Bill Dube via EV wrote:
The key is that the cell electronics are the simple part. They don't
have to be very sensitive or selective at all. They are just listening
to a a 100 kW radio station that is transmitting FM on its PWM carrier.
It is actually difficult _not_ to listen.
That's true. The problem is that this requires that the charger and
controller be designed together with the BMS. That works for a big auto
company. It does not work for small manufacturers or hobby EVs.
The transmission band can be in the high MHz, or low GHz band.
If it's in the low MHz range (AM radio), then switching transient from
the sharp-edged charger and controller interfere. Try operating an AM
radio in an EV with its antenna near the propulsion wiring.
If it's in the high MHz range (FM radio), then ringing and reflections
within the wiring will create ghosts and echoes. These force the data
rate way down into the range where controller and charger harmonics
cause trouble. Look at what happens to a TTL signal at the end of a 3
ft. piece of wire.
If it's in GHz range (cellphone frequencies), EV noise won't bother it.
But then transmission line effects will create peaks and nulls every few
inches.
All these problems are solvable if you throw enough engineering and
money at them. But it's not goiong to lead to a cheap simple system.
That's why everyone avoids using the propulsion wiring itself to carry
data. It's far cheaper and more reliable to run separate wires for data.
Lee Hart
--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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