Battery Master Switch?

[Wandering Sagebrush]

I’ve noticed a couple of threads about installing a battery master switch, so I assume that for some reason Oliver decided not to include one.  If there is, I haven’t found it.  There are times when I’d like to have all power off, with no parasitic loads.

In my first career, I was an aircraft electrician and have (had?) the skills to install a master switch, but as I’ve aged, I’ve become plain old lazy.  I’m thinking about simply disconnecting the negative lead from the battery bank.  Am I missing anything?  Thoughts?

[Mike and Carol]

2 minutes ago, Wandering Sagebrush said:

Am I missing anything?  Thoughts?

Installing a switch is just a matter of disconnecting cables from the battery and reconnecting to the switch.  The challenge for me was just figuring out the best spot for the switch!  Mike

[Wandering Sagebrush]

12 minutes ago, Mike and Carol said:

Installing a switch is just a matter of disconnecting cables from the battery and reconnecting to the switch.  The challenge for me was just figuring out the best spot for the switch!  Mike

Mike, thank you.  Location is exactly why I’m being lazy.  Plus the Ollie is so new (and elegant) to me that I’m hesitant to drill holes for cable routing and mounting screws.  I don’t understand why RV builders don’t provide a master switch for all circuits.  Even my Northern Lite has one parasitic circuit with the switch off.  The Airstream has several.

[topgun2]

Yep - what Mike said above.

The disconnect switches I've used just make the disconnect a bit easier (at least after the initial install) and are located right at the negative battery post.

Like THIS one.

Bill

[Rolind]

I installed a master kill switch on my prior trailer, primarily to remove any parasitic loads during storage under cover and because the batteries were very difficult to access. If you want to stir the pot, ask whether it should be on the positive or negative side of the battery. LOL I’ve seen strong agreements for both. I’m a negative side kinda guy. Removing the negative lead from the battery will accomplish what you need. 

[Wandering Sagebrush]

35 minutes ago, topgun2 said:

Yep - what Mike said above.

The disconnect switches I've used just make the disconnect a bit easier (at least after the initial install) and are located right at the negative battery post.

Like THIS one.

Bill

Bill, thank you!  I had not seen that style of switch, I was thinking along the lines of the big red Perko style.

[Geronimo John]

I'm a bit of a nerd and if I have a 300 amp fuse in my battery + cable in route to the Inverter (as Ollie installs), then I'm not going to use a 125 amp disco.

For my use, I installed the BlueSeas 350 amp version. Used a small bus bar to connect it to the RED (+) terminal and then reconnected the cables to the 350 amp rated Master Kill Switch.  Granted it costs significantly more than $8.  But for something critical like this.... Peace of mind rules.

GJ

 

[Mike and Carol]

5 hours ago, Wandering Sagebrush said:

Mike, thank you.  Location is exactly why I’m being lazy.  Plus the Ollie is so new (and elegant) to me that I’m hesitant to drill holes for cable routing and mounting screws.  I don’t understand why RV builders don’t provide a master switch for all circuits.  Even my Northern Lite has one parasitic circuit with the switch off.  The Airstream has several.

I didn’t drill any holes.  The switch sits on top of the middle battery inside the battery box.  Not fancy but functional and easy,  Mike 

[thompsonkd]

Would someone who has installed the battery cutoff, would you mind posting a picture? Because of the way the batteries are wired together, I find it difficult to know which battery to put it on. Seems like the negative post is more of a favorite than the positive post? 

[topgun2]

15 minutes ago, thompsonkd said:

Would someone who has installed the battery cutoff, would you mind posting a picture?

Note that this is a pic of when I had a cutoff switch installed and that these batteries a 4 Trojan T-105 wet cell batteries (not AGM).  It is also interesting that these are the original batteries - now well into their 8th year and still going strong.

Hope it helps you.

Bill

[Geronimo John]

2 hours ago, thompsonkd said:

Seems like the negative post is more of a favorite than the positive post? 

For the electrical wizards skip this post.  You know it already.

Most DC systems with fuses (Like our 300 Amp fuse on the + side of our OEM batteries) would have their master On/Off convenience switch on the same side of the battery as the fuse.  Granted, both will get the job done.  Just that being on the positive side is more prevalent than on the negative side.  Not a big deal for most applications.  But it could be for a first responder not familiar with your owner mod.  For example, Fire Fighters are trained to to look for a RED handle or device on the primary current carrying lines during a fire operation. This is because they are taught that when working with DC Electrical, there typically are only just four different colors:  

• Red – Red cables carry the positive current.
• Black – Black cables will be the negative cable.
• Grey or White – Grey or white cables are the ground wires.

