Driving dynamics and charging data files

[JimmyMachE]

100% soc reported is 95.7% real soc, and 387.5V after an overnight soak to stabilize the voltages

What was the kWh content in the fullly charged battery (100% soc reported) in Car Scanner?

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[Mach-Lee]

Update here on the front motor thermal design after today's Munro video. It is a permanent magnet motor (just like the rear) rather than inductive as previously reported. The thermal design is basically what I expected after seeing the heating data, it's just a simple cooling jacket around the stator. No internal squirters or pumps like the rear motor, so it's a passive design inside the case. This means it will take longer to fully extract all the heat out of the motor (especially from the rotor core) since it can only be removed around the outside where the stator is touching the case.

I disagree with Munro in that I believe the rear motor has a much better thermal design than the front. Actively pumping fluid around inside the motor and running through a heat exchanger is much more effective than relying on passive diffusion. His opinion seems to be solely based on the number of components in the system. Rear has more things to go wrong, but that's the price you pay for better performance.

In regards to the overheating issues going downhill, it seems much more likely that the front motor would accumulate heat rather than the rear based on the thermal design and the data I've seen here. It would be interesting to know if any RWD cars had the overheating issues, or if they were only seen in AWD vehicles with a front motor.

 

[phidauex]

What was the kWh content in the fullly charged battery (100% soc reported) in Car Scanner?

Sorry, I didn’t capture the “energy remaining until empty” point, so I don’t have the value in kWhs, only raw SOC and displayed SOC. I’ll check that point next time I charge up fully.

Update here on the front motor thermal design after today's Munro video. It is a permanent magnet motor (just like the rear) rather than inductive as previously reported. The thermal design is basically what I expected after seeing the heating data, it's just a simple cooling jacket around the stator. No internal squirters or pumps like the rear motor, so it's a passive design inside the case. This means it will take longer to fully extract all the heat out of the motor (especially from the rotor core) since it can only be removed around the outside where the stator is touching the case.

I disagree with Munro in that I believe the rear motor has a much better thermal design than the front. Actively pumping fluid around inside the motor and running through a heat exchanger is much more effective than relying on passive diffusion. His opinion seems to be solely based on the number of components in the system. Rear has more things to go wrong, but that's the price you pay for better performance.

In regards to the overheating issues going downhill, it seems much more likely that the front motor would accumulate heat rather than the rear based on the thermal design and the data I've seen here. It would be interesting to know if any RWD cars had the overheating issues, or if they were only seen in AWD vehicles with a front motor.

It does seem like the front motor can’t shed heat as fast, and proportionally it is used more for regen than when accelerating, so it makes sense that it would be the limiting factor for long descents.

My biggest question is what the maximum operating temp limits are for these parts - particularly the motor coils and the inverters. I know Borg Warner advertises a 120C max temp (248F) on many of their motors, but I don’t know about the Ford motors.

 

[Mach-Lee]

My biggest question is what the maximum operating temp limits are for these parts - particularly the motor coils and the inverters. I know Borg Warner advertises a 120C max temp (248F) on many of their motors, but I don’t know about the Ford motors.

Yes, the overheat temp is 120ºC for both motors and 115ºC for both inverters (service manual). Hotter than 120ºC you're going to start boiling coolant.

The motor temp is measured in the coil, it's possible certain parts are heating up rapidly during regen before the sensor registers. Personally I think heating is causing the clearance gap between the rotor and stator to close due to thermal expansion until they touch and the motor seizes (until it cools back down). This could be a manufacturing defect if the clearances are out of tolerance and the gap is closed at a lower temperature than designed.

 

[phidauex]

Yes, the overheat temp is 120ºC for both motors and 115ºC for both inverters (service manual). Hotter than 120ºC you're going to start boiling coolant.

The motor temp is measured in the coil, it's possible certain parts are heating up rapidly during regen before the sensor registers. Personally I think heating is causing the clearance gap between the rotor and stator to close due to thermal expansion until they touch and the motor seizes (until it cools back down). This could be a manufacturing defect if the clearances are out of tolerance and the gap is closed at a lower temperature than designed.

