Peeking in the electronic brain of the Mach-e: How does energy flow?

[RobbertPatrison]

I used to drive a Chevy Bolt and Volt before my shiny new extended range AWD Mach-e. Chevy's electric cars displayed the propulsion and regenerative power flow conveniently on the dashboard. The Mach-e doesn't do that, so I configured car scanner pro to display and track a few nerdy parameters from the OBD2 bus. It matters: I am an electrical engineer
The MagSafe charging mount places the iPhone in a perfect position to the left of the main screen. The built-in lower wireless charging pad tends to heat up the phone, which is very bad for battery degradation. In the location next to the screen the air from the AC cools the phone perfectly:

Out of the dozens of OBD2 signals, I picked a few interesting ones that are relevant while driving. Here is what I observe in my extended range AWD:

• During normal acceleration, the front motor produces power only until 16mph(25km/h). At speeds above that, it switches off, unless you push the pedal to the metal. This is what you would expect in 4wd cars.
• If both the front and rear motors are engaged, the rear wheels do about 70% of the work.
• At speeds above 16mph/25kmh, the rear motor does all the work in normal driving: both acceleration and regenerative braking. There is no front re-generation at higher speeds. I presume that is also because the rear motor is more efficient.
• When braking at speeds below 15mph, both front and back motors regenerate energy to slow down the Mach-e. The braking torque is divided evenly front/back. That makes sense as it reduces the chance of a wheel slipping.
• When flooring the pedal for a 0-60 dash in unbridled mode, OBD2 reported a peak battery power draw of 429kW, which - at first - seems oddly more than spec. With the rated 355hp, the expected peak output power should be 265kW. But it might make makes sense because there are losses while converting electrical power into mechanical power. The 38% difference could indeed be the loss burnt in the inverters and the electric motors. Both motor and inverter will quite a bit less efficient when driven to the limit at maximum output. Though an energy loss of 48% might look bad, it is still much better than an Internal Combustion Engine that loses over 80% of the power.
• During the 0-60mph sprint, I see a maximum torque of 121Front+ 393Rear = 513nm torque. According to the spec it is 580nm but this could be a measurement error. I suspect that the torque is not measured but calculated from motor current and rpm.
• There is no difference in braking action between 1-pedal driving and normal mode. The computer blends in a lot of regenerative braking before any friction brakes are applied. In normal use, all braking is regenerative. Only with very aggressive braking do the friction brakes kick in. So you need to drive like a madman to heat up the brake pads.
• Unfortunately, the brake pressure signal is too coarse to track how the Mach-e blends friction and regenerative braking. I suspect that all braking is regenerative based on what I see.

Then let's look at the 'cost' of running the AC and the heater:

• The heater power draw in 50F/10C weather is between 2kW and 4kW continuously. That seems about right: It would add about 10-20kWh of energy burn on a full charge. It would account for a range drop of about 30-60 miles. It will be worse with colder weather. If you want range, you must switch off the e-heat. Unfortunately, the Mach-e has a habit of sneakily switching on e-heat. The GM cars had an 'ECO mode' that avoided the hidden climate-energy burn.
• The AirConditioner power is remarkably low. I measure about 0.7kW in 27C/80F sunny weather. That would 'cost' ~10 miles of range. This is less than what I saw in my Volt and Bolt.
• The seat heater draws about 0.06kW, which is negligible. The heated steering wheel is too small to measure.
• Note that there is no heater power reported in the OBD2 signal list. So I derived that from measuring the battery power difference when switching things on or off. There is a signal that shows the AS compressor current. I see current values of approx 4A when running, which is off because at 370V that would suggest a lot higher power draw.

Then a few other power signals:

• With the radio on, the power-on battery draw is only 450Watts. That is slightly better than what I saw in the Volt and Bolt.
• The Headlights add ~70Watts: it is insignificant. LEDs are very efficient. The old Halogens used to be 50 Watt each.

