Chademo charging too fast?

[deonb]

I tried my Chademo adapter today for the first time.

I plugged in with 153 miles showing and went for a walk around the block. When I arrived back, 37 minutes later, it just ticked over from 256 to to 257 miles (which is the max my car gets on a range charge).

Thus, the Chademo added the last 104 miles of charge (40%) of a range charge, in 37 minutes. This is WAY faster than a SuperCharger, which takes 40 minutes to add the last 20% of charge.

So it looks like the Chademo charger is charging over spec?

I didn't take much notice of the charging speed when I left (I think it may have been 133mi/h), but when I got back it was charging at 125mi/h 402V 38A.


Has anybody else experience this?

 

[ra-san]

I haven't but do hope you'll report this to tesla and update us with any response.

 

[David99]

I just recently did a 100% charge at a Supercharger from 10%. It did take 1.5 hours. But it was at 100% at just over an hour and then kept reducing the power while it remained at 100%. 402 Volt at 38 Amp is 15 kW which is normal at 98-99%. Not at 100%, though.

 

[deonb]

402 Volt at 38 Amp is 15 kW which is normal at 98-99%. Not at 100%, though.

Interesting. I did notice a discrepancy on the Blink charger... It thought at 257 my car was at 96%. My car thought it was at 100% (or maybe 99.9%).

My car has always been rock-solid on range charges, whether at home or a SuperCharger, it always has maxed out to 257 - since day 1, and still now (2 years 4 months, 22000 miles).


I wonder if the SuperChargers have a better understanding of an individual car's range, vs. the Blink Chademo is hardcoded at a 267 mile range? So it's effectively charging my car at a charge curve that's ~4% offset of where it should be.

 

[glhs272]

One thing to note on the Chademo is that it will actually ramp up the KW as the voltage in the pack goes higher (very pronounced on the 60 and 70 cars). This being because of the steady 125amp limit on the adapter, so as voltage goes higher KW does too. Up until the typical charge taper that is.

 

[deonb]

One thing to note on the Chademo is that it will actually ramp up the KW as the voltage in the pack goes higher (very pronounced on the 60 and 70 cars). This being because of the steady 125amp limit on the adapter, so as voltage goes higher KW does too. Up until the typical charge taper that is.

If it's safe, why don't the SuperChargers do this? It will shave 20 minutes off a range charge.

 

[glhs272]

Well superchargers are doing much better by not limiting KW based on amps like a chademo does. Therefore the supercharger can put out full blast KW from the beginning, therefore much faster than the Chademo. But to answer the crux of your question (does supercharger vs chademo charge taper the same?) I am not sure if the tapers are the same, but kman (islandbayy) has a bunch of side by side videos of all types of Model S's charging, so the data is there if someone was willing to pull the data out of the videos.

 

[islandbayy]

Well superchargers are doing much better by not limiting KW based on amps like a chademo does. Therefore the supercharger can put out full blast KW from the beginning, therefore much faster than the Chademo. But to answer the crux of your question (does supercharger vs chademo charge taper the same?) I am not sure if the tapers are the same, but kman (islandbayy) has a bunch of side by side videos of all types of Model S's charging, so the data is there if someone was willing to pull the data out of the videos.

Thanks for the mention. Since most wont dig for it, here it is:

 

[deonb]

Thanks for the mention. Since most wont dig for it, here it is:[/video]

Great post, but unfortunately this is only up to 80%, which is the other side of this equation. My hypothesis is that after you hit 80%, that Chademo is faster than a SuperCharger.

Before that, SuperCharger is of course faster.

 

[Cottonwood]

If it's safe, why don't the SuperChargers do this? It will shave 20 minutes off a range charge.

My experience is that once the CHAdeMO limits current due to the taper, the Voltage, Current, and Power are the same on a CHAdeMO and a Supercharger; neither is faster. This does not start to happen until the battery is at about 85-86% SoC on an 85 on a full power/full current CHAdeMO.

Be very careful looking at reported charging mph on a Tesla; it is the average of the entire charging session, not the instantaneous value at that point in time. Charging rate is best measured in kW, and especially, late in the taper, you need to multiply Volts times Amps to get Watts to be accurate kW quantization is just too course.

On my car, I have found the taper to be the same on Supercharger, CHAdeMO, and HPWC. Until you hit the taper, each charger has a power or current limit, 120 kW and 330 Amps for a Supercharger, power limit and 125 Amps or less for a CHAdeMO, and VxAx90% for HPWC's (about 90% AC to DC conversion efficiency).

YMMV, but those are my experiences...

