6 power
segments to talk with someone interested in my car. It popped up to 14
in about 4-5 minutes. In the pix above you can see meter behind warning
and how many power segments are gone.
There is no longer a question that Nissan has GREATLY hampered DCFC sessions. Charging slowdowns start about 86º, getting significant by the mid 100's at any starting SOC. But that is only part of the problem. As mentioned in earlier blogs, the BMS is using two criteria to control charge rates; starting battery temps and ongoing SOC. So even in the event of cooler battery temps, the slowdown can happen anyway because the SOC is over 58-65%. Remember the 86º comment above? That is starting temperature. Look at what happens when its the ending temperature combined with high starting SOC.
On the flipside, I did notice when pack was colder, the knee started at a lower SOC of 58%. But this is rather easy to fix. Simply charge long enough to heat the pack into the 70's or so, unplug and plug back in to resume at full speed with a knee near the mid 60's % SOC. Below is an example except in reverse. (What can I say? Its Summer time) I started a charge with temps at 80º at full speed. Then unplugged and immediately restarted the charge with temps at 88º. Look at how the drop in the charge rate. I immediately dropped from 46 KW to 42 KW.
Note; Notice that a slower charging rate is not all bad. The slower the charge, the higher the knee. THIS IS HUGE. In this case, there isn't a big enough change in charging speed to see this but I did the same thing unplugging at 100º and the charge rate dropped from 46 KW to 35 KW but the knee moved up to 72%. So yeah, the charging speed is slower but the additional charging time isn't as bad as we might think.
The same thing happens when starting a charge at an SOC that is near or above the normal knee range of 58-63%. Below, we still have the good temperature range in the low 80's but a high SOC which means no full speed charging but notice where the knee is?
Charging speed 35.8-37.1 KW, SOC 58.3%, knee 71.2%
Now maybe we shouldn't complain about slowing down at 63%. A lot of EVs do the same thing. The Bolt slows down MUCH earlier to a much slower rate BUT, it will still charge quickly from low SOC into the 55% range. But here we have a LEAF that can still charge at near full speed (will gain some temperature from driving) despite it being the 2nd QC of the day. Keep in mind; high ambient temps and spirited driving can add 15º dropping the charging speed from 45 KW to 33 KW. Not a huge drop but you have to think "How much time did I save driving 70 mph while I spend an extra 15 minutes charging?" Keep in mind that higher temperatures AND a shorter range makes driving faster a double whammy.
Well, its hard to deny the fact that despite a nice Spring day and batteries at ambient. We have gained 32% SOC with a 10º temperature rise. This makes it hard to argue that Nissan was too conservative here. Notice the lack of temperature spread on the temperature sensors? This is not an anomaly. Previous LEAFs I have had were normally 10+º difference and the hotter the pack, the greater the spread. Looks like temp sensors are better placed? Better indication of true state of the batteries, maybe?
20º spread was not all that unusual on my 2016 S 30
Jennifer from Arizona claims to have had success accessing the quick disconnect port located between the back seats on the floor and dumping ice there to cool the sensors to allow a faster QC. Realize she was seeing less than half speed charging on her first charge of the day!
Now, we all know that the ice is only cooling the sensors and not the pack. How dangerous is this? Would this allow the pack to get to "runaway thermal" danger? Well, probably not. Nissan's lowering the charge rate of the pack has made it difficult for me to hit 11 temperature bars due to the slowdown. I could probably do it by heating up the pack to the mid 120's and sprinting up the Cascades or something stupid, but simply not into nonsensical pack degradation. After all, its all about how to make the LEAF work for me, right?
Ever be in a hurry but still needed to stop for a fast QC? Well, I generally go for a walk to stretch the legs most of the time but there were a few times I had conference calls or "something" that made leaving the car inconvenient. I NEVER used heat in those situations but A/C on a sunny day with temps in the mid 60's was almost always a given due to solar loading. So I tried it and yeah. It will affect your charging speed. With charging rates as low as 20 KW, this could add a significant amount of time to the charge. What is significant when you are in a hurry? Luckily, the power draw for AC generally drops into the 300-500 watt range within 10 minutes on all but the hottest of days.
On the chart below, its not that easy to see but power draw was near 2500 watts initially but dropped to 700 watts during the short period it was on. Normally, it settles at 300-500 watts.
AC effect on charge rate.
Just happened to see this when it was at 363 GIDs which also happens to be the new pack GIDs on the 30 kwh LEAF and also 28.1 kwh available is same as what I saw so... just had to capture it but lost a GID while getting camera ready.... Oh well, you get the idea!
40 kwh pack matching 30 kwh pack stats
Previously, LEAF Spy stats on battery packs were difficult to interpret. The numbers bounced around from season to season, charge to charge and sometimes for no discernible reason at all. Gaining or losing 5% capacity was commonplace. The ability to manipulate the battery numbers by changing driving habits or charging habits became well known. This was largely overcome by recording and reviewing stats over a long period of time. I record mine every day before the first drive of the day (if I go somewhere...) and I recommend you do the same. If every day is too much, then pick a specific time and circumstance like every Friday evening when you get home from work or every Monday morning before you go to work, etc.
The flakiness of LEAF instrumentation came into the spotlight when Nissan announced they had made an error on how the LBC (Lithium Battery Controller) calculated the capacity of the 30 kwh battery packs which meant the BMS (Battery Management System) needlessly restricted full access to the usable capacity of the pack which resulted in apparent rapid degradation. The error was apparently discovered when Nissan started to examine the degraded packs that were replaced under warranty only to find out the remaining capacity was well above the replacement level.
A software update was issued and so far, the results have been positive. Nearly everyone has reported increased capacity and no one yet has noticed any change in the fast charge profile. All is good!...for them.
Since I track my battery stats EVERY day (I drive it or am in town to check it) I have NEVER seen the ahr or SOC go up. Not even a tiny bit. Now, they don't always go down. In fact, probably 50% of the time or more, the numbers stay the same. But its been a steady decline from day one. But the decline has been slow. a few hundredths usually. In just under 10,000 miles and 110 QCs, I have lost a pinch over 3%. At that pace, I will get a replacement pack should I decide to keep the LEAF, but there were two very large drops that happened in one day. One happened for no apparent reason while the 2nd happened the day I returned from a 2 week vacation where my LEAF sat in uncovered storage during that time.
But if I take out those two big drops, I will fall just short of the required loss to qualify for a pack replacement. Granted, its all conjecture based on the rate of degradation being the same thru out. Keep in mind, a shorter range means more cycling which could mean quicker degradation as well.
The other battery stat is the Hx; the mysterious metric several have speculated on and although I hesitate to say its this or that, the largest vote seems to center on it being a reverse measure of internal resistance where higher the number, the lower the resistance. Lower resistance means less loss to heat so its a good thing. My Hx peaked 116.46 and is currently at 114.14 but it follows the "old school" flakiness of bouncing around although I do see a general downwards trend that has been relatively consistent over the past few weeks. This could also be a result of the higher than normal Summer temps we are suffering thru as well.
**Yesterday on Facebook, someone reported they have not had "any" change to their battery stats over the last 1000 km spanning several days. This is the first I have heard of this from anyone. If you have seen this as well on your LEAF Spy stats. Please chime in! We need to know why you are special!!**
Regrets and the Future;
I can only speak for myself when evaluating how well the 2018 decision works for me. I will say, I am not completely happy with the lower knee on the QCs, the drastic charge rate slowdowns, etc. but I do see a possible benefit if it will give my pack an extra several thousand miles of useful life.
I will say, I am different in that pitstops for charging don't bother me all that much. Its partially due to the area I live in where most of the time, it simply takes forever to get anywhere which frequently means I have to stop for personal reasons so timing those stops with a charging location is simply a no brainer. My most robust abuse of free public charging happened on my Oregon Coast trip where my first 4 stops to charge perfectly coincided with personal needs. In a few cases, it was almost a race to the charging station due to an overwhelming need.
The other reason is simply me getting old. Fighting traffic is very tiring mentally so stopping to charge allows me to get out, walk around, recharge my personal batteries, etc. So, again, its all about opportunity charging.
But the bottom line becomes should "you" wait for a more expensive, more capable EV that might be here in 6 months or less? That is a decision that each of us has to make. Due to my accident, I was forced to pick and in that sense, I don't regret my choice. I missed the window to grab a Bolt super cheap but I don't think I would have been very happy with the decision. Range is not everything and right now, the new CCS stations that are popping up all over the place are not treating Bolters very kindly. That will change soon. FYI; "All" the road trips I have blogged about well exceeded the range of "any" EV on the road today.
The other thing is I will be hitting Central WA AGAIN! tomorrow with my Son to watch the Perseids at th 3500 ft elevation of Wild Horse Renewable Energy Complex. We will be camping in the car and pretty sure my air mattress would not have come even close to fitting in a Bolt (it barely fits in the LEAF!)
But just around the corner is the 2019 LEAF; 60 kwh, 100 KW charging and TMS!! but for a higher price. The fed credit will still be there (assuming its not done away with altogether) but the rumored $5000 higher price is sure to be a challenge for me financially. A challenge my new job is not likely to allow me to take on.
I am in my lease until Feb 2021 so I can either cry about my situation or figure out the best way to make my LEAF work. This means
More planning for road trips; This is something I have never had an issue with. Plugshare makes it easy and their new trip planner option even provides an elevation profile to help with your range estimations.
More and longer charging stops; Sometimes this can be a bear, but so far, I have IMMENSELY enjoyed my time exploring the areas during my stops. I guess this will eventually get old as the rate of new station openings slows down but that is not likely to happen any time soon!
More time on the road; Yep, driving slower to keep range high and batt temps low is something that I need to schedule now. But that is what I got, so I deal with it. With the traffic issues I have here, extra time on the road a given so the driving slow part is frequently unavoidable anyway. The other day, I was coming home from highway 18 to I-5 and my estimated get home time was 7:47 PM with 72 mins of traffic slowdown with a 30 min stop in Tacoma to charge. I was already hungry so I opted to stop in North Bend instead and SLOWLY charge my hot pack and grab food there instead. Because of the extra range 40 kwh provides, even with the slow 18 KW charging, I still gained enough range to skip the Tacoma charge stop and still got home 23 minutes earlier than projected!
So this blog is not intended to persuade or change anyone's mind about anything. But if you have a 2018 in a lease or purchase agreement and you want to get all you can from it, hopefully this blog will help you a bit.