Measuring Power - III

Well, it's Labor Day, the traditional Last Day of Summer in the USA. I've kept track of my electricity usage and trip distance all summer. Here is the result in graphical form (the blue bars are the distances of each trip; the red lines are the efficiency of each trip):

Unlike the earlier data, there is very definitely a correlation between trip length and efficiency. I'm measuring the actual electricity used to charge the vehicle. Plotting the data another way, and fitting a least-squares line to it, shows this correlation very well:


Basically, you can model the driving costs as 379 Wh/mi efficiency with a fixed 1.23 kWh cost per charge.

I drove 498 miles this summer, and used 244.3 kWh of electricity to charge it during that period (including the per-charge overhead). At 7.5 cents per kWh (my cost in Fort Collins, CO), that means I spent $18.32 on electricity to drive, at an average cost of 3.7 cents per mile. At $4.00 per gallon gasoline, this is the equivalent to about 109 miles per gallon.

Measuring Power - II

As the previous post indicates, I am now measuring the kWh used to charge the car. I've been keeping track of per-day costs, and here is the chart for the first couple of weeks. As you can see, the cost per mile does not correlate well with the miles driven - which means that the theory I had about the rebalancing contributing a major portion of the cost for short trips seems to be incorrect (at least, for the length of trip that I've been taking).

The gap in the chart is for when I watered the batteries - no miles on that charge, so no wH / mi.

Over this period, I have driven 111.4 miles, and used 54.9 kWh to recharge. This nets out to an average of 493 Wh / mi (as shown by the green line on the chart). My electricity costs 7.5 cents per kWh, which means my average cost per mile is 3.7 cents, which, at $4.00 per gallon, is the equivalent of 108 MPG.

Measuring Power

I've had many people ask, "how much does it cost to run your car" . So far, I've been unable to answer very accurately. I have a decent understanding of the Wh/mile performance - but that does not account for charging loss, running the fans, etc. So, I picked up this little device over at ekmmetering.com:


I then made a 24-inch long extension cord with this inline to see how well it works. Seems to be working well so far. If I continue to be happy with it, I'll get it mounted in the wall next to the 240V outlet (this extension cord thing is just a temporary kludge). I'll update this post later with the actual *measured* wall-to-road Wh/mile performance of my car.

June 3 2008 edit: I used 6.70 kWh to charge last night - roughly 50 cents worth of electricity. I drove 13.1 miles, which gives 489 wH/m - twice the cost I calculated from watts used while driving. This is likely because of the "finish" / "balancing" stage of charge, and also likely because I bet my tires need filling and my batteries need watering. I'll chart out this over the summer, and include significant maintenance events on the chart.

Replacing the Transmission Main Seal

Five months ago, when I first got the Volt914 on the road, I noticed a transmission fluid leak. Here is the kind of mess it would leave:


I spent today fixing it (better late than never!). After dropping the tranny (leaving the motor installed, with a jack supporting it), I popped the transmission main seal out with a slide hammer. Here is what it looks like on the back - no wonder it leaked!


Here is the new seal installed. I added a couple of other pictures at 914world if you're curious about the process.


While I had the tranny out, I also replaced the clutch on the theory that the tranny fluid would have impregnated and ruined the clutch disk. Which it did. The old disk is on the left, the new (not shiny!) disk is on the right:


I also took the opportunity to put new transmission drain plugs in (the old ones were fairly well stripped, you can see my adventures with them on 914world):


I took it for a quick spin around the block - I think the old oil-impregnated disk was slipping occasionally. I did not notice anything this time, but I'll keep my eye on it.

A Parade - Finally!

Some of you may remember that the original impetus behind me going 72 hours or so without sleep last fall was to have my car in the Colorado State University / Poudre School District Homecoming Parade. That, alas, was not to be. However, this Saturday, my car was in the Fort Collins Downtown Business Association's Saint Patrick's Day parade. I was part of the Debut Theatre Company entry - we won first place in Most Creative - it was a blast. The young lady standing and waving at the audience is named Paulina, and she will be playing Sleeping Beauty in Debut's production this May:


The car is plastered with magnetic signs, and the dragon head (my wife Jill's creation) on the hood is magnetically attached too.

Fixing suspension squeaks

I've been generally happy with the car - except for one thing: an increasingly annoying "popping" or "grinding" sound coming from the front passenger's suspension. The culprit turned out to be the A-arm bushings. I blogged the whole process on 914 World, but here are a few pictures. First, the A-arm before refurb:


The culprit - the old bearing and rusty bearing surfaces:


And the refurbished A-arm reinstalled:


The pops, squeaks, and grinds are all gone, and I'm going enjoy driving the car that much more...

Video Tour of the Volt914

A short video showing the main features of the Volt914, and giving a good sense of what it sounds like to drive around in it:



Youtube link