# wh/mile



## Rational (Nov 26, 2011)

dladd said:


> 306 Wh/mile


And if you cover a mile in 3 minutes (1/20 hr) you get 306 x 20 = 6120 w = ~8 hp. At 60 mph it'd be ~24 hp.

I guess it primarily depends on vehicle weight, effective cross section and how many times you go from a standing start.


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## major (Apr 4, 2008)

dladd said:


> I've started tracking my ah/mile usage a little bit (just two 5 mile trips in town so far) and want to make sure I have my math right. ah/mile x pack voltage = Wh/mile.
> 
> so in my case (on very limited data so far) I'm around 2 ah/mile, and have a nominal 153v pack. 2 x 153 = 306 Wh/mile.
> 
> ...


Hi dladd,

It appears correct to me for "nominal" calculations. Where and how do you measure Ah and/or Ah/mile?

Regards,

major


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## dladd (Jun 1, 2011)

My controller (synkromotive) shows ah used, and just the odometer for miles. It doesn't account for the dc/dc, but it's what I've got for now.

Eventually I'll have an EV display, but I'm waiting to see how the bluetooth display version looks.


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## dtbaker (Jan 5, 2008)

dladd said:


> so in my case (on very limited data so far) I'm around 2 ah/mile, and have a nominal 153v pack. 2 x 153 = 306 Wh/mile.



sounds like a reasonable ballpark.... but remember that your voltage is not 'nominal' all the time as it is likely higher and sags a little under heavy loads. Your consumption is probably a little higher, but not a lot, which sounds about right for a Saturn assuming normal suburban medium speed medium stop and go driving.


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## tomofreno (Mar 3, 2009)

Yep, that's the way it is usually estimated. As dt mentioned there is likely some voltage sag at higher currents which may pull the cells below their nominal voltage. It doesn't matter though as far as estimating energy per mile since the sag is due to voltage across some internal resistance of the cells which results in energy dissipation in the cells. The energy/time, or power, dissipated is equal the product of the voltage sag and the current. That energy isn't expended to do useful work - moving the car - but it is still energy/mile being used from the cells. You could use the lower, sagged, voltage of the pack to estimate energy per mile, which would give you a lower energy per mile and reflect the actual energy used for useful work, but of course if you tried to drive a range based on that you would run out of charge. Some people just record energy from the wall into the car which includes charger and cell losses during charging in addition to the above, or the total energy into the car per mile. My opinion is, report whatever you want, just specify what it is.


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## Rational (Nov 26, 2011)

dladd said:


> 306 Wh/mile.


For what vehicle + driver weight?

For ~2723 lbs, like the Tesla Roadster, your relative energy consumption would be 0.11 w-h/[mile-lb].


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## ElectriCar (Jun 15, 2008)

dladd said:


> My controller (synkromotive) shows ah used, and just the odometer for miles. It doesn't account for the dc/dc, but it's what I've got for now.
> 
> Eventually I'll have an EV display, but I'm waiting to see how the bluetooth display version looks.


I highly highly recommend the Cycle Analyst. It also comes in a large display format to display lots of data at once. It's an awesome device, gives you tons of data and isn't expensive. It's also very user friendly as in you can adjust it easily if something is not right, ie watts running up while no current is flowing or the speedometer/odometer measurement is off a bit.


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## dladd (Jun 1, 2011)

Thanks for the replies. I'll check out the Cycle Analyst, looks good at first glance. although I do really like that the EV display is non-invasive (no shunt).

It seems to me that AH/mile is my best estimator, since miles are easy to track, and my controller outputs AH used. The downside is that it is not at all comparable to other vehicles that's why I was wanting to convert it to the more universal Wh/mi, or the oem used mi/kWh. just wanting to verify I'm doing the math right.

I'll track it for a while and see how it looks. The biggest downside of using the controller outputted AH for a fuel gauge is that not only does it not include the accessory loads, but it doesn't 'see' the charger so I can't get any info on partial charges. It only reads discharge, then resets to full upon a complete charge. Better than nothing, but not a replacement for a full system amp hour counter.


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## Rational (Nov 26, 2011)

Some benchmarks

four wheeled electric vehicles 

Column key 
A	w-h/mile 
B	weight in lbs 
C	w-h/mile per pound of vehicle weight 
D	hp 
E	lb-ft torque 
F	top speed, mph 
G	zero to 60 mph time 
H	1/4 mile time 

A	B	C	D	E	F	G	H	notes
217	2723	0.080	248	200 tesla roadster
275	4800	0.057 truck
225 
340	3354	0.101	110	210 Nissan Leaf
240 
240 99	4.6 evS450, Varley
265 
300 
310 
320	3000	0.107 ptcruisin
325 
161	1250	0.129 
400 

278	=average w-h/mile 
0.095	=average w-h/mile per pound of vehicle weight 

3/4ths of the vehicles sampled did better than 
320	w-h/mile 
and better than 
0.107	w-h/mile-lb 

half the vehicles weighed between 
3354 
and 
2723 
pounds


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## frodus (Apr 12, 2008)

So, all of those Wh/mi measurements...... what speed are you using for a benchmark?


