jmead

90% of my driving is the same route, every day. I commute to school each day, 24 miles each way. The drive takes me about 25 minutes and costs me about $7 a day in fuel at todays gas prices. This is with and "fuel effecient sedan" EPA rated 32mpg highway. If you factor in oil, maintenence, and the depreciation over time of the vehicle each mile may cost considerably more than this. I spent $2300 on a pack of 12 PC1750 Hawker Odyssey sealed AGM batteries that are warrantied for 4 years free replacement. Assuming the pack lasts only those 4 years, my battery costs are $575 a year. When you add electricity to this ((5 recharges/week X 52wks) X 10kwh/charge X $0.10/kwh) = $252 in electricity "fuel" costs. Now, how many mpg do I need to get to match $827 in transportation costs for 12,480 miles for commuting? How much is peace of mind that you can afford to keep your job if gas hits $5, $6, $7, $8 a gallon worth?

That would be a very cool setup. Eliminate the diff, transmission, driveshaft. Plus you could use 2 smaller (cheaper) motors and still exceed the output of one large (expensive) motor. This would also allow for the batteries to be strategically placed as low as possible, with wiggle room to adjust the front/rear weight distribution to be balanced perfectly. The motor to half-shaft connection is the only problem, likely requiring belts or chains of some kind.

I am eager to see some NiZn cells actually become available for testing. The technical specs are impressive, especially the peak output per pound figures. It seems like the future of battery technology is very bright. Hopefully the marketplace becomes very competitive (as I'm sure it will) and we see price wars bring the cost down. Electric vehicles are right on the edge of being a cost per mile winner with high gas prices, but if capacity increases as price drops it won't even be a fair fight at that point.

I wouldn't hold your breath for a commercially available wheel motor any time soon. They have existed for decades, the problem unsprung weight and durability. The entirety of the assembly is subjected to the extreme vibration of a suspended wheel, as wheel as the shock associated with wheel hop, launch, etc. A normal motor as least has a mechanical gear reduction and several joints to dampen the extreme instantaneous forces encountered in an automotive application. Also, I don't believe 1500km for a second. 250wh/mi is a typical figure for a car with a standard series wound motor. These are typically ~85% efficient. Even with a wheel motor that is 95% efficient you're only talking a 10% improvement. That means 1500km (~900 miles) would take 202,000wh of battery capacity. At a current price of $1/wh thats a very expensive battery pack, not to mention a weight of something like 4,000lbs even with the highest tech lithium cells available.

Based on the 135ft-lbs of a transwarp 11, a 3.73 rear end would give you 504 ft-lbs to the wheels at 450 amps. The same vehicle with a transmission in first gear (assuming ~4:1 in first) would be over 2000 ft-lbs to the wheels. It'd be just like starting in forth, which I haven't tried, but I have accelerated from a stop in third and I certainly wouldn't want to do it pulling 3400 lbs behind me.

I've looked into this. The transmission tunnel narrows down so much between the seats that its just not possible. You'd either have to live with a driveshaft or flip the differential around and have the motor behind the wheels. This would require a new differential mount to be fabricated but would be interesting.

I know the project as a whole may appear complex, but if your break it down into little pieces there isn't anything that can't be accomplished with basic tools and skills. The hardest part in my opinion is fabricating the motor to transmission mounting plate. This is commonly outsourced and there are companies that specialize in this. I looked into having this done but they did not have a pattern on file for the Z car transmission. If there were to be enough interest I would even be up for putting together a kit tailored specifically for Z cars. With the major hurdles taken care of a conversion is little more than an engine swap, it could even be a weekend project.

The motor speed is completely under the control of the 1000A PWM controller shown in the upper left corner. I have a small potentiometer connected to the throttle that tells the controller how much juice to apply. I'm not using a clutch, and you've got it right. To shift I just let off the throttle and slowly apply pressure to the gear I'd like to shift to. I don't force it and it simply goes into gear when it is ready. Downshifting is a little harder, you need to rev up the motor and do the same thing, it engages when the rpms match. It took me a few days to get used to it but now all my shifts are smooth and grind free. Plus there is no need to shift when you come to a stop, so alot of the time its just like driving an automatic.

150 miles is a little optimistic unless you go lithium. I did find one example; http://www.evalbum.com/037 "Red Beastie" that can do 150 miles city, 120 highway. That is 2 strings of 20 6v flooded batteries. Total weight of "5,260 Pounds" http://www.evalbum.com/popupimg.php?2067

Very popular conversion, there are even companies that sell pre made motor adapter plates and stuff. Plus the ability to use lower rated components (6.7" motor instead of a 9", 72v controller instead of 144v, etc) would really keep the costs down alot. http://www.evalbum.com/type/GEO Lots of good examples there.

