charging losses for DC quick charge

What are the charging losses for the DC quick charger? I just used one for the first time and it gave me 40% according to the dash and the DC quick charger reported that 8.7 kWh was dispensed. It also raised the temperature from 71F to 81 F (thanks LeafSpy) in those 15 minutes of charging. So if nothing else, I suppose that there was about 0.4-0.5 kWh (or more perhaps) of energy turned to heat during the charging process. So this alone makes the charging process 95% efficient at best.

A separate note is that this charger only dispensed energy at the average rate of 34 kW. I noticed in the charger's information menu that it was rated for 40 kW. But I also thought that quick chargers were rated for 50 kW. It did have a max current rating of 100A and max voltage rating of 500 V. Is this 34 kW typical for a DC quick charger? (It was an Eaton model)

This quick charger is going to be great in the winter so that I can heat up my battery to something reasonable (like 60) for a longer trip.

losses from charger to car is pretty small. with no real way to measure charge in layman's terms all I have is GIDs and the reading from the charger itself.

most recent fast charge (first public charge in over a month having successfully completed the month of March without using public charging at all) was today and received 12 Kwh according to the charger at Puyallup Nissan gaining 146 GIDs (48 to 194). using the GID=80 wh guideline brings us to 11.68 kwh whic equates to 97.3% efficiency. this is in the ballpark for every measurement (95.4 - 98.1) I have taken which will soon cover the range of temperatures and weather conditions at least for my area.
as far as charging rates; you have a 48 KW capacity for fast charging so whether the fast charger is 50, 60 or whatever, doesnt matter, you wont get over 48. FYI; most I have seen is 46.5 KW and that lasted about 3 mins before starting its decline

problem with all that is that 80 wh per GID is an overage average value at best. today it was 60º and saw 6 bars for the first time this season but its appearance was strange since I was at 5 bars, drove 10 mins down the road after the charge, parked for 10 mins, come back out the batt temp actually went down a degree but have 6 bars anyway...

best i can say is the gauges are guidelines...nothing more

95% charging efficiency is really good, as battery tech goes! Obviously you're putting a lot of power in, so there is a proportionately higher power lost to heating.

Fast charging is a constant voltage technique, and so if your battery is already partially charged then it will draw less power than if it has less charge to start with. The charge current should drop off while the voltage stays constant, hence the power drops off as you charge up.

No, fast charging is constant current then constant voltage. The car requests maximum amperage that the station can provide till around 50%, then holds a constant voltage till 80% (or >90% on '13-'14 Leafs, unless limited by the station) ramping down the current in the process.

donald said:

95% charging efficiency is really good, as battery tech goes!

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Don't get too excited... All the numbers talked about thus far in this thread are for the losses between the charger and the car. What hasn't been mentioned, and where most of the losses likely take place, are the losses within the charger itself.

JeremyW said:

No, fast charging is constant current then constant voltage. The car requests maximum amperage that the station can provide till around 50%, then holds a constant voltage till 80% (or >90% on '13-'14 Leafs, unless limited by the station) ramping down the current in the process.

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OK. :/ Delete "is a constant voltage technique", insert "includes a constant voltage technique". My point was, there is a point at which the power drops off when the permitted volts are maximum and the current ramps down.

donald said:

95% charging efficiency is really good

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Don't get me wrong. I don't know what efficiency it is. I just mean that it CAN'T be higher than 95% because of at least the heat loss.
I would also assume that when the Eaton charger says 'energy dispensed', surely that is what they mean. The energy that entered my car at the plug. That doesn't seem difficult at all for the charger to measure, so I would tend to believe the amount it reports. But I'm wondering is if there are any other losses on my car's side?

JeremyW said:

or >90% on '13-'14 Leafs

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Do you mean that I could charge higher than 80% on my 2013 Leaf? I had it turn off at 75% just because that was all I needed, but this weekend, I could really use 100% from the fast charge, so I'll be giving that a try. It would be nice to know ahead of time if that is what I should expect.

That last 10% is pretty slow ... especially if someone's tapping their foot waiting for you to hurry up & finish.
.

GroundHog said:

Do you mean that I could charge higher than 80% on my 2013 Leaf? I had it turn off at 75% just because that was all I needed, but this weekend, I could really use 100% from the fast charge, so I'll be giving that a try. It would be nice to know ahead of time if that is what I should expect.

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Depends on the station but usually yes. For example some of the QC's at dealers around here in Southern California are set to only allow an 80% charge. It is quite slow above that, but faster than L2 (usually)... but still if you've got somebody waiting behind you be considerate.

GroundHog said:

Do you mean that I could charge higher than 80% on my 2013 Leaf? I had it turn off at 75% just because that was all I needed, but this weekend, I could really use 100% from the fast charge, so I'll be giving that a try. It would be nice to know ahead of time if that is what I should expect.

