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Discussion Starter #41
Is there a way to figure out battery degradation from PID codes?
I do actually have some theories on this, but I'd like to play first.

The battery impedance and resistance are apparently available, but not in my PID list yet. I'm hoping that either working with some more expensive tools, or waiting for the service manual to come out (next week?) will let us know those details.

However, there may be an easier way. Let me crunch some log files and see.
 

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What does your Torque benchmark say for PIDs/second when you are logging almost all mode 22 PIDs?

The VeePak and even OBDLink LX both get about 15 mode-22 PIDs per second (but up to about 60 standard PIDs/second).
I don't have Torque Pro, I have Engine Link since I'm on iOS. FWIW, from looking at the logs of readings, it seems like it typically manages 11 mode-22 PIDs per second. Possibly it'd do better in a synthetic benchmark.

I suspect that all the cheaper ones are using basically the same hardware: an ELM327 clone and a Bluetooth (LE) chip.
 

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Discussion Starter #43
I don't have Torque Pro, I have Engine Link since I'm on iOS. FWIW, from looking at the logs of readings, it seems like it typically manages 11 mode-22 PIDs per second. Possibly it'd do better in a synthetic benchmark.

I suspect that all the cheaper ones are using basically the same hardware: an ELM327 clone and a Bluetooth (LE) chip.
Ahh ok. I'm on Torque, but I get some log files from EngineLink friends. How do you process the log files from EngineLink? I'm finding it very hard to put into a proper table since sometimes individual measurements are missed (I assume due to bus errors).
 

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Ahh ok. I'm on Torque, but I get some log files from EngineLink friends. How do you process the log files from EngineLink? I'm finding it very hard to put into a proper table since sometimes individual measurements are missed (I assume due to bus errors).
Every reading has a precise timestamp and no two readings have the same timestamp (unless they're both calculated from the same PID(s)), so no matter what you need to deal with the mismatch.

My approach is to take the readings and create a continuous function that interpolates between them — linear interpolation is fine. Thus to combine multiple readings, I use one reading with its precise time and all the other readings with their interpolated values for that time.

With that in place, I can draw graphs like the charging kW for both AC input and DC output (combining voltage and current readings). And then I can do numerical integration on these to draw graphs of total kWh. See attached images. The AC kWh graph can be checked against the car's recorded AC kWh used for the charge, and it turns out to be 99.97% accurate.

From this charging session, I find the EVSE -> Car to be 99.2% efficient, AC -> DC power conversion to be 95.0% efficient, and storage of power into the battery to also be 95.8% efficient. Overall, for this charging session, wall to battery is 90% efficient, which is better than the EPA number. When calculating MPGe, they assume 89% efficiency.
 

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Discussion Starter #45
Every reading has a precise timestamp and no two readings have the same timestamp (unless they're both calculated from the same PID(s)), so no matter what you need to deal with the mismatch.

My approach is to take the readings and create a continuous function that interpolates between them — linear interpolation is fine. Thus to combine multiple readings, I use one reading with its precise time and all the other readings with their interpolated values for that time.

With that in place, I can draw graphs like the charging kW for both AC input and DC output (combining voltage and current readings). And then I can do numerical integration on these to draw graphs of total kWh. See attached images. The AC kWh graph can be checked against the car's recorded AC kWh used for the charge, and it turns out to be 99.97% accurate.

From this charging session, I find the EVSE -> Car to be 99.2% efficient, AC -> DC power conversion to be 95.0% efficient, and storage of power into the battery to also be 95.8% efficient. Overall, for this charging session, wall to battery is 90% efficient, which is better than the EPA number. When calculating MPGe, they assume 89% efficiency.
Nice! How did you do that function? Something inside excel or an external app?

The EVSE->Car seems reasonable based on voltage drop in the cable. The other numbers seem quite reasonable too.

I'm really loving what you're doing with the graphs, I just caution that I'm not 100% sure that these numbers are accurate. I still have some concerns over what the different voltage values are, as there are about a dozen different voltages that we have which are all close, track similarly, but slightly off. I'm not convinced that the ones that we have are exactly what you're graphing. Look at my other "MG Voltage" ones to see what I'm talking about.

