Master Cutoff Switch

[Pat McCue]

I'll take a shot at answering the master cut off switch for electric vehicles question.. Jeff, team and I built the eCOPO as well as the orange car "Shock and Awe" that has run around division 6 for a few years.

All our cars, per General Rule 8.4, have master cut off switches. They are push off and clearly marked. When pushed they remove all low voltage power to the rest of the car (including to the low voltage components that connect the high voltage to the propulsion system).

We also have an "oh-sh#*" switch on the dash, that if ever needed (hasn't been needed in almost 175 electric runs) would remove 12v power to the master contactor in the hv motor system. That too is push off. That does not remove 12v power from the entire vehicle, just disconnects the HV.

Here's a picture of the back of the orange high school car.....
Pat

[FireSale]

Originally Posted by Pat McCue

I'll take a shot at answering the master cut off switch for electric vehicles question.. Jeff, team and I built the eCOPO as well as the orange car "Shock and Awe" that has run around division 6 for a few years.

All our cars, per General Rule 8.4, have master cut off switches. They are push off and clearly marked. When pushed they remove all low voltage power to the rest of the car (including to the low voltage components that connect the high voltage to the propulsion system).

We also have an "oh-sh#*" switch on the dash, that if ever needed (hasn't been needed in almost 175 electric runs) would remove 12v power to the master contactor in the hv motor system. That too is push off. That does not remove 12v power from the entire vehicle, just disconnects the HV.

Here's a picture of the back of the orange high school car.....
Pat

Thank you for the answer. In regards to the questions about EV cutoffs from others, the rule book has cutoff switch requirements. It must disconnect the motor and power pack. It's in the EV section buried up with ET Snowmobiles.

[Tom P]

It is worth mentioning that the cutoff is supposed to be on the Positive side. If you have it the other way and crash and fold the quarter panel into the Negative terminal the switch won't work,
The rules are written in blood as they say.

[J&S Racing]

I’ve decided to run a switch even though I don’t plan on putting a battery in the truck just yet.

My question is about the wire from the alternator, can it run to the battery or does it need to be run to the switch?

[Myron Piatek]

Coincidently, NHRARacer.com has a battery question this week. I never had or plan to have a car faster than 9.99 or 135 mph. but I never knew or even noticed that they apparently need a cut-off regardless of battery placement. External switch also?

http://www.nhraracer.com/content/gen...336&zoneid=132

[Ernie Neal]

Originally Posted by J&S Racing

I’ve decided to run a switch even though I don’t plan on putting a battery in the truck just yet.

My question is about the wire from the alternator, can it run to the battery or does it need to be run to the switch?

probably need a cutoff like this one

[Jon Sarrett]

Originally Posted by J&S Racing

I’ve decided to run a switch even though I don’t plan on putting a battery in the truck just yet.

My question is about the wire from the alternator, can it run to the battery or does it need to be run to the switch?

Your alternator wire and battery cable should be on the same post on the switch. The other post on the switch will run the cable to your starter solenoid.

[FireSale]

Originally Posted by Jon Sarrett

Your alternator wire and battery cable should be on the same post on the switch. The other post on the switch will run the cable to your starter solenoid.

I had a double pole Moroso to kill the alternator until a short at the starter burned it out. I replaced it with a single pole rotary at half the price wired like this and it works fine. No engine run-on.

[CMcAllister]

Originally Posted by FireSale

I had a double pole Moroso to kill the alternator until a short at the starter burned it out. I replaced it with a single pole rotary at half the price wired like this and it works fine. No engine run-on.

This is the simple legal way to do it without extra wiring, solenoids, etc. You just have to be mindful that the alternator lead is always hot, and pay attention to making sure it is protected where it is routed and when working on the car..