The display while braking at low speed: Both front and rear motors have about the same braking torque. The combined regenerative braking power is 6kW at the time of this snapshot.
You can see the power flow of the past 2 minutes in the second row. I was driving downhill, so most of the power is negative. Below that is the speed in the same 2-minute period. The bottom row I picked the battery energy (with min and max markers) and temperature. I like SI-units.

 

[Logal727]

I used to drive a Bolt and Volt. Those electric cars displayed the propulsion and regenerative power flow directly on the dashboard. The Mach-e doesn't do that, so I configured car scanner pro to display and track a few nerdy parameters from the OBD2 bus. It matters: I am an electrical engineer
The MagSafe charging mount places the iPhone in a perfect position to the left of the main screen. The built-in lower wireless charging pad tends to heat up the phone, which is very bad for battery degradation. In the location next to the screen the air from the AC cools the phone perfectly:

Out of the dozens of OBD2 signals, I picked a few interesting ones that are relevant while driving. Here is what I observe in my extended range AWD:

• During normal acceleration, the front motor produces power only until 16mph(25km/h). At speeds above that, it switches off, unless you push the pedal to the metal. This is what you put expect in 4wd cars.
• If both the front and rear motors are engaged, the rear wheels do about 70% of the work.
• At speeds above 16mph/25kmh, the rear motor does all the work in normal driving: both acceleration and regenerative braking. There is no front re-generation at higher speeds.
• When braking at speeds below 15mph, both front and back motors regenerate energy to slow down the Mach-e. The braking torque is divided evenly front/back. That makes sense for maximum grip.
• When flooring the pedal for a 0-60 dash in unbridled mode, OBD2 reported a peak battery power draw of 429kW, which - at first - seems oddly more than spec. With the rated 355hp, the expected peak output power should be 265kW. But it makes sense because there are losses while converting electrical power to mechanical power. The 20% difference is a loss burnt in the inverters, and the electric motors get less efficient as well at maximum output. An energy loss of 20% is still MUCH better than an Internal Combustion Engine that loses over 80% of the power.
• During the 0-60 sprint I see a maximum torque of 121 + 393 = 513nm torque. According to the spec it is 580nm but this could be a measurement error.

Then let's look at the 'cost' of running the AC and the heater:

• The heater power in 50F/10C weather is between 2kW and 4kW continuously. That seems about right: It would add about 10-20kWh of energy burn on a full charge. It would account for a range drop of about 30-60 miles. It will be worse with colder weather. If you want range, you must switch off the e-heat. Unfortunately, the Mach-e has a habit of sneakily switching on e-heat. The GM-cars had an ECO-mode that avoided the hidden climate-energy burn.
• The AirConditioner power is remarkably low. I measure about 0.7kW in 27C/80F sunny weather. That would 'cost' ~10 miles of range. This is less than what I saw in my Volt and Bolt.
• The seat heater draws about 0.06kW, which is negligible. The heated steering wheel is too small to measure.
• Note that there is no heater power reported in the OBD2 signal list. So I derived that from measuring the battery power difference when switching things on or off. There is a signal that shows the AS compressor current. I see current values of approx 4A when running, which is off because at 370V that would suggest a lot higher power draw.

Then a few other power signals:

• With the radio on, the power-on battery draw is only 450Watts. That is slightly better than what I saw in the Volt and Bolt.
• The Headlights add ~70Watts: it is insignificant. LEDs are very efficient. The old Halogens used to be 50 Watt each.

The display while braking at low speed: Both front and rear motors have about the same braking torque. The combined regenerative braking power is 6kW at the time of this snapshot.
You can see the power flow of the past 2 minutes in the second row. I was driving downhill, so most of the power is negative. Below that is the speed in the same 2-minute period. The bottom row I picked the battery energy (with min and max markers) and temperature. I like SI-units.

