How is the range calculated?

Faults and Technical chat for the Honda E
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hondaeboy
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Post by hondaeboy »

Does anyone know how the range is calculated exactly in the Honda e?

I almost always do the slowest possible trickle charge upto 100% and the range then usually shows to be around 200-220 km of range at the beginning. This does seem reasonable when the average consumption is usually between 13 to 14 kWh per 100 km (and assuming the battery is around 28 kWh).

However, yesterday I looked into a bit more, but the math doesn't seem to add up entirely. I arrived home with only 1 km left in the battery (0%), but could see I had only travelled around 181 km with an average consumption of 14 kWh/100 km. Assuming that the battery is about 28 kWh, I would think this would have allowed for 200 km of travel in stead 180.

How do I interpret this or how do I calculate this correctly?

honda-e-trips.jpg

2021 Honda e Advance on 16" RC30 wheels with Goodyear 195/55 & 205/55 tyres.
Wrapped in Red metallic with full black and cinnamon leather interior.

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londiniumperson
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Post by londiniumperson »

You cannot calculate this correctly.
The reading doesn't take into account the energy used during pre-heat or any energy used to heat the battery.
At a displayed 0% SoC there is actually some power still left in the battery, if you had the nerve to get to the actual 0% SoC then it's likely you would get 200km, but it is detrimental to the battery running it until the BMS (Battery Management System) states it is flat and the car stops.

I'm shocked that you got on average 14 kWh/100 km, this 4.4m/kWh, unless I turn off the HVAC system this figure is a dream for me as I average 3.1m/kWh (20 kWh/100km) over 18000 miles.

There are quite a few threads on here about battery usage, range, displayed range/efficiency, usable kWh.
Last edited by londiniumperson on Thu Feb 09, 2023 9:15 pm, edited 1 time in total.
2022 Advance in Crystal Black Pearl on 17's - 08/2020-Current
2015 VW Tiguan (Pure White) - 04/2018-Current
1991 Honda Beat PP1 (Festival Red) - 11/2022-Current
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EEEE
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Post by EEEE »

There are too many variables. I don't try and second guess it or work out what its doing.

All I know is you can't go very far, and if you do just make sure you charge up before its too late :lol: My enjoyment of the car improved when i stopped trying to understand it and just enjoyed driving it to and from work and in town etc. Long journeys i just take the prelude or the civic.

The way to understand why the numbers don't make sense is that 0% and 100% are not absolute states, and are most likely altered with some 'fudge factor'. I suspect that even that fudge factor has a layer beneath it of further fudge factors, with the car being a loose collection of components integrated from many vendors.

I suspect also that not all power usage is taken account in the usage either. In order to improve 'economy' reported , I suspect some non essential non-motive usage is 'discounted' away from the total, in line with the some charitable interpretation of the testing methodology (and of course, no car manufacture would ever game efficiency measurements would they).

Like a mobile phone, as long as it doesn't go flat, I never care what percentage I'm on.
'21 e Advance - Charge Yellow - E1702RR alloys
'17 Civic Sport CVT
'00 Prelude 2.2VTi
zemdega
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Post by zemdega »

I'm mostly surprised about 14kwh/100. I have about 9K on the clock and now it's 19kwh/100 on average (winter driving didn't help as it was about 16-17 in summer) . And I really try to be gentle on throttle. I'm not sure how do you need to drive to get 14.
Accord
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Post by Accord »

At higher speeds the car is unfortunately inefficient.
So at the highway you’re wasting some energy in heat.

