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nickjonesn4
Montreal


Joined: 10 Aug 2017
Posts: 542
Location: Edinburgh


PostPosted: Thu Jul 04, 2019 4:27 pm    Post subject: battery disconnect/kill switch Reply with quote

Hi All,

Would like to fit one of these but have managed to get confused looking at options. Can someone recommend a simple DIY option please.

Was looking at the rennline options but not sure what parts I need

thanks in advance

Nick
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 436
Location: Scotland


PostPosted: Thu Jul 04, 2019 5:23 pm    Post subject: Reply with quote

Nick, much depends on what you want to fit the switch to and what you hope to achieve. For safety the usual is to break the main earth from the battery to the chassis.

For additional security there are switches with removable keys.

Problem for ECU controlled vehicles is that operating such switches can create ECU issues involving re learning and possible lost personal settings of some kit..

There are quite a selection of switches on the market..

https://www.demon-tweeks.com/uk/motorsport/electrical-gauges/switches-circuit-protection/battery-isolators-master-switches/

Good luck in your choices.
 
  
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ToreB
Approved Trader


Joined: 13 May 2010
Posts: 593
Location: Oslo, Norway


PostPosted: Thu Jul 04, 2019 5:40 pm    Post subject: Reply with quote

This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707
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Zorro
Spa-Francorchamps


Joined: 05 Oct 2014
Posts: 258
Location: East Sussex


PostPosted: Thu Jul 04, 2019 6:01 pm    Post subject: Reply with quote

ToreB wrote:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707


Good old Google Translate. Smile
 
  
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Albionmuz
Montreal


Joined: 28 Oct 2016
Posts: 591
Location: West Sussex


PostPosted: Thu Jul 04, 2019 6:42 pm    Post subject: Reply with quote

ToreB wrote:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707


Exactly what I use on my GTV since it started having a slow battery drain. Takes seconds to turn off and on, car is seldom used so it works well for me. Recommend it
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Endoman
Barcelona


Joined: 11 Apr 2011
Posts: 1395
Location: Bolton U.K.


PostPosted: Thu Jul 04, 2019 7:29 pm    Post subject: Reply with quote

The wiring of a battery isolator is different to a kill switch.
It is possible to damage the altenator if the isolator is used on the earth terminal and switched off when the engine is running.
A kill switch fits on the live side, cuts the altenator feed and diverts it to a large ceramic resistor, more complicated and reserved for motosport use.
I tried a Cartek one on the 944 but it played havoc with the immobiliser. The simple ones connected to the earth with a fused spur to keep radio and ecu live (to avoid reset) will still allow a current drain but the fuse blows if the starter is removed.
I use a motor sport one fitted as per RS, the one mentioned above is made of brittle brass and will snap off if you throw anything in the frunk.
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gunner
Hockenheim


Joined: 04 Jul 2014
Posts: 739
Location: Kent


PostPosted: Fri Jul 05, 2019 7:41 am    Post subject: Reply with quote

Albionmuz wrote:
ToreB wrote:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707


Exactly what I use on my GTV since it started having a slow battery drain. Takes seconds to turn off and on, car is seldom used so it works well for me. Recommend it


I have one of these too. Don't use it often but nice to have the option.
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gunner
Hockenheim


Joined: 04 Jul 2014
Posts: 739
Location: Kent


PostPosted: Fri Jul 05, 2019 7:50 am    Post subject: Reply with quote

Albionmuz wrote:
ToreB wrote:
This works fine in both my 993 and VW veteran.
Be sure to not overtighten, it will break off.
Tore

https://www.biltema.no/bil---mc/elektrisk-anlegg/strombrytere/batteribryter-pa-pol-2000031707


Exactly what I use on my GTV since it started having a slow battery drain. Takes seconds to turn off and on, car is seldom used so it works well for me. Recommend it


I have one of these too. Don't use it often but nice to have the option.
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Fuchs
Shanghai


Joined: 22 Dec 2004
Posts: 4991
Location: Switzerland

1994 Porsche 993 Carrera 2

PostPosted: Fri Jul 05, 2019 11:04 am    Post subject: Reply with quote

I use this on my 993 for last 10 years or so - https://richbrook.co.uk/product/discarnect-battery-master-switch/

Dont buy a cheaper knock off from ebay or similar!
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 436
Location: Scotland


PostPosted: Fri Jul 05, 2019 11:50 am    Post subject: Reply with quote

Great that there are a variety of switches in use and they all seem to work for the folk who fitted them...other than Endoman`s contribution where he determines that there is a good chance of damage to the alternator if the battery isolator is switched off...

