Daniel,
I read this entire thread and I have to say that I am very sorry for your EV conversion experience. I have done 2 EV conversions so far and I am offering EV conversions in Tampa Bay to people like you, who are fascinated by electric propulsion, but not DIY type.
I have taken many points from your experience with Paul of what NOT to do with my customers.
I applaud that you remained positive after all that experience, it takes a lot of character...
Biggest issues to learn from here is that it takes a lot more effort to build freeway capable EV with good range, much more than to build a decent EV. You got a decent EV , ridiculously overpriced, but decent EV, not freeway capable and not a lot of range, but still a decent EV conversion. Not much decency in Paul's behaviour towards you, but that it impossible to know up front unless you checked many references, sadly it doesn't sound like you did.
A lot has been said here of possible improvements, many things from people who never built an EV, although they tend to think they understand the challenge very well. With 2 EVs under my belt, recent one being practically the same specs as your Porsche, I can point out things that make a big difference and things that make very little difference.
Big things:
- 11" motor is a huge overkill for this car, it carries extra 50Lb of metal and eats huge current at acceleration, none of which is good for the range.
- Curtis controller is a huge underperformer, although it is very dependable, but not suitable for the specs of your EV
- any controller that puts out the power you need for freeway will have to be water cooled, especially if you keep that 11" monster of a motor
- starting in 3rd gear is a range killer, anyone who speaks of direct drive has no idea of currents involved, direct drive is possible, but not effective at all, you need gears, especially with air cooled DC motor, which doesn't have much useful RPM band.
- your battery config is OK, its not even close to promised range and was grossly miscalculated, but its the best for this car, you wouldn't get any better battery of LiFePo4 chemistry, unless you wanted to pay the premium for small cylindrical cells, but its not worth the trouble IMHO.
- the best possible DC conversion of this car would give you perhaps 80-90 miles of low freeway speed with modest driving style. So promised 120+ range was always out of the question, no matter what Paul was hoping for.
- it takes 2 times energy to travel at 70mph vs. 50mph, due to exponential nature of air drag, that's why I said that freeway capable EV is far far away from a decent around town EV.
Small things:
- changing AC and PS from belt to separate electric drives is not going to save you. Results will not be as impressive as cost and labor to implement them. PS pump does not waste energy while driving straight line, nor does AC unless its turned on. Mechanical losses in belt drive are so small compared to overall energy levels involved that its negligible.
Your best bet is to improve this EV with help of local EV club guys, get a better controller, at least consider what it would take to switch to smaller 9" Warp motor, this might be too much of mechanical work involved to adapt plates and shaft couplers.
Synkromotive controller is very promising , but I am not sure it can drive 11" motor at freeway speeds with air cooling.
I am a lucky beta tester of EVNetics controller, which would do the job perfectly, but only when water cooled and it still won't help with the range issue.
Also, I wanted to mention that your conversion should not cost more than $25K, although I am sure you paid Paul much more, unfortunately.
Hope this helps.
Dimitri
Clean Power Auto - Home Dimitri Butvinik's 2002 Mazda E-Protege5
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