Hi folks,

I'm kind of surprised that with the surge in fuel costs that a thread on
electric vehicles (EV) had not got jump started here.

I have questions at the bottom if you are not interested in the background.

I have the goal of quickly putting together a lead sled, a pickup full of
lead acid golf cart batteries, for daily driving in order to bring some
cost control to my transportation costs.

I'm well aware that there are a ton of other options, including lithium
based batteries. I'm also aware of the limitations. However, I'm determined
to get off gas for the regular commute in a cost effective manner.

If you're interested in seeing a video blog of an EV being put together go
to youtube and search for n2confusion. He has about 37 videos of the actual
destruction/reconstruction process of a lightweight EV.

Also there's a very active forum community at diyelectriccar.com. I'm
posting over there as ga2500ev.

An EV really isn't too terribly complicated, with only 4 major components:

1) Donor vehicle with manual transmission
2) Battery bank.
3) Electric Motor
4) Control, charging, and monitoring electronics

The first three are fairly stock entities with (so far) static costs. Find
a vechicle with a busted Internal Combustion Engine (ICE), pull the engine,
mate the electric motor to the transmission and hook up the battery bank to
the motor. My plan is to start this project with cheap available
components:

1) Still looking for a donor truck. Probably will end up with on off
craigslist. With a blown engine, it won't be more than $500.

2) Going to start with a battery bank consisting of Eveready GC2 Golf Cart
batteries from Sams. 6V, 225 Ah, $75 each. A 144V system of 24 batteries
will run $1650 + tax, no shipping and weigh about 1650 lbs.

3) Still searching for good availably and price. WarP 9's have 6 week or
more lead times and run in the $1700 to $1800 ballpark.

That leaves the electronics. From both a cost and integration standpoint
there's a lot to be left desired with control electronics. The major
subsystems:

1) PWM motor controller. Not a fundamentally complicated piece of
equipment. Accepts a limited number of control inputs (5k throttle pot,
brake switch) and controls via PWM a high powered switch between the
battery bank and the motor. An example is the Curtis 1231C controller:

http://www.electricvehiclesusa.com/product_p/co-1231c-8601.htm

I'm almost ready to choke on the $1400 price tag.

2) Battery charger. Again not too complicated for lead acid battery packs.
A lot of DIYers use individual chargers to each battery. But a decent charger
runs upwards of $800.

3) DC-DC converter. Takes the battery pack and replaces the alternator with
a converter.

4) Voltage and current monitoring. A lot of systems have separate current
monitoring for display and for the controller to prevent overstressing the
motor. The battery charger also requires voltage monitoring.

The prices for these components seem outrageous when you consider that the
core of most of these modules are high powered switches. IGBT modules such
as:

http://tinyurl.com/3t86km

Are available surplus for less than $50. These modules are more than stout
enough to handle both the controller and charging loads.

It seems to me that a DIY electronics builder could put together an
integrated controller/charger for a fraction of the cost of the commercial
equipment. I think my problem is the difference in understanding the theory
and the actual engineering.

Questions:

For the controller does the power electronics consists of more than the
IGBT, freewheeling diode, and smoothing cap bank?

Any suggestions for a freewheeling diode for a 144V x 600A controller?

Battery charging is a voltage/current limited charge dump. Presuming that
you have a 240VAC source, would the best control be to rectify to DC then
use a buck converter to get the correct voltage/current? If that's the case
then any suggestions on how to get an appropriate inductor? Same for the
DC/DC converter.

It seems to me that a significant cost in EV development could be greatly
reduced with the judicious application of DIY electronics. With PICs,
IGBTs, and a bit of knowledge, a complete electronics system for an EV
could be realized for a couple of hundred bucks instead of a couple of
thousand.

Thanks for reading. Look forward to any suggestions you may offer.

BAJ
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