Does anyone have good literature/references to suggest for such application ? My initial plan is to get an industrial VFD with full vector control ( like cerus industrial S series or something ) and a motor with aluminium casing off of eBay, try get them to work on the bench and mount it in my donor car. Most of the industrial drives take 3-phase 380-480V power supply, but internally they all should have a DC rail that i can supply battery pack voltage directly to, right ? Im planning to use a pack of regular car batteries to get things going at first with far future plans to maybe get li-ion with supercaps in there.
This would be a very interesting project, it makes somes sense to me, not that I know much. Please keep us posted. Just 20 batteries could give you 240V.
Your going to need a very big drive, all the big drives are 380 volt which means a 600v dc bus so lots of batteries as well. I assume your keeping the original engine as well. You will most likely find it's cheaper to buy hybrid car than try and make one.
Keeping the original engine for what ? My donor actually does not have the running engine. Im ( initally ) keeping the gearbox for easier transmission setup and mounting. I dont think 600v DC bus is absolutely required,
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these for example are running on
400v. I might need to go with small SLA batteries instead still.
There is an ongoing discussion with lots of good (and some really bad) information and ideas on the group:
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The motor should be at least 20 HP and probably 40 HP is ideal for a 3000 lb vehicle. I am a big fan of 3 phase induction motors, and I have rewound a few motors for low voltage (about 8 VAC). You should probably get something like an 1800 (4 pole) or 1200 (6 pole) RPM motor for more torque, and you can V/F it for 2x or 3x. You will need a DC bus about 1.5 times the motor VAC rating, so a 208/240 VAC motor would require less batteries (380 VDC), but that's still about 30 12 VDC batteries, and the high voltages are a bit risky.
It would probably cost somewhere around $1000 to rewind a 20-40 HP motor for lower voltage, and you may be able to get 2x, 3x, or even more HP by using a V/F drive, and you might get by with a 10-15 HP motor. However, the controller would need to be specially designed.
Another option is to use inverters to boost 12 VDC to 120 VAC and then rectify that to get 180 VDC. I've seen 2000 Watt (3 HP) inverters at Harbor Freight for $149. Four of these would give you 12 HP continuous, and a 720 VDC bus, which would be perfect for a 480 VAC V/F drive. You would need some rather large capacitors for acceleration surges of a few seconds, or maybe a second bank of much smaller batteries. A 5 second surge of 12000 watts is 60000 W-Sec. Regular capacitors are about 0.3 cubic inches per Joule, and this capacitor pack would be about a 4 foot cube costing about $15,000. Super capacitors are about 0.015 cubic inch per joule, so you would have about a 1 foot cube costing about $8000. You could make a bank of 200 3.6V 2 A-H Lithium Ion batteries for about $3200, or 60 7 A-H 12 V SLA batteries for about $900. These would provide additional storage capacity of 1400 W-H and 5000 W-H respectively. The main four 12 V 100 A-H batteries would provide 4800 W-H. You probably use an average of about 5 HP (7 kW) at highway speeds, so you will get about 1 hour running time without regen, and maybe twice that if you can store the energy on downhills and braking.
I know I have reversed my original idea of a special low voltage motor and controller, but the high voltage inverter option uses standard components. This will save the cost of motor rewinding and controller engineering. For a production vehicle, however, I think the low voltage design will be better.
For some quick figures on vehicle power, torque, acceleration, top speed, etc., try my Excel spreadsheet at
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There is also a more sophisticated (but harder to use) on-line calculator specifically or EV conversions. See the SEV newsgroup for the link.
Just wanted to say big thanks for all the useful info, it'll take a while before i dig through all this. Im thinking of going the low voltage route, because i had plans of doing my own controller eventually anyway, might as well bite the bullet now. Time to look up prices on Freescale DSP56F80x devkits i guess.
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