openinverter forum

So, putting this out there for comment. On my bike, there's an "Engine stop" switch that you're supposed to flick in the event you fall off. Normally it cuts power to the engine.
In my conversion, I'm using KiloVac EV200 contactors to isolate the battery terminals. These can of course be opened just by cutting power to the energising coil. I will be wiring the coils via a standard "crash sensor" switch like you find on modern vehicles to provide some impact safety.

My question is this: would you
1) also wire the contactor coils directly through this kill switch, or
2) use the switch as an input to the VCU (leaving control of the contactors to software).

I quite like the idea of running the coils through this switch, as it gives an ultimate "emergency off" if something bad happens. On the other hand, it is possible to accidentally operate the switch while riding. Or some idiot might operate the switch while it's on charge.

What are the dangers of killing the battery connection while the motor is spinning? Might the inverter destroy itself? What about while charging? Would it be better to have a "hidden" kill switch instead?
I know KiloVacs don't take kindly to interrupting current and I've heard that Bad Things Happen with spinning motors and unpowered inverters...

From my perspective, "saving" the hardware is the least of my concerns if the system requires an EMERGENCY shut-down.

1) Save life/health
2) Don't endanger others (first responders etc)
3) Prevent a fire
4) Stop an unsafe operating condition (stuck throttle)

For 3 of those, a kill switch that interrupts the DC Relay(s) will work, to address #3, you would likely need to "break" the battery interconnect circuits.

I plan to do much as you suggest, with a few modifications:
- Control the PC and DC relay power via an ignition switched relay with the smallest fuse that will work (measure inrush and add 25%)
- Close the PC relay with the Ign = Start (the Leaf PC cicruit is fused for like 10A)
- Use the VCU to activate the DC relay, thru an in-line "roll over switch" and Inverter Lid Switch (Prius Gen2)
- Install a "Safety Disconnect" to break the pack interconnect circuit (like Prius/Leaf packs have) and somehow allow disconnecting remotely(??) - although no production EV has this feature that I am aware of.

Due to the *potential* for batteries to experience "thermal run-away", I would like to integrate temperature sensing to allow an auto-disconnect system, but that could shut the vehicle down unexpectedly. As a work-around, I plan to use a battery temperature monitor set for 50*C, which is a very safe upper limit.

Hmm, you've given me an idea to put a (non-resettable) thermal fuse in the circuit as well. Then if it does run away (and/or any of the electronics fail), at least the will be HV disconnected...

I considered a simple NC "snap switch" clipped on a cable, it might work