DC Charging observation.

I had a leaf for two days and yesterday evening after starting DC charging I noticed it started at 58 Kw @30% battery charge and then by 50% it was at 36 kw.

I wouldn't have thought the battery current would ramp down so quickly by around 20 Kw ?

58kW? What are you charging on? The most powerful CHAdeMO in my area start up around 42 kW at most. They do ramp down fast sometimes, more so in the cold.

Good Lord, I've never seen 58. That's nuts. We have some 60 kW Blink chargers around me, but that's only 60 kW at like 500 volts, which the Leaf will never ask for. And I never thought the Leaf would pull that much anyway.

My charges usually start out at about 40, then slowly taper down. At 75% it's at 25, then falls off a cliff, going under 20 by 80%. I never stay attached longer than that.

I saw 48 one time. Not for long though. I know the car tells the charger the maximum it will take at any given time and the charger complies if it is capable. It would be interesting to see that graph. Probably 3 dimensional. SOC and Battery temp, vs maximum charge rate.

I can't actually say how long it was @58 Kw but I did notice it about 44 kw before I checked it the last time at about 50% which then showed about 36 kw.

I just didn't expect the charge to ramp down to 36kw by 50% but yeah it might have been cold, it was about 9-10 Deg C about 50 F.

It had been sitting all day after work. I honestly can't say what the battery temp was because I couldn't find my bluetooth dongle. I wouldn't have thought 10 Deg C was too cold though.

The previous day was 3 degrees and -1 C by the time I got to work. I had fast charged though which would have warmed it up a bit.

If it is due to cold then the Kia Soul EV with it's battery heater should prove most useful. Available in the U.K, not Ireland. I wish I could take that for two days.

Batteries just charge slower as their state of charge rises. Doesn't even have to be related to heat at all. It's just what happens.

Yes I know that the charge rate reduces as the voltage rises, but I didn't think it would reduce to 36 Kw by 50% charge.

The charger shows the Kw out and the Kw used.

o00scorpion00o said:

Yes I know that the charge rate reduces as the voltage rises, but I didn't think it would reduce to 36 Kw by 50% charge.

The charger shows the Kw out and the Kw used.

Click to expand...

No CHAdeMO charger in the world will go above 125 amps, which means that your 395 volt LEAF will charge at a MAXIMUM of 125* 395 = about 50kW.

58kW is just wrong.

See pages 15-18:

IEA IA-HEV: DC Fast Charger Use,
Fees, Battery Impacts and
Temperature Impacts on Charge
Rates
Jim Francfort
Issues Related to the Fast Charging of Batteries in
Plug-in Electric Vehicles
IEA Implementing Agreement on Hybrid and
Electric Vehicles (IA-HEV) – Nice, France
September 22 & 23, 2014

Click to expand...

http://avt.inl.gov/pdf/prog_info/IEA_DCFCImpactStudySept2014.pdf" onclick="window.open(this.href);return false;

Note the various kW/time curves at 0, 25, and 50 degrees C (p 18) showing power limited for both hotter and colder batteries.

Looks like charge was limited to ~47 kW, even at 25 C.

TonyWilliams said:

o00scorpion00o said:

Yes I know that the charge rate reduces as the voltage rises, but I didn't think it would reduce to 36 Kw by 50% charge.

The charger shows the Kw out and the Kw used.

Click to expand...

No CHAdeMO charger in the world will go above 125 amps, which means that your 395 volt LEAF will charge at a MAXIMUM of 125* 395 = about 50kW.

58kW is just wrong.

Click to expand...

Is 395 volts what the leaf battery has at 100 percent? If so it would never even draw the 125 amps. what would be a voltage where it would accept that much current?

It's constant current (125A maximum) till the pack voltage hits 395V then it's constant voltage with a tapering down of the current till the pack is at 80% (2011-2012 cars) or ~93% (2013+)

JeremyW said:

It's constant current (125A maximum) till the pack voltage hits 395V then it's constant voltage with a tapering down of the current till the pack is at 80% (2011-2012 cars) or ~93% (2013+)

Click to expand...

Wait... So all this stuff about charges slowing way down at 80%; for new cars that line is 93%?

No. The car starts "slowing down" as soon as it starts backing off the amps in the constant voltage phase of charging. I don't know what the threshold is for slowing way down on the newer cars since I don't have one!

Here's a graphs of pack amps on a 2011-2012 car charging to 80% and starting just under 50%. Notice the flat part in the beginning, that's constant current, then the slope downward as the voltage threshold is reached and the current is dialed down to keep that voltage steady.



Older cars will charge even slower due to the increased internal resistance which causes the car to hit the voltage threshold below 50%.

All this still doesn't explain why when the charging first started at 58 Kw with a charge of about 30% ?

This reading was taking from the charger itself.

Could this have been the power going into the charger itself rather than the output ?

58kW is not possible. What is the make and model of this CHAdeMO? Can you post a photo of the screen readout?

DNAinaGoodWay said:

58kW is not possible. What is the make and model of this CHAdeMO? Can you post a photo of the screen readout?

Click to expand...

Unfortunately I didn't take a picture of it charging at 58 Kw but this is a pic from the exact same charger about 4-5 months ago with the same car. I don't know what percentage it was at at this stage of charge or how long after I connected the charger.

I didn't get the make and model of the charger but I'll see if I can find out.

Fascinating. It does read over 50kW, which isn't supposed to be possible, but there it is. I'm not qualified to explain this, so I hope someone else can. The unit is labeled "Lovato" and I can find a Lovato Electric, but no reference to a CHAdeMO. If you can get a photo of the rating plate and model info that might help. I do love a mystery.

It could be power input, rather than output.

Yup, looks like power input. Following the image to the photobucket site where it's hosted gives a higher resolution where you can see it's a 3 phase revenue meter. Here's the data sheet.

Now I'm curious. If a LEAF won't draw more than 50 kW, and this QC displayed an input of 58 kW, then it was losing 8 kW in the process? Seems a lot, doesn't it?