I have a theory that the best results can be obtained using N as much as possible. On hills be ready to not exceed posted speed limits by engaging D. Have your cruise ready to rengage at your preferred speed. The results will be more believable over say 100ks. I will post my own tests in the future.
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Post your best "mpg" kWhrs/100k
- Thread starter eclectricdave
- Start date
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- Australia New Zealand
lonewolf313
Member
I am not an electrician or an engineer but I would like to put in my two cents worth here.
What is the point of coasting in neutral down a hill to claim a theoretical "better MPG or kWh/100km" when you lose out on your cars range between charges.
The real question is how far can you go per kWh? How much will it cost you to recharge if you need to plug in on the grid?
Why waste your opportunity to claim the real "free charging" for your car by not regenerating your battery while going downhill.
Sure, an 85 or 90 kWh battery pack may get you to your destination with oodles of energy to spare but for those owners with 60 or 70kWh battery packs, not regenerating whilst on the road may mean the difference between making or not making your destination before the battery pack runs out of juice.
What is the point of coasting in neutral down a hill to claim a theoretical "better MPG or kWh/100km" when you lose out on your cars range between charges.
The real question is how far can you go per kWh? How much will it cost you to recharge if you need to plug in on the grid?
Why waste your opportunity to claim the real "free charging" for your car by not regenerating your battery while going downhill.
Sure, an 85 or 90 kWh battery pack may get you to your destination with oodles of energy to spare but for those owners with 60 or 70kWh battery packs, not regenerating whilst on the road may mean the difference between making or not making your destination before the battery pack runs out of juice.
omniwolf
eNizl
I think he's trying to say that you'll get better range by coasting in neutral. So better for any battery pack I guess. All hypothetical until we get some stats.
Well I am an electrical engineer although I do other things now. Various people have their opinions on this subject of coasting which I have explored with heat-engine vehicles. I once did Melb-Syd rtn on one tank of fuel with my Peugeot HDI. My theory is that it is better to convert potential energy PE into kinetic energy KE limiting speeds to about 90kph such that a hybrid driving style may be reqd under these circumstances. If you leave the Tes in D the conversions of PE or KE to chemical energy CE is not 100% efficient such that you loose energy that might have been better used to overcome the forces of movement (gravity-positive & negative, rolling resistance & air resistance & pumping losses on wet roads. i have only had my Tes for a little over a month but I have noticed it does roll with much less resistance than other cars I have owned. The next best is a Honda Insight I own but dont use. This could do 3 litres per 100ks and weighed only 800 kgs. I have a trip to Balranald planned by Tes which I will put my ideas to test.
WhiteStar
Member
With the utmost respect for your experimental explorations, I think you may be trying to achieve what is already being achieved with Torque Sleep without any driver intervention in both D and non-D vehicles.
The alternative would be to just use AP and relax but then I know sometimes you need to take over and so I understand your curiosity but safety, stability & roadholding are way more important than gaining extra kilometres, so personally, I wouldn’t attempt it just like I won’t be drafting again for relatively small gains. In any case, once the planned SC’s are operational, there won’t be a need for any of this.
From memory, my best figures are something like 165 Wh/km @ ~100 km/h but that wasn’t the average for a whole hour. Then there are so many other variables apart from speed: gradient & elevation, wind direction & velocity, total passenger & cargo weight, barometric pressure, external temperature, humidity
?), HVAC settings, tire type & pressure, rolling resistance (as you say), road surface & quality, vehicle model & age, etc. all have an effect to varying degrees…but then I think you already know all of this, being an EE
The alternative would be to just use AP and relax but then I know sometimes you need to take over and so I understand your curiosity but safety, stability & roadholding are way more important than gaining extra kilometres, so personally, I wouldn’t attempt it just like I won’t be drafting again for relatively small gains. In any case, once the planned SC’s are operational, there won’t be a need for any of this.
From memory, my best figures are something like 165 Wh/km @ ~100 km/h but that wasn’t the average for a whole hour. Then there are so many other variables apart from speed: gradient & elevation, wind direction & velocity, total passenger & cargo weight, barometric pressure, external temperature, humidity
?), HVAC settings, tire type & pressure, rolling resistance (as you say), road surface & quality, vehicle model & age, etc. all have an effect to varying degrees…but then I think you already know all of this, being an EE 
Really, who cares. I have a V8 and churn through the juice but it serves a purpose. I have a hybrid which saves fuel around town (not on the open roads) and the fuel saving won't justify the original purchase price, but the wife wanted it. I have a Tesla which costs literally nothing in fuel (I use SC's) but even if I had to pay I would have still bought the vehicle due to other factors. If range anxiety is a problem, then plan your trips allowing for stops that will obviously take longer than filling a tank of petrol. If that doesn't suit then an EV (currently) is probably not a mode of transport you should consider.