Very interesting. I never would have looked at something like that as a possibility. 480 is a bit much but there are ways of stepping it down, so I don't see any reason why not. 60hz isn't required, in fact, something like 400hz might be even better. Any idea of the amps one of those can put out?

Anything over 200 miles is beyond the capability of even cutting edge technology on battery power alone. With the affordable tech even 100 is near impossible, unless you design a car around the batteries (john wayland's truck "red beastie" can do 100 miles on lead acid I believe). I think the best bet for that range is a hybrid, similar to what I'm planning. You can't beat fuel for kw/lb. A BMW wagon would be a very cool project. Lots of room for batteries, but with alot more style than the rusty ford wagon that seems to be so common. Those LiFePO4 look very interesting, I had no idea they had made it to industrial use in forklifts and such yet. hopefully it won't be long before you can score them in junkyards and second hand with thousands of cycles remaining for a fraction of the cost new. It seems to me that LiFePO4 is the future, and we're on the verge of the transportation revolution because of it. They just need to crank up the production to millions of units and get the price down. I can't wait for the Lithium Z.

20,000 watts would require about 2000 square feet of solar panels, in bright sun. I think the most you could reasonably fit on a datsun would be around 40 sq ft. You could achieve that output with a diesel, but it would have to be about twice the size of the one I'm using. If I were building the car for sustained highway travel (at higher speeds) I'd probably go with a 3cyl metro engine. They put out about 50hp peak, so it would be comfortable running at a sustained 15-20kw. At this point there really isn't any advantage to electric though. Your taking fuel (chemical energy), converting it into rotary motion (mechanical energy), into electricity (electrical energy), and then using it to propel the car (mechanical energy). An electric really excels at city driving where your speed is always changing, lots of sitting motionless, quick stops followed by quick accelerations etc. Up to a couple hundred miles you may see some benefit because a percentage of the energy is still coming from the batteries instead of fuel, but you also have to consider the penalty of the increased weight and the energy conversion losses.

You just need a generator with an output sufficient to maintain whatever speed you want. For long distance highway travel I think about 20kw would be just right, which would require something like 30-40hp.

My motor has a turbo

I'm working on it. I'm finishing up painting all the fresh steel under the hood, re-wiring for the voltage upgrade, upgrading the whimpy 400A fuse to a 800A unit, and replacing the controller with a unit that gives me control over current limiting, throttle ramp, etc. Plus it might actually be legal to drive on the road after this afternoon! But that also means I'll only have 10 days to finish the rear brake upgrade, headlights, horn, and turn signal upgrade before I need to get it inspected. Long story short - More vids in a few days. I will be sure to record the first actual drive, and it would be priceless to capture the look on the guys face when he pops the hood to inspect it!

I now have protective boots around all the battery terminals. Bad things are much less likely to happen now. I will be getting my controller back in a few days (now with user adjustable current limit, throttle ramp rate). By that time I hope to finish the POR-15 treatment of all exposed steel, additional bracing/bracket for 13th battery, main contactor installation along with mid-pack 800A fuse, DC/DC converter installed and running 12v loads with a small battery to provide pull in for the main contactor to energize the other systems. I will then re-assemble the battery pack and hopefully take it to the strip. Then I shift my focus the charging/balancing stuff and the APU in the back.

I'll tell you a secret, the video of the "maiden voyage" isn't the actual first time it moved. When I realized I was close to that point I stayed up all night working on it. It was around 5am that I finished and I just had to see it move before I went to sleep. The video wasn't until the next morning when the camera woman was with me. I will post the log of all my expenses on the blog when I'm pretty sure its complete. Right now its around $6.5k.

In NY the temperature swings around alot, from 100s in the summer (sometimes) to below freezing in the winter. That is one reason I chose these particular batteries, unlike "flooded" lead acid batteries which actually have liquid inside of them that can freeze when discharged, the AGM have something more like a gel. They are much more cold tolerant than a normal EV battery. There are several tricks the EV folks have come up with to deal with cold conditions that you don't see on my conversion. Its pretty common to insulate the batteries with a layer of styrofoam insulation. The batteries have alot of mass, and therefore thermal mass, so as long as they start at a good temperature they will stay that temperature for a pretty long time. Long enough to do what you need to do and get it back in the garage. Another system (often used in conjunction with insulation) is to add small flexible self-adhesive sheet heaters to the pack. Sometimes this lines the bottom of the battery box, or sometimes stuck to each individual battery. A small thermostat keeps the batteries warm while it is plugged in so they are ready to go. As far as I know these aren't used while driving. Even batteries that don't like the cold will still work, they just don't give you as much usable energy when warm. In fact, EV drag racers use this same principal and heat their batteries up even more on purpose (through lots of high amp discharges and quick charges) to get them to produce even more current for their short runs. If you need 30 miles of range when cold all you need to do is plan things out so that you'll have 50 miles of range when warm. I am running all the accessories from the traction pack. I am in the process of installing a device called a DC/DC converter which takes the high voltage from the pack and turns it into the 12v needed. Compared to the huge amount of power needed to move the car (something like 100A at 156v on the highway) the draw of the headlights and such (maybe 2A from the pack) probably wont make a big difference. I decided it was better to add another battery to the big pack and use some of the total energy for the accessories than to have a battery just for them that will end up being barely discharged most of the time (dead weight). I'm planning on installing an electric heater. People often hack apart those 3000 watt space heaters and install the heating elements where the heater core used to be. They work equally well on AC or DC.

