Thursday, March 29, 2018

Fast Charge Test; Part Two.

On my 2nd charge on March 26th,  started charge at 35.97% SOC,  B temps, 93.8/91.0/84.0, starting 120 amps.  OAT  50.9º

110 amps;  63.77 % SOC,  B temps 111.5/109.7/98.4
100 amps;  66.64% SOC   B temps  112.7/111.2/9934
90 amps  ;  70.41%  SOC B temps  114.3/112.5/100.4
80 amps  ;  74.09 % SOC  B temps 115.3/113.5/101.3
76.9 amps; 75.43 % SOC  B temps 115.6/133.8/101.8

3rd charge;  started 69.89 % SOC,  B temps 114.0/110.7/99.2, OAT 49.4º

     SOC       KW            volts          amps      Batt temps
698879 21.687 372.67 -58.196 114 110.7 99.2
720557 21.617 376.99 -57.342 114.3 110.9 99.2
825470 21.674391.1 -55.419 115.1 111.7 99.2
851834 21.376 394.18 -54.229 115.1 111.7 99.2
891454 20.553398.98 -51.513 115.6 112 99.4

The above was the first part of my data collection to add to my first blog about charge speed.  Well, you can ignore all that.  Its not valid.  The data is real enough but its not what we need to concern ourselves with.  That is the conclusion. Now for the rest. 


Previously my concern with lease miles and the multitudes of opportunities to drive a lot for work controlled my experimental parameters.  But after several multi QC days, I started seeing a pattern. One I had to confirm and the only way to do it was to do a trip like other people do trips.  

In my work day, I would charge once in the morning, drive 30 to 100+ miles, work, then drive a bit, stop and charge and go home. This is not how people travel and I also noticed that charging speed was not dependent solely on SOC OR battery temperatures.  So I could post 5X more of the above to show the inconsistencies or not. 

So I decided to hit the Outlet mall in Woodburn OR. I  generally go there 1-2 times a year. I always plan to do it on a good weather day since its a long drive and I need to stretch my legs which I do while the car is charging and I'd rather stay dry if possible.  So this would be a 155 mile trip one way with layover of less than 2 hours (one hour and 12 mins actually) with an immediate return to Olympia.  IOW, a trip driven like "you" would drive it.   Now we could look at it as a 300+ mile trip which is near the length many would drive in a day in an EV anyway.  I would aim for 400 but didn't have a reason to go farther South or I would have done that too. 


The goal was being both realistic and consistent so whenever possible, I set cruise control to 65 mph. To make the timer realistic, I decided to let the car run all the time while charging other than the brief periods I have to shut it off while initiating the charge.  I was also going to test AV stations in Ridgefield and Woodburn and you know how lllllooooonnng it takes for them to start up so I added 10 mins of idle time to the clock. Despite my best efforts to record everything, I somehow missed a few pix... lost somewhere or sent to wrong place? I will add them when I find them.  But I also recorded the data so info is still provided. 

Notice the 173 mile estimate? Well, We shall see. I set LEAF Spy to 4.0 miles per kwh
and it says 158.6 miles and no, Kwh available  multiplied does not correlate. 

This  was my first full charge in several days so I was not expecting a good pack read and LEAF Spy did not disappoint.  From log;  488 GIDs, 37.8 kwh available, 96.57% SOC.  Temps 70.9/65.5/63.6  anbient 57.2.  Previous QC;  4/5/18 end 2 PM. Unlike my 30 kwh LEAF which cooled to ambient in 12-14 hours , this one has "carryover" heat!  

GOM Verses LEAF Spy!

Ok, so this was going to be a LOOONG trip. I expected to average 50 mph driving which means 6+ hours with traffic, stops, etc. along with 3 planned QCs of 30 mins each but the reality it would be mostly sitting there driving... Boring!  So I had to combine experiments to keep my awake!

As you can see above, the GOM is stating 173 miles and as we now know, there is a rather large reserve as well so does that mean 173 miles plus reserve?? Well, no because the "173" is actually "151" in disguise so its 151 plus reserve.  Anyway, its my contention that no matter what the miles/kwh meter on the GOM says, my static 4.0 miles/kwh to 1% on the LEAF Spy customizable range estimator will be more accurate but both will end up in the same place taking a different route... I guess. 

So off we go! and the GOM holds out well at first. Obviously this pix was taken with the utmost goal of complete safety.  Unfortunately, conditions weren't always conducive to picture taking. FYI; I am not holding phone. Its holder is long enough to bend to this position.  

So as you can see, the GOM starts out well but... 