As to coasting in neutral - why bother? I can't see any advantage or reason or need imho.
As to coasting in neutral - why bother? I can't see any advantage or reason or need imho.
garyjac
Member
Exactly so. fwiw, I drive a 70 and the best energy economy on a trip was 152 Wh/km (around 15.2 kWh/100km). Around 215 km trip. Cost (well, zero, given solar power), but at T11 rates around $7. Just another reason to own a Tesla, but not a selling point on its own, unless a payback period of 90 years appeals to you :wink:
Based on that theory the 90year payback is substantially better than the impossibility of payback on the ice comparison.
EcoCloudIT
Active Member
I have a 70 and even with the 21"s I have also achieved (easily without trying) 153 Wh/km over 100km+
To note, it wasn't raining, fairly flat (or as many downs as ups), no strong winds that I could detect.
-ECIT
To note, it wasn't raining, fairly flat (or as many downs as ups), no strong winds that I could detect.
-ECIT
garyjac
Member
No argument about the "payback" on ICE cars... The trip I mentioned above was up and down a mountain range (but not the exact same road), so a few more than usual losses. I put it down to the AP, since I don't drive that smoothly.
The trip I mentioned above was up and down a mountain range (but not the exact same road), so a few more than usual losses. I put it down to the AP, since I don't drive that smoothly.
Miggy
Member
WhiteStar
Member
Interestingly MPGe (miles per gallon equivalent) is a thing but I agree it has less or zero meaning for those who don’t figure or have forgotten MPG. It was introduced by the EPA in 2010 as a means of comparing efficiencies of ICE vehicles with alternative fuel & electric vehicles in the US. This calculates 33.7 kWh being equivalent to 1 gallon of petrol. For example, a 90D is rated at 100 MPGe or about 210 Wh/km.
Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia
Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia
On my recent return trip from Melb to Syd I was able to test my techniques on quiet side roads the parallel the Hume Freeway. The roads are reasonably flat Wodonga to Wang, The best result was 8 kWhrs per 100ks meaning a theoretical range on 80kWhrs of 1000ks. The technique was to accel up to 75ks back off & put the car into neutral down to 45-50 ks & repeat. Measured over 10ks. Not practical for most folk I know but if you are ever low on "gas" (sorry Miggy) this might help you get to your destination. I once drove from Melb to Syd rtn on a tank of distillate as the oil companies call it in my Peugeot 406HDI which has an 80 litre tank. I ran up to 75ks & coasted down to about 50ks but didnt turn the engine off as the power steering & brakes need a running engine.
baillies
Member
I am not condoning this as it is dangerous (and sometimes unlawful) to drive so far below the speed limit unless you really need the range but I think you should calculate your average speed and repeat as a constant speed. Note that wind speed and direction will have a large impact so without controlling for this it is not possible to completely compare results.
I guess you already know but you maybe interested in these posts from tesla
Driving Range for the Model S Family
Model S Efficiency and Range
Also you could check the various record attempts including Björns YouTube video and he has various others trying to check range but the error is often too large. There are lots of blog posts as well.
It is possible that your method is better than constant speed due to torque sleep of both motors during idle (not certain this occurs although rear motor should and is software version dependant) but the wind resistance at the higher speed is also an issue. I am sure Tesla could run a simulation which would give a more definitive answer without the vagaries of wind, traffic, battery temp etc.
I think most Tesla owners are more interested in getting to the destination than worrying about driving so slow and especially with the on off acceleration. Would be much easier to use autopilot at a low speed and watch the rear view to avoid pissing off following traffic.
Another theory is to travel at the speed of your next charge so if you can charge with 3 phase and dual chargers you are better off at a higher speed, especially if you can eat etc whilst charging.
I guess you already know but you maybe interested in these posts from tesla
Driving Range for the Model S Family
Model S Efficiency and Range
Also you could check the various record attempts including Björns YouTube video and he has various others trying to check range but the error is often too large. There are lots of blog posts as well.
It is possible that your method is better than constant speed due to torque sleep of both motors during idle (not certain this occurs although rear motor should and is software version dependant) but the wind resistance at the higher speed is also an issue. I am sure Tesla could run a simulation which would give a more definitive answer without the vagaries of wind, traffic, battery temp etc.
I think most Tesla owners are more interested in getting to the destination than worrying about driving so slow and especially with the on off acceleration. Would be much easier to use autopilot at a low speed and watch the rear view to avoid pissing off following traffic.
Another theory is to travel at the speed of your next charge so if you can charge with 3 phase and dual chargers you are better off at a higher speed, especially if you can eat etc whilst charging.
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