I've skirted around the issue because I'm not totally done with the charging setup. These batteries are capable of being charged incredibly quickly, even in less than 1/2 an hour if you could supply enough juice. It all comes down to how much energy you can safely draw from your source and controlling it while it is being fed to the pack. I am planning on charging at home from a 240vac 30amp circuit. Assuming I can get 25 amps of charge current actually making it into the batteries, my charge time for the 75 amp-hour pack will be around 3 hours. If I were charging from a 120vac 15amp circuit it might be closer to 5 or 6. This is for a 100% drained pack, if all you've done is drive it down to the grocery store you could probably replace that energy in just 15 minutes. Perhaps in the future I could upgrade to a 50 amp circuit and cut it down to a little over an hour. The electricity is fed into the whole string of batteries at first. But each one is slightly different and one will finish charging before the rest. I'm designing a system so that a battery monitor sees when this happens, shuts of bulk charging and then goes around with a smaller computer controller charger and tops each one up until they are all exactly 100% full. It isn't necessary to let this happen before you can drive it, its more of a background system to keep the batteries all happy and balanced without any work on my part.

No regen. It'd be nice but there is no 500+ amp controller available with regen, and they have a habit of dying an early death I've heard.

Voltage upgrade. I've purchased a 13th battery, making for a total of 156v now. This takes me from 144,000 watts to 156,000 watts, or 166hp mechanical (based on 80% efficiency). Total pack capacity is 11,700 watt-hours now from 10,800. I am in the process of welding in the new battery steel, painting the new steel surfaces with POR-15 to prevent them from ever rusting. I'm also installing the DC/DC converter to run all the 12v appliances from the 156v traction string. And I've found a drag strip within 7 miles of my house, perfect! Cruise to the strip, make a few blasts down the track, cruise home without dropping below 50% charge.

Yeah, I'm not a big fan of the xebra. Making slow, underpowered cars that just look like a novelty to most people does the image of electric cars a huge disservice in the long run. But I guess cheap transportation isn't a bad thing, and the more choices there are the better, even if I'd never be caught dead in one myself.

Not too worried about water, it wouldn't cause too many problems as it is not terribly conductive normally. Now, if salt water were to be dumped on the batteries that could be bad, but in that case each battery would short against itself and the exposed metal wouldn't pose any additional hazard. I do think you're right through, those terminal boots are the best solution. I am placing an order for 13 reds and 13 blacks as we speak. (While I only have 12 batteries at the moment my controller supports up to 13, so its just a matter of time before I need that extra anyhow, who could resist ~8% more power?)

Yeah, I don't like that either. I have already modified their placement a little bit, moved them closer to the middle, in order to minimize that risk. They are clamped down with several hundred pounds of force, as much as I was comfortable wouldn't crack the battery cases. I'm in the process of installing rubber strips between the clamp bars and the batteries which will compress, spread the force out, and hopefully ensure that the bolts do not loosen under vibration. Still, I think I would like further protection against this potentially catastrophic occurrence. My list of options: Weld cross pieces to lock the bars in alignment with one another, so even if one bolt should loosen there is no chance of the bar flopping around and coming in contact with a terminal Weld the bolts that hold them underneath the batteries perpendicular to the brace so that the threaded rod holding them resists movement in either direction Insulate the bars in some way (they are already slated to receive several coatings of POR-15, a rust inhibitor which is also non-conductive). Aesthetics are important and I can't think of any insulation which wont be ugly. Insulate the terminals so that even if the bars did come loose and make contact with a terminal there would be a layer of insulation. A dead short across multiple batteries would be very, very, very bad. They are rated to have a short circuit current of 3,500 amps. Pretty much enough to vaporize anything that gets in the way. I'd rather now find out what that looks like.