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## EVfun (Mar 14, 2010)

My Buggy runs about 200 watt hours per mile in city traffic. That is typically between 0 and 45 mph. Consumption goes up to about 300 watt hours per mile on the freeway holding the speeds between 55 and 65 mph. The buggy weighs around 1100 lb. and has a cd estimated to be somewhat over 0.6. Range is estimated based on amp hours to recharge (assuming 100% charge efficiency) and a pack voltage of 100 volts (3.125 vpc.)

I am currently increasing its battery pack from 32, 60 amp hour TS cells to 38, 60 amp hour TS cells. I also plan a front suspension rebuild as the 47 year old parts are getting a bit sloppy.


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## major (Apr 4, 2008)

Rational said:


> Some benchmarks
> ....C w-h/mile per pound of vehicle weight
> .....0.095 =average w-h/mile per pound of vehicle weight
> ........0.107 w-h/mile-lb


This is an example of useless statistics as far as I can tell.


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## Rational (Nov 26, 2011)

frodus said:


> So, all of those Wh/mi measurements...... what speed are you using for a benchmark?


Whatever average speeds all these vehicles ran at, which is probably pretty difficult to find out.
It's kind of a global average. If somebody has data at specific speeds that would be a more precise benchmark, but vehicles are hardly ever run at a constant speed.
Statistics has a summarizing function and can tell what percent of all vehicles did worse than or better than some selected point.
So far, it seems that if your vehicle uses 400 wh/mile or above it is certainly different from the crowd. That may be explainable or it may be an outlier.

Hardly anyone or any company I worked with or in used statistics, not even the basics, even though their companies could have benefited. 
It's only recently that ProPublica used them in a newspaper article to analyze patterns in Presidential pardons. Stats cannot tell what the truth is but it can certainly tell what are probably lies. And my using these methods is what got me illegally forced out of an agency that I worked for [even though this was supposedly my job]. I guess I haven't learned my lesson. 

I need practice with real data, so that's one motive for me being here. And this forum is unusual in that the members are very motivated to succeed. Their money is riding on it, literally.


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## dtbaker (Jan 5, 2008)

Rational said:


> Hardly anyone or any company I worked with or in used statistics,



???? maybe because you are picking strange things to attempt to correlate?
pleanty of people and companies use statistics, some to find patterns, some to create trends using criteria that fit results they want.

it all boils down to data, and whether it truely reflects what you are after. garbage in-garbage out is true no matter how smart you sound.


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## drgrieve (Apr 14, 2011)

A different approach would be to take published aerodynamic figures for vechicles and existing formuals to calculate expected Wh/mile for a given speed, assumed rolling resitance and drive train efficiency.

Sounds good? A spreadsheet that does this is on the forum. Just hasn't been updated for a while but for the cars I'm looking at I added them in easily enough.

Next step would be take peoples real world data and see if it matches up.


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## Rational (Nov 26, 2011)

EVfun said:


> My Buggy runs about 200 watt hours per mile in city traffic. That is typically between 0 and 45 mph. Consumption goes up to about 300 watt hours per mile on the freeway holding the speeds between 55 and 65 mph. The buggy weighs around 1100 lb. and has a cd estimated to be somewhat over 0.6. Range is estimated based on amp hours to recharge (assuming 100% charge efficiency) and a pack voltage of 100 volts (3.125 vpc.)
> 
> I am currently increasing its battery pack from 32, 60 amp hour TS cells to 38, 60 amp hour TS cells. I also plan a front suspension rebuild as the 47 year old parts are getting a bit sloppy.


Thanks, EV. Your addt'l numbers changed the overall outcomes somewhat. Of course, with more data the overall effect of each single data point is somewhat lessened.

275	=average w-h/mile 
0.133	=average w-h/mile per pound of vehicle weight 

3/4ths of the vehicles sampled did better than 
315	w-h/mile 
and better than 
0.155	w-h/mile-lb 

half the vehicles weighed between 
3177 
and 
1175 
pounds


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## coulombKid (Jan 10, 2009)

I see projects here where the dash displays show pack voltage and usage amps. For those of us coming from a micro-controller basics background it would seem that one would want to (round-robin) sample instantaneous pack voltage, current, and VSS pulse train then multiply them and then divide by the calculated (from VSS) current speedometer reading before sending the resultant watt-hours per mile figure to a stepper motor display. All three data streams should be logged to an SD card that can easily be pulled and analyzed back at the shop. Do any of the current display offerings give a true instantaneous watt-hour per mile usage read out. Standard moving average routines can take the jitter out of the displayed value. To me this would promote smart EV operation much like a common vacuum gauge did back in the ICE age.


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