Where Rubber Meets the Road: 217.8 MPGe

So much for all the estimates, equations and calculations, they’re great estimators but truly utter B.S. until rubber hits the road and you see what you and your vehicle are actually made of. We now know exactly how far Seven can go on a charge….more or less, that is.

I was feeling a bit adventurous this past Sunday and decided to take Seven out on a range test. What would be the best way to do a range test…on a closed course? With a chase vehicle and trailer? With a support crew? On a smooth level road with no stops? Driving the same distance in opposite directions to account for hills, wind, road conditions, etc.?

Well, yes, most of those would probably be advisable…however, knowing me by now you probably guessed I didn’t do any of those, except for the driving in both directions to account for wind and road conditions. I just hopped in the car and headed off toward the highway. After driving about 2 miles remembered to reset the tripometer…oops. Ok, so, I take off heading south on I-55 from my hometown toward St. Louis, stopping and turning at exit 23 (didn’t want to hit St. Louis traffic) and heading back North. Made it up to Springfield and turned back around. Made it to Carlinville and turned around again to head back home with about 175 miles on the tripometer.

Things we’re looking great, 17.5% state of charge left, enough to go another 35 miles and I had about 25 to get home. At about 192 miles things started getting interesting. I was paying close attention to my state of charge on our Victron gauge, at this point I also started watching voltage. Voltage tends to drop as the pack gets low on charge and you can go just so low in voltage before damaging the batteries. I’m not 100% sure what that voltage is. I know what it’s supposed to be…but again that whole number and calculation B.S. factor to …well factor in.

So anyway at about 192 miles the voltage started dropping…280…278…270…260…249…235…. “OH SHIT!” I thought. Well, 240V was our cut off point and over the past 4 miles the pack just dropped more than in the last 192 miles combined!! “I’m running on battery fumes,” is what I was thinking, and I really didn’t want to start smelling them. Our batteries are great and terrible at the same time, they’ll give power as long as you ask for it, even if it kills them, and that’s exactly what I didn’t want to do.

Now I have a dilemma. I ran off to do a range test without any support team and the only person I’ve been able to reach all morning is Dad, and he’s in Chicago…just a few hours away, and I’m still 3 to 4 miles from home but the meter still reads 10% state of charge.

Ends up the meter was right, however when you look at a graph of our battery discharge characteristics the last 10% is a lot like the last ¼ tank on your gas gauge, smaller than the other ¼’s. In our case the last 10% is actually about 2%(-ish, more testing required), and I was just finding out what that really meant as I rolled off the highway in “creep” mode hoping I’d be able to coast the few miles back home.

Um, well, yeah, that was a great idea and all but it left me 2.2 miles short…that’s a long push with a 3100 lb car. Next I thought, “wait, maybe if I let the batteries rest I’ll be able to get just a little more out of them” and it worked…200 feet farther down the road I had to stop. But that was it, I was done, no more go-go juice in the batteries, however, I did stop right in front of the cell phone tower the spot where I remembered to reset the tripometer, so that meant if I could drag the car home I’d know exactly how far it could go on a charge! Always an up side.

Enter Stage Left, Our Heroine:
Jen came to my rescue in her Pontiac Vibe armed with a tow strap. So, after a little tying off, away we went with Seven in tow. To make a long story short (oh wait, too late for that), we got her home and the odometer read 199.3 miles.

So, our range with a full pack is 199.3 miles…but wait, I thought we were getting about 230 MPGe on the highway??? What’s up with that?? Ends up we still had 6% charge on the batteries, also, we’ve never been able to cram more than 32.5 Kwhr’s into our pack…a gallon equivalent is 33.4 Kwhr’s. So, we got 199.3 miles on 94% of 32.5 Kwh (within the accuracy of our measuring devices) which we can now apply some of that B.S. math to with a bit more confidence and accuracy.

Why do I say that after calling it B.S? On the front end of any calculations you’re dealing with a lot of estimates and manufacturer guarantees, so your numbers reflect what you should get within the accuracy of the numbers you have to work with, which can vary greatly making any answer you get contain a degree of B.S. Now that we have actual numbers for range and state of charge our numbers should be far more accurate.

So, 32.5 is 97.3 % of 33.4, and 94% of that (our state of charge after the run) is 91.47%. 91.5% is what I’ll use to account for round off error.

That means to go 199.3 miles Seven used 91.5% of 1 gallon of gas. Using a ratio to find out how far Seven would have gone on a full gallon based on these numbers gives you 217.8 MPGe.

So, our range as of Sunday was 199.3 miles on a charge which equals about 217.8 MPGe

Not too shabby. Obviously not what we were originally hoping for or calculated, but we now have actual numbers to base our mileage on, not estimates or manufacturers guarantees, which, by the way, is the only thing usually available to anyone when they start this type of project, and you do the best with what you’re given. Facts are facts, after all.

Now that I’ve completely divulged all of the Illuminati’s top secret information, and given you the numbers needed to make whatever determinations/estimates you wish to run on our car, something new comes up. I drove Seven to and from work yesterday, on the way to work I drove the highway portion of my commute at about 65 mph without any fast accelerations or racing – just a normal drive. However, on my way home I was feeling a bit of the old ‘Need for Speed’!!! Peeling out of the EPA’s parking lot and continuing in that fashion until I got to the highway at which time 70 felt like crawling.

I met a fellow driver in a Toyota Spyder who apparently was feeling the same. After he took a quick pic of Seven on his iPhone, I motioned “wanna race???” And he nodded, with a smile, yepper, lets go. So, I hit the “gas” and zipped around a couple cars leaving the spyder somewhere behind me. I slowed down a bit and waited for him to catch up. The grin on his face was worth the tickets we didn’t get but probably had earned. With a huge smile he gave me the thumbs up and took another look at the car before waving ‘later’ and taking off to his exit.

My high spirited driving continued on the way home. I thought, “screw it, the pack’s full. I can have fun for about 150 miles before it goes dry driving it like this”.

Well I got home and checked the mileage and state of charge….???? I was confused. The numbers were pretty good. Some fast mental math (meaning round everything and it’s close enough to see if you see something interesting and want to grab the calculator and do some real math) and I wanted to grab the calculator and double check. The numbers were good…really good. I’d gone 59.4 miles and used 17% Sate of Charge. Knowing that we can hold 32.5 kwh, and 33.4 kwh is the amount of energy in a gallon of gas….has anyone figured it out yet??

Well, I’ll tell you, it comes out to 359.1 MPGe!!

Just when you thought it was safe to use math again (cue ominous music…Dum Dum Dum)

What does this actually tell us?? I’d like to tell you that, but other than it tells us we need to do more testing and that our data points thus far are limited (seeing we’ve only done one range test, one is a pretty limited set of numbers). So, again, what does it tell us?? It tells me that we may have a lot more potential in our car than we thought, or a gauge is acting up, or our batteries are more fully charged now and weren’t before, or or or…

Well, bottom line, you never know until rubber meets road, everything else is B.S., and we now also know that our best numbers so far tell us that we can get 359 MPGe but our best range so far is 199.3. How can both be true, only more testing will tell, however, we do know that both numbers fall easily within the range of our original calculations, so are they both possible, Yes. Are they repeatable??? We’ll find out. And again, Facts are Facts and we’ll keep giving you the best and all the info we have as we get it…whether it be B.S. calculations based on best available data or actual on the road testing on real highways and cities, under real traffic and weather conditions.

Until Next Time


Kevin Smith

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