Getting the Most From a Quick Charge Station

[tomsax]

In June, Cathy and I discovered that the "percent battery charged" value shown on the AeroVironment quick charge stations is not the car's state of charge (SOC). At first we thought this was a nerdy little detail that few would notice, but have since found out this is causing a lot of confusion among Leaf owners, both novice and expert. The Blink quick charge stations have the same issue, and compound it with requiring the driver to choose a percent charge level, defaulting to 80%, which doesn't work correctly because the station's idea of the SOC is quite wrong.

In brief, the charge percent shown on the station shoots up more quickly than that actual SOC, hits somewhere around mid 90's when the actual SOC is only in the low 80's, and then holds there looking like no more progress is being made even though the car is still charging at a rate significantly faster than Level 2.

I understand that it's difficult to determine the exact SOC of a car's battery. Even the best estimate of the battery's SOC may be off by a few percent. That's not what's going on here. The SOC value reported by the station is completely artificial and differs significantly from the car's estimate of the true SOC.

So, two important tips every Leaf owner needs to know when charging at a quick charge station that displays a charge percent:

1. Ignore what the station shows. Put a sticky over it if you have to. Only look at the car's representation of the SOC.

2. If the station offers you different charge levels, choose 100% charge so that you get the car's best available charge level. If you want to stop the charge early for some reason, do it based on the SOC shown by the car.

Here's a graph showing our Leaf charging from just above 50% to full at a Blink quick charge station (requesting a 100% charge from the station), comparing the car's SOC (as read from a garygid SOC meter) and the charge percent shown on the station's display. As you can see, the station's value rises sharply to 95%, flattens out, and even drops back down, all the while the car is steadily charging.

For more info...

Our first quick charge experience, documenting the issue with AeroVironment stations: http://www.saxton.org/tom_saxton/2012/06/dcqc-roadtrip.html" onclick="window.open(this.href);return false;

Summary of the issue with documentation of the issue on a Blink station: http://www.saxton.org/tom_saxton/2012/09/dcqc-soc.html" onclick="window.open(this.href);return false;

Our complete list of Quick Charge tips: http://www.saxton.org/EV/quickcharging.php" onclick="window.open(this.href);return false;

Updates

9/4/12: added graph of station charge percent vs. actual SOC
9/5/12: gbarry42 reports that an early prototype Andromeda quick charger also displays the misleading charge percent. http://www.mynissanleaf.com/viewtopic.php?p=225199#p225199" onclick="window.open(this.href);return false; Tony Williams notes that the final product will debut at the National Plug In Day event in San Diego on September 23rd.

 

[garygid]

If starting a QC below 50%, the LEAF will terminate the charging
at what it thinks is 80%, or so.

To continue charging to maximum, just restart the charging.

Normally the LEAF terminates the charging, and the user
might decide to stop the charging at any time.
However, the QC can also stop or limit the process.

The car provides the QC machine with a value that increases
as the charging continues. The QC probably uses that value
to generate the "progress" bar/value it shows.
I do not know how this value from the LEAF relates to real
(estimated) SOC, or GIDs, etc.

 

[tomsax]

The car provides the QC machine with a value that increases as the charging continues. The QC probably uses that value to generate the "progress" bar/value it shows. I do not know how this value from the LEAF relates to real (estimated) SOC, or GIDs, etc.

I don't know what the value is, but it's labeled as being the charge percent on both AeroVironment and Blink stations.

I added a graph showing the stations's reported charge percent and the charge percent read from one of your indispensable SOC meters. Even without an SOC meter, you can see that something wacky is going on: when the 10th bar came on, the station showed 89%. Halfway through bar 10, the station said 97%. It slowly climbed to 99%, then dropped down to 98%, so it isn't even strictly increasing as the charge progresses.

 

[abasile]

Thank you for the nice data! This past weekend we used the AV quick charger that was being demonstrated at Fontana Nissan. The QC indicated 97% SOC, while our gid-meter indicated "80%" (we do have some capacity loss). I wasn't sure which to believe. Of course, the AV representatives believed their number to be correct. We stopped charging and sure enough, found that we had less charge than desired, necessitating some L2 later that evening to get home (we had another commitment that lengthened our drive).

