Main Battery Disconnect Install

[Boilermaker Chemist]

I am a new Oliver owner and am surprised to find that there is no main battery disconnect. Since we will be making frequent, short trips in and out of storage I would like to add one. I plan to purchase a Blue Seas 350 amp switch and connect it on the negative side. I have seen posts about using a short cable or small bus bar to connect the switch directly to the battery post. That seems like a simpler solution than others I have seen. I would appreciate hearing your comments about exactly how to do that – parts needed and where to purchase. We have the solar package with AGM batteries connected with 4/0 cables. Thanks in advance for any and all advice on this!

 

[mossemi]

49 minutes ago, Boilermaker Chemist said:

I have seen posts about using a short cable or small bus bar to connect the switch directly to the battery post. That seems like a simpler solution than others I have seen.

Your disconnect needs are different than mine, so I choose a location under the rear dinette seat.  I was interested in a disconnect switch in order to allow battery removal for a future battery upgrade and I wanted less obstacles in the battery box.  It will work for your needs wherever you place it.  I have some small pieces of 4/0 cable and I can make a short jumper if you provide the connectors and cover the shipping cost.

Mossey

[HappyCamper7424]

Thanks

Edited July 8 by HappyCamper7424
wrong account

[Boilermaker Chemist]

Thank so much for the offer, Mossey. I actually have a local shop nearby that has made cables for me in the past, so it will be quicker and more cost effective should I decide to go the cable route. But thanks again.

[katanapilot]

A Google search of this site will lead you to several posts of how owners have installed these switches.  Here is a picture of how I did mine during the lithium battery upgrade (which was shamelessly copied from Geronimo John).  Tie down straps added after the picture was taken. 

[Boilermaker Chemist]

Thanks for the photo, it is pretty close to what I am looking for.  Exactly what is the connector from the battery terminal to the battery switch?  Where did you purchase?

[katanapilot]

3 hours ago, Boilermaker Chemist said:

Thanks for the photo, it is pretty close to what I am looking for.  Exactly what is the connector from the battery terminal to the battery switch?  Where did you purchase?

I used some copper bus bar I had left over from one of my airplane builds.  I either got it from Aircraft Spruce, or more likely McMaster-Carr.  1/8" thick by 1" wide.  I bent it to shape in a vise, used an annular cutter to make the holes for the battery stud and disconnect.  Used heat shrink to cover as much of the exposed copper as possible. 

Edited July 9 by katanapilot

[Boilermaker Chemist]

Thanks for the detailed info, I like your approach rather than using a cable.  Now I can order my parts . . .

[rferg800]

Just remember that if you disconnect the batteries from everything including the solar charge controller you need to disconnect the  charge controller first from the solar panels. Or risk damaging the solar charge controller.

[Boilermaker Chemist]

Thanks for that warning, I guess that is one reason there is a disconnect from the solar panels!

[Boilermaker Chemist]

11 hours ago, katanapilot said:

I used some copper bus bar I had left over from one of my airplane builds.  I either got it from Aircraft Spruce, or more likely McMaster-Carr.  1/8" thick by 1" wide.  I bent it to shape in a vise, used an annular cutter to make the holes for the battery stud and disconnect.  Used heat shrink to cover as much of the exposed copper as possible. 

Since this disconnect switch will be handling a lot of amps I wanted to be sure to use the proper size busbar for this application. So I did a little more research and found a very helpful document on the Victron Energy website entitled “Wiring Unlimited” by Margreet Leeftink. Assuming that I did my calculations right, a 1/8” x 1” copper busbar only has a surface area of about 80 mm². According to the table below, the surface area for my 4/0 cable is 107 mm². So I am going to do a little more investigating before I order those parts.

[katanapilot]

A copper bus bar of 1/8x1” will conservatively handle 275 amps at 40c ambient with a 30c temp rise.  If you don’t think that’s enough, then upsize the bus bar. 

[jd1923]

1 hour ago, katanapilot said:

A copper bus bar of 1/8x1” will conservatively handle 275 amps at 40c ambient with a 30c temp rise.  If you don’t think that’s enough, then upsize the bus bar. 

It’s enough! 275A x 12 VDV = 3,300W. So you can run your A/C plus your microwave, at the  same time across this beautiful piece of copper! Limiting factors will never be the copper bus, but instead your inverter or the cabling to it. Go with the proven design that @katanapilot has illustrated. Nice install!

This copper 1/8x1x6” busbar on your B- terminal is likely a superior conductor than what your LifePo4 battery manufacturer has designed internal to the battery terminal, for sure! That’s all that counts at the final ground to the battery. 

Edited July 10 by jd1923
Added last sentence.

[katanapilot]

I have to ask why so many of you are using 4/0 cable? My Oliver came with 2/0.  Victron specifies 1/0 for the feed to the 3000va Multiplus 2 inverter for lengths less than 5 meters and 2/0 for 5 to 10 meters.

Just concerned that I’m misunderstanding the wire ampacity tables. 

[Boilermaker Chemist]

4/0 is what was factory installed on our 2023 model.  Since main fuse is 300 amp, conductors have to be rated for that amount of current.

