Solar Powered Electric Vehicle

As I’ve met people and shared the my story, I kept getting the same question around Lithium mining and recyling.

“Electric cars have all these lithium batteries. Isn’t lithium mining and recycling hazardous and bad for the environment?”

Here are my thoughts on this topic. Whether we like it or not, battery technology is here to stay, think about how many electronics gadgets we have in our lives these days. The IPADs, iPhones, android phones, music players, GPS devices, laptops, etc. All these devices contain lithium batteries. And we get new ones every year or two! What do we do with all these batteries? The question is not whether the electric car will contribute much more to the pollutions associated with mining and recylcing lithium batteries, but how we go about engineering a solution for the safe mining and recycling of all these batteries that are in our lives.

I came across a very useful resource on Electric cars (http://electric-cars-are-for-girls.com). This page talks about the different kinds of lithium batteries and how mining lithium is a pretty safe process. Lithium Battery Article

Here are some recent shots of my lithium cells in the front compartment and rear compartment:

If you ever get inspired to want to install solar panels. Here’s a site that does a great job explaining step by step how to do it yourself. Bill Crozier (the owner of the site) takes Do-it-yourself to another level!

Installing solar panels

It took about 2 weekends to repair the damages caused by the CV drive shaft coming loose. I had to first take all the batteries in the rear compartment out. Then take the motor and transmission assembly out so that I can clean the oil out of the damaged section on the transmission for welding repair.

After talking to the owner at a local transmission shop Pete’s Gear Shop and my welder friend, I decided to epoxy weld (JB weld) the cracked transmission case instead of doing an aluminum weld repair.

First, I had to drain out the transmission oil completely, then use brake cleaner to clean out the area to be welded (be careful with brake cleaner, it is nasty stuff.)

Once that’s done, sand the area with some coarse sand paper and then apply the 2 part epoxy.

I also had to order a new CV shaft since the old one had a crack in the mounting plate and had lost its cover.

I also had to replace the cracked differential oil seal.

Repaired motor/transmission assembly ready to be mounted again!

The JB weld repair worked surprisingly well based on my past month of driving.

Since I had to take apart everything for the repair. I took the opportunity to make some improvements to the car that had been on my todo list:
1. Got the stock tachometer working to display the motor RPM, this actually was harder then I thought it would be, see below for details.
2. I installed a modified curtis 1231C controller that is capable of outputing a max of 750amps of current compared to 500amps stock. This theoretically gives me 190 ft-lbs of take off torque as opposed to 110 ft-lbs. The car performs much better than before!
3. Ran wires for remote trunk open and keyless door entry and alarm. Now the car is much more convenient to drive!
4. I also found the check engine light signal wire and connected it to the motor overheat switch so that if the motor ever overheats, the check engine light will come on to let me know.

Tachometer:
I purchased this speed sensor kit to drive my stock tachometer. My Advanced DC FB4001A motor has an auxilary shaft that I can use to signal the speed sensor. Here are some pictures of the mounts that I made for the speed sensor.

After wiring everything up, it took a while to figure out that the signal generated by the speed sensor is too low to drive the stock tachometer because the stock gauge took a much higher amp gain signal from the igniter. I got some tips from this MR2 forum to change out a couple of the resistors on the tachometer and it works!

I had to modify the stock tachometer by replacing the largest resistor 33K to 20k and the second largest resistor 30k to 10k.

After getting it to work, I calibrated the tachometer with an inexpensive digital tachometer from amazon

750A controller
My controller is mounted inside the rear compartment on the passenger side of the car where the original fan driven air intake used to be.

The controller itself is mounted on an aluminum plate that has a 12V DC fan mounted on the other side.

The fan is on whenever the ignition is on.

Check Engine light signal wire found and wired to the motor overheat switch.

So I thought the transmission leak was just from a damaged oil seal… There is more. As I more closely inspected the area around drive shaft, I noticed a couple of cracks in the transmission housing.

Looks like I will be working on this thing for a bit longer… If I’d only torqued the nuts on properly when I put the thing back together 6 months ago…

After getting the electric MR2 up on jack stands in my garage, I found that the driver side drive shaft is missing the m8 1.25mm serration bolts (6 of them) and nuts. I looked all over the web and the local Kragens and Autozone stores for replacements and came up empty. I finally ordered some from the Toyota dealer in Dublin, $4 each and they came next day, not so bad, but there is more…

The driver side drive shaft has also been damaged. Pictured below, you can see the broken bolt hole. There is also supposed to be a plate on top of the tripod housing I think.

I will head out to the salvage yard to look for a replacement. The other bad news is that the differential gear shaft seal is damaged. That explains the oil leak. In the meantime, I’ve rebolted the drive shaft back to the differential and can drive the car for short distances without worrying about loosing too much transmission fluid.

