July 18, 2008 by Rob.

I’ve been getting a FLOOD of email lately about EV conversions.  I’m happy to answer the email directly, but would be just as glad to have them as comments on the blog so other people can see the questions.  I’m planning to edit and publish the emails on the blog.  They are mostly the same:

• Should I convert my car to be an EV?  If you are passionate about change, not just to save gas.
• Should I buy an EV?  There are few real choices.  Aptera is the most interesting one, but not here yet.  I cannot recommend any NEV.
• I want an EV that goes 50 miles per charge.  Can I do that?  Yes, but it will be expensive (estimate $30k)
• Can you give me plans to convert my car?  Yes, read the blog.  It’s all in the history.
• Is the RAV4 a good EV choice?  Yes, but you need a manual transmission.
• I only have 1 car, should I convert that?  No, I don’t think you should rely on an EV as your only car.
• I have an exact budget using a kit.  What do you think?  Hmmm,  prepare for the unexpected.

(Aptera nose)

Posted in RAV4, Electric Vehicles, Storyline, Conversion, Planning | No Comments »

April 7, 2008 by Rob.

I got some questions from Mike R in Wellington NEW ZEALAND . I’m glad to help with the warning that, like most EV questions, answers will depend on your budget!

Here are the questions:

I am looking at the possibility of having a Toyota RAV4 professionally converted from petrol to electric and have spent some time searching the forums for information. I have a couple of questions you might be able to help me with:

1. In New Zealand most RAV4 petrol versions are automatic not manual. Is there any disadvantage if I used an automatic as a donor vehicle? Are all the manual or auto “bits” removed, or was the manual an essential part of the conversion?

Answer: Generally, EV conversions avoid automatic transmissions because they are tuned to shift at the wrong RPMs. Electric motors have a very different torque curve than an ICE. I’ve heard that you CAN convert an automatic, but it’s not that common. They are also heavier and less efficient.

However, if you are interested in an AC system ($$$) then you may be able to use a direct drive and eliminate the transmission. This is fairly common on rear wheel drive conversions (unfortunately, a RAV4 does not qualify as RWD). AC motors can support a wider RPM range and also support reverse. That makes it possible to omit a transmission. Unfortunately, AC systems are more expensive.

2. The same applies with 2WD and 4WD. Very few 2 wheel drives in NZ. Can an experienced mechanic remove the additional 4WD parts without a significant loss in efficiency?

Answer: I have no idea about eliminating the rear drive. I suspect that you could diasble the rear drive, but you’ll need to check with a mechanic. If possible, I’d avoid 4WD because of the extra mechanical load from the gearing.

Thank you for your help. It is a big step to take in New Zealand, as we are a long way from any RAV4-EV owners!

Regards

Mike R

Posted in Conversion, Planning | 4 Comments »

December 15, 2007 by Rob.

Someone asked me at a holiday party if I would do another conversion. It was not a simple question to answer now that I have a working EV. I would love the learning and discovery of converting another car, but I doubt that I will.

I’m am very glad to have an EV to drive and have gotten comfortable with it’s limitations. However, to repeat the experience, I would want to take it up a notch and go for an AC motor with lithium batteries. That type of system would run about $30k and I could not justify putting that into a beat-up glider. That means spending something like $20k (or more) for a nice car. I’m just not willing to spend $50k on a car no matter how green.

All this is subject to change since my 6 year old daughter has already informed me that we are building a car together when she is old enough to drive. How can I argue with that!

Posted in Storyline, Conversion, Planning | No Comments »

August 18, 2007 by Rob.

I’ve been trying to track how much power the RAVolt uses. This involves a new ritual where I walk through our spider invested side yard to read the cryptic meter dials every morning and evening. Without a dedicated meter, I’ve had to work out a rough balance between miles and hours of house use. I’m still refining the calculation, but I think it’s pretty close.

The results are that the RAVolt uses about 0.58 kwh of electricity for every mile I drive. If you read my earlier MPG conversion post, (33 kwh/gallon) / (0.58 kwh/mile) = 56 MPG. That’s based on the theoretical amount of 33 kwh of energy in a gallon of gas.

If you care more about $ then here is my savings over gas: 300%. At Austin Energy’s highest residential rate ($0.078/kwh), my commute works out to about 66 cents. My Volvo’s 20 MPG (of plus or premium gas) costs me about $2.50 for the same commute.

The graph below shows my attempt to figure out the mix of car (red) and house (blue) power use based on hours and miles. I ended up using a static 1.6 kw/hr estimate for the house usage. This is not perfect because temperature and time make a difference in the house power use, but it appears to be pretty accurate.

The graph below shows the match between my estimate of car load from the meter and actual miles driven. One deficiency is that I don’t factor temperature or difficulty of the driving into the calculation. Accuracy is nice, but not super critical: the information is just for my edification.

