Supercharging curve.. Is there an issue with my Battery/BMS?

[jbuszkie]

Recently I've decided to take advantage of my free 6mo of Super charging since my home electricity is expensive (0.25/kWh) and I don't have solar yet. I've been getting what I would call poor SC performance.
Now it is winter here.. But I've been trying to make sure my battery is warm before I start. I've had full regen each time.
My best charge was when the battery was at 19%. I got like 113kW charge rate to start. Then it tapered right away?
Isn't it supposed to start to taper at like 60%?

All my charges have this taper no matter where I start. And my charge rate starting point really depends on my starting SOC. I would have though that would get the max until hit like 50% or 60%. If I start charging with 50% SOC, I would think I would get the same rate when I got to 50% when I started with 20%. But If I start with 50% it's much less. I've seen other curves like this from electrek from an European 175kW CCS but with a super charger.

This is what I would expect. Flat, constant rate until a certain point.

So is it just charging weird because it's cold outside? Or is there something weird with my battery?
I've seen this taper/slow rate at 2 different chargers.

What do you guys charging curves look like?

Thanks,

Jim

 

[Troy]

Do you have a chart where X= minutes and Y=% ?

 

[jbuszkie]

Do you have a chart where X= minutes and Y=% ?

That's the blue curve on the graph above. "Battery level"

 

[SigNC]

full regen does not equal full charge speed. The battery still needs to be warmed significantly after full regen is achieved to get full charge speeds. In my non scientific testing ive found if you have a cold soaked battery around 32f it takes 2 hours of highway driving before you see full charge speeds. Obviously this will vary with outside temp and how fast you are driving.

 

[Troy]

Your chart is too difficult to read.

1. It's a long rectangle. Can you make it a square?
2. Do you have 0% to 100% instead of 19% to 80%?
3. Can you show just this one chart so that the Y axis goes from 0% to 100% instead of 0 to 400? This makes the important part difficult to see.

 

[jbuszkie]

Your chart is too difficult to read.

1. It's a long rectangle. Can you make it a square?
2. Do you have 0% to 100% instead of 19% to 80%?
3. Can you show just this one chart so that the Y axis goes from 0% to 100% instead of 0 to 400? This makes the important part difficult to see.

That's how the data comes from TeslaFi. I can't figure out how to export the data so I can put it into excel...

 

[jbuszkie]

full regen does not equal full charge speed. The battery still needs to be warmed significantly after full regen is achieved to get full charge speeds. In my non scientific testing ive found if you have a cold soaked battery around 32f it takes 2 hours of highway driving before you see full charge speeds. Obviously this will vary with outside temp and how fast you are driving.

But if I'm already charging at a specific rate, shouldn't it be able to maintain that rate? (As long as it's not in the taper zone...)

 

[Troy]

Here is a video that shows how the tapering curve (the blue curve) is supposed to look like.

 

[jbuszkie]

Here is a better view. The charge rate is in mi/hr.. It what I was able to grab from TeslaFi

 

[Troy]

This chart is much better! The blue curve here looks more balanced and initially less steep than in the video. As far as I know, there are 3 different pre-defined tapering curves the car chooses from depending on initial battery temperature. It would be interesting to see if it uses a different curve in warm weather.

 

[jbuszkie]

As far as I know, there are 3 different pre-defined tapering curves the car chooses from depending on initial battery temperature.

Where do you get this information?

 

[Troy]

I was obsessed with this topic in the past. I extracted data from 7 Supercharging videos that I could find and they all seemed to follow one of three curves regardless of battery size. This makes sense because it would mean each cell Supercharges the same way regardless of pack size.

 

[SigNC]

But if I'm already charging at a specific rate, shouldn't it be able to maintain that rate? (As long as it's not in the taper zone...)

The initial speed you get is kind of a red herring. It will drop to it's real workable charge rate quickly as you saw. Then it will taper more rapidly as it fills as the batteries aren't warm enough to accept the max tapered speed.

 

[SSonnentag]

Just for kicks, I took Electrek's graph from above and overlaid it with data I collected from one of my recent S100D charging sessions (120 kW supercharger).

 

[jbuszkie]

The initial speed you get is kind of a red herring. It will drop to it's real workable charge rate quickly as you saw. Then it will taper more rapidly as it fills as the batteries aren't warm enough to accept the max tapered speed.

How are the batteries not at ideal temp after accepting a charge >60kW for 15 minutes?

I have not seen any other videos that have a charge curve like mine. They all seem to have a flat-ish part where mine doesn't

 

[jbuszkie]

Here it is again normalized against time. Attached is the raw data

 

[Troy]

@jbuszkie,
I added your data to the same chart. It looks like the other curves.

 

[animorph]

Are you always using the same Supercharger? Actually this sounds like it might be just your first Supercharge out of a total of one. I've charted Supercharges during travel and found a wide range of curves. It may have just been a bad charger, or some kind of demand charge or temperature limiting by the Supercharger. It doesn't mean something is wrong with your car unless it always happens at different Superchargers.

 

[jbuszkie]

@jbuszkie,
I added your data to the same chart. It looks like the other curves.

Yeah.. I checked a couple points too by printing out your graph and hand plotting a couple points. Damn.. So it looks like I'm right in the middle. Well this is good to know. Thanks for adding this! Now I just need to check to see that when I start at a higher SOC, I get the same curve.

 

[jbuszkie]

Are you always using the same Supercharger? Actually this sounds like it might be just your first Supercharge out of a total of one. I've charted Supercharges during travel and found a wide range of curves. It may have just been a bad charger, or some kind of demand charge or temperature limiting by the Supercharger. It doesn't mean something is wrong with your car unless it always happens at different Superchargers.

No this is 2 different chargers and about 10 SC sessions.