You’re also charging the 12V-system etc, so you are using some energy for other things even though the HVAC is off.
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keithr
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Post by keithr »

zemdega wrote: Thu Feb 09, 2023 9:41 pm I'm mostly surprised about 14kwh/100.
That's an advantage of having 16" wheels instead of 17"?
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hondaeboy
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Post by hondaeboy »

londiniumperson wrote: Thu Feb 09, 2023 8:53 pm You cannot calculate this correctly.
Accord wrote: Fri Feb 10, 2023 7:53 am You’re also charging the 12V-system etc, so you are using some energy for other things even though the HVAC is off.
EEEE wrote: Thu Feb 09, 2023 9:05 pm I suspect also that not all power usage is taken account in the usage either. In order to improve 'economy' reported , I suspect some non essential non-motive usage is 'discounted' away from the total, in line with the some charitable interpretation of the testing methodology (and of course, no car manufacture would ever game efficiency measurements would they).
OK, those were quite sobering remarks. lol. I think I just expected the car to recalculate the average energy consumption from such idle battery use. Just like it would with a regular ICE car. So, let's say you use 14 kWh/100 km - and you then use the air conditioning while standing still, it would simply change the energy consumption to 15 kWh / 100 km for instance to reflect the extra battery usage while not driving. It's unfortunate that it doesn't do that.
londiniumperson wrote: Thu Feb 09, 2023 8:53 pm I'm shocked that you got on average 14 kWh/100 km, this 4.4m/kWh, unless I turn off the HVAC system this figure is a dream for me as I average 3.1m/kWh (20 kWh/100km) over 18000 miles.
Just changed the car from km to miles, and the 4.4 actually seemed to have been the 'worst' of the past couple of trips. The trip A computer resets every time I charge. I am a careful driver though, and tend to drive in such a way that I avoid regen. And I try to drive between accelerating and regen as much as possible. On highways I often drive with ACC and don't mind coasting behind somewhat slower cars or trucks. It might also help that the maximum speed during the day has been reduced from 80 to 60 mph nationwide. And I guess living in a ridiculously flat country might also help.

But also...
keithr wrote: Fri Feb 10, 2023 1:45 pm
zemdega wrote: Thu Feb 09, 2023 9:41 pm I'm mostly surprised about 14kwh/100.
That's an advantage of having 16" wheels instead of 17"?
...I hope this is one of the contributing factors, as I did put a neurotically ridiculous amount of time into choosing an optimised set of rims and tyres. I sold the original Honda e 17" rims, along with the really weird default LingLong type tyres that go along with it. I found a very nice rim that seemed to be custom made for the Honda e (the measurements were exactly right for both the front - 6J -and the back - 7J), and they only weighed something like 8 kg (18 lbs):
https://www.brock.de/en/felgen/rc-design-rc30-en/

I also made some good use of the EU's EPREL database, and tried to find the size that would still be acceptable both front and back, but also had the lowest rolling resistance. Goodyear Vector 4Seasons Gen-3 had an A rating for the exact size I needed. 195/55R16 91H (front) and 205/55R16 94V (back):
https://eprel.ec.europa.eu/

honda-e-trips-mph.jpg

2021 Honda e Advance on 16" RC30 wheels with Goodyear 195/55 & 205/55 tyres.
Wrapped in Red metallic with full black and cinnamon leather interior.
Accord
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Post by Accord »

It seems like “avg.” in trip isn’t used for any calculation. Also the avg. for current drive (since starting the car) isn’t involved either.

I drove on highway downhill, got like 10kwh/100km. Then it flattened out and of course the avg. consumption started increasing. But the range was also increasing… So it seems to have a separate hidden calculation dependent on consumption for xx last kilometers driven. Even after stopping and driving back, the range was the same, but avg. consumption was nearly doubled (since I was now driving up again).
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advance2020
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Post by advance2020 »

Hi londiniumperson

“I'm shocked that you got on average 14 kWh/100 km, this 4.4m/kWh, unless I turn off the HVAC system this figure is a dream for me as I average 3.1m/kWh (20 kWh/100km) over 18000 miles.”

I think we have been here before, and knowing where you live, and the pace of life there, I’m not surprised your avg is 3.1 you can’t drive slowly there. However I took our son to our local Rail Station this morning 6:20 to 6:45am 11°C 13.9 miles round trip 4.6m/kWh - which was extremely good with headlights on - no heating - but I had charged to 85% overnight. So battery was still warm and I think 80-85% SoC is sweet spot for efficiency.
Platinum White Pearl: e-driving green at last, on R17 Michelin Pilot Sport
AVG economy and Predicted Mileage has increased lately, not sure why.
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