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JeremyW said:

Depends on the station but usually yes. For example some of the QC's at dealers around here in Southern California are set to only allow an 80% charge. It is quite slow above that, but faster than L2 (usually)... but still if you've got somebody waiting behind you be considerate.

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Most of my experience has been with Blink DCFC (50kW). Last night, I used an ABB DCFC (20kW) for the first time

The Blinks will stop charging just over 85%, even if you select 90% or 100% - this is due to not being able to accurately measure the battery state during such high charge rates. I've also measured charge rates (initially recording time to charge by 5% as indicated by the Blink, then later logging the charge process using LeafSpyPro/Android & Elm327). In each case, charging to about 65% was quite rapid (<3min for 5%), but slowing significantly before reaching 85% (5min for 5%) when the Blink stopped at 86%. At that point, you could charge just as fast to 100% using an L2 charger.

The ABB was a different animal - physically MUCH smaller (slightly larger than Blink L2 pedestal footprint and about 5Ft tall), quieter, and judging by the nameplate data, could be hosted by quite a few more businesses as the power supply requirements were not so extreme. Anyway, it reported estimated time to 100% charge, and I suspect it would actually get there (I had to go before I could verify this). At 20kW, a charge from 0 to 100% would take about 1Hr (or about 5-6 times faster than L2 @ 3.5kW). I haven't yet looked at the LeafSpy log, but I'm curious.

brettcgb said:

The Blinks will stop charging just over 85%, even if you select 90% or 100% - this is due to not being able to accurately measure the battery state during such high charge rates

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No, this is a failure of the car to report the SOC properly. The '11-'12 model years do this. The CHAdeMO session is actually controlled by the on board charger made by Nichicon. Somewhere along the line they (Nissan or Nichicon) screwed up how the car reports it's state of charge to the machine. This is NOT a blink problem, you will see it with any other QC that shows SOC from the car. It's close at low SOC and diverges as you get closer to 80%.

brettcgb said:

The Blinks will stop charging just over 85%, even if you select 90% or 100% - this is due to not being able to accurately measure the battery state during such high charge rates

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JeremyW said:

No, this is a failure of the car to report the SOC properly. The '11-'12 model years do this. The CHAdeMO session is actually controlled by the on board charger made by Nichicon. Somewhere along the line they (Nissan or Nichicon) screwed up how the car reports it's state of charge to the machine.

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So the on-board charger (which still controls the fast charge) is reporting higher SOC the longer the fast charge continues... As long as that estimate is slightly high, I'm OK with that. During fast charge, it's not possible to accurately estimate the batteries SOC (common problem for all batteries, all chemistries), so a slightly high estimate triggers an early charge termination, also in line with safe battery charging practices (which is to terminate the QC somewhere in the range of 80-90 percent when charging faster than 1C (full charge in one hour).) I'd rather stop the charge a little early than risk a battery failure in the form of venting or a fire.

JeremyW said:

This is NOT a blink problem, you will see it with any other QC that shows SOC from the car. It's close at low SOC and diverges as you get closer to 80%.

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I would amend that to "close at start of charge (for all SOC), but increasingly over-estimates the SOC as the charge continues."

I would agree that the QC is accurately displaying what is being reported to it. It is the responsibility of the on-board charger to ensure safe operation of the battery.

JeremyW said:

brettcgb said:

The Blinks will stop charging just over 85%, even if you select 90% or 100% - this is due to not being able to accurately measure the battery state during such high charge rates

Click to expand...

No, this is a failure of the car to report the SOC properly. The '11-'12 model years do this. The CHAdeMO session is actually controlled by the on board charger made by Nichicon. Somewhere along the line they (Nissan or Nichicon) screwed up how the car reports it's state of charge to the machine. This is NOT a blink problem, you will see it with any other QC that shows SOC from the car. It's close at low SOC and diverges as you get closer to 80%.

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I've noticed this ... however, years back, the 1st time I used the Blink QC at FWY's 57 & 60 (south coast AQMD) - when it was 1st commissioned, that Blink was charging up past 90% ... right up to when I hit the e stop ... & I was wondering why the heck it hadn't shut down. That only happened the one time - and the couple times after that, it shut down around 85% ...
.

As far as I know, the '11/'12 cars will go to 100% if and only if you start above 50% SOC. Otherwise they shut down at 80/85%. If you let the Blink default to 80% in this scenario, then it sill stop even sooner. However if you start above 50% AND set the Blink to 100% it will charge all the way up.

davewill said:

As far as I know, the '11/'12 cars will go to 100% if and only if you start above 50% SOC. Otherwise they shut down at 80/85%. If you let the Blink default to 80% in this scenario, then it sill stop even sooner. However if you start above 50% AND set the Blink to 100% it will charge all the way up.

