Yeah I'm gonna agree with Lee here. I've been thinking about this for
years also, going as far as testing some ac powerline comm chips adapted
to DC power busses. I found it's impossible with all the noise coming
from the drive on an EV. But Lee, you don't even need a spectrum
analyser, just fire up your EV drive train, looking at any of the phases
with a oscilloscope. It's wide band noise, and the motor control is
modulating to operate the motor, but with sinewave drives, or even the
old PWM drives, there is noise during the entire cycle, and the only way
you get a quiet time is if you actually shut off and short the motor for
a brief period. But if you do that there will be high peak currents that
will not be good for the efficiency of the drive. If reliability is the
key, you will not want to use the DC busses, unless it's a low noise
application, and you can control and build all of the power devices,
like maybe a powerwall with a pure sinewave inverter, and you make the
charger (solar charge controller) and the inverter. But for motor
control, it's a difficult problem to solve.
Tim Economu
On 4/28/2020 6:48 PM, [email protected] wrote:
It sounds easy; but put a spectrum analyzer on your battery leads to see
what's*really* there. I think you'd be shocked at the noise level.
There are a few clever tricks you can employ. During charging, you can
have the charger pause for a regular "moment of silence" in which the
BMS can communicate quickly and in the clear without having to "shout"
over the charger PWM. Perhaps the same thing could occur to a lesser
extent with the inverter.
Same as above. Are you going to design a special charger that must be
used with your BMS?
There are lots of solutions that work*some* of the time. There are a
few that work*most* of the time. But it gets damnably difficult to find
schemes that work*all* of the time.
The problem is that a BMS is a safety system that you want to work*all*
of the time.
Lee Hart
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