If you’ve got some statistical background, the graph below has some meaning: it shows the correlation between miles driven and estimated power use. Ideally, all the points would lie on the line showing a 100% correlation. This graph shows an even distribution and indicates that I’ve got a pretty good rough estimate.

Posted in Daily Use, Pictures, Storyline, Conversion, Planning | 2 Comments »

July 24, 2007 by Rob.

One of EVAmerica’s design recommendations is to use a relay on the pot box that open whenever the driver gets off the gas.  This is a safety feature because the relay turns off the positive contactor which kills power to the controller.  The safety feature is supposed to provide an emergency kill for the motor & controller if the driver lets go of the gas.  Apparently, on risk with DC systems is that a controller failure results in a short sending 100% of the traction voltage to the motor.  The effect would be the same as a stuck gas pedal and could be dangerous.  Sounds great in theory.

Unfortunately, this feature fights with the controller’s hardwired high pedal lockout (HPL) safety feature.  HPL ensures that controller does not go from 0 to 100% instantly if the driver has pressed on the gas when they turn the ignition key.  Imagine that I’m in a rush and I step on the gas and then turn the key.  There is no cranking start up like an ICE: the EV can launch like a rocket from it’s parking place.  To prevent this the controller will not start if the pedal input is too high.  Wow, another great safety feature!

Now, imagine that I’m stopped on a light at a hill.  The light changes and I step on the gas pedal fast to keep from rolling backwards.  The pedal relay activates the contactor which powers up the controller which then reads the pot box and starts the motor turning.  Most of the time the car follows this script and the controller’s solid state electronics start *nearly* instantly while the two mechanical relays appear to click instantly; however, I’m pressing the gas pedal down pretty fast on a hill.  In that case, the delays are enough that the pedal is too high when the controller wakes up so it goes into HPL mode.  The car is effectively dead and rolling backwards!

Without known the cause, I’ve been using the hand brake for hill starts.  It also happens while moving if I want to accelerate quickly.  Once I put all the pieces together it was easier to avoid, but still annoying and unsafe.  I’m considering alternatives for fixing the problem including eliminating the relay on the positive contactor, adding an override switch, or using the clutch position as an override.  I can’t disable the HPL feature of the Curtis.  I’m open to suggestions - just comment to this post.

Posted in Safety, Improvements, Conversion, Planning | 1 Comment »

July 14, 2007 by Rob.

Alex and I installed the air springs today. They are really just hard balloons that fit inside the rear springs. They don’t provide much extra lift because their max pressures is just 25 lbs. Even so, they did manage to lift the RAVolt a little and correct some of the wheel cant. This may work for a while, but I’ll need new springs eventually.

That’s a little better, but still canted.

Posted in Parts, Pictures, Conversion, Planning | 1 Comment »

July 9, 2007 by Rob.

I was reviewing my pre-parade punch list and I’m happy to say that I’ve completed everything critical on the list.  The only laggards are the p/s pump (which needs fixing) and replacing the under engine panels.  Those two items go together and will wait for a little while.

Posted in Storyline, Planning | No Comments »

July 9, 2007 by Rob.

Looking at the geometry of the rear suspension tie bars, it looks the the canting is due to the rear load. The picture overlay shows that more lift from the springs should definitely improve the wheel angle.

I’m ordering some RAV4 air springs ($65) to try and address the problem.

Posted in Parts, RAV4, Improvements, Pictures, Conversion, Planning | 1 Comment »

July 8, 2007 by Rob.

During my last few drives I noticed a very slight stutter.  It was noticeable mainly in the ammeter during acceleration because the needle would jump around while I was accelerating.  The dips matched bumps in the road so I suspected that some of the battery terminals were not bolted tightly.

A quick check of the batteries confirmed some loose(ish) connections.  A few which turns of the wrench seems to have fixed the problem on a short test drive.  I think some lock washers may be needed for a long term fix.

Posted in Improvements, Planning | No Comments »

July 5, 2007 by Rob.

The buzzing turn signal is caused because the flasher relay timer uses the resistance from the incandescent bulbs as part of the timing circuit (time = resistance * capacitance). The LEDs have a very different electrical characteristic so the timer does not work correctly. This was a clearly documented probability at the LED vendor’s web site.

The solution is to buy a replacement Flasher. I could not find the part # match: looking at the chart and actual relay I determined that the RAV’s replacement unit is CF13JL-02. I’m keeping my fingers crossed that this is the right $20 part to buy.

This blurry picture was taken blindly. It’s just below the steering column near the clutch peddle. The flasher (now buzzer) is the box on the right.

Posted in Parts, Pictures, Conversion, Planning | 2 Comments »