@ lower SOC, miles traveled/GOM/LS estimate   Batt temps, ambient

90% 18.8 152 141 73 63 65.8 53.8
80% 33.8 137 125 74.5 71 67.3 54.5
70% 45 114 110 77 73 69.6 52.7
60% 61.5 101 97.4 78.3 75 70.5 56.3
50% 76 86 84.4 79.9 76 72.1 56.3
40% 89.3 68 71.3 80.8 77 73.2 55.4
30% 98.6 52 61.1 82.4 79 74.5 57.2
Ahh!!! looks like GOM "lost its lead"  I took the liberty of snapping a shot (about 3 in fact but none really turned out too well but at least you can see most of this one) of the moment LEAF Spy took the lead! 

Anyway, that was a fun little side trip!  I did record batt temps so it wasn't a completely frivolous journey!  It seems every day, I find something different about the 2018. Here I am coasting in neutral about 65-70 mph.  The amount of power shown is... well shocking!  My S 30 would show anywhere from 200-500 watts... 

AV Testing

Well, this was easy. Tried Ridgefield and Woodburn and neither one worked!  So had to sweat it out to Vancouver to charge on Blink at Fred Meyer.  I just barely made it...

Charge Curve # 1

And, as we shall soon see. It will be the ONLY curve of the day. 

Vancouver arrival. Ok, so maybe I had a bit extra range...FYI; LEAF Spy range
estimator jumped. (I probably tapped it by accident) but still showed 
same range estimate as it did at mile ZERO

The only curve of the day!

So plugged in to the Blink and as you know, Blink is the ONLY NCTC provider where you can incur additional charges after your free 30 mins. Blink does not provide a timer and it starts billing at 30:01.  So naturally, I was dinged for 6 cents. 

Charge started at 119.71 amps 34.70% SOC,  finishing at 70.31 amps and 80.61% SOC. 20.31 kwh.  Notice the rather predictable rate of charge verses SOC.  There are two distinct slope changes but the remainder above 75% SOC is rather static.   On this charge, the ramp down started at 63.91% which is about the norm. 

Vancouver Departure

So on to Woodburn with high hopes... (see above for results!)  So naturally now the pack is hot and any hopes of a decent charging speed is all but gone.  So the plan is hit the outlet mall first then charge on way out of town. This is best anyway. Last thing we want to do is boost the SOC, heat the pack then park it!   But!!!

            Woodburn; AV stop (failed) / Outlet 

In the time I was shopping, the temps dropped to "near" the range where I could expect to get a decent charging speed!  It was my hope that maybe I could drop it a few more degrees and the reasons will be discussed later.   But was not to be.  Despite temps dropping to 102º,  the charge at Woodburn failed so I decided to hit Woodland on the way home instead. My objective was to show a "curve" with warm batts but SOC had to be similar and I also wanted to beat Portland traffic (didn't work).  The drive ended up being a lot of stop and go and sprints. Not a good way to cool off the pack plus we had full Sun with temps hitting 70º in Oregon. 

Woodland Arrival 

Not Part 2; Symptom 2!

As predicted in previous blogs, it appeared that a charge rate of 30-35 KW was possible when batt temps were at or just below 100º.   Woodland EVGO did not disappoint.  started at 80 amps dropping to 77 amps which meant a rather static charge with increasing voltage of the higher SOC.  Charge gained 13.87 kwh.  That is 6.44 kwh less than Vancouver but important to note this charger max'es at 100 amps while the Blink did 120 amps so there would have been less charge under any circumstances. 

The Revelation

First thing that should jump out is that despite rising temperatures and rising SOC, charge rate is flat.  This verifies SEVERAL observations I have had where charge rate is controlled by two factors;

Beginning SOC;  This is the obvious one. This is also VERY much unlike my S 30 where the charge rate always started at the full rate of the charger. In cases where the SOC was high, the ramp down started quickly but in most all cases, I was getting full speed for at least a few minutes.  Using the charge curve from Vancouver, its easy to predict the charge rates at various SOCs, right? 

Beginning battery temperature; As we now know, battery temps are also creating their own ramp down curve but it now appears that is ONLY based on battery temperatures at the beginning of the charge.  After the initial charge rate is set, the SOC takes over controlling the remaining charge, hence the flat charging rate. 

To prove the latter, another charge was required.  To maintain temps, my trip to Castle Rock averaged 70-75 mph.  

I arrived at Castle Rock with temps still above 110º but not high enough to trigger a 22 KW charging speed which generally needs to be 114-115º.   SOC 20.82%, 74 amps charge rate increasing to 77 amps finishing at 73 amps. 34 min charge time,  14.23 kwh gained. 