The logical question would seem to be why would the switch be operated with the engine running...?

There can be a number of reasons to fit a kill switch but like most MODIFICATIONS to an ORIGINAL design it is perhaps best to accurately determine what you hope to achieve, and also more importantly to consider the possible domino effect on other aspects of the vehicles operation as the result of the mods...?

As has been mentioned in the few replies to date, there can be issues arising, perhaps not originally considered when switches were originally fitted...?

Just thinking in type.
 
  
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nickjonesn4
Montreal


Joined: 10 Aug 2017
Posts: 542
Location: Edinburgh


PostPosted: Fri Jul 05, 2019 1:12 pm    Post subject: Reply with quote

thanks all, very helpful

Richbrook Discarnect ordered
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Endoman
Barcelona


Joined: 11 Apr 2011
Posts: 1395
Location: Bolton U.K.


PostPosted: Fri Jul 05, 2019 8:58 pm    Post subject: Reply with quote

Luddite wrote:
Great that there are a variety of switches in use and they all seem to work for the folk who fitted them...other than Endoman`s contribution where he determines that there is a good chance of damage to the alternator if the battery isolator is switched off...

The logical question would seem to be why would the switch be operated with the engine running...?

There can be a number of reasons to fit a kill switch but like most MODIFICATIONS to an ORIGINAL design it is perhaps best to accurately determine what you hope to achieve, and also more importantly to consider the possible domino effect on other aspects of the vehicles operation as the result of the mods...?

As has been mentioned in the few replies to date, there can be issues arising, perhaps not originally considered when switches were originally fitted...?

Just thinking in type.


That's the difference between a kill switch and an isolator. A kill switch is mandatory in motorsport, but if you use an isolator attached to the earth as a kill it will not kill the engine only the altenator. It used to work, sort of with dynamos but not immediate, the idea is to stop fuel flow in case of a prang. Some cars are fitted with a fuel flow cut off as standard when the airbags blow not sure if the 993 has one.
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treefrog99
Newbie


Joined: 19 Apr 2013
Posts: 34
Location: Derbyshire


PostPosted: Fri Jul 05, 2019 9:11 pm    Post subject: Reply with quote

I use this on my 964 it's basic but functions fine
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 436
Location: Scotland


PostPosted: Sat Jul 06, 2019 10:02 pm    Post subject: Reply with quote

Endoman, many thanks for the heads up on the difference betwixt a kill switch and a battery isolator.

As Nick did not provide any info on what he hoped his switch would achieve, I assumed he was perhaps into battery isolation for a road car to cut down on battery drain when not in use, as opposed to requiring to fit a kill switch to a competition vehicle that requires to comply with RAC regs..

Strange as it may seem, my old sports car has an automatic "safety" fuel pump shut off circuit, in that the supply to the fuel pump is switched through the oil pressure switch... in the case of an accident and the engine shutting down with the ign still left switched on, the oil pressure drops breaking the contacts in the oil pressure switch and killing the fuel pump and thus avoiding possibly damaged fuel line spewing fuel around the locality..

The disadvantage in the above scenario for a vehicle that may spend varying amounts of time laid-up is that fuel can evaporate or loose pressure in varying degrees, and with a battery which may be somewhat lacking relative to the time laid up, the requirement to spin the engine until oil pressure builds up enough to close the pressure switch contacts to then bring the fuel pump into operation which again will require time to restore fuel volume/pressure.... The battery may just not have enough power, to manage to complete the whole start up process..?

I note that Iain typed of the fuel pump on some Porsches being activated by operating the door handle to pre pressurise the fuel system to provide a quick start up... However if the battery is isolated, that first step in the logic would have been by-passed, and when the battery connection was finally made in the frunk, it may create a measure of confusion in the control stratedgy...?
 
  
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Fuchs
Shanghai


Joined: 22 Dec 2004
Posts: 4991
Location: Switzerland

1994 Porsche 993 Carrera 2

PostPosted: Mon Jul 08, 2019 11:05 am    Post subject: Reply with quote

nickjonesn4 wrote:
thanks all, very helpful

Richbrook Discarnect ordered


It can be a bit fiddly getting this onto the battery cable, if i remember correctly i had to move the battery cable to go around the side of the battery to get that little bit extra length needed to get the discarnect on.

As others have said dont overtighten the removable wheel!

I didnt bother fitting the fuse link as this allows the clock to still run, which is exactly what drains the battery.

Very Happy
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