Do you think the downhill failures people are having is a physical problem with the motor? That seems scary - I had assumed it was a temperature setpoint being reached and errors being triggered, rather than something actually binding up.

In my case a pretty long descent at high regen only got me to 71C (160F), meaning quite a bit of headroom was left.

 

[Mach-Lee]

Do you think the downhill failures people are having is a physical problem with the motor? That seems scary - I had assumed it was a temperature setpoint being reached and errors being triggered, rather than something actually binding up.

In my case a pretty long descent at high regen only got me to 71C (160F), meaning quite a bit of headroom was left.

If I'm not mistaken some people said they heard grinding or rock noises and it "locked up" as in skidding or didn't move in neutral. I can't remember exactly but it definitely sounded like it had a mechanical aspect. Perhaps someone could chime in.

 

[phidauex]

Update with another data file (added to the OP too):

Added another datafile, this one from 8/14/21 which roughly follows this route from Boulder to Buena Vista: https://abetterrouteplanner.com/?plan_uuid=0967e052-15cd-4e3c-82c3-e707dda11552

The trip was 131 miles, and used 44.1kWhs. In ABRP this aligns with a reference consumption of 3.55 miles/kWh. My actual consumption was 2.97 mi/kWh, but this route has a lot of big climbs up into the mountains, and I was going pretty quick. I also had the vehicle heavily loaded with gear, including a hitch rack with two bikes. This suggests that the default reference consumption in ABRP is fairly conservative.

Here is some longer run voltage information. In this case we see the voltage at 387V when the SOC is 100% reported (95.6% real). This graph is filtered for times when power is close to zero to prevent voltage drop/rise from affecting the values. Incidentally, this is why the SOC is so important for drag racing - at 100% SOC there is fully 12% more voltage available to the motors compared to 50% SOC.

Looking at it a different way, we can calculate the internal resistance of the battery and the cables feeding the inverters. Here we see Current vs. Voltage, filtered for 89% SOC. The measured voltage is in blue, and calculated voltage is in orange. The calculated voltage is just the "resting" voltage for each SOC (calculated from the above graph's linear regression), minus the voltage drop from the current * a fixed resistance (V = I*R). I varied the resistance until things looked good (chimping it). My estimate for the internal resistance of the Extended Range battery is 0.0355 ohms, or 36.5 mOhms, which is right in line for this type of battery.

This should help people trying to troubleshoot the poor gent with the GTPE and his trap speed.

 

[pt19713]

Good insights, thanks for the look - yes, the speed sensitivity of the front motor pops out in your graph - it uses the motor to get going then backs off of it quickly. It relies on it a lot more during regen. That doesn't feel very "typical AWD" for me, but I'm mostly used to Subaru symmetric AWD which is FWD biased, but rarely splits power wider than 70/30.

The Mach-E setup is similar to the Model Y dual motors in terms of front & rear motor interaction. The Model Y front (induction) motor is not active unless the rear has traction issues, or the throttle pedal is above 20-30% (more aggressive acceleration). Essentially it's 100% RWD until more front traction is needed, and/or more power is needed for acceleration.

Below is a graph showing the rear motor torque output (teal) compared to the front (pink). The bottom portion is the throttle position (blue). You can see the front motor barely activating during this 33 minute drive. The three times it generated more than 25 ft-lb of torque, the throttle was at 40% or higher. All the other little blips generated around 5 ft-lb of torque and acceleration was at 20-35% throttle.

 

[EVmodeler]

Update with another data file (added to the OP too):

Added another datafile, this one from 8/14/21 which roughly follows this route from Boulder to Buena Vista: https://abetterrouteplanner.com/?plan_uuid=0967e052-15cd-4e3c-82c3-e707dda11552

...My estimate for the internal resistance of the Extended Range battery is 0.0355 ohms, or 36.5 mOhms, which is right in line for this type of battery.