[jd1923]

2 hours ago, katanapilot said:

I have to ask why so many of you are using 4/0 cable? My Oliver came with 2/0.  Victron specifies 1/0 for the feed to the 3000va Multiplus 2 inverter for lengths less than 5 meters and 2/0 for 5 to 10 meters.

Just concerned that I’m misunderstanding the wire ampacity tables. 

You're not misunderstanding. Without doing the math myself, Victron's numbers appear correct. Over-engineering is common in DIY efforts and going to heavier gauge cable doesn't hurt, just costs more money.

OTT installed 4/0 in our hull too. The length of the run, from the batteries to our 2KW inverter under the rear dinette seat is about 1m or 4 ft at most. The Oliver is over-engineered in many ways, and we appreciate that. The cost difference of 2-3m of 4/0 over 1/0 cable, at wholesale to a manufacture, is not much and they are being over-safe for a few bucks.

When I go to install a DC-to-DC charger, two cables the length of TV and TT, likely over 25m, I will buy the gauge required and nothing more due to the retail cost of copper today!

[Ronbrink]

15 hours ago, jd1923 said:

When I go to install a DC-to-DC charger, two cables the length of TV and TT, likely over 25m, I will buy the gauge required and nothing more due to the retail cost of copper today!

I used 4AWG cable for my DC-DC install, bought 50’ red+, 50’ black-.

[katanapilot]

18 hours ago, jd1923 said:

You're not misunderstanding. Without doing the math myself, Victron's numbers appear correct. Over-engineering is common in DIY efforts and going to heavier gauge cable doesn't hurt, just costs more money.

OTT installed 4/0 in our hull too. The length of the run, from the batteries to our 2KW inverter under the rear dinette seat is about 1m or 4 ft at most. The Oliver is over-engineered in many ways, and we appreciate that. The cost difference of 2-3m of 4/0 over 1/0 cable, at wholesale to a manufacture, is not much and they are being over-safe for a few bucks.

When I go to install a DC-to-DC charger, two cables the length of TV and TT, likely over 25m, I will buy the gauge required and nothing more due to the retail cost of copper today!

"No kill like overkill" 😉 4/0 cable and connectors are just harder to install and bend radius is higher. 

Victron is perfectly happy with 1/0 cable up to 5 meters long and a 400 amp fuse. I'll use 2/0 for 4 foot run and feel perfectly comfortable with that.  And I am typically the king of overkill.

 

[Boilermaker Chemist]

8 hours ago, katanapilot said:

Victron is perfectly happy with 1/0 cable up to 5 meters long and a 400 amp fuse. I'll use 2/0 for 4 foot run and feel perfectly comfortable with that.  And I am typically the king of overkill.

 

 

 The way I read it, TWO 1/0 cables would be required, which is equivalent to a single 4/0 cable.  Admittedly, I am not an electrician, so if I am missing something, please feel free to correct me.

[katanapilot]

11 hours ago, Boilermaker Chemist said:

 The way I read it, TWO 1/0 cables would be required, which is equivalent to a single 4/0 cable.  Admittedly, I am not an electrician, so if I am missing something, please feel free to correct me.

You are absolutely correct.  What I don't know is if Victron requires the two cable connection - to spread the load over the two input studs - or if a single 4/0 connection would be sufficient.  I will reach out to them to ask. 

I looked again and my OEM cables are indeed 4/0.  That being said, I currently (pun intended) believe the 2/0 battery interconnects are sufficient given the very short length of these cables and the 300 amp fuse I have installed.  I am going to consider piggybacking an additional 2/0 cable between the 3 batteries.

Thanks for being persistent and forcing me to RTFM a couple of times.  

[Geronimo John]

Another caution:  Different hulls have different dimensions, trays, and batteries,  Hence one pic may not work for all as our stack heights vary.

On my 2018 with 100 AH batteries I could not use such a thick cutting board.  

Check yours before purchase is a good plan.

GJ

 

 

[Boilermaker Chemist]

6 hours ago, katanapilot said:

Thanks for being persistent and forcing me to RTFM a couple of times.  

Haha, reminds me of what my brother-in-law said he learned in the marines about assume - it makes an ASS out of U and ME. I hate to admit that the older I get, the more I am reminded of that quote!

[jd1923]

6 hours ago, katanapilot said:

You are absolutely correct.  What I don't know is if Victron requires the two cable connection - to spread the load over the two input studs - or if a single 4/0 connection would be sufficient.

Doubling up cables can increase the overall amperage in the connection. They have tables for that online. The dual terminals in the Victron multiplus can be used in this way, but as evidenced above, one 4/1 is already overkill.

I'm going to use the second post to connect 12VDC +/- to the Oliver 12VDC fuse panel. The OEM wiring has both connected directly to the batteries. This will clean up the battery bay, using the built-in Victron bus vs. adding another.

The true reason for the dual terminal is that Victron products are designed to be installed in multiples. Use of the second terminal can daisy-chain multiple inverters side-by-side.