As we can see, again no charge rate curve despite very high temps. It was my plan to charge to 90% since AV does not have a timer but another LEAF showed up so I decided to unplug so they could charge (they only had 24 kwh pack).  At 90%, the charge rate should drop below 20 KW.  (See below) Previously my other multi QC days did not get me over 115º even when doing 2 30 min QCs within a few mins of each other.  This time, I smashed thru that number! 

Temp rolled to 123.1 about 2 seconds after I took this...SomeMurphy" thing I think... 

Now, it was on to home. I mulled the idea of going to Tacoma but realized the 30 min time limit of EVGO would not allow me to see the curve I wanted to see. 

And finally, HOME!!

Back at home we know understand why the car was on for all of the charging. Because now we have a true sense of the time it would "really" take while driving on a 300 mile trip.  If we take out the 94 mins of charging, we averaged about 51 mph which is not really that bad. I have taken several trips in the Prius on longer distance trips and averaged the same so in the absence of pee bottles and recklessness, My trip was in all matter, "normal" for an EV.... 


Well first off, can't make conclusions because we need to do a Summer trip!  Its my hope that the AVE compatibility issue will be resolved so we can do a 700 mile two day trip down the Oregon Coast and across to Roseville to the Safari and then home up I-5.   Its my guess, it will be a VERY long first day...

But this test created almost as many questions as it answered.  We now know that starting temperature is the key factor in the starting charge rates but rising temperatures do not play a part.  Below is a chart of a charge (actually there is a few here) starting with "cool" pack temps low 90's at 75% SOC. Here you see several slopes at 78% SOC gradually dropping to 90% SOC where the slope gets steeper while charging at roughly 22 KW.  Notice the pack temps just getting to the major slow down stage at just over 100º?  But this graph is more dependent on the battery temps and not SOC so again, its taking the most beneficial of the two ramp down slopes (although BOTH suck...) as shown by the short but steep ramp down at the beginning of the charge. 

The big test now becomes monopolizing a station for over an hour to charge from a low SOC below 20% to 90% starting with a pack cool enough to get the full amperage from the charger.  Here we need to record the differences in the knee from 120-125 amp chargers and 100 amp chargers as I suspect there will be no difference.  This leads to the conclusion that the ramp down is determined by percentage of the maximum amperage available and not necessarily the starting amperage. 

Now what does this mean for travelers?  Knowing the maximum charging speed would be key.  Also using a station that doesn't automatically cut off at 30 mins would be another.  You would be better off to charge to a higher SOC since you are likely to charge as much as 5 KW faster than if you were to move farther down the road to another charger.  Even with the lower SOC, if your pack is hot enough, it won't matter. You will be doing 20-22 KW if your pack is above the 115º range. 

So what is the sweet spot?  Well, low SOC and room temperature!  But the reality is what did the slow charging cost me as far as time? Well, in this case, not a lot.  The length of the trip would have required several stops and the reality quickly hit me that the longer range was outdistancing my bladder so each stop was VERY welcomed!  In truth, I also stopped two other times without charging.  But if looking just at real time.  I did this trip in my S30 and it required more but shorter charging stops mostly because I didn't stop at rest stops on the freeway to pee. I stopped where I could plug in and pee.  So it didn't really save me any time when charging faster. But there is an obvious advantage to being able to charge full speed at low SOC no matter how hot the battery as my S30 did. Check my blog from last March. I charged full speed in Centralia at 125 amps with batt temps over 125º.  So Nissan has simply got it wrong. Their concern is high battery temps while my concern is high SOC AT ANY TEMPERATURE.  So we have a double whammy; slower fast charging and a one option 100% overnight charge... 


  1. Well Dave, I just can't believe that nobody's commented on this yet. Guess I'm going to have to take the plunge. Just want to thank you for doing what you do with your attention to detail. It is always interesting to read your blog and find out what you and your cars up to. Keep up the good work. By the way thanks for your tip about the Tacoma Mall fast charger, worked like a charm for me and my Bolt on the way to and from Port Angeles. The infrastructure for the CCs is severely lacking at the moment, as more and more EVS hit the road I would hate to have to put all of my eggs in one or two baskets, which is which is essentially what I did for my trip. It reminds me of some of the Early Adventures I had with my leaf 6 years ago and the confidence that I had that when I got to a charging station I wouldn't have to wait for other EV's. It's a good problem to have but I think with more and more of them hitting the road, the need for greater redundancy of charging options becomes more and more of a concern.

    1. Hey Chaz! This is still a draft. I think I hit the "publish" instead of "Save" which are next to each other!

      But no matter. I am actually headed to Woodburn Outlets this morning so will be doing double duty to check Woodburn and Ridgefield AV for functionality along with another fast charge profile data set collection!