battery disconnect issue

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mll1446

Senior Member
I install a battery disconnect switch on the negative side of the battery and when I switch it doesn't kill the power ? the switch is mounted in floor and cable grounded to frameand either way I'll switch it I still have power
 
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mll1446 said:
I install a battery disconnect switch on the negative side of the battery and when I switch it doesn't kill the power ? the switch is mounted in floor and cable grounded to frameand either way I'll switch it I still have power
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Are the cable terminals touching each other on the back of the switch?
The posts on the switch are kind of close together.
Bill
 
Are you 6 volt or 12 volt. If you are 6 volt and the switch is on the negative (hot side), it will not kill the car if it is running. If the engine is off, it should prevent everything from working. If you are 12 volt and your negative is on the ground side you must have additional grounding somewhere.
 
The switch should isolate the 'hot' side of the battery. This would be the Negative post if you are using a Positive Ground system or the Positive post if using Negative Ground.
 
As with kd4lok above, I always thought you put the switch on the "hot" side of the battery, e.g., in my case with the original 6 volt positive ground, that means the cable attached to the negative post of my battery runs to the "battery disconnect" switch and then leaving the switch runs to the starter. When I turn off my battery disconnect switch the car won't start and no options operate. With the engine running and the generator charging, I can actually turn off the battery disconnect switch and the engine will continue to run, that is with the generator providing adequate charge to energize the coil, but if the charge rate is slow enough, e.g., a slight discharge on the amp meter at slow idle, the coil can't energize any more and the engine dies.
 
The disconnect switch should be on the GROUND side of the battery. There should be only a short insulated cable between the GROUND post on the battery and one terminal of the switch. All ground connections to the chassis and anything else you are grounding should be connected to the other terminal of the switch.

This provides the best protection when the car is not in use.

With the switch on the ground side, if the cable from the battery to the switch is compromised and makes contact with a metal part of the chassis or the terminal on the switch should become grounded, nothing happens except when the switch is in the off position the battery will not isolate. You can check for this by turning off the switch when the engine is not running and see if the lights work. If the lights turn on, there is a ground fault somewhere between the battery ground post and the switch.

With the switch on the HOT side of the battery, with the switch is in the OFF position, if the insulation on the cable is compromised, the cable itself can arc to a chassis component, or if the terminal on the back of the switch contacts a chassis component, an arc will result, which is essentially shorting across the battery.

I have worked with race cars for many years and it is specified that the disconnect switch is on the GROUND side of the battery and the cable between the battery and switch must be insulated.

Turning the disconnect switch OFF while the engine is running will not always kill the engine. The engine may continue to run off the generator or alternator. It is NOT a good idea to turn OFF the disconnect switch while the engine is running. The generator or alternator needs the battery to properly control charging voltage.

Chris W.
 
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Technically the switch will work to remove power from the car in either side the of the battery. The safest when working near the battery or the switch is on the ground side.


Check your wiring again as the only wire from the ground side of the battery must pass through the switch..
 

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Tom Wesenberg concurs with cwpasadena, in his post from 11-26-15 below..

"I'd install the master switch on the ground side of the battery. If you use a wrench to disconnect either battery cable and happen to touch the frame, no spark will fly.

With the switch on the starter cable, using a wrench on the negative post or master switch can cause sparks to fly if the wrench touches ground. Sparks around batteries can cause the battery to explode."
 
I now agree with those who recommend placing the switch in the GROUND path to the battery for safety reasons. I stand corrected and will change it on my car.
 
I was taught the safest way to disconnect a battery (with or without a disconnect switch) was the grounded terminal first and then the hot, avoiding any chance of sparks near the battery.
 
That switch should work either on ground or hot wire.

If there still is power to the starter in the off position, there is a problem. Either the switch is bad [ check for continuity], or, as said, the cables at the switch are touching each other.
 
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