And they are generally looking for the red wires to kill the power with their super sized cutters. I have seen this several times.  Sadly, I have also seen first responders cut wires within inches of a master On/Off switch.  None the less, it is no coincidence that the vast majority of RV master on/off switches are red in color and are mounted on the RED positive lead.  As many of you have seen this at least three times.... once again:  If you are going to add a convenient and quick way to totally kill the DC power of your trailer, I highly recommended this unit:  Blue Sea Systems 9003E (350 amp rated).  It just happens to be...... wait for it...... RED

 

WHY?  RV and NEC codes require that all high power DC circuits have at least one current limiting device.  In the case OE2's, most if not all have a 300 amp fuse on the + side of the battery. (See Note Below).   If a second current limiting device, such as a supplemental On/Off Master Switch, is installed, it MUST be rated for at least the capability as the primary current limiting device (IE. generally our 300 amp fuse).  For this reason the minimum size any engineer worth their salt would insist on using is at least a 300A master switch.  The impact of using a smaller switch can be "enlightening" and very costly.  PM me if you want the full monte explanation.  

I personally chose the above one.

John Russell  (AKA GJ)

Registered Professional Engineer, Former USAF Fire Marshall and  Incident Commander

NOTE:  For our OE2's, I have not yet seen any OEM Inverters beyond 3,000 watts.  And 3,000 watts at 12.7 volts = 236 amps.  So it is likely that ALL our OE2's have 300 A  fuses on their man positive battery cable fuses as OTT tends to design the wiring for all options offered, and the 3,000 watt inverter is the big boy unit.  If your fuse is higher or lower, please let us know. 

[John E Davies]

Under the dinette, the placard is upside down so you can actually read it with your head that way.

https://olivertraveltrailers.com/forums/topic/5450-how-to-battery-master-cutoff-switch-under-the-rear-dinette-seat/

John Davies

Spokane WA

[MAX Burner]

6 hours ago, Geronimo John said:

For my use, I installed the BlueSeas 350 amp version.

Ah!  Just saw this @Geronimo John !  Thanks for posting!!!

 

[MAX Burner]

6 hours ago, Geronimo John said:

Peace of mind rules.

AMEN, Brother!

[John E Davies]

44 minutes ago, Geronimo John said:

NOTE:  For our OE2's, I have not yet seen any OEM Inverters beyond 3,000 watts.  And 3,000 watts at 12.7 volts = 236 amps.  So it is likely that ALL our OE2's have 300 A  fuses on their man positive battery cable fuses as OTT tends to design the wiring for all options offered, and the 3,000 watt inverter is the big boy unit.  If your fuse is higher or lower, please let us know. 

Hull 218 has a 2000 w inverter and a 250 amp main fuse. I added a 175 amp terminal fuse block to each Battle Born battery. I dislike having unprotected hot wires, even very short ones.

https://olivertraveltrailers.com/forums/topic/5377-how-to-battery-feed-through-post-installation-reduce-the-clutter-in-the-battery-box-lithium-batteries-only/

John Davies

Spokane WA

 

[MAX Burner]

3 minutes ago, John E Davies said:

I dislike having unprotected hot wires, even very short ones.

Very smart set-up, @John E Davies

[mossemi]

Under the aft dinette seat.

Mossey

[Wandering Sagebrush]

5 hours ago, thompsonkd said:

<snip>  Seems like the negative post is more of a favorite than the positive post? 

I mentioned that I was an aircraft electrician in an earlier life.  I too prefer a master switch on the negative side.  Here’s why…

In my first squadron, right out of AE A school, I was sent out my very first job, to change a torn terminal cover on a battery bus bar (24VDC).  I removed the rubber terminal cover and proceeded to apply wrench to nut so I could slip the cover over the cable.  Suddenly… there was a bright flash of light, accompanied by the sound of a stick welder.  The wrench touched the airframe and became a wonderful conductor of 24VDC straight to ground.  Luckily, the wrench didn’t stick to that rib, but it did leave a very small divot, and I needed a change of skivie drawers.

I don’t remember if we were taught to always disconnect the power source before working on power systems, but we probably were, and common sense should have made me do so.   I suspect I was just an excited 19 year old LCpl who was elated to get his first solo job, and didn’t stop to think.

To this day, I always pull the negative lead before turning a wrench on a DC system.  The chances of grounding a wrench are real.

[Geronimo John]

19 hours ago, John E Davies said:

I dislike having unprotected hot wires, even very short ones.

Me TOO!  Hence here is how I did it using a solid copper buss bar from the Blue Seas On/Off and then direct connected to a buss bar with ALL the + loads.

Just be aware of the stack-up height and the clearance above the switch.  May limit your poly cutting board thickness.

GJ

[BBL]

All Lithionics Batteries have their own On/Off switch for changing cables or putting your trailer into storage. I still like some ideas shared here. Having an aircraft operations and maintenance background and a love for boats, battery disconnects are very familiar.

Brian