How are you calculating power into the battery? Just using raw % and assuming 60kWh?
 

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Nice! How did you do that function? Something inside excel or an external app?
I'm pretty sure you could do it in Excel, but I'm actually using Wolfram Mathematica. It's proprietary, but it's free on the Raspberry Pi. I'm sure you could do essentially the same thing with Jupyter and matplotlib.

The EVSE->Car seems reasonable based on voltage drop in the cable. The other numbers seem quite reasonable too.

I'm really loving what you're doing with the graphs, I just caution that I'm not 100% sure that these numbers are accurate. I still have some concerns over what the different voltage values are, as there are about a dozen different voltages that we have which are all close, track similarly, but slightly off. I'm not convinced that the ones that we have are exactly what you're graphing. Look at my other "MG Voltage" ones to see what I'm talking about.
I'm using these PIDs, which are the same numbers as the Volt (they seem like something I can be fairly confident in):
  • 224369,Charger AC Current,0,40,A,A*.2,7E4
  • 224368,Charger AC Voltage,0,500,V,A*2,7E4
  • 22436C,Charger HV Current,0,200,A,((Signed(A)*256+b))/20,7E4
  • 22436B,Charger HV Voltage,0,500,V,((A*256)+B)/2,7E4

How are you calculating power into the battery? Just using raw % and assuming 60kWh?
I assume that when I charge back up (to the same SoC as it was before I left), it puts back the energy the car claimed I used on my trip. For this trip (which included running the AC and driving at normal freeway speeds), I drove 57.8 miles, used 12.7 kWh according to the car (4.55 miles/kWh). My EVSE (JuiceBox Pro) claims 14.05 kWh for 57.8/(14.05/33.7) = 138.6 MPGe (wall-to-wheels energy-equivalent MPG). Right now, I pay $0.13 per kWh, so that's $1.82 total or $0.03 per mile, or with gas at $3.65 a gallon, 57.8 / (1.82/3.65) = 115.5 MPGce (cost-equivalent-MPG).

Since you like graphs, here's a histogram of my speed(s) for this trip (speed averaged at 10-second intervals, time stopped not counted).
 

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I bought the LELink one. Seems to work fine for me, but I have nothing to compare it to. Any thoughts?
So I bought that OBDII adapter and tested it out...but I still can't get the battery capacity PID to give me any readings (other than a sporadic and very wrong -8.X figure). Every other PID I can pretty much get a reading from.
Any idea why I can't get the capacity PID to work? I'm using the latest version of TorquePro, running latest Android version available (7.0) on my stock Moto G 5 Plus.

BatteryCapacity 2241A3 ((A*256)+B)/30 65kWh 70000

edit: wait, I think I may know the problem. When copying the PID.csv to my google drive, some column values got formatted incorrectly. I'll see if fixing the formatting fixes my PID reading issue.
 

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Discussion Starter #48 (Edited)
So I bought that OBDII adapter and tested it out...but I still can't get the battery capacity PID to give me any readings (other than a sporadic and very wrong -8.X figure). Every other PID I can pretty much get a reading from.
Any idea why I can't get the capacity PID to work? I'm using the latest version of TorquePro, running latest Android version available (7.0) on my stock Moto G 5 Plus.

BatteryCapacity 2241A3 ((A*256)+B)/30 65kWh 70000

edit: wait, I think I may know the problem. When copying the PID.csv to my google drive, some column values got formatted incorrectly. I'll see if fixing the formatting fixes my PID reading issue.
Yeah you can't import back again because it interprets the 7E4 as 7000 for example. Just download the CSV to your phone and you can share it directly into Torque, no messy directory nonsense :D
 

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Just a quick report on battery capacity.
I've been up and running on Torque Pro for a couple of weeks
and showed 59.7 for the 1st week looking at capacity.
Since yesterday, it's showing 60.9.
Those are the only 2 numbers it's showed.
 

