Extending battery cables using junction posts in to install new inverter?

[Bourgon]

Hi Everyone,
My first post. Been reading a lot of interesting information on this site but now I have some questions.

First, I have a 2019 Outlook 22C class C. I upgraded the batteries and now have 232 Ah. The OEM 1000w inverter is located in the cabinet, under the stove top, on the floor, in a really crowded space. I would like to install a 2000w but there’s no room. Plus, even if I could squeeze a new inverter in there, the battery cables are too short.

There is lots of room under one of the dinette seats, on the other side of the RV, where there’s already some electrical running. There’s a convenient chase way running from under the dinette seat, under the floor, to where the current inverter is. I’m pretty handy and knowledgeable when it comes to home wiring, so the 110v re-wiring doesn’t scare me, but battery cables, I don’t have much experience with.

I’ve seen battery power junction posts on sale on different sites. I’ve seen various installations to power winches and all sorts of things but I haven’t found anything relating to RVs.

My questions are: could I simply install black and red junction posts in the cabinet where the current battery cables run, and connect new battery cables that would extend under the floor to the new inverter (I would insulate them once installed with something like liquid tape)? Is that safe? Legal? Or do I have to run whole new cables from the batteries, through the floor, to the new inverter (seems more difficult to me)?

Any help would be greatly appreciated.

Luc

[DavidM]

First of all your new 2,000 watt inverter is going to use twice the amps of your old 1,000 watt inverter. That means that the battery cables need to be two sizes or maybe four sizes bigger due to the increased current and the longer distance. So do not use the existing cable.

Run two new cables from the positive and negative battery posts to the inverter. A 2,000 watt inverter will pull 2,000/12= 170 amps. To keep the voltage drop down to a half a volt you will need the following gauge wire, depending on distance from the battery to the inverter:

10 feet- #2 wire
15 feet- #1, preferably 1/0 wire
20 feet- 2/0 wire

Auto parts stores can usually supply the wire and crimp on the terminal connectors for you.

David

[Bourgon]

Hi David,

Thanks for the advice. I hadn’t really thought of that but I did notice that all the battery cables on the house side are #2/0 when I replaced the batteries. The max cable lengths are maybe 6 feet, so they really went on the safe side on those. I would have used the same size.

Any idea what the grey expanding spray foam is they use to seal up the holes is? I’ve never seen that stuff anywhere. The only one I’ve ever seen is the standard yellow stuff you get at any big box hardware store. The grey stuff used by Winnebago seems harder.

Thanks again,

Luc

[Marine359]

If you use a junction post, or bus bar, make sure it is rated for 250amps and that you put a 250-300 amp terminal block fuse on it. 1/0 wire very difficult to work with, so it might be better to stick with 2 gauge.

[imnprsd]

Why do you need a 2000W inverter? What sort of appliance are you trying to run?

What about the idea of keeping our existing 1000W inverter AS-IS and adding another 1000W inverter for your extra loads... and add an extra wall outlet that is dedicated to your second inverter.

You can still use both batteries and 2 inverters.

Remember, the wires to the inverter should have an appropriate size fuse located as close to the batteries as possible, because the unprotected battery cable is like a welding cable if it shorts out; and that will start a fire.

[Elkman]

DC current drop is significant with distance which is why the inverters are usually placed as close as possible to the battery compartment. Lots of tables that show the current loss with distance for different size cables and if the new inverter location is 10 feet from the batteries then use 20 feet in sizing the cable. It is the area of the cross section that determines the current capacity and not the diameter of the wire. Often the wire sizing is to have no more than 3% current loss which leads to people using much larger cables than is necessary for the RV.

delcity.net is a great place to buy cable and connectors that use solder plugs. Put some flux in the end of the connector and insert the solder pellet and heat the connector with a propane torch until the solder melts and then push in the bare wires from the cable. Makes for a solid connection, mechanically and electrically.

https://www.delcity.net/store/Termin..._1036.h_103464

And use heat shrink adhesive lined tubing over the wire and the connector end.

One thing I noticed with the inverter installation by Winnebago on my 2021 Navion is that it is upside down in its orientation which makes it doubly difficult to read the display and change settings.

[MadMaxWinny]

Kudos to Elkman. So many people neglect to double the distance for the wire gauge charts. Like he said, if it's 10 feet away, you use the 20 foot value on the chart for roundtrip. I only use marine grade electro-tinned cables, which are horribly expensive. To insure I'm not buying too much (or worse, too LITTLE), I do my cable routes with light rope, adding enough for stress-relief.

As for the ongoing solder/crimp controversy (almost 80 years now), an overheated wire can melt solder. If it is tinned wire, a torch can break the molecular Tin/Copper bond which promotes poor connections and corrosion. A proper crimp holds up under heat, vibration, and corrosion. If it's less than 20 gauge, solder to your heart's content, otherwise crimp (properly).

[Elkman]

The connections that fail either mechanically or from corrosion are the ones with crimped connectors. Crimping is faster and no need for head but there is much less wire to connector in contact with a crimp connection.

Crimping is cheaper and less labor is involved but when I am doing an installation the last thing I want is to do it twice. I was using a special crimping tool and a hammer for connections with large gauge wire until I learned of the solder plugs sold by delcity.net that provide a far superior connection for automotive and solar bank battery wiring.

[MadMaxWinny]

Originally Posted by Elkman

The connections that fail either mechanically or from corrosion are the ones with crimped connectors. Crimping is faster and no need for head but there is much less wire to connector in contact with a crimp connection.

Crimping is cheaper and less labor is involved but when I am doing an installation the last thing I want is to do it twice. I was using a special crimping tool and a hammer for connections with large gauge wire until I learned of the solder plugs sold by delcity.net that provide a far superior connection for automotive and solar bank battery wiring.

We'll have to agree to disagree. Only if you are using cheap welding cable or automotive wire can you have a degraded connection from a crimp. A multi-strand, electro-tinned, properly crimped connection forms a superior molecular bond. I would not include a hammer in a properly performed crimp connection.

[Mogen]

I have a 2019 Outlook 25J. I think the stove cabinet assembly is the same. Below the stove is a cabinet, below that a drawer that must be removed to access the inverter.
I got my inverter off the floor and mounted it upside down to the cabinet floor above the drawer. The 110v wiring mounted up there, too.
I had to get all the slack out of the battery cables to get them to connect without having the drawer interfere with them but, since you are upgrading the cables you can make them plenty long.