Again, thinking back, I remember that torquing the bolts on the drive shaft was a pain because I had to get under the car to tighten after I’ve engaged the parking brakes. However, to reach all 12 nuts (6 on each side), I had to get out from underneath the car, release the parking brake, and turn the shaft so that I can reach the next set of bolts, etc. Perhaps it was because of this that I had failed to tighten all 6 bolts. I’m going over all the nuts and bolts all over the car just to make sure that I didn’t forget to tighten anything else.

On my way home from work, I heard a sound that resembled change falling out of my pockets coming from underneath the car… For some reason, I immediately thought, “oh crap, the bolts that I used to bolt the battery racks on the bottom of the car must have unthreaded themselves!”, and pulled off right away to a parking lot. It was good that I did that, because as soon as I got to the lot, the car stopped moving. I got out of the car and saw this:

The rear draft shaft on the driver side had disconnected from the differential on the transmission!! I am so glad that I caught this before I headed on the freeway. The 6 bolts that held the shaft to the transmission are all gone and left a leaky mess. I ended up towing the car home for $165.

Thinking back, I torqued the bolts to 27 ft-lbs as suggested by the Hayne’s repair manual, but googling last night I found this:
Toyota Torque Specs
Which suggested a torque spec of 48 ft-lbs. My EV friends suggested that I put some Loctite on the threads to prevent this from happending in the future. I will do that! And thank God I’m safe and there is not more serious damage…

Here are some random photos of the electric car charging at one of those ChargePoint chargers using the high voltage, level 2 port, with the J1772 adaptor. I’ve charged at the Pleasanton Stoneridge Mall, Hayward Walgreens, and SFO airport.

With the knowledge of my new limited range, I need to find charging stations around the bay area to extend my range. The good news is that there is plenty of free charging around the bay area. San Francisco has announced that it will charge EVs for free in public garages until 2013, READ HERE

I’ve charged a couple of times at San Francisco International Airport.

The chargers in San Francisco seems to be mostly run by Chargepoint. I needed to apply for an access card that unlocks the stations that I want to use.

Also, since I use a Nema L15-30 plug for 220V charging and these stations are using the new EV standard SAE J1772 connectors, I ordered an adapter box so that the car can accept SAE J1772 connectors at these stations from Tucson EV.

Here’s another source for the connectors and adapters.
CurrentEVTech

Here are a few links on lists of charging stations through out the US/Bay Area.
EV Charger News
The EV Project
www.afdc.energy.gov

I’ve also downloaded the following Android apps to help me locate charging stations. Look for them on your phone!
Car Stations
Chargepoint
Blink

Now that it’s getting dark early, my ammeter display has not been visible on the drive home from work. Also the original dash lights were also not working, so reading the dashboard was difficult. I purchased some LED bulbs from autolumination.com
and now I have a lighted dash and light ammeter.

I also replaced the analog voltmeter with an EV display 2, which tracks state of charge using Coulomb counting, pack voltage, and a bunch of other power stats per suggestion from my EV friend Honn. It has been great for tracking my energy usage.

A update on my range. With the new data from the EV display, I’ve determined that I use about 2.15Ah per mile on average in my daily commute. The battery pack is 144 V nominal, so the power usage per mile is ~310wh/mi (2.15Ah * 144 V). This seems in line with what other EV’ers are reporting for their conversions. Since I do not want to shorten the life of the batteries, I do not want to discharge more than 80% of the pack. With an 180Ah pack, the effective range is (180Ah/2.15Ah)*.80 or 67 miles. Not as good as I had hoped with 80-100 miles, but at least it will get me to and from work with a bit of energy to spare.

According to the Sky energy battery manufacturer, cycle life is 2000 cycles if I discharge the batteries to 20% and 3000 cycles for a 30% depth of charge. With this information, I estimate that the battery pack, which costed me $10k should last me:

~134,000 miles if I discharge the batteries to 20% each time.
(180/2.15) *.80 *2000 = 133,953 miles.

~175,800 miles if I discharge the batteries to 30% each time.
(180/2.15) *.70 * 3000 = 175,814 miles.

Since my daily commute is only about 50 miles, I am well within the 30% discharge depth daily of 58 miles, these batteries should last me a long while.

Here is a compelling calculation for those of you that are contemplating the purchase of solar panels.

We purchased our 3.6KW solar panels almost 4 years ago for a net cost of $22,500 after tax incentives. In the 4 years, we’ve saved an average of $90 per month on normal electricity usage.
That’s $1080/year savings. At that rate, we would have the panels paid off in 20 years. Commuting daily for about 50 miles in my electric car, we are saving an additional $120 per month on gas, that’s an added ~$1400/year savings. Including the gas savings from the car, the panel payoff accelerates to 9 years. I am now tracking the actual payback of the solar panels here:

Solar Payoff Progress

I am contemplating the sale of my 2009 Corolla S and purchasing an all electric Nissan Leaf for my wife. Assume she commutes for the same distance daily, our payoff should accelerate to 5 years.