Installing chassis battery disconnect

[kl2657]

I recently went to take out my Diplomat and learned the hard way that there is a draw on my chassis batteries while the motorhome sits unused. My batteries are brand new and I'd like to preserve their lifespan as well as be able to start my motorhome... I don't have the benefit of being able to leave it plugged in to an AC source while in storage so I'm planning on installing a perko battery disconnect to ensure that the chassis batteries will have enough juice to start the MH after sitting for a month or so.

Is it better to install the disconnect on the positive leads or negative? Or, does it not really matter?

Thanks,

Jason

[BFlinn181]

Negative is safest.

WARNING!!! Automotive Battery Disconnect Switches - YouTube

[Stretch]

It is customarily installed on the positive leads, however I don't think it makes much difference. Install the Perko near the battery. So that you are sure that there is not a stray ground or positive lead somewhere in the system

[nothermark]

Bad grounds are a source of a lot of problems. Bad power supply line not so much. I would never put a switch in the ground return of a power source. YMMV.

[BFlinn181]

Perko recommends putting the switch in the (+) side of the circuit.
http://www.perko.com/images/catalog/...(9703INS1).pdf
The video I contributed says the (-) terminal. Make sure the post clamp on the cable fits to post. They are different sizes between (+) & (-). Perhaps the difference in recommendations is that the Perko switch is an enclosed switch while the ones in the video are all pretty open and uninsulated. I also looked up the power cut off switch required in most race cars. They recommend the kill switch on the (+) terminal.
How to Install a Race Car Emergency Kill Switch

[ShapeShifter]

Originally Posted by BFlinn181

Perhaps the difference in recommendations is that the Perko switch is an enclosed switch while the ones in the video are all pretty open and uninsulated.

I believe that is exactly the reason for the difference. With the switches that go on the batteries, all that exposed metal could be a safety concern if it were on the positive terminal.

With an enclosed and insulated switch, like the Perko, I think it would be a bit better to have it on the positive side. My rig came from the factory with house and chassis battery cutoff switches, and both are on the positive side.

Special note: before installing a cutoff switch, or doing any work on any of the high current battery leads, ALWAYS disconnect the negative terminal first, and reconnect it last. Make sure the negative lead can't accidentally contact the negative battery post: tape it in a safe position if you must. If you leave the negative lead connected while you have a wrench on the positive lead, that wrench could turn into a dangerous short circuit if it touches anything metal near the battery!

Note to those with the factory switches: not all loads are necessarily cut off when you open those switches. On mine, when the house switch is open, power is still sent to the slideout controller board, and to the optional solar battery controller. When the chassis switch is open, power is still sent to the starter motor plus two circuits to the engine. So, if you're going to replace the starter, for example, don't just open the cutoff switch and begin wrenching on the starter's cable connector - you still should remove the battery negative cable first!