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the fast charger might say 100% (more likely 98%) but that is not what happens. they usually get to just over 90%. a few times I saw 92% but will admit have only a few times where my patience was sufficient to run it to the end of the cycle.

hill said:

JeremyW said:

brettcgb said:

The Blinks will stop charging just over 85%, even if you select 90% or 100% - this is due to not being able to accurately measure the battery state during such high charge rates

Click to expand...

No, this is a failure of the car to report the SOC properly. The '11-'12 model years do this. The CHAdeMO session is actually controlled by the on board charger made by Nichicon. Somewhere along the line they (Nissan or Nichicon) screwed up how the car reports it's state of charge to the machine. This is NOT a blink problem, you will see it with any other QC that shows SOC from the car. It's close at low SOC and diverges as you get closer to 80%.

Click to expand...

I've noticed this ... however, years back, the 1st time I used the Blink QC at FWY's 57 & 60 (south coast AQMD) - when it was 1st commissioned, that Blink was charging up past 90% ... right up to when I hit the e stop ... & I was wondering why the heck it hadn't shut down. That only happened the one time - and the couple times after that, it shut down around 85% ...
.

Click to expand...

LeafSpy Pro has been very useful, especially it's latest version. I've been able to monitor charging progress with considerable detail.

I recently logged the progress of a fast charge from an ABB Terra SC charger (20kW/50A/180-500V). For the first half of the charge, the charger was operating full out (about 48Amps) while the battery voltage was below 393V. After that, charge current was tapered down to maintain voltage at 393V. At about 18Amps (7.3kW), charging was terminated (85% full charge). This is entirely driven by the battery, although the on-board charger makes fine adjustments to the thresholds based on battery temperature, age, and possibly charging current.

This is exactly how Li Ion batteries are supposed to be charged. Even your laptop computer battery charges this way. Constant Current (CC) until reaching a target voltage, then Constant Voltage (CV) while the current tapers down. When current has decreased to some threshold, the charge is terminated.

Nowhere does SOC factor into this. SOC is tracked by the on-board charger (necessary!), but if SOC is reported to the DCFC, it's a courtesy.

I suspect the distinction between various DCFC is visible mostly in the CC and early CV phases of the charge. Somewhere in the CV phase, all chargers end up following the same decreasing current curve.

Logs and spreadsheets can be your friends.

I'll stick to my original post, then, rather than the retraction. The fact that it is constant current in the first phase, rather than constant voltage, is simply because the charger itself cannot deliver more current.

A standard way of fast charging Li is constant voltage delivering the nominal battery voltage, then the current will taper off and full charge is assumed when it drops to 10% (or whatever the algorithm sets) of the charge rate at the end of the constant voltage phase.

Any lower or constant current before the constant voltage phase is a limitation or design-function of the charging equipment, not the battery.

GroundHog said:

...
A separate note is that this charger only dispensed energy at the average rate of 34 kW. I noticed in the charger's information menu that it was rated for 40 kW. But I also thought that quick chargers were rated for 50 kW. It did have a max current rating of 100A and max voltage rating of 500 V. Is this 34 kW typical for a DC quick charger? (It was an Eaton model)
...

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The Eaton has five racks in it.
Each DC output module is 10 kW.
So depending on how many modules are purchased it could be 10, 20, 30, 40, or 50.
See photographs of internals of 50 kW Eaton at http://www.mynissanleaf.com/viewtopic.php?f=26&t=5349&hilit=eaton&start=20#p134782" onclick="window.open(this.href);return false;.
Link to Eaton brochure is on page two of the thread at http://www.mynissanleaf.com/viewtopic.php?f=26&t=5349&hilit=eaton&start=10#p126444" onclick="window.open(this.href);return false;.

DaveinOlyWA said:

the fast charger might say 100% (more likely 98%) but that is not what happens. they usually get to just over 90%. a few times I saw 92% but will admit have only a few times where my patience was sufficient to run it to the end of the cycle.

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Dave is correct 2011 LEAF will not charge to twelve status of charge bars and maximum GIDS on a DCQC.
My 2011 with one missing capacity bar and likely very soon two missing takes another 10 to 20 minutes on L2 to get to maximum charge.

And since Jim added the charging power graph to LEAF Spy Pro it is clear that the last 10 minutes waiting for DCQC to auto stop is at charging power levels way lower than the 3.8 kW of the 2011 on board charger.
The last five to ten minutes is 2.3 kW and trails off to something like 1.5 to 1.8 kW when it auto stops.

The only reason to sit and wait for that last little bit would be if you have paid set fee for the session, or don't have L2 at the location to finish up to maximum charge.

Especially if you have the newer LEAF with 6.0 kW on board charger it is much quicker to move to L2 long before the auto stop.
Get LEAF Spy Pro and use the graph to monitor charging power.
Great improvement by Jim.