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Telek, thanks for sharing and developing PIDs. Been a long time Torque Pro user and used custom PIDs on the BMW 335d, along with PerfExpert, to tune/modify/compare modification impacts on that vehicle. I could then overlay a road dyno test with the logged data from that exact same pull, as well as doing other acceleration testing. I've found PerfExpert to be extremely useful for power measurements and is wonderfully repeatable (if you are extremely careful and have a good smooth, flat road, and only do tests when there's no wind, and follow the same procedure/process each time).

I got the Bolt earlier last week and got your PIDs installed this morning, and I haven't seen anyone post/compare dyno results with the Bolt yet ... so here's my initial contribution.

Its interesting to see the torque/power curve and how the controller limits peak torque at the low end and then reduces torque as the max limit on the power is achieved to keep a flat pwr curve. Also interesting to see how the battery voltage drops as power/amperage/electron flow increases.

I'm using published numbers for the Cd (.308) and frontal area (which PerfExpert uses to backout power losses from wind drag) and weight (1616kG) along with my weight of 86kg. Also using a power correction factor as close to 1 as I can (because the electric powertrain doesn't rely on air density like an ICE does). The way the power curve is shaped it looks to me like the Cd might be lower than published 0.308 as it appears PerfExpert thinks there should be more drag due to wind at the upper speeds (as evidenced by peak power occuring near the top speed).

This mornings pull was on an 83% SOC (based on your PIDs) and not on my normal test road. The 2nd attachment shows a pull from yesterday morning at a higher SOC (did not have your PIDs in place for that one so don't have the precise SOC to compare) on my normal test road that is altimeter and google earth verified to be flat.

The PerfExpert data is at the wheels, so the drivetrain losses seem pretty low for this vehicle, which it should be considering what it is.
 

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Looks like you're using an area of 2.39 m^2. Where did you get that number? I use 2.2 m^2 but don't recall where I got it from.
I tried replying with a link, but evidently I don't have enough posts to use pictures or links ... but my original post had the pics of the Torque logs with the PerfExpert data ... weird.

If you search chevy bolt 25.8 (that's the frontal area in square feet) you should see some references.
 

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Thanks, evidently Car & Driver posted it over 2 yrs ago and I reposted it then. My empirical data also supports either a lower Cd or frontal area.
 

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I have EngineLink, and for some reason the Instant Power field doesn't work in EngineLink. Is there something special that I need to do in EngineLink to add a calculated field?
Sorry, I am not familiar with EngineLink. If you get this figured out, please post back here to help others who might have a similar question.
 

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BTW, earlier in the thread we were discussing what we thought the raw capacity of the Bolt's battery was. Apparently (according to this thread) someone from GM let the cat out of the bag (Facebook link), saying:

Good Morning Mr. Langlois,

I was able to look into the information you requested further.

Now, when you charge the battery to full, the vehicle is smart to keep a safe zone in the battery to prevent over charge condition. The vehicle does not use the full battery capacity (65kW) to ensure that it keeps some space to prevent overcharging. You can charge the vehicle to full without any worries!

Thank you for allowing me to look into this further for you
So, full capacity is 65 kW.
 

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BTW, earlier in the thread we were discussing what we thought the raw capacity of the Bolt's battery was. Apparently (according to this thread) someone from GM let the cat out of the bag (Facebook link), saying:

So, full capacity is 65 kW.
That meshes with my SOC% observations I've done with TorquePro. ~60 kWh usable, ~3-4% buffer top and bottom, which means about a 64-65 kWh overall battery size.
 

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Anybody know how to get Torque Pro to display
integer values instead of decimals? For some values
I'd like to have whole numbers showing.
For example I'd like to see 16 rather than 16.0 satellites.
 

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Anybody know how to get Torque Pro to display
integer values instead of decimals? For some values
I'd like to have whole numbers showing.
For example I'd like to see 16 rather than 16.0 satellites.
Press and hold the individual gauge. This brings up a config menu where you can set number of decimals.
 
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