DBC
Well-Known Member
- First Name
- Don
- Joined
- Oct 1, 2020
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- 8
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- Location
- San Diego
- Vehicles
- Volt ELR
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- #1
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.
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.
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