 

[LEAFfan]

You will never get a full charge (even using '100%') using DCQC no matter if you have lost capacity or not. L1 or L2 will give you the most. And your gid meter doesn't tel you the SoC. If you have lost 10% capacity, and you L2 to 100%, you will have 12 fuel bars which is 100% SoC, but your gid meter may only show 89 or 90%. I've been QCing since Nov., and posted info about it shortly after.

 

[gbarry42]

I will add a third data point, having played around with the Andromeda charger. I was the last in line, so we decided to start it back up and let it charge all the way. We got as far as 97% (as indicated on the charging unit) and the current had dropped to a very low value, and it was time to pack up, so that's where we stopped. When I turned the car on, it was right around 80%. I figured that the DC charge folks just thought 80% meant "full charge" for some reason. Now it looks like the common thread is whatever the car is reporting to charger.

 

[TonyWilliams]

I haven't done many DC charges starting above 50% SOC, so they will hopefully stop at 80%, as designed. Then, I hit the start button again, and it happily charges up to 100%-ish. But, there were few times where i wanted to charge to 100%. But, to be honest, I can't recall a single time when the car actually had 100% capacity when I wanted 100%. Some closer than others, as you'll see below.

I'm specifically not referring to the % data on the DC charger, because I really don't care what it says. I just want it to keep pumping electrons as fast as possible.

As to the Andromeda unit, I only got to use it once, and that was from near empty to 100%. It actually shut off at 244 / 86% Gid. I charged the rest of the way with 120 volts. The AV chargers in Oregon / Washington did charge to a higher value (over 90%), and I don't remember on the Blink (only one of four worked for me). I also used the 350green charger (I can't remember the odd brand name), and the Eaton branded Takaoka manufactured unit in Cypress, California. I don't recall a single time one charged fully to 100%, but what's more odd is they all charge to different levels. Again, I'm not referring to whatever the DC itself is reporting, because that gets even more bizarre.

See if you can identify all these forum members around my car while getting a DC charge !!!

 

[DarkStar]

Here in Portland, our Eaton DCQC seems to be the only machine that properly reports the correct SOC while charging and I've noticed the same issue on our local Blink stations here in Portland too. I usually start below 50% SOC, but on the Blink when I restart charging after the car stops the first session, it usually jumps up fairly quick to 97% and stays there for a really long time even though the actual SOC is in the 80% range.

 

[tomsax]

Here in Portland, our Eaton DCQC seems to be the only machine that properly reports the correct SOC while charging...

Very interesting. How do you determine that the value shown on the Eaton is correct?

I'd love to get more information. If you're up for collecting data, here's what I suggest:

If you have an SOC meter, record station and car SOC every minute for the duration of the charge. I also recorded charge bars and temperature bars, but that turns out to be a lot of data to record every minute especially if you have to get in and out of the car to read everything.

If you don't have an SOC meter, or don't want to collect that much data, you can just check the SOC bars one per minute, then each time a bar is added record the bar number, the time, and the charge percent shown on the station.

We only have Blink and AeroVironment stations in the Seattle area, so I'd really appreciate data from anyone who has access to other quick charge stations.

 

[TonyWilliams]

9/5/12: gbarry42 reports that the Andromeda quick charger also displays the misleading charge percent. http://www.mynissanleaf.com/viewtopic.php?p=225199#p225199" onclick="window.open(this.href);return false;

Let's take that out of the equation. The Andromeda unit that he used, and that I set up, was a pre-production PROTOTYPE that did not have any of the final product firmware.

As an anecdote, it's fine to note. But the design is far from final until later this month when we display the first production model at National Plug In Day in San Diego (Sept 23).

 

[tomsax]

Thanks, Tony. I updated the note in the first post. I'll be interested to hear about the final product when it's ready.

 

[DarkStar]

Here in Portland, our Eaton DCQC seems to be the only machine that properly reports the correct SOC while charging...

Very interesting. How do you determine that the value shown on the Eaton is correct?

I believe it is correct since when starting to charge below 50% SOC, the car turns off the Eaton when it reaches just above 80% SOC and when I restart the DCQC it will slowly work from 81 or 82% to 99%. The GOM in the car matches this behavior where the Blink definitely does not.