Byron Jeff clayton.edu> writes: > My goal is to build something that I can afford. I battle with the guys on > the DIYEV list all day long about investing tens of thousands of dollars > into lithium batteries. But it's an investment that doesn't make sense to me. So don't buy lithium. But why buy an immense golf cart battery stack? It will work for sure, in fact there is an ancient (circa 1900) electric truck (pickup) in the local technical museum. The bed is paved with lead acid batteries and there is a cover above it so it can take some cargo too. The entire body and cabin was made of wood, as expected, and the batteries were not 100Ahish from the size. It has been a long time since I saw it, I was a kid at the time. > Can't store a battery bank at work, which is the only logical place to > swap. The bottom line is that I'm stuck carrying the bank around. Why is it the only logical place to swap? And why swap if you only have one set? Swapping is an idea to keep in mind. Today you swap lead acid, tomorrow lithium or who knows what. You have to start somewhere, why not start small and see where it is going. > > Available data suggests 20-100 km range for curb weight << 1 ton. > > I'm well aware. The challenge is that to carry enough lead to get a useful > range, you exceed the GVWR of the vehicle. > > Trucks are designed to carry that kind of weight. True, they are also designed not to drive very fast and fuel efficiency was not quite so high on the priority list for US pickups afaik. Most electric cars aren't speed cars either. > OK. That's a start. Why kind of hardware is necessary to handle these issues? > I thought the dynamic braking and back EMF was handled by the freewheeling > diode? What freewheeling diode? Surely you know that most design topologies will not scale for a power level 1000 times greater than that of the original design? Please locate the relevant course curriculum at your university (you are on an edu domain) and see the reading list there for recommended articles and books. Try Google with: electric traction power electronics site:.edu filetype:pdf for >10k links. > > Plus the torque/rpm characteristics of usual electric motors are not > > suitable > for road traction use without some suitable controllers. The easiest hack is > to > > rely on the gearbox and implement a step relay that will shunt in more or > > fewer cells (tapped series stack). > > No. Bad idea. The one thing that I've learned in my research is that you'll > destroy the pack using that technique. Not if the voltage equalization devices work as deisgned (i.e. in *both* directions). > Series wound motors. Not going to do regen braking. That energy is just > going to be lost. Too bad. Literature seems to indicate compound or parallel motors with separate excitation are best for traction if using simple pwm controllers as you intend to use. > They are called Isolated Gates for a reason. What makes you think those > kickbacks are going to cross back into the gate? There is no need for the kickbacks to cross into the gate. You will have something like 200 Amps at 150 Volts switched (at pwm frequency if you do it your way) into a loop of wire at least a meter long with a coil of several Henrys at the other end (the motor) inside a reflective metal box, with harmonics into VHF and UHF. That will put enough volts into circuit board tracks nearby to glitch almost anything even without pwm. > Thanks for the encouragement! I just said what I know. I doubt whether the 'expensive' controler makers break even when the market is slow (like it seems to be all the time for some reason). > But I'm going to press on. Because at the end of the day my time is > currently worth less than my dollars. So if I can spend time solving these > problems instead of spending money, then I'll come out ahead in the end. That's a good excuse to buy, borrow most of the relevant books you can lay hands on. There is no point in rediscovering hot water or repeating other people's mistakes. You could make your own ^^ . Besides $100 in (used) books should get you further than $1600 in batteries at this time imho. $0.001 Peter -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist