12volt system and high-voltage system
With any modern
EV, it is an essential safety item to have the propulsion pack isolated from
the vehicle frame
and the ordinary 12volt systems ( lights, horn, radio, etc. ). This helps
prevent electric shock and nuisance tripping
of ground-fault-interruptor circuit breakers ( which are another good bit of
safety equipment for your charger ).
To provide power for all the usual 12volt stuff in a car, there are several
options. I chose to use a sealed
battery and a DC-DC converter. This uses a small amount of power from the propulsion
pack to keep this small
12volt battery charged up, and this battery provides the capability to handle
sudden power surges like
those that the headlights will draw when they're first switched on.
The high-voltage
propulsion pack MUST have several methods of disconnecting it, to cater for
possible
failures. DC motor controllers
can have a nasty failure mode - full on ! So big contactors are used that
can interrupt the fault current.
I also have a BIG
RED PANIC BUTTON, which will be inside the
cabin where I can whack it to
kill the power if things go haywire !
above: the
Big Red Panic Button ( minus its button! ) installed just ahead of the handbrake,
where the gear lever used to be
top left: Fwd/Rev switch ( an old Saab headlights switch ), and the Big Red
Button kill switch ( minus its red button! ) ;
top right: DC-DC converter, 12v battery ;
bottom left: more contactors ;
bottom right: Curtis 1221B controller
Below is the controller and some of the contactors, installed in the
motor bay. I've been doing some testing, that's why some of the wiring
is exposed! I've also turned the controller over, so I have room to
attach the big heatsink without it fouling the motor casing. The contactors
will either be in a waterproof box, or will have a shield to stop water
getting onto them.
I'm also rebulding the potbox, since the previous one was not very
good!
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