My Range Numbers

DBC

Well-Known Member
First Name
Don
Joined
Oct 1, 2020
Threads
8
Messages
1,224
Reaction score
1,428
Location
San Diego
Vehicles
Volt ELR
Country flag
Here is what I've found so far with the MME. My process was to charge to 90%, drive it for two days, capture the information from the MME, and then measure how many kWh went back into the MME when charging back up to 90%. For background purposes I reset the driving history the first day I had my MME.

The driving was a 85% freeway and 15% surface streets. The speed on surface streets was between 0 MPH at traffic lights and 55 MPH when moving. Pretty standard SoCal suburban. The speed on the freeways, other than merges, was between 68 MPH and 85 MH. IOW fairly aggressive but not crazed. The terrain was all hills all the time because that's what we have. The temperature was around 50F.

After two days the car reported it had gone 77.4 miles, was going 3 miles/kWh, and had a remaining range of 133 miles and a remaining battery SOC of 59%. When I charged the MME to 90% it took 30.4 kWh from the wall. The MME indicated it had 90% SOC available and a range of 211 miles.

Assuming my 3.3 kW charger was about 85% efficient (about what I've gotten on it on several BEVs), this meant the charging event put 25.84 kWh into the battery when charging to 90%. Doing the math gave a efficiency of 2.9954 miles/kWh, which is consistent with the 3.0 miles/kWh reported by the MME. It was also consistent with the EPA numbers for kWh per 100 miles if you assume the EPA's charging event was 90% efficient (a reasonable assumption).

While these numbers hung together the range and battery SOC available from the MME did not. On the range, if the efficiency is 3 miles/kWh and the battery makes 88 kWh available, then the range should be 264 miles (impressive for this drive cycle), and 90% of this range should be 238 miles. This doesn't correspond very closely with the 211 miles reported by the MME though not different by a huge amount. Similar issue with the reported SOC. If 35.84 kWh is 31% of the SOC, then 100% SOC would be 83.35 kWh. That's 4-5 kWh less than advertised.

One explanation would be that the MME doesn't make 88 kWh of energy available. That doesn't seem likely. The other explanation, which is more likely, is that the range estimate is biased downward -- IOW if driving history suggests an efficiency of 3.0 miles/kWh the MME will use 2.8 miles/kWh. That's not a bad strategy that it's more likely to avoid someone pushing things a bit too far and getting stranded.

Additionally it appears the MME "hides" some of the SOC, at least when the SOC is high. In essence you have a few more kWh than reported, which accounts for an additional 15 miles or so. Much like how when the gas gauge hits "E" it's not really empty, there is a gallon or so left. Again, probably not a bad strategy.
Sponsored

 

JamieGeek

Well-Known Member
Joined
Dec 29, 2019
Threads
82
Messages
3,556
Reaction score
6,746
Location
Southeastern Michigan
Website
spareelectrons.wordpress.com
Vehicles
Mach-E, old: Bolt, C-Max Energi, Focus Electric
Country flag
  • Like
Reactions: UW2
OP
OP

DBC

Well-Known Member
First Name
Don
Joined
Oct 1, 2020
Threads
8
Messages
1,224
Reaction score
1,428
Location
San Diego
Vehicles
Volt ELR
Country flag

JamieGeek

Well-Known Member
Joined
Dec 29, 2019
Threads
82
Messages
3,556
Reaction score
6,746
Location
Southeastern Michigan
Website
spareelectrons.wordpress.com
Vehicles
Mach-E, old: Bolt, C-Max Energi, Focus Electric
Country flag
I think your trip meter was correct. I think the range estimate was biased to less than 2.3 miles/kWh but the MME isn't using 88 kWh as the available SOC. IOW when the MME says 80% available it means 80% of something less than 88 kWh.

But yes, the range estimate is conservative.
Sadly we have no way of knowing given the instrumentation on the Mach-E. Nowhere is there a display of kWh consumed. Not sure if I saw that when I had the OBD-II reader plugged in or not.

It really needs some kWh displays (and kW charging/discharging).
 
  • Like
Reactions: UW2

Mirak

Well-Known Member
Joined
Oct 8, 2020
Threads
109
Messages
3,657
Reaction score
5,839
Location
Kansas
Vehicles
"Sonic" 2021 MME Grabber Blue First Edition
Country flag
Sorry for the rookie question, but how are you confident you’re getting 3mi/kWh? Does the car tell you how much juice you put back in?

I really don’t care what the GOM says - if we can get 3mi/kWh with that sort of highway driving, that’s very good news.
 


OP
OP

DBC

Well-Known Member
First Name
Don
Joined
Oct 1, 2020
Threads
8
Messages
1,224
Reaction score
1,428
Location
San Diego
Vehicles
Volt ELR
Country flag
Sorry for the rookie question, but how are you confident you’re getting 3mi/kWh? Does the car tell you how much juice you put back in?
I measured the number of kWh that were sent to the MME. To be more precise, I know from previous measurements that I use 2.4 kWh of electricity between midnight and six thirty if I don't run the HVAC, dishwasher, etc. I just subtracted this number from the total used last night between those times. Confirmed with the graph which shows usage though that wasn't necessary. Might be off by a hundred watts or something but nothing significant.

My measured/calculated number was essentially the same number as what the MME reported, assuming 85% charging efficiency. I think that's right from past experience.

And yes, very impressive performance. Seems to be quite efficient at higher speeds. For comparison, my Bolt gets about 3.5 miles/kWh on similar drives. I suspect the differences would be much larger if there was more local driving.
 
  • Like
Reactions: UW2
OP
OP

DBC

Well-Known Member
First Name
Don
Joined
Oct 1, 2020
Threads
8
Messages
1,224
Reaction score
1,428
Location
San Diego
Vehicles
Volt ELR
Country flag
Sadly we have no way of knowing given the instrumentation on the Mach-E. Nowhere is there a display of kWh consumed. Not sure if I saw that when I had the OBD-II reader plugged in or not.
The kWh consumed as reported by the MME would just be the reported Miles Driven divided by the reported Miles/kWh. This isn't displayed but not hard to calculate. If we assume the miles driven is correct then the only issue is whether number of miles/kWh is correct. That was what I was trying to check.
Sponsored

 
 




Top