Driver's Seat Battery Disconnect Ideas?

daepp · 01-05-2020, 08:11 AM

I own a very stock (excepting pistons, buckets and cams) 1972 911 T Targa. I drive it to work every Friday, and for most of my running around on the weekends. And I park it in my garage, which is attached to my house. I used to have a second floor above my garage, but now that I've moved it's at the far end of a 1 story structure.

That said, I'm still worried about fire. Two 12V high amperage batteries, mixed with 50 year old wiring and a lot of gasoline really makes me wonder. And there have been some horror stories about 911's that have smoldered etc and burned up over night.

I installed a "heat detector" on the ceiling over where I park, and it's tied to a central (and monitored) alarm. A nice fire sprinkler over it would def. add some piece of mind - maybe someday.

Sorry for the long backstory. My question is, has anyone seen a battery disconnect - that I can install to separate the two batteries from all that old wiring - but that I can also open and close said switch from the driver's seat. I've seen a million of them up on the left fender, but I think the only way I'd use it religiously is if it was just another switch - like the key. And keeping a stock look - or being able to revert back to stock - is a definite plus.

Any ideas/pics would be appreciated. TIA!

Signed,

Mr. Worry Wart

blucille · 01-05-2020, 08:30 AM

Replace the clock with a blank plate and install kill switch there.

I’ve also seen guys put them in the removable speaker panel in the center of the dash. Really it could go anywhere that you like the aesthetic.

daepp · 01-05-2020, 10:01 AM

Quote:

Originally Posted by blucille

Replace the clock with a blank plate and install kill switch there.

I’ve also seen guys put them in the removable speaker panel in the center of the dash. Really it could go anywhere that you like the aesthetic.

...and, my clock is inoperative. I have had some thoughts about converting that clock location to a fresh air vent as there is zero ventilation without windows or top off. I love top down driving, but on 400-800 mile trips that "drone" can get wearisome.

I also hsould have asked if anyone has made a kit for a driver's battery cutoff.

blucille · 01:02 PM

Quote:

Originally Posted by daepp

...and, my clock is inoperative. I have had some thoughts about converting that clock location to a fresh air vent as there is zero ventilation without windows or top off. I love top down driving, but on 400-800 mile trips that "drone" can get wearisome.

I also hsould have asked if anyone has made a kit for a driver's battery cutoff.

Ventilation is another question.....there’s an Audi vent (a3/4/TT) that fits perfectly where the clock or the fuel gauge goes....also Ford F-150 and probably a ton others. Just for fun, the ford vent isn’t an exact fit, it’s a little too big to fit, once you trim it to make it fit, the bezel doesn’t sit proud like the gauges, it slides into the gauge opening a little too far....the Audi gauge is a perfect fit, including the factory rubber ring.

gomezoneill · gomezoneill's Garage

Don't forget you're going to have to run heavy 6 gauge cables back and forth to the battery from the switch. Be very cautious routing those wires. You may cause a problem you're trying to prevent.

FrenchToast · 12:56 PM

On the motorsport 964s and 993s Porsche mounted a cut off switch in the trunk adjacent to the battery. They ran a cable up to the dash and mounted a pull switch next to the ignition. But it is off only. Turning on requires going to main switch. You can probably see it in the PET. It likely won't fit a pre-964 car though.

I have no idea how where they ran the cable. They probably welded a tube on the shell just for the cable.

That said, the point of that switch is to quickly stop power to the battery, alternator, fuel pump, and other systems. It is not designed to be pulled and then forgotten (you would go to the main switch and ensure it is off).

Some current motorsport cars use a similar idea. Many are moving to an electronic solid-state system like the one from Cartek. I think most mount the interior cutoff switch on the center console now (along with all the other switches).

Totally different interior, but here is the GT2 RS Clubsport. Uses a toggle switch for the main power (probably in conjunction with a Cartek or similar system).

daepp · 01-05-2020, 04:33 PM

Thanks for all the good info.

I did consider the heavy cables, but figured someone had been-there-done-that and solved the tougher issues.

I hadn’t thought about a solid-state solution. Maybe something like a 12V relay just after the point where the two positives merge...? Then light gauge wire and switch inside.

geoff_68s · 01-06-2020, 10:22 AM

Rennline makes a cable-actuated remote-pull for their battery disconnect switches, intended for the actual disconnect switch to remain at the battery, but be actuated at the cowl or fender by a safety worker on the track. If you were so inclined, you could run the cable to the cockpit for the driver to use instead. You'd also have to rig it to be able to be turned back on remotely, but from the looks of the product illustrations, that might be as simple as one more cable clamp:

https://www.rennline.com/Rennline-Remote-Pull-Cable-Kit-with-T-Handle/productinfo/EL20.21/

73pcar · 01-06-2020, 10:50 AM

My 72 gets the same use (perhaps a little less) and I keep the batteries disconnected when not in use...easy with the stock wing nuts that secure the negative cables to the ground studs on the body. I don't find that regimen inconvenient and as quickly as I disconnect the batteries the hard-wired Battery Tenders are plugged in. I share your concerns and don't keep anything 'old' connected in my garage. I'm not giving up my clock or running the seriously 'fat' gauge wires to a remote location, but from the responses you have options if manually disconnecting them is a hassle for you.

juanbenae · juanbenae's Garage

there was a post recently regarding an early car two battery issue and starting the car with a single battery in place while using jumper cables. anyway, it ended well for the guy after a second, admittedly tired battery was installed into the car's the two battery system and it started with that same jump.

it got me to wondering how does the two battery system work? in parallel or series? I don't have the electrical gene my engineer pops does, but I guess im again wondering with the 911 system in your car would you have to disconnect one, or both batteries to accomplish your mission at hand?

as I stated in the other thread after suggesting he install the second battery good or not and try jumping and it worked for him, somebody smarter than me might be better suited for answering this. it'd obviously be easier if you only had to kill a single battery to shut the entire system down. the racecar kill switches are cable pull mechanical, so if you went that route you'd need two of them in place if the batts were not independent of each other,

daepp · 01-07-2020, 12:04 PM

They’re hooked I series - this yielding 12rather than 24 volts.

76FJ55 · 01-07-2020, 12:40 PM

Quote:

Originally Posted by daepp

They’re hooked I series - this yielding 12rather than 24 volts.

Series adds the voltages. Parallel adds the capacity (Amp-Hours)

So... if you are using 12V batteries they need to be in parallel. If you are using 6V batteries they should be in series.

darrin · 01-07-2020, 01:34 PM

another thought -- what about setting up a relay (similar concept to a headlight relay) that would use a very low current/power switch in the cockpit to remotely trigger a relay adjacent to the battery that would cut off the current coming off the battery's positive terminal. Should be relatively straightforward to source a relay that can handle far more current than a 911 would require when energized.

daepp · 01-07-2020, 02:17 PM

Quote:

Originally Posted by 76FJ55

Series adds the voltages. Parallel adds the capacity (Amp-Hours)

So... if you are using 12V batteries they need to be in parallel. If you are using 6V batteries they should be in series.

Oops - my bad - had that ass backwards. You are of course correct. 12V and additional capacity.

Cory M · 01-08-2020, 06:44 AM

A lot of racecars are moving from the traditional simple kill switch to a battery isolator switch. It allows you to place the buttons wherever you need rather than routing pull cables and adding extra wire length. Also allows you to turn both off and on. Downside is cost is significantly higher at about $350, while a normal racing kill switch is under $100.

https://www.cartekmotorsport.com/battery-isolators/

https://www.pegasusautoracing.com/group.asp?GroupID=CARTEKBATT