RV Electricity – Just Ask Mike (J.A.M.): Battery disconnect switch options

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By Mike Sokol

Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.


Dear Mike,
Thank you for the informative and helpful articles (and newsletter) you provide to the RV community. After reading your recent article on installing a battery disconnect switch, I am interested in doing this. I did not see anything in this article or through a search on the RV Travel newsletter website as to which type of switch to install.

I am not used to dealing with 12-volt systems, and as you note in your article, the amperage rating for batteries can be considerable. Does there need to be an amperage rating on the switch?
Since mounting space for a disconnect switch will vary from RV to RV, there is most likely not a universal switch that you can recommend. Perhaps an inline switch might be the best option for certain applications. Any light you can shed on this would be greatly appreciated.
Thank you very much. Michael Theis
Dear other Mike,
That’s a great follow-up question to my article HERE. You are correct that you can’t use just any old switch due to the hundreds of amperes of current that flows at times from a 12-volt battery. There are two basic types of battery disconnects, the first one being for top-mount terminals more typical of 6-volt batteries.

Here’s one that looks good and gets excellent ratings on Amazon.com.

The second type of battery disconnect uses an inline cable, so it’s much more flexible in how you mount it. Here’s one that’s Marine Rated so it’s more vibration and corrosion resistant than some of the cheaper units.

Finally, if you have the room there’s a plug-n-play version of a battery disconnect switch that doesn’t require cutting or reterminating any wires. Looks like a little knife switch, which is exactly what it is.

Hope this helps.

OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.

See you next week. In the meantime let’s play safe out there….

 

Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

##RVDT 1140;##RVT908


2 COMMENTS

  1. I use the knife switch type to disconnect my Toad battery while underway. Stops battery drain. Towing lights and braking system get powered from the RV.

  2. I didn’t see the article on installing the battery disconnect switch, therefore I don’t know if my questions have been answered or not. So here goes. I have a four 6 volt battery bank with a generator hook up. The cable size for all connections are 1/0. I just purchased a Blue Sea 3000 to install in the battery compartment. I think I will need 4 to 5 feet of cable for the installation. I saw an article by a RV’er who installed the same system on his DP and he said he used 4/0 wire for the new connector. So my question is what size wire do I need?

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