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Old July 11th 04, 03:35 AM
Aaron Coolidge
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Chris Kennedy wrote:

: 14v and change. Even if the set point was too high it doesn't explain
: the tendency to intermittently show discharge with spiking loads, nor
: the occasionally-observed behavior of a largely resistive load (turning
: on the landing lights) tripping the thing off (the working theory is
: that the halogens have a high cold inrush current but quickly settle
: down to a lower operating current -- quick enough that the regulator
: overshoots).

You are right about the high inrush for halogen (or, in fact, any
incandescent) lamp. Don't forget that the full name is "tungsten-halogen",
and the cold resistance of these 12V units is probably like 0.2 ohms.
Of course, the resistance rises as the filament temp goes up. Handling
tungsten inrush is a very tough job for switches, both mechanical and
solid-state.

Instead of a MOV across the gear motor, I would try zener diodes in inverse
series, say about 14V 5W units.

It could also be bad connections to your battery - the battery is supposed to
soak up the junk on the bus, as well as handle transient inrush currents.
Did you check the voltage drops across the battery ground braid, and the
master contactor? If you've got an oscilloscope current probe, check the
battery current when you get these OV trips. If the OV is reaching the
battery terminals its current should spike too. A 400 Hz current probe,
such as those sold by Sperry or Amprobe probably won't have the bandwidth
needed to see these transients. Where are you located?

--
Aaron Coolidge