Efficiency >7 miles/kWh

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londiniumperson
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Post by londiniumperson » Tue May 10, 2022 2:29 pm

As the threads of the Honda e efficiency have dropped off the recent list I thought that I’d start yet another 😀

I’ll start off with some boasting because I easily managed 7.1 miles/kWh on a 3.3 trip (the outbound was only 4.6 miles/kWh).
I took it easy, didn’t use one pedal and turned off the HVAC (not even ‘Only Fans’ as Bjorn would say). I have confirmed my suspicions of how peeps get high efficiency readings, which is:
  • Accelerate slowly
  • Drive slowly
  • Switch off HVAC
  • Drive at the warmer time of the day
  • Pre-heat the battery, either by charging or driving
  • Drive on flat’ish terrain
I was only on 30-40 roads but never held anyone up so I think that with a little discipline I could get over 8 miles/kWh, possibly more if I kept my speed low.
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EEEE
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Post by EEEE » Tue May 10, 2022 2:53 pm

I cannot see how this would be done without slight downhill assistance the whole way and over inflated tyres.

My e is going in for service on Saturday so I will soon tell if software is to blame (my car is a 2020 model registered 2021 on a '21). Best I ever get is 4.2m/kwh on a run. Rarely any higher than 4.4m/kwh on a short journey after already warm...

It may be worth plotting your journey on the various cycling trackers/planners which can give you good detail about the inclination of any journey.

May I ask the method of your pre-heating? Using the app or using the in car system, or the fob? I'm not sure I know the difference between cabin pre-conditioning or battery pre-heating. Are they the same thing?

Even if there is a boost to efficiency from the preheating, it must be short lived (First 10/20 miles or so until battery is cooled?) and at the cost of on peak tariff. Something to try when you need to do a 125m journey perhaps, but not something I'd try to aim for.

I can envisage the first honda e meetup - we all drive in convoy on the same day and conditions the same route, then compare notes at the end :lol:
'21 e Advance - Charge Yellow - E1702RR alloys
'17 Civic Sport CVT
'00 Prelude 2.2VTi

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londiniumperson
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Post by londiniumperson » Tue May 10, 2022 7:40 pm

@EEEE
I was like you when I bought my car, not able to understand how anyone could ever get over 4.5 miles/kWh. My usual commute averages around 3 to 3.5 miles/kWh so this is unusual.

I’m pretty sure that there’s very little downhill assistance going on here because the drive was fairly level (there are 4 routes out of my home town and 3 have steep hills up within a couple of miles in the North, East & South directions, this time I headed West where the nearest hill is quite a way away.

I wonder if having driven over 15k miles has loosened something up that’s noticeable when driving sedately.

As for pre heating, this time I think it was the drive out which I drove in my normal style and the car was sat for about an hour before the return trip.
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Post by londiniumperson » Fri May 13, 2022 2:29 pm

I found a way to show the elevation of that 3.3 mile trip on Google Maps, just need to choose cycling as the transport mothed and ensure that the correct route is taken.
Only a drop of 95ft:

Elevation.png

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londiniumperson
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Post by londiniumperson » Fri May 13, 2022 8:50 pm

I've just experienced another high efficiency, this time driving in my normal mode of fairly rapid acceleration, with the HVAC on keeping the car cool inside, outside temp was 17C and I had a passenger this time on 30-50 mph roads:
6.3 miles/kWh on a 7.5 mile trip

It would have been very easy to get over 7m/kWh if I'd driving slightly more gentle.
Again here's the Google Maps elevation info, does driving down to a lower elevation of that height really make a huge difference?
I think that seeing that I'd let the car sit half an hour after a short drive made more of an impact.

Elevation.png

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hquer
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Post by hquer » Sat May 14, 2022 9:11 am

londiniumperson wrote:
Fri May 13, 2022 8:50 pm
I've just experienced another high efficiency, this time driving in my normal mode of fairly rapid acceleration, with the HVAC on keeping the car cool inside, outside temp was 17C and I had a passenger this time on 30-50 mph roads:
6.3 miles/kWh on a 7.5 mile trip

It would have been very easy to get over 7m/kWh if I'd driving slightly more gentle.
Again here's the Google Maps elevation info, does driving down to a lower elevation of that height really make a huge difference?
I think that seeing that I'd let the car sit half an hour after a short drive made more of an impact.
Elevation.png
That's simple physics: Doing some math ;-)

on the 7.5 mile trip with 6.3 miles/kWh you had a total energy consumption of 1.19 kWh.

However, by riding downhill you gained E=mgh=1700 x 9.81 x (420-82)x0.305 /1000 / 3600 = 0.48 kWh.

So, the real energy consumption on a flat road would have been 1.67 kWh for 7.5 miles, which is 4.49 miles/kWh...

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londiniumperson
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Post by londiniumperson » Sat May 14, 2022 1:22 pm

hquer wrote:
Sat May 14, 2022 9:11 am
That's simple physics: Doing some math ;-)

on the 7.5 mile trip with 6.3 miles/kWh you had a total energy consumption of 1.19 kWh.

However, by riding downhill you gained E=mgh=1700 x 9.81 x (420-82)x0.305 /1000 / 3600 = 0.48 kWh.

So, the real energy consumption on a flat road would have been 1.67 kWh for 7.5 miles, which is 4.49 miles/kWh...
If only it was that simple.
That may well be the gravitational potential energy increase, however how much of that energy would actually impact the kWh used by the motor?
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hquer
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Post by hquer » Sat May 14, 2022 2:36 pm

It basically is that simple...try driving the same route in the opposite direction (uphill) and your energy consumption will be around 2.7 miles/kWh. The electric motor simply needs to deliver less power downhill compared to moving the car on a flat road....the difference is just the gained potential energy. Of course, the calculation is not 100% correct since the efficiency of regenerative braking is not 100% and if you possibly use the mechanical brakes you produce additional heat losses.

All in all: even if you drive very gently it is very hard to beat the WLTP range. Maybe you can reach 5 miles/kWh (on a round trip or a perfectly flat road) but not much more...

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londiniumperson
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Post by londiniumperson » Sat May 14, 2022 2:58 pm

hquer wrote:
Sat May 14, 2022 2:36 pm
It basically is that simple...try driving the same route in the opposite direction (uphill) and your energy consumption will be around 2.7 miles/kWh. The electric motor simply needs to deliver less power downhill compared to moving the car on a flat road....the difference is just the gained potential energy. Of course, the calculation is not 100% correct since the efficiency of regenerative braking is not 100% and if you possibly use the mechanical brakes you produce additional heat losses.

All in all: even if you drive very gently it is very hard to beat the WLTP range. Maybe you can reach 5 miles/kWh (on a round trip or a perfectly flat road) but not much more...
The actual efficiency on the outbound route was 3.2 miles/kWh, significantly different to your calculated 2.7 miles/kWh.
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hquer
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Post by hquer » Sat May 14, 2022 9:51 pm

Same conditions? Two people in the car? Same speed/acceleration? In any case you see, that 7miles/kWh is not realistic...

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