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Discussion Starter · #1 ·
Hi All - =


I'm new to the EV world (only just rode in one two weeks ago) but am in the=
process of buying one (yeah!). As I read some of the posts here, I'm a =
bit overwhelmed by some of the circuitry discussions, like installing an am=
meter, shunts, floating voltages ... etc. =


Is there a really good start to finish reference for understanding EV (or s=
imilar) circuitry anybody can recommend? =


Iread "Build Your Own Electric Vehicle" and have "Convert It!" and "The =
Zero-Carbon Car" ...but all seem kind of light oncircuit details.

Thanks,

Dan Gallagher
Ephrata PA


=

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Discussion Starter · #2 ·
Hi Dan,

Welcome to the group! I see you have been bitten by the bug 8^).

I actually would have recommended "Build Your Own Electric Vehicle" as one
of the more technical books I've seen, but you already have it. I would
also recommend paying close attention to the pages of "Convert It!" where
the circuit diagrams and their description are contained. There are subtle
points covered in those areas that need to sink in. (It took me two or
three tries).

This might sound strange, but I think your best reference might be the
archives of EVDL (this email list). In particular, I would recommend
paying attention to anything that Lee Hart has written. He has a good
mixture of theory, practical advice and good ideas on reliable techniques.
Roland also has good advice and techniques.

If you look up my posts, you will see some typical new owner issues and
questions that might be helpful. I've learned some of the lessons a little
bit the hard way but so far haven't blown up anything more expensive than a
meter. I don't have good advice yet. I have newbie questions that spawn
good advice.

I'm finding the fine points of hooking up the meters to be more touchy than
almost anything else I've done so far. Hooking up the main wiring between
batteries, controller and motor is simple compared to the meters.

Bottom-line, you need to understand how the parts will interact and react
that are connected to your high-voltage (150V in my case) traction pack.
Contactor, controller, pre-charge resistor, etc. are pretty well covered in
the books. The current shunt for the ammeter isn't mentioned so much.

Most ammeters actually measure a carefully calibrated 75 mV voltage range.
The shunt is designed so that it goes from 0V to 75 mV over its current
range. It is really a metal bar with a very low resistance in the middle.
The voltage is measured on both sides of the middle resistance. Using Ohm's
Law (V=3DIR) one can calculate that a voltage drop of 75 mV (0.075V) for a
200A draw requires the resistor to be .000375 ohms (.375 milliohms). =


The subtle point is that the sense wires connected to that shunt are also
carrying the voltage of the circuit at that point. Depending upon where the
shunt is installed, that can be full pack voltage. Lee provided a great way
to isolate the ammeter from this voltage.

I was the one that asked this question, but to be fair, I should point out
that I have owned and been driving my conversion for about 8 months. If
your electric car comes with instruments already installed (mine didn't),
you might be able to avoid this entire question.

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Daniel Gallagher
Sent: Friday, March 18, 2011 2:13 PM
To: [email protected]
Subject: [EVDL] Basic EV Electrical Circuits Reference

Hi All - =


I'm new to the EV world (only just rode in one two weeks ago) but am in the
process of buying one (yeah!). As I read some of the posts here, I'm a b=
it
overwhelmed by some of the circuitry discussions, like installing an
ammeter, shunts, floating voltages ... etc. =


Is there a really good start to finish reference for understanding EV (or
similar) circuitry anybody can recommend? =


Iread "Build Your Own Electric Vehicle" and have "Convert It!" and "The
Zero-Carbon Car" ...but all seem kind of light oncircuit details.

Thanks,

Dan Gallagher
Ephrata PA


=

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Discussion Starter · #3 ·
Hi Dan,
In addition to what Mike and Lee said, another great resource is diyelectricar.com -- http://www.diyelectriccar.com/forums/ -- the forums are quite useful and are packed with a lot of information. I (scarily) didn't buy any books when doing my conversion, but I had a lot of help from people on this list and the forums. One of the initial places I read was this page on DIY: http://www.diyelectriccar.com/forums/showthread.php/ev-information-669.html

corbin


Daniel Gallagher wrote:

> Hi All -
>
> I'm new to the EV world (only just rode in one two weeks ago) but am in the process of buying one (yeah!). As I read some of the posts here, I'm a bit overwhelmed by some of the circuitry discussions, like installing an ammeter, shunts, floating voltages ... etc.
>
> Is there a really good start to finish reference for understanding EV (or similar) circuitry anybody can recommend?
>
> I read "Build Your Own Electric Vehicle" and have "Convert It!" and "The Zero-Carbon Car" ... but all seem kind of light on circuit details.
>
> Thanks,
>
> Dan Gallagher
> Ephrata PA
>
>
>
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