Battery Kill Switch Question

Buickguy3 · February 13, 2015, 12:13:01 PM

On the Salt Cat ll car we have two shutoffs in series. The one that is in reach of the driver kills all power except to the computer for the datalog, and the helmet fan. The main disconnect at the rear kills all power. If it gets to that point, I won't need the data from that run anyhow.
Doug

NathanStewart · February 17, 2015, 10:50:30 PM

One action should make the car completely dead. If you hit the main kill and can still hear the whirring of a fan going some where then I'd say you'd be a no-go in tech. IMO perm power to a logger or ECU isn't a concern so long as it's only power to maintain memory and isn't actually used to power coils or injectors or anything else.

tauruck · February 18, 2015, 01:53:13 AM

Nathan, my car isn't done but there's a main switch in the cockpit and one each at the front and back for rescue.
If either are activated it cuts off everything and the main in the cockpit needs to be set to "on" manually after activation.

Is this the right system?.

Thanks, Mike.

Sumner · February 18, 2015, 05:20:04 AM

Quote from: NathanStewart on February 17, 2015, 10:50:30 PM
One action should make the car completely dead. If you hit the main kill and can still hear the whirring of a fan going some where then I'd say you'd be a no-go in tech. IMO perm power to a logger or ECU isn't a concern so long as it's only power to maintain memory and isn't actually used to power coils or injectors or anything else.

Nate is it not a ruling to avoid any hot wires in the car that could possibly spark and ignite fuel not just those that are required to run the engine?

I could see where someone has an incident and the car is on its side and the power is off so the engine can't run but while turning the car over or possibly having to cut it open to get to the driver a wire going to the data recorder or ECU was cut or a damaged wire to it contacted ground and caused a spark and there was fuel you could have a problem well after the initial accident.

Sumner

SPARKY · February 18, 2015, 06:54:42 AM

I was "told" that no hot wires was the objective of the battery cut off it was to function as a MASTER KILL SWITCH for all power.

NathanStewart · February 18, 2015, 09:01:26 AM

You can theorize it however you want. I've not yet witnessed a fire that was started due to a spark from a damaged 22 gauge wire that's keeping your logger memory. That sounds a lot like the rule change scenario Chris described with his wreck leaving broken headlight glass on the course. I have been on scene at a fire that couldn't be put out because a fuel pump was still running and pouring fuel on a hot not running engine because the main kill couldn't be found and the driver was unconscious... oh and the car was upside down. Getting that front or rear kill switch location rule through really made a lot of sense.

If a wreck is bad enough that someone is getting cut out of it, the battery is probably long gone having been flung a quarter mile from the accident epicenter. If the rule was to prevent any hot wires from arching against the chassis wouldn't the rule require that you cut off the ground side of the battery? Anyways, I think getting engines and fuel pumps turned off is a bigger concern that sparks. A hot engine is a lot more likely to ignite a fire than a stray spark.

manta22 · February 18, 2015, 09:54:18 AM

Nathan;

A cut-off switch in either side of the battery will work. It doesn't matter if it is in the positive or negative side of the battery-- the key is that the circuit is broken so no current can flow.

Regards, Neil Tucson, AZ

Stainless1 · February 18, 2015, 07:29:40 PM

Not to mention the battery should stay in its place if it is installed according to the rules. In my little incident, the back of the car broke off, and the cutoff switch was no longer attached, although it did manage to turn itself off before the wires were ripped loose. The battery stayed in its location until I put it in the truck when one of its batteries went south.

SPARKY · February 18, 2015, 07:44:06 PM

ronnieroadster · February 19, 2015, 07:40:29 PM

The intent is to kill power so engine and fuel delivery is dead during an emergency that's no problem. Example being the main battery feeding engine/fuel is located in the rear of vehicle and battery kill is located in the rear also. Main feed wires from this battery are then short in length with battery location to kill switch. Potential for problem developing from this battery is lessened by the shorter cables. Second battery is located in the front of vehicle to help with center of balance this battery is not used to feed any engine functions. If the wiring from this second battery is run the length of the vehicle to the kill switch location the potential for a short due to a crash has not been eliminated the additional length of the battery feed wires have now been run the length of the vehicle and back to the battery located up front adding to the potential of an issue due to these longer wires one of which will always have a feed on it. Using a relay to open the feed wire from the front battery seems to be the answer. BUT it has to be located at the battery to be of any value if that's truly what the rule imply's

NathanStewart · February 19, 2015, 09:42:11 PM

Nothing says you can't run two switches - one for the front and one for the rear BUT they should both be able to be activated simultaneously from one location. Most are achieving this using cables but I'm sure there are many ways to skin this cat.

Stainless I'm surprised to hear that your battery was intact after your wreck. I did not see the extent of your accident although I heard it was pretty bad and that you were lucky to have gotten away with what you did, but, the majority of accidents I've responded to have the batteries launched very far from where the car winds up.

Shorts, sparks, and shocks are all good concern but I think a higher priority is getting engines and fuel pumps shut down.

Sumner · February 22, 2015, 06:18:07 PM

My take is that it is so easy to put a cut-off relay, costing a few bucks, at the data logging battery why not do it? Then you have your bases covered,

Sumner

jimmy six · February 22, 2015, 06:45:55 PM

My battery is located in front of engine and under the fuel tank. The electric fuel pump is right beside it. The cut off switch is on a side hood panel 6" from the front and VERY visually marked.
Sounds like I did everything wrong......but follow the rule book.....

Anyone know where the battery disconnect is on a NASCAR? I don't believe it's in the rear....JD

ronnieroadster · February 23, 2015, 05:13:47 PM

Quote from: jimmy six on February 22, 2015, 06:45:55 PM
My battery is located in front of engine and under the fuel tank. The electric fuel pump is right beside it. The cut off switch is on a side hood panel 6" from the front and VERY visually marked.
Sounds like I did everything wrong......but follow the rule book.....

Anyone know where the battery disconnect is on a NASCAR? I don't believe it's in the rear....JD

Watched the Daytona Race noticed the battery disconect was on the drivers dash.

jimmy six · February 23, 2015, 10:09:07 PM

Ronnie... Makes perfect sense since now NASCAR now uses an electric pump. (Dah inside the car) I know it means nothing to our style of motorsports but NASCAR doesn't have a shut off like we need either. I personally think the shut off we first used for an electric pump that was tied to the oil pressure of the engine was a better idea.....oh well

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Battery Kill Switch Question