Very cool, good to finally get confirmation about the front motor, I’ve heard very different things about what it does at higher speeds

 

[kltye]

I used to drive a Chevy Bolt and Volt before my shiny new extended range AWD Mach-e. Chevy's electric cars displayed the propulsion and regenerative power flow conveniently on the dashboard. The Mach-e doesn't do that, so I configured car scanner pro to display and track a few nerdy parameters from the OBD2 bus. It matters: I am an electrical engineer
The MagSafe charging mount places the iPhone in a perfect position to the left of the main screen. The built-in lower wireless charging pad tends to heat up the phone, which is very bad for battery degradation. In the location next to the screen the air from the AC cools the phone perfectly:

• When flooring the pedal for a 0-60 dash in unbridled mode, OBD2 reported a peak battery power draw of 429kW, which - at first - seems oddly more than spec. With the rated 355hp, the expected peak output power should be 265kW. But it makes sense because there are losses while converting electrical power to mechanical power. The 20% difference is a loss burnt in the inverters, and the electric motors get less efficient as well at maximum output. An energy loss of 20% is still MUCH better than an Internal Combustion Engine that loses over 80% of the power.

I assume you mean 329kW, rather than 429. Even so, that's a loss of 64kW. That's a lot of heat to dissipate, isn't it? That seems like a very large delta, to me.

 

[RobbertPatrison]

I assume you mean 329kW, rather than 429. Even so, that's a loss of 64kW. That's a lot of heat to dissipate, isn't it? That seems like a very large delta, to me.

Good point, but I do measure 429kW consistently. That is a 38% momentary loss for a few seconds. It could also be that the measurement is off, but the battery current and voltage (=power) do seem to match. It is OK if that heat is only there for a few seconds...

 

[jhalkias]

Really interesting. Thanks for posting this!

 

[Mach-Lee]

Yes I’ve also seen the front motor only works up to about 20ish mph and shuts off unless you’re on the pedal hard.

I think you should see 100+ kW of regen happening. In one pedal brakes don’t engage until you’ve been stopped for a second or two, it’s all regen.

You should calculate kW from pack volts and amps and compare. Something seems off with the calibration of that parameter in your data.

 

[SnBGC]

I used to drive a Chevy Bolt and Volt before my shiny new extended range AWD Mach-e. Chevy's electric cars displayed the propulsion and regenerative power flow conveniently on the dashboard. The Mach-e doesn't do that, so I configured car scanner pro to display and track a few nerdy parameters from the OBD2 bus. It matters: I am an electrical engineer
The MagSafe charging mount places the iPhone in a perfect position to the left of the main screen. The built-in lower wireless charging pad tends to heat up the phone, which is very bad for battery degradation. In the location next to the screen the air from the AC cools the phone perfectly:

Out of the dozens of OBD2 signals, I picked a few interesting ones that are relevant while driving. Here is what I observe in my extended range AWD:

• During normal acceleration, the front motor produces power only until 16mph(25km/h). At speeds above that, it switches off, unless you push the pedal to the metal. This is what you put expect in 4wd cars.
• If both the front and rear motors are engaged, the rear wheels do about 70% of the work.
• At speeds above 16mph/25kmh, the rear motor does all the work in normal driving: both acceleration and regenerative braking. There is no front re-generation at higher speeds.
• When braking at speeds below 15mph, both front and back motors regenerate energy to slow down the Mach-e. The braking torque is divided evenly front/back. That makes sense for maximum grip.
• When flooring the pedal for a 0-60 dash in unbridled mode, OBD2 reported a peak battery power draw of 429kW, which - at first - seems oddly more than spec. With the rated 355hp, the expected peak output power should be 265kW. But it might make makes sense because there are losses while converting electrical power into mechanical power. The 38% difference is a loss burnt in the inverters and the electric motors. All will get quite a bit less efficient when driven to the limit at maximum output. An energy loss of 48% is bad, but still MUCH better than an Internal Combustion Engine that loses over 80% of the power.
• During the 0-60mph sprint I see a maximum torque of 121Front+ 393Rear = 513nm torque. According to the spec it is 580nm but this could be a measurement error. I suspect that the torque is not measured but calculated from motor current and rpm.
• Unfortunately, the brake pressure signal is too coarse to track how the Mach-e blends friction and regenerative braking. I suspect that all braking is regenerative based on what I see.

