RV Inverter Install: Four Different DIY Methods to Get off the Grid

Hopefully you have read my previous post “How to choose the Best RV Inverter” which means you did your research, estimated your power requirements, and finally came to a decision. You ordered your inverter and today, it arrived. You are now ready begin your do-it-yourself RV inverter install.

rv-inverter-install-1

If you went with a small inverter (around 75 watts), then it can be plugged into a cigarette lighter outlet. Anything larger will need to be wired directly to your batteries. In order to reduce the voltage loss, you need to install the inverter as close to your batteries as possible. The inverter manual will probably suggest a wire size. Use the recommended size or larger. Remember that the bigger the wire the smaller the gauge number. Whatever you do, you want to limit the voltage drop as much as possible. You should make every effort to keep the loss below 0.075 volt.  The table below gives the voltage drop per foot of wire for various sized inverters which is very important to consider for your RV inverter install. For other inverter sizes, the drop will be proportional.

As an example, using the table below, assume that you will be installing a 2000 watt inverter (Scroll top to bottom and find 2000 watts). It will be connected to the batteries with 5 feet of #4 AWG cable (scroll right to left from the 2000 watt load till you find the 4 column). The voltage loss will be .0420 x 5(length of wire between battery and RV inverter) = .210 volts. This means that if your batteries are charged up to 13 volts, the inverter will only be seeing 12.79 volts (13 Volts - .210 of loss). It might seem to work, but you won’t like the results. It would be much better to go to a #00 AWG cable, which will have a total of .066 volt loss which is well under the recommended .075 volt loss threshold. The best approach is simply to use the largest size that will fit in the inverter’s terminals.

RV Inverter Install: Voltage Loss Per Foot of Wire

Wire gauge (AWG)
#0000
#000
#00
#0
#2
#4
#6
#8
For 100 Watt Load0.00040.00050.00070.00080.00130.00210.00330.0052
For 500 Watt Load0.00210.00560.00330.00410.00650.0110.01650.026
For 1000 Watt Load0.00410.00510.00650.00810.0130.0210.0330.052
For 1500 Watt Load0.00620.00830.00980.01220.01950.03150.04950.078
For 2000 Watt Load0.00820.01020.01320.01620.0260.0420.0660.104
For 3000 Watt Load0.01230.01530.01950.02430.0390.0630.0660.156

If you have trouble finding suitable wire for your RV inverter install, automotive battery cable or jumper cables are readily available in 4, 6, and 8 AWG (American Wire Gauge). Welding cable comes in larger sizes, but is expensive as many times you have to buy a whole spool. If there is a supplier near you, see if they will sell the short lengths that you need instead. You might get lucky at your local welding shop.

The AC (Connecting the inverter to the RV electrical system) side of the RV inverter install can get more complicated. For starters, you need to ensure that you do not have either shore power or generator power connected to the output of the inverter. Otherwise, you will destroy it. There are several possible ways to accomplish this. Whichever option you select, you can do the wiring with standard 14 AWG, household type nonmetallic cable.

However you do it, you absolutely must ensure that you do not have your converter turned on when the inverter is on. The problem with having both on at once, is that you are pulling current out of your batteries with the inverter, while pushing current back into them with the converter. Since neither the inverter nor the converter are 100% efficient, each trip that current makes around the loop will waste some power as heat. You will very quickly run down the batteries until the inverter shuts off for low voltage. That will happen even if no load is connected to the inverter.

On The Next Page: RV Inverter Installation Methods

Comments

  1. William says

    Thanks. Now I’m sure I will use option 4 and plug the rv into it. Will the fridge and water pump be getting power from the inverter with this installation option? Thanks.

    • says

      Everything in your RV will be getting power as it would at a campsite hookup. This can be a problem because you will need a large enough battery bank and inverter to run it all! Our fridge uses 350-450 watts but it could be significantly more depending on your model. Keep that in mind when purchasing your inverter and setting up your batteries. But the basic answer to your question is yes.

  2. William says

    I have another question. Do you turn off the converter for options 3 and 4 or just for option 4? Thanks.

  3. Scott says

    Your articles are great. Thanks to you I now have an inverter in my RV that works very well. However I want to make it idiot proof and install a Packard pr341 relay. I can’t find a wiring diagram showing which posts to hook the inverter to and which posts to hook the converter to. Would appreciate any help you could give me.

  4. Gerry Branson says

    William, the short answer to your question is yes on using the inverter while the RV is running. It should not hurt to do so, we know many who have a crockpot running off an inverter with their favorite slow cook meal while traveling between destinations (my wife and I included). The inverter takes 12 volt power from the house batteries and changes it into 120 volts AC which you can use to power your microwave, your TV, etc. That reference of push or pull refers to the inverter itself being only able to do one at a time. Keep in mind I am not a trained electrical technician. But I hope my experience helps!
    Gerry

  5. William says

    I really appreciate your articles. I’ve learned a lot from them. My question is: if I turn off the converter to use the inverter, can I use the inverter while the RV is running? You mentioned that you can only either push or pull power from the house battery. And since the alternator charges the house battery when the RV is running, will it hurt to use the inverter while RV is running?

  6. Gary_RVRoamer says

    Nope, you aren’t missing anything. Some RVs are wired that way right from the factory. Winnebago has used that method in quite a few models that have small inverters dedicated to the entertainment systems only.

    Good luck with your project!

  7. Jim says

    First, thanks for the article and ideas.

    I’m considering option #3, dedicating an outlet to the inverter ( just for the entertainment center ).

    If this is the case, I should have clean power to the input side of the inverter, regardless of if the DC power is just from the battery cells themselves, or if the charger happened to be “on” due to shore power supply.

    So, basically, the TV is plugged in all the time to DC inverted power: sourced from battery provided DC power or shore provided DC power.

    Am I missing anything?

  8. Dan says

    Thanks for the informative write up. I’m going to try option one with the transfer switch in my 1986 class C RV which has a Parallax 6300 series power center with the optional battery charger. My question is: Do I need to do anything about the converter if there is no battery attached to it? I have a separate bank of batteries that will be charging from solar panels which connect to the inverter which will supply AC power to the AC power center.

    From your first page, you indicated that the danger of the converter and inverter being on at the same time is that you would be creating a loop which would discharge your battery when no load is being applied. Obviously this couldn’t happen if the converter and inverter are not attached to the same battery. However, I’m still wondering if you could see any problems arising if there is no battery connected to the converter and only the inverter is being powered? Should I just disconnect the converter as a precaution against a possible phantom load?

    Cheers,

    Dan

    • says

      “As long as the batteries