> On Sun, May 25, 2008 at 03:35:44PM -0400, Harold Hallikainen wrote:
>> When I attempt to do high power electronics, I tend to generate a lot of
>> smoke and dead parts. Good luck on the controller!
>
> Thanks. What do you find is the typical cause of the release of the "magic
> smoke"?
>

I think the chief cause is inexperience in design of high power circuitry.
I used to work in broadcast and could keep 20kW stations running, bud did
not have to design the transmitters.


>> 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.
>
> Again did you ground it to the chassis?

The high voltage string was isolated from the chassis. The negative side
of the 12V was connected to the chassis.

>
>> 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.
>
> Interesting. Did you do empirical measurements to figure out the current
> draw on the cable?

Yes... A clamp on DC ammeter was used to come up with a scaling factor.


>
> Also how exactly did the individual PIC monitors affect the overall state
> of charging? You only dumped charge current at the top of the string,
> right? So if some batteries were above the set point and others were
> below,
> then what did the overal charging system do?

There was one of these monitor and charge balancing boards on each
battery, so power was dumped on each battery that had excessive voltage.
Something I did not mention before is that the circuit boards are mounted
on the negative side of each battery. I used a TO-220 resistor for the
power dump. The thermal path heat sunk the resistor to the battery
negative terminal, since it has a lot of mass.

Harold

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