Well, yes you could, but would it be under $33,000 ? and have similar components and electric range ?
Lets have a look. (disclaimer: this post turned into a fudged math laden beast in a hurry, all figures are estimates, but prices are real. I could be 100% fatally wrong about all of this :)
First, read up on the Volt here.
What do we have, a 4 passenger car, 16kw Lithium Ion battery pack, 53kw Generator (3 cyl turbo), 40 mile electric range and a price tag of $33,000 after a $7,500 rebate.
Ok, first things first. You’re not going to be able to buy a new car and gut it to become your Volt-beater (or Equal-er) that would be silly. A used car comparable to the volt could be had for around $4-6k depending on your budget or standards.
Rip out the engine and sell it, that’ll probably net you between $500-1000
Now, the main difference between what GM can build and sell thousands of and what you can do “on the cheap” in your garage is AC verses DC. The old argument goes that AC is more efficient, and DC can be more powerful. At least at the cost levels we’re talking about.
You’re going to want a DC setup; cheaper, nuff said. The Chevy Volt of course is 3 phase AC. For the purposes of moving a 3,000lb car from A-B there’s almost no difference. (in fact DC is cheaper to make faster of course, but more on that later.)
We’ll get to the motor, controller and batteries in a bit, right now I want to talk about the generator and how much that will cost, as its a pretty important part of the Volt package. The “main job” of the generator is to maintain the battery pack SOC (state of charge) at 30% to avoid over-discharge, shortening the battery life. (according to this link) Now depending on driving situation, the load on the batteries to maintain a constant speed is going to reach as high as 25kw accelerating moderately at freeway speeds.
Now I can’t figure out how the Chevy Volt generator is rated at 53kw, that must be a peak rating it can probably sustain for about 20 seconds or something. Most range-extenders are in the region of 8-15kw (my experience in this area is limited! please correct me if I’m wrong)
Where the volt has the advantage is that their generator is turbo’d. Nope, you can’t beat that.
A 15kw (22.5kw peak) portable gasoline genset will set you back about $2,500 (we’ll do some math later with the battery pack, and heres the killer, you can make it removable.)
(so we’re at roughly $6,500 so far assuming our car cost 5k and our engine netted us 1k)
Total so far is $28,825 not including shipping and possible taxes. Its looking ok for probably shaving a couple of grand off the volt’s price, but now you’ve got to design and build it too ;)
Ok, what about range and battery DOD (depth of discharge) with our 28.8kw battery pack and 15kw generator ?
28.8kwh / estimated 250wh (watt hours) per mile = a range of approximately 115 miles and a really dead battery (bad) so we’re going to aim for the same 30% constant SOC as the Volt (70% DOD) (giving us an all-electric range of about 80 miles)
That means we need to maintain the battery SOC at about 8.64kwh Now, can our 15kw generator handle this, say cruising at 60 mph ? I’m not sure on the math, but it probably doesn’t look good.
Different amp draws from the motor will be associated with acceleration (for 5-10 seconds) and cruising (constant)
Acceleration will likely draw upwards of 4-500 amps. (800+ if hard from a dead stop) but this will only be for a fraction of the operating time, so they will average out against the more constant draw of between (estimated) 100-150 amps while cruising at about 60 mph
If you hadn’t guessed theres a lot of fudging going on here. Unless we could pick a vehicle and nail down weight and wh/mile we wouldn’t know if we’ve equaled or beaten a volt at its game.
So, with a DC system voltage of 144v and a cruising ampereage of say 125 amps we’re sucking about 18kw of power. Our 15kw generator isn’t going to be able to maintain 30% SOC at this rate (it would have a fighting chance given its 22.5kw peak rating), so we’re going to have to revise our generator estimate, and its going to get more pricey.
But, again I’ve chosen a battery pack that is larger than the Volt’s perhaps if it where resized we could bring the price down.
If we could find some 100ah cells we halve the battery pack capacity and price and also the range. GM is using a battery pack that delivers 350v so that divided into 16kw gives us a 45ah figure. (?) And we could also up our system voltage and decrease weight with a 100ah pack to give us close to 160v (the motor max rated is 170v)
160v / 3.2v = 50 cells
160v x 100ah = tada! 16kwh
100ah cells at $130 a piece is $6,500
So our total minus the genset is $22,175
A generator capable of 20-22kw continuous is probably going to set you back about 3-4k. But I can’t find one. :( Cruising at 60mph with a 160v pack will (I think) draw less amps (the fact that we’re hauling less battery weight will mean improved efficiency 435lbs instead of 714lbs a difference of 279lbs), but I’m not sure probably only 20-30 less ? so we’ll be drawing about 16kw (160v x 100amps) Our regular 15kw genset would just about keep up with this (depending on how overloaded you want it for how long :), but you’d want one that could not break a sweat at 20kw.
Bottom line, its doable. Anybody who has more of a clue than me please let me know !
To be continued.