kenneth house:
There was mention in the report that the contactor had dual coils, but i
have not found a datasheet for the device to see the electrical schematic.
Can't say for this one, but it's quite common for contactors of high
rating to have dual coils. The contact pressure required needs a strong
spring to keep contact resistance low, which in turn needs high magnetic
field strength to operate against the spring. The first coil is low
resistance, high current to close the magnetic circuit, while the second
or holding coil is much higher resistance and is enabled by an auxilliary
contact. Typically, the two windings would be in series at rest, with the
high resistance winding shorted out, then unshorted as the solenoid
operates.
There was some discussion of the contactor earlier in this thread.
Post #902, for example...
The really worrying thing is that the battery subsystem appears to have
been designed on the assumption that the cells would never leak electrolyte.
If they do, then the bmu boards are quickly toast. The contactor, which
is driven from one of those boards, may never operate, leaving the
battery connected as it self destructs.
I wonder if the long term fix will be to put the boards in a sealed
enclosure within the box, or will they fudge that as well ?. Until there's
more detailed info on the solution, there can be little confidence that
they have done it right. An armoured box doesn't qualify as a solution, imo,
though presentation often wins over substance these days, it seems ...