 

[deonb]

Be very careful looking at reported charging mph on a Tesla; it is the average of the entire charging session, not the instantaneous value at that point in time. Charging rate is best measured in kW, and especially, late in the taper, you need to multiply Volts times Amps to get Watts to be accurate kW quantization is just too course.

Oh, yeah, I don't care about the mph rating at all.

What I'm measuring above is 37 minutes for the final 40% of charge (on a range charge). You can't get that speed on a SuperCharger AFAIK.

 

[islandbayy]

Great post, but unfortunately this is only up to 80%, which is the other side of this equation. My hypothesis is that after you hit 80%, that Chademo is faster than a SuperCharger.

Before that, SuperCharger is of course faster.

My experience was that just as it hit it's maximum output, it started to taper immediately at the 80%. You can see the CHAdeMO VS the Supercharger right in the video, compare the charge rate at the same %%% between the two.

 

[MDK]

I graphed the taper on a 50kW (122A) Tritium Veefil CHAdeMO
The current was maxed at 122A until 74% (47.2kW) and was 111A (43.1kW) at 75%
It was still charging (at 8A) 15 minutes after reaching 100%

 

[deonb]

I graphed the taper on a 50kW (122A) Tritium Veefil CHAdeMO
The current was maxed at 122A until 74% (47.2kW) and was 111A (43.1kW) at 75%
It was still charging (at 8A) 15 minutes after reaching 100%

So this graph is exactly what I was expecting going into my first Chademo expedition. However, instead of my car going from 75% to 100% in that time, it went from 60% (actually 57%) to 100% in slightly less time.

Unfortunately I don't have a graph, just the start point and end point.

 

[MDK]

when I got back it was charging at 125mi/h 402V 38A.

So this graph is exactly what I was expecting going into my first Chademo expedition. However, instead of my car going from 75% to 100% in that time, it went from 60% (actually 57%) to 100% in slightly less time.

You may also be interested to know that my car reached 402V at 91% and was still charging at 80A

I saw 38A at 98%, at which stage voltage was 404V.

404V is the highest voltage I saw, and it was 404V from 93% to 100%

It seems the CHAdeMO thought you were at a lower state of charge (based on Voltage?) than you really were

 

[mgboyes]

A CHAdeMO charger just does what the car tells it (i.e. the car specifies the required voltage and current; the charger's "opinion" isn't relevant). So if you are seeing 402V and 80A it's because the car asked for its battery to receive 80A at 402V. 402 x 80 = 32kW which is pretty normal at 91% SOC, as is 15kW at 98% SOC.

 

[David99]

The voltage depends a little on the temperature and of course mostly in current flow. Just looking at voltage alone doesn't tell you the state of charge. 404 Volt at 80 Amp isn't 100% full. 404 at 5 Amp is pretty close to full. Voltage, state of charge and current are all connected. You can have a 70% charged battery at 404 Volt if you pushed a high current. At 85% state of charge you could reach the same voltage with less current.

Simple Lithium chargers work that way. They limit the voltage to the max of the cell. As the cell gets charged and gets 'fuller' it reduces the current while keeping the voltage constant. Once the current is close to zero the battery is considered fully charged. The disadvantage is that you keep the cell at the top voltage which isn't healthy for it.

 

[deonb]

I haven't but do hope you'll report this to tesla and update us with any response.

I got a non-answer from the SC today:

"We sent the logs from your vehicle to our engineering team and they confirmed that everything is operating safely and as designed. The battery management system itself (internal to your high voltage pack) is responsible for managing the charge (and protecting itself), and it is operating correctly. The tapering on a CHAdeMO station is not as dramatic as on a Supercharger because the power output from the station is lower, but the vehicle will adjust as needed."


Argh... Yes, I know the tapering curve is not as dramatic. I'm not concerned about the shape of the taper curve in the overall graph, but the fact that it charges 20 minutes faster than a SuperCharger for the same exact 2 points on the graph.

I give up - if something happens with the battery for over-speed charging, I'll have this to show for warranty purposes.

My battery has shows 0 degradation over 2 years so far, I'd hate for it to start now. It be very annoying if the battery degrades even a couple of miles in the near future, since then I won't know if it's normal wear or Chademo related.

 

[rdrcrmatt]

If it's safe, why don't the SuperChargers do this? It will shave 20 minutes off a range charge.

Its not really.

as the voltage gets near the max on a battery the internal resistance of the battery comes up as well which causes the current to slow down. If you want to charge faster just up the voltage. this works fine till a certain point in a lithium battery charge cycle. You reach a point where higher voltage is harmful to the battery.