Excellent data - Thanks! Your extracted Rint is about half of what I estimated (based on extrapolating some other cell properties) for nominal SOC and temperature (50% SOC, ~25 C). Do you have any feel (or data? ) for how sensitive the internal resistance is to SOC and temp? I would expect SOC not to matter much between about 20 - 90 % or so (I note that your data is 89%), decrease some as temp rises above 10-20 C, increase perhaps quite a bit as temp goes below 0 C.

 

[phidauex]

Excellent data - Thanks! Your extracted Rint is about half of what I estimated (based on extrapolating some other cell properties) for nominal SOC and temperature (50% SOC, ~25 C). Do you have any feel (or data? ) for how sensitive the internal resistance is to SOC and temp? I would expect SOC not to matter much between about 20 - 90 % or so (I note that your data is 89%), decrease some as temp rises above 10-20 C, increase perhaps quite a bit as temp goes below 0 C.

Didn't want to leave you hanging forever - I went back through the last datalog and sampled the internal resistance at a few different SOCs. As far as my limited dataset goes, there is no clear correlation with SOC, and the temperature ranges were narrow enough that there was no clear temperature sensitivity either (23C to 32C - 28C average). The average resistance between 52% and 89% SOC was 35.5 mOhms, which stayed pretty stable.

I'm still learning the dynamics of EV batteries, but for the energy batteries I work with the main sensitivity for internal resistance is age - it tends to about double over the life of the battery.

It will be interesting to see how it changes - I'll try to get another log showing a more clear run from 100% to very low SOC. This winter we can get some cold weather logs too. Such fun!

 

[EVmodeler]

Didn't want to leave you hanging forever - I went back through the last datalog and sampled the internal resistance at a few different SOCs. As far as my limited dataset goes, there is no clear correlation with SOC, and the temperature ranges were narrow enough that there was no clear temperature sensitivity either (23C to 32C - 28C average). The average resistance between 52% and 89% SOC was 35.5 mOhms, which stayed pretty stable.

Great - Thanks. Real data is generally better than extrapolation! The internal resistance in such large packs is pretty low, so not a lot of heat generation or voltage drop.

 

[phidauex]

Ok, posting a little more data, this is from a drive that included two 0-60mph pulls, totally floored, near the beginning of the logs. The second one at 190 seconds in was launched using a brake hold, Unbridled, 66% SOC (not great), 60F outdoor temp, climate control on low, no extra weight in the car.

CarScanner's acceleration timer put this at a 5.8s 0-60 (including the rollout). That is probably realistic given the lowish SOC, and it isn't a perfect timer or a prepped run.

The datalog has been resampled to 0.5 seconds, but was capturing around 0.7 seconds, this makes it a bit hard to tell what is going on at this high rate of change, but here are a few observations.

On a speed and power basis, you can see that I floored it (pedal position is dashed green line), power came up a bit, and then I launched. Power ramped up as I accelerated, and I hit peak power at about 44mph. The front motor came up to 50kW quickly and stayed there. The rear motor went to 200kW, but took a little longer to get there. It looks like it folds back a bit at the last second, but it is possible that is a sampling error. 250kW at the motors is about 335hp, not to bad given the low SOC.

On a torque and motor speed basis things are interesting. After the launch the torque slams up to max, as expected. The rear motor peaks at 431 Nm, and starts to fold back torque at 3727 RPM. The front motor peaks at 145 Nm, and starts folding back sooner, at 2718 RPM.

When I let off the pedal, both motors drop to a -75 Nm of torque. Interestingly when driving the car is heavily rear biased, but when regening it is very balanced, probably to create more controlled braking.

Data file attached, as usual.

 

[phidauex]

Just posting here for anyone following - posted some data in another thread about brake pressure, power and deceleration on a 1hr long drive. 1PD does not engage the brakes - ever.

https://www.macheforum.com/site/threads/look-ma-no-brakes.11284/

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