[asymptonic]

Am I on the right track here? I'm designing a split front/rear battery pack with a contactor on the positive leg of each for redundancy. I had a thought of adding a relay to the setup of the front contactor that would interface with the accessory leg of the contactor to ensure that the rear contactor only activates if power is being supplied to the coil and the accessory leg was closed. Said the other way around, if the accessory leg is closed but power wasn't applied (stuck contactor) at least the rear contactor wouldn't latch. Thoughts?

Diagram:

 

[asymptonic]

And by accessory leg I meant auxilliary...

 

[MesquiteTim]

You should be able to add a second contactor easily but how will your controller deal with half voltage? What are your goals? What scenarios are you worried about?

EVWest places fuses on pos and contactors on neg side. EV West general schematic

 

[asymptonic]

What do you mean by half voltage? The contactors in the circuit are in serial. One stands between the rear battery positive and the front battery negative, and the second between front battery positive and hypothetically the controller. Re positioning, that's fine, I can put it on the negative side wrt to the fuse.

 

[asymptonic]

Sorry, to answer your other question, this circuit is basically to have a single 12v pack on signal operate two contactors, and only have both on if Power on signal is present AND Front contactor is closed.

The intermediate relay acts as an AND for those two conditions. In the case the front contactor has fused shut but power on is off, the rear contactor will still be open presuming it hasn't also failed. Just an extra measure of safety.

 

[asymptonic]

Never mind, just realized the middle relay is redundant to just running the 12v signal through the auxilliary path of the contactor.