CARTEK Motorsport Electronics GT Kill Switch Unit
Early types of electrical isolation were by large mechanical master-switches while more modern systems have utilized electro-mechanical solenoids. Both of these types of systems contain mechanical electrical contacts which, due to the combination of high electrical current and the shocks and vibration of the race car environment, sparking between the contacts occurs which results in contact erosion and eventual unreliability.
OLD SCHOOL MECHANICAL MASTER KILL SWITCHES
All Wheel to Wheel road race cars and even most Drag Race cars have to incorporate a battery isolator or "main battery kill" switch somewhere on the vehicle. For drag racers it is usually placed at the rear of the vehicle, as shown below.
For W2W cars the switch needs to be within reach of the driver and corner worker, so this presents a few challenges for mounting (see options below). This switch is there to quickly shut off all power from the battery (and kill the alternator) when something goes wrong - after a crash, during a fire, or if something goes wrong enough to require the electrical power to be shut off and isolated completely.
In the 1960s there was the traditional main power "rotary switch" that was popular - and still legal to use in some series up to this day. This was the $25-50 solution that was a mechanical switch wired in-line with the battery and when rotated or switched it would shut off power from the battery. A separate line had to be run for the alternator field to kill that. These are cheap but can suffer from mechanical problems, arcing, and you have to route the heavy cables through the passenger compartment near the driver to make it work. This made for long battery cable runs that added weight and sapped voltage, too.
To make remote mounting possible with these mechanical switches a pushrod or cable operated switch is possible. Some folks will also wire in TWO of these voltage hogs in series to have them in two places - one external and one in the cabin near the driver. This doubles your chances for switch failure with two switches, plus the cable or rod are just mechanical bits to fail.
REMOTE ELECTRO-MECHANICAL SOLENOID DISCONNECT
In the 1990s people figured out ways to run a low amperage switch(es) to trigger a remote solenoid switch, which interrupts the high voltage battery cable as well as the ignition/alternator field wires to do the job a little smoother.
This way you can keep the battery cables routed as directly as possible (shorter runs) and the solenoid could be right next to the battery. Lower amperage switches could be added near the driver with small gauge wiring, and a second switch could be added to the cowl or otherwise outside the car for a corner work to access - in the event that a driver was incapacitated after a crash.
We've done these on many builds here at Vorshlag and they work reasonably well and don't have the downsides of the old school mechanical switches. With these setups it is much easier to add multiple kill switches (see above right), so we tend to put one inside the cabin (driver) and outside at the cowl or A-pillar (corner worker). But these systems still have a solenoid controlled by a magnetic field the moves the switch mechanically - so there are still moving parts, and moving parts will fail when you least expect it. Could cost you a race, could cost you a weekend.
SOLID STATE BATTERY ISOLATORS
In the mid-2000s the solid state battery kills came into the market with limited success. We tried one of these on a race build years ago that failed in the field, so we went back to the remote solenoid method for all builds up until 2017.
In 2017 we found CARTEK's solid state unit - and put it on one of our customer race car builds with multiple remote kill switches. At this point CARTEK have been producing the Solid State Battery Isolators for over 10 years and they are world renowned. Their boxes are fully sealed and have no moving parts, which matters in the tough environments of Motorsports. FIA race and rally championships require cars to be fitted with a spark-proof master switch to isolate the battery from all electrical systems and stop the engine. The Cartek Battery Isolator meets these requirements.
HOW DOES IT WORK?
CARTEK Motorsport Electronics XR Kill Switch Unit
Cartek produces two types of Battery Isolator kits: the GT and XR (shown above). Both systems isolate the battery from all electrical circuits, in accordance with FIA requirements, by disconnecting the negative terminal of the battery from chassis/earth. However, the main difference between these two units is the method used to stop the engine.
The Solid State Isolator contains two isolation circuits, as shown above. The first breaks the connection between the negative side of the vehicle’s battery from chassis/earth, thereby isolating the battery power from all electrical circuits, while the second cuts power to the engine electrics and thereby stops the engine from running.
The GT Battery Isolator unit has a 30A switched power output which can be used as the main power feed for most ECUs and/or ignition systems while the XR unit outputs a low current, ‘Ignition Off’, signal which is compatible with most motorsport ECUs and PDMs. This latter method of engine kill means that the XR is smaller and lighter than the GT and incorporates a sealed, circular connector.
Power Distribution Modules or PDMs are what many high end Motorsport race cars use for wiring control. By incorporating power switching electronics with over-current protection and intelligent functionality, these units remove the need for multiple switches, relays, fuses and circuit breakers thereby greatly simplifying the wiring, saving weight and maximizing reliability. If you car was built with a PDM you want the "XR" battery isolator.
Likewise almost all Motorsports ECUs are also capable of working with the XR. MoTeC, EMtron, Life Racing, AEM and the many other Engine Control Units built for Motorsport use can control the power of the alternator and with the XR isolator they can work more effectively to kill the engine and isolate the battery in an emergency.
The Battery Isolator XR features a 0.5 sec time delay between transmitting the engine kill signal and disconnecting the battery, allowing these ECUs time to perform an internal shutdown sequence before electrical power is lost (shut down ignition, shut down fuel, shut down fans, shut down power). This unit does not have a power input or power output. Instead it sends a signal which is wired up to either to the PDU Motorsport ECU that has an ignition switch signal input. The ECU or Power Distribution Module will then shut down when it see’s this signal - which then kills the engine.
We are trying to keep the GT isolator in stock here at Vorshlag at a price that is significantly better than what the other US resellers are posting. There are some options for the push buttons (colors, etc), too. Got more questions? We can help you pick the model (GT vs XR) that is right for your race car, putting your car in the 21st century with a lighter, more reliable solid state battery isolator.
Thanks,