Battery disconnect switch October 27, 2011 12:01PM
When installing a disconnect switch do you hook it up to the positive or ground side? I have had two people tell me two diferent answers.
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Re: Battery disconnect switch October 27, 2011 12:38PM
I have mine on the ground side and have never had a problem. Have heard a couple Guy's with them on the positive side and burned them.
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Re: Battery disconnect switch October 27, 2011 12:39PM
i would hook it to the ground side if for some reason you have a voltage feedback it would still kill everything
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Re: Battery disconnect switch October 27, 2011 12:56PM
For the switch to serve it's intended purpose with regard to safety, it needs to be between B+ and the load, as close to the battery as possible. Putting it on the ground side means everything in the electrical system has electric potential whether the switch is on or not. If a short to ground were to develop and start a fire, turning off a switch in the ground side of the system isn't going to cut the power that's causing the fire. BTW, amperage is the same in all parts of a series circuit, so installing the switch in the hot side versus the ground side would not cause it to burn up. Just make sure your switch is rated for the max load it will carry plus a safety factor of at least 20%.
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Re: Battery disconnect switch October 27, 2011 01:44PM
What "not me" said is 100% correct.
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Re: Battery disconnect switch October 27, 2011 02:47PM
voltage is always looking for ground, in any electrical system, when a battery is the voltage source, it does not matter at all which
side the disconnect switch is on. example: if the disconnect switch is on the ground side, and close to the battery, the positive
cable could be clamped directly to the frame and it will not burn, because the voltage cannot get back to the negative side of the
battery. also after working with batteries for many years there does seem to be less arcing when disconnecting grounds before
positives, which i do not understand, but arcing will ruin the disconnect switch much faster.
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Re: Battery disconnect switch October 27, 2011 10:30PM
Do not forget that you should use a switch that also has a separate alternator connection point,that is if you are running an alternator? because with most alt. once you excite them,they will quite happily keep cranking out the current, battery or not! unless of course every thing has stopped turning?
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Re: Battery disconnect switch October 28, 2011 03:27AM
NHRA requires it in the pos cable. I run the alt hot wire to the battery side of the switch. Will kill the engine when turned off as required. Should work for a tractor same as a drag car. hope this info helps.
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Re: Battery disconnect switch October 29, 2011 04:03AM
All heavy OEM equipment I have worked on always had the disconnect on the ground side. It takes a heavier switch on the + side. Why do you think the + post is bigger on a battery? Any time you read instructions to install electrical components they state to disconnect the ground cable first. An electrical circut cannot be completed without a ground therefore the potential amperage in the circut is usless until a ground is provided to the battery. Will it work on the + side? absoultely but it will take a bit heavier switch and I just prefer the ground side.
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Re: Battery disconnect switch October 29, 2011 05:04AM
Yea.. I never understood the battery cable size thing.. Current flow is the same at any point in a series circuit.. so its the same on both sides of the circuit..
injpumped and Jim.. never thought about something as simple as running the alt wire to the other side of the switch.. most just run it to the starter..
Bryan
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Re: Battery disconnect switch October 29, 2011 01:12PM
The + post on a battery is bigger than the - post in an effort to keep people from inadvertantly connecting it backwards, sort of like having left hand threads on the acetylene regulator on your cutting torch. Basic Ohm's law dictates that current (amperage) is the same in all parts of a series circuit, so the statement about needing a heavier switch on the positive side is ridiculous. You are instructed to remove the negative cable first because there is less likelihood of arcing back to the battery (see electrical potential mentioned above) and no fireworks if your wrench slips and grounds the ground to the fender.
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Re: Battery disconnect switch October 31, 2011 12:17AM
Most switches I have installed came with instrutions stating to install on pos. I go with neg..less trouble to install...ground cables are usually shorter.. longer the cable the heaver guage required to carry the same amps as a short cable...
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Battery disconnect switch for both pos and neg November 02, 2011 05:19AM
Anyone ever use a disconnect that is for both sides at the same time?


We are considering this after data logging issues that are getting blamed on disconnecting.
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