Then let's look at the 'cost' of running the AC and the heater:

• The heater power draw in 50F/10C weather is between 2kW and 4kW continuously. That seems about right: It would add about 10-20kWh of energy burn on a full charge. It would account for a range drop of about 30-60 miles. It will be worse with colder weather. If you want range, you must switch off the e-heat. Unfortunately, the Mach-e has a habit of sneakily switching on e-heat. The GM-cars had an ECO-mode that avoided the hidden climate-energy burn.
• The AirConditioner power is remarkably low. I measure about 0.7kW in 27C/80F sunny weather. That would 'cost' ~10 miles of range. This is less than what I saw in my Volt and Bolt.
• The seat heater draws about 0.06kW, which is negligible. The heated steering wheel is too small to measure.
• Note that there is no heater power reported in the OBD2 signal list. So I derived that from measuring the battery power difference when switching things on or off. There is a signal that shows the AS compressor current. I see current values of approx 4A when running, which is off because at 370V that would suggest a lot higher power draw.

Then a few other power signals:

• With the radio on, the power-on battery draw is only 450Watts. That is slightly better than what I saw in the Volt and Bolt.
• The Headlights add ~70Watts: it is insignificant. LEDs are very efficient. The old Halogens used to be 50 Watt each.

The display while braking at low speed: Both front and rear motors have about the same braking torque. The combined regenerative braking power is 6kW at the time of this snapshot.
You can see the power flow of the past 2 minutes in the second row. I was driving downhill, so most of the power is negative. Below that is the speed in the same 2-minute period. The bottom row I picked the battery energy (with min and max markers) and temperature. I like SI-units.

If your scanner is able to submit commands then you can force the ACCM to 4000 rpm and see what the actual power draw is. I think 4k is max speed if I remember correctly....

 

[metalpro2021]

@RobbertPatrison Nice stuff. Can you publish this with the powerup/module versions currently used please? I can imagine the results will differ with module updates (already)....

 

[ElectrifyCLT]

Interesting that Regen braking is all on the rear. You'd think they'd lean on the front a bit more to behave more like a traditional braking setup (most braking is done by front brakes these days).

 

[RobbertPatrison]

Interesting that Regen braking is all on the rear. You'd think they'd lean on the front a bit more to behave more like a traditional braking setup (most braking is done by front brakes these days).

I agree. I suspect that the rear motor is more efficient, so that is selected during normal usage.

 

[Chainspell]

Does the usage pattern for front and rear hold across the different drive modes?

 

[RobbertPatrison]

Yes I’ve also seen the front motor only works up to about 20ish mph and shuts off unless you’re on the pedal hard.

I think you should see 100+ kW of regen happening. In one pedal brakes don’t engage until you’ve been stopped for a second or two, it’s all regen.

You should calculate kW from pack volts and amps and compare. Something seems off with the calibration of that parameter in your data.

Indeed, I have seen close to 100kW regen braking. The Chevy Bolt could do more than 60kW.
When I multiply HVB voltage by Current I get exactly the reported power. So I presume that the OBD2 signal is calculated the same way and is correct.

The Chevies had separate power signals for the heater and the A/C. Here IO cannot find that. It would be useful to get a quick view on climate control power usage.

 

[voxel]

Great info!

The forthcoming EV6 GT also pushes out 400+ kW but I always wondered if higher voltage (800V) would lead to some efficiency gain (lower amps - less heat?)

 

[SnBGC]

I agree. I suspect that the rear motor is more efficient, so that is selected during normal usage.

It is a stronger motor in back so that is why it does the work. A GT might be different. Would be interesting to see some of that data....

 

[RobbertPatrison]

Does the usage pattern for front and rear hold across the different drive modes?

Yes, it seems the same across drive modes. There is no difference in maximum power output, but the braking action in unbridled mode is more aggressive. It seems to me a steeper mapping of pedal input to power output.

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