In The Beginning
Back in 2010 when we were all anxiously awaiting the LEAF (the only real option back then) to arrive, we all evaluated our range needs based on two things; Nissan's claim of a 100 mile range and the EPA claim of 80 something miles (later changed to 73 miles due to the 80% charge setting according to them anyway...)
But that was not real world and despite Nissan issuing a chart detailing several driving scenarios and ranges expected, most people ignored the chart or simply didn't know it existed. There is not one single report of a chart sighting at any dealership in the US... not one.
But if customers had seen the chart, they would have realized that their 100 mile EV could do no better than 47 miles under certain conditions. I would post the chart but even the chart gets it wrong... Ah! I will post the chart anyway since many do not believe it ever existed.
Now that we see the chart, experienced LEAFers will immediately point out that the bottom two ranges are flip flopped. A/C uses nowhere near as much power as the heat. 47 miles in Winter especially with snow on the ground could make even 47 miles a challenge and you didn't have to drive 4 hours to find out!
Driving Blind
January 18, 2011 I made the journey about 50 miles to pick up my 2011 SL with charge. I expected to hit the dealership just before noon with my 3 year old Son in tow so expected to be home by late afternoon. That did not happen. This was one of the first LEAF deliveries in the state and my dealer had no clue what was going on. I had intended to purchase the car but while fighting with the dealership over sales tax (of which there was none) I had an epiphany and realized that spending over $28,000 (after credits, etc) for V 1.0 was a mistake.
So I flipped to a lease. This created another delay. So after spending over 3 hours trying to figure out how to create a lease that did not include sales tax, they finally decided to call corporate who spent about 5 minutes providing them a workaround. To make a long story short, I left the dealership around 7 PM. (I had to return a few days later to sign another lease form anyway)
Anyway, I am now driving home in the dark of a January night with heat enough to keep my son from freezing (later I realized he is MUCH more cold tolerant than I am) and my range display starts blinking and the dash lights up with all these dire warnings and I am still more than 10 miles from home. I was unceremoniously introduced to the World of range anxiety!
Scotch Tape Is Your Friend
Later, I realized that all my panic was for naught. It was a brand new car with nearly 22 kwh of energy of which I could easily use over 20 kwh to get me anywhere. Even in winter (which ours is relatively mild and nowhere near as bad as the scenario in the chart above) I had more than enough range. Soon new acronyms flooded the LEAF online community; LBW, VLB, GOM, POS... (JK on last one!)
Jan 26, 2012; A few weeks before GIDmeter. Notice only 3 power circles remain? Proof 100 miles in Winter was possible (No, it was far far far from easy!)
By now, it was obvious that 100 miles on a charge required a lot of things to go right which means the real question is how far can the average person go? Who was willing to have a tow truck follow them to find out? Realize this was waaaaay before public charging was commonplace. In my city, we had Lacey City Halls level 1 plugs that had been there for years and the summer before, the water treatment plant had a level 2 installed and due to proactive NEVer, we had a half dozen businesses around town offering wall plugs for the needy to plug into but that was about it. Realize how little we had BUT it was much much more than nearly everywhere else in country who had NOTHING.
But the LEAF was cutting edge tech which naturally drew a lot of techies. Soon DIY projects started popping up. The main goal was digging up what Nissan was hiding under the LEAF dash. Soon, the "Gidmeter" was available in a kit you could build. It's various displays showed voltage, current but the most important thing; it revealed the actual capacity of the pack in GID's.
Now, we don't really know what a GID actually is other than it counts down as the power is taken from the pack and it counts up when power is added to the pack. Thru some reverse math, observations, etc. It was initially determined a GID was about 80 watt hours of stored power.
Later, a value of 77.5 watt hours of power was settled on. the 2011-12's had 281 GID at full power while my 2013 had 284 GID and several 2015'ers reported 292 GID (if you ever needed proof Nissan WAS working the battery issue ALL the time, this is it)
Now we knew how much the LEAF had when full and that was nice and all but not really what we needed. It was all about avoiding walking, pushing, or sitting in the front seat of a tow truck. The real question was how low can we go! (Thank you Limbo dancers for that phrase!) but the GIDmeter allowed us to report to each other what we were able to obtain. Some got to 4, some to 6 before Turtle arrived (the point when LEAF restricts current draw from battery). This allowed us to know within a few 10th of a mile how much range we had.
Armed with GIDmeter, the "100 mile" challenge quickly lost its appeal. It simply wasn't that hard any more.
Despite being a few miles from 100 with plenty to spare, it was no longer worth
circling the neighborhood like the "pre GIDmeter" days.
But despite a ton of pictorial evidence, people still freaked out over the GOM to which we advised; If you want a LEAF with longer range, tape over the GOM and get GIDmeter!
Degradation
Soon the "good old days" (which kinda sucked actually) evolved to the life of plenty. We now have a bunch of charging options.
AV Tumwater May 2012
Packs grew and soon the challenge was 300 miles but there was still a case of packs degrading. Some went downhill fast, some lasted a long time. This caused a HUGE amount of misinformation on social media including many who thought that Nissan had "fixed" something so the reason they removed the 80% charge setting was because it was now ok to charge to 100% all the time. This couldn't be farther from the truth. There are major physical challenges Lithium based packs face and NO AMOUNT OF TMS, BMS will fix it and that is higher rates of degradation at high voltages. EVERY EV manufacturer knows this and EVERY EV manufacturer who has TMS also has custom charge settings to help the user preserve their packs.
To add to the confusion; LEAF battery reports which only evaluates the driver NOT the battery pack had people claiming they still had 100% SOH because they earned 5 stars. Others who admittedly never challenged the range of their LEAFs claiming no degradation while charging to 100% unnecessarily because they still had 12 capacity bars.
For some reason; many LEAFers thought the #1 reason for degradation was lack of TMS and that is simply NOT TRUE. It definitely doesn't help and heat is a problem but not the main problem. Degradation is a combination of a lot of things;
Climate
driving style
driving need
charging habits
DoD (depth of discharge)
Time
Time
Add in TMS and the list is
driving style
driving need
charging habits
DoD
Time
Time
A Tale of Two LEAFers
The Pacific Northwest, particularly the Puget Sound region of Western Washington has long been known as a sort of "EV Nirvana" Our near idyllic weather which is not too cold, not too hot, has mitigated a lot of the climate issues which minimizes the benefits of TMS here. This is illustrated quite well with Steve "the quarter million mile LEAFer" and John. Both live in the area and have long commutes but there are huge differences in their LEAF experience.
Steve
Steve had two LEAFs; a 2011 and 2014. Both basically fared the same. Both lost their first bars at just over 70,000 miles. Steve's commute was about 67 miles one way. He charge to full on level 2 every night and plugged in immediately to level 2 charger upon arriving to work in the morning usually being fully charged by early afternoon. His commute was nearly all freeway and he drove conservatively usually around 65 mph. By 100,000 miles both his LEAFs were all but done. DC charging did help him get more use out of his LEAFs but he was all but forced to get something different and at the time 30 kwh was not enough.
John
John has a 2015 LEAF. His commute was a bit shorter at 50 miles. He charged to full every night on level 2 then stopped at a DC charger near his work and charged up to around 80-90% give or take for the drive home. Unlike Steve, the bulk of his commute was on state highways with speed limits of 55 mph that passed thru several small towns with speed limits dropping to as low as 20 mph. Although his drive seems inconvenient, it avoided the mess on I-5 so really only took a bit more time and was quite a bit less stressful of a drive. At 100,000 miles his LEAF was LESS THAN halfway to losing its first bar.
12 bars @ 150,000 miles
DoD
Now everyone with a 2015 will confirm the "Lizard" pack improvements were nowhere near enough to explain the disparity. So why were these two experiences so different? Climate (and TMS) wouldn't have changed anything. A deeper look suggests that DoD was a key factor. With an estimated 73 miles of range, Steve's commute used 84% DoD (based on 80 mile range) while John's commute used 63% or less. The 2015 pack had more power available but probably less than a kwh over Steve's 2014. Steve charged to 100% twice a day while John only charged to 100% once per day.
Even if they had it, 80% charging would not have covered their needs very well. It should be noted that the difference in driving conditions and styles probably plays a part. John likely used regen a lot more due to more speed changes required on his route and he prided himself on gentle driving with very modest acceleration and maintaining constant velocity as much as possible. This would have lowered his DoD needs as well. But Steve's real claim to fame (IMHO) was his ability to get over 80,000 miles from his OEM Ecopia's. Yes, he was the first LEAFer to go over 100,000 miles in a LEAF in the US but to my knowledge; his tire longevity record still stands alone with no one even close. This means his driving style was unlikely to be radical.
I could realistically access a dozen past blogs and simply cut and paste this entire section. I have repeated this information over and over and over. Sadly, Nissan is now the ONLY major EV manufacturer without custom charge settings and it is literally KILLING their reputation. Lithium packs have the same needs and desires as people. They don't like living on the edge. They sweat in the heat, shiver in the cold. They simply want to live a comfortable stress free life just like us. So what does all that mean?
Lithium prefers life in the middle; 50% SOC as much as possible. (actually its closer to 45% for long term storage) This is the ONLY thing you need to keep in mind when charging the car.
Back in the "good old days" we charged the car daily because it simply didn't have "2 day range." Nowadays, my car has 5 day range and TBH, that includes a MONSTEROUS buffer. So my charging habits have morphed from a top 5 priority to...well nothing really. I don't even think about it any more and its hurting my pack.
My mind is literally still in "24 kwh" mode. I used to get home from work nearly every day with less than 10 GID in the tank and that was accomplished by carefully monitoring my speed, distance, and power usage. My 2013 and 2016 had an SOC meter on the dash and I venture to say the total number of times I referenced that information on BOTH cars was well less than half a dozen times. It was all about understanding how the GOM worked and how much farther I had to go.
Today in my E Plus, I glance at the GOM, see 60 miles knowing I am only going 20 and poof! No longer care about speed, power usage or charging... HUGE MISTAKE!!
Charge Every Day!
Battery U has done a lot of testing on Lithium and it is or should be well known that many many shallow DoD charges are better for long term battery life than a few big DoD charges.
In one test, they determined cycles to degrade a pack to 70% of its original capacity. In the 80% test (90 to 10% SOC) which many think is a good thing because its not charging to full; it took ~300 cycles to degrade the pack. Multiplying; we can assign a "range value" of 24,000 which is simply 80% capacity added * 300 charges.
60% DoD took about 600 cycles with a range value of 36,000 (remember the two LEAFers above?)
40% DoD took 1,000 cycles or a range value of 40,000.
My current daily commute is about 24.5 miles more or less (depending on where I park at work) and my E Plus has a range of 250 miles at this time of year so I use about 10% DoD daily. At 10% DoD, my range value is 60,000.
So why charge every day? As mentioned, the battery wants to be around 50% SOC. Be it 45 to 55% like me or 20 to 80% like John. Even in more extreme cases like John, the predominance of time spent is around the midrange SOC level. Another reason why its important is heat. Yes, I said its not the main cause of degradation because its not but it's still a factor and I mention it now because too many people have the wrong idea about what heat means. Even at very moderate temperatures commonly seen in the Pacific Northwest, the relationship between SOC, temperature AND time is critical. Below a chart and realize this chart should only be used for relational information only. Chemistries have improved which help but the phenomena is a simple fact of physics and chemistry. Heat is a catalyst, not a cause.
Without TMS, this is the least controllable factor of degradation; temperature. This chart should make it plainly obvious what our options are. Looking at the 25º C line (that is 77º F) , its a 500% increase in degradation if charged to 100%. In my world, 77º is a nice warm day. Nowhere near hot. Raise the temperature, raise the degradation. Granted we are talking a year which is a good thing in that charging to 100% when you need it even if you need it a lot isn't going to hurt "a lot" but it will hurt, make no mistake on that. But its also a bad thing because the "hit" is so small. We lose the ability to understand how detrimental our day to day actions are especially when we are doing this needlessly which brings me to something that all of you have heard me say.
Charge ONLY to the level you need to cover today's driving needs.
You and you alone are the only one who can determine what that level will be because it not only has to cover your expected daily needs but also a buffer that will cover your likely unexpected needs. Now we are all by and large creatures of habit especially during the work week. My schedule varies so little on days I work its...well boring. I have a half dozen places I may stop at on the way home but they are literally on the way so I might add 10 miles to the commute but most of the times I am adding less than 2 miles.
Now on my days off, its wide open. Road trips, family stuff, etc. It covers a very wide range of driving needs but all that is planned in advance so no real surprises and yeah 62 kwh helps a TON with that. It is nice to charge to 50% and have enough to cover my needs plus a 100 mile buffer!
My Recommendation
If you have done your charging needs evaluation and you feel you have to charge to 100% then you are driving the wrong car. FYI; the "90% to 10%" idea is BS. Anyone using more than 70% of their range should be charging to full but that is a LOT of need and few of us are there unless we are in the used EV market.
So if you want an EV that will last you 10 years, get one that covers your needs with a 40% DoD
No comments:
Post a Comment