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Re: Questions on Electric Vehicle high power electronics
by Harold Hallikainen-2
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When I attempt to do high power electronics, I tend to generate a lot of
smoke and dead parts. Good luck on the controller!
On the charger, I did a very simple one for an EV. The high voltage
battery circuitry is isolated from the chassis. The neutral of the AC line
is connected to the negative side of the battery string. Each phase (two
sides of a 240VAC line or thee phases of a 3 phase wye) goes through an
SCR, then are commoned, then go through an incandescent lamp to the
positive end of the battery string. The SCRs allow you to turn the charger
on and off. The incandescent lamp provides a current limit. By choosing
battery voltage and lamp, you can charge the battery string pretty simply.
The brightness of the lamp starts bright, then dims as the batteries
charge.
To power 12V equipment, I used a universal input switching supply (one
that takes 90VAC to 250VAC with no line voltage switch). It can be driven
directly by the battery string.
To monitor battery condition, I did a simple PIC based monitor on each
battery. It measures battery voltage, temperature, and current. Current is
measured by measuring the voltage drop on the cable going to the battery
"below" this one in the string. The monitor also has a big resistor and an
FET driven by the PIC. When the battery voltage gets too high, charge
current is shunted around the battery (power dumped into the resistor) by
PWMing the FET. If the battery voltage is higher than the set point, the
duty cycle is stepped up. If the battery voltage is below the set point,
the duty cycle is stepped down. Finally, the battery condition is reported
over an opto isolated "Aloha" network. Each unit randomly sends a packet
of data out its uart. The uart drives an opto where the LED is off in the
mark condition and on in the space conditions. The phototransistor on the
opto drives an open collector bus that is isolated from the PIC. The bus
drives another PIC that drives a display and control system that shows
battery condition and controls the charger (drives those SCRs).
This was done for a friend's EV. I ride the bus to work...
Harold
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smoke and dead parts. Good luck on the controller!
On the charger, I did a very simple one for an EV. The high voltage
battery circuitry is isolated from the chassis. The neutral of the AC line
is connected to the negative side of the battery string. Each phase (two
sides of a 240VAC line or thee phases of a 3 phase wye) goes through an
SCR, then are commoned, then go through an incandescent lamp to the
positive end of the battery string. The SCRs allow you to turn the charger
on and off. The incandescent lamp provides a current limit. By choosing
battery voltage and lamp, you can charge the battery string pretty simply.
The brightness of the lamp starts bright, then dims as the batteries
charge.
To power 12V equipment, I used a universal input switching supply (one
that takes 90VAC to 250VAC with no line voltage switch). It can be driven
directly by the battery string.
To monitor battery condition, I did a simple PIC based monitor on each
battery. It measures battery voltage, temperature, and current. Current is
measured by measuring the voltage drop on the cable going to the battery
"below" this one in the string. The monitor also has a big resistor and an
FET driven by the PIC. When the battery voltage gets too high, charge
current is shunted around the battery (power dumped into the resistor) by
PWMing the FET. If the battery voltage is higher than the set point, the
duty cycle is stepped up. If the battery voltage is below the set point,
the duty cycle is stepped down. Finally, the battery condition is reported
over an opto isolated "Aloha" network. Each unit randomly sends a packet
of data out its uart. The uart drives an opto where the LED is off in the
mark condition and on in the space conditions. The phototransistor on the
opto drives an open collector bus that is isolated from the PIC. The bus
drives another PIC that drives a display and control system that shows
battery condition and controls the charger (drives those SCRs).
This was done for a friend's EV. I ride the bus to work...
Harold
--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!
--
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
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