Re: I need help and newbie enquiry

["Steve" <steve43@starpower.net>]

A great book for EV construction and engineering is "The New Electric Vehicles" by Michael Hackleman from http://www.homepower.com/products.htm.  This was written several years ago now so doesn't cover the latest fuelcell information but is still a great introduction.

Steve Love steve43@starpower.net  

-----Original Message-----
From: Jon "Sheer" Pullen <sheer@sheer.org>
To: ev@listproc.sjsu.edu <ev@listproc.sjsu.edu>
Date: Thursday, November 29, 2001 7:38 PM
Subject: Re: I need help


>> I'm a student of mechanical-electric engineering
>> and I'd like to build a EV as part of my tesis .
>> I think to develop a bussines with the conversion to electric car in Peru
>> But I want to get more Knowledge about EV's before to doing it.
>> First I want to know What is the best DC or AC?
>
>Unfortunately, this isn't a question that can be easily answered. It's like
>asking 'Which is best, a car or a motorcycle'. The answer of course is that
>it depends on what you're trying to do. ;-)
>
>AC has several good points:
>
>    1) easy to perform 'regenetarive braking', which extends range (10-30%
>in stop and go driving) and the life of your brake pads.
>    2) No brushes, hence no arc-overs, flare-outs, or brush replacement to
>worry about
>    3) most AC drives are high voltage, which has pros and cons [see below]
>    4) AC drives are sometimes better built than DC drives. [in particular,
>the one I've got is rock solid]
>    5) because the inverter must be operational and performing decisions
>several hundred times a second for the drive to be spinning, a runaway
>condition is extremely unlikely
>    6) AC motors are simpler, and therefore less likely to break. They can
>also be easily sealed against the elements.
>    7) AC motors can withstand higher RPMS.. and in fact put out torque at
>higher RPMS.. AC motor power output can best be described as 'linear' ;-)
>
>DC has several good points:
>
>    1) DC drives are more common, and therefore cheaper
>    2) EV machinists are familiar with DC motors, and can more easily build
>adapters for them. [this may not even apply in your country, though]
>    3) DC drives can have more low-end torque more easily..
>    4) DC controllors are simpler, and therefore less likely to break.
>[well, you'd like to think so anyway ;-)]. Actually, the simplest DC
>controllor is just a collection of big relays!
>    5) DC systems tend to be lower voltage, which has its pros and cons
>
>Low voltage has a few good points
>
>    1) A mistake probebly won't kill you. Don't underestimate the value of
>this. My first EV was HV, but I'm used to working around high voltage, and
>young and foolish besides. If you're not familiar with electronics, do
>yourself a favor and build a LV EV first, because voltages > 200V can very
>easily be lethal.
>    2) It's the 'tried and true' way. You'll have lots of people to compare
>notes with when you have problems, and lots of chargers, fuses, breakers,
>battery level indicators, etc to choose from.
>
>High voltage has a few good points
>
>    1) The interconnects can be thinner, lowering the total weight of the
>car. [by maybe 50 lbs ;-)]
>    2) certain types of power electronics tend to be more efficient at
>higher voltages.
>    3) a high voltage series string of batteries is likely to give less
>headaches than a buddy-paired low voltage string. [this is my opinion
>anyway]
>    4) in my case, my drive gives me a set number of amps no matter what the
>voltage, so the higher the voltage I use, the more watts I can pump into the
>load - i.e. the faster the car gets up to speed. If you've driven a 'lead
>sled', you know that being able to dump watts in the drive to get out of the
>way of other cars is really nice. ;-)
>
>Now, the next question that will occur to you is what battery chemistry is
>best.
>
>There's _definately_ not a easy answer to that one. Read the list archives,
>we spend most of our time discussing this question  ;-) [or moaning about
>what peice of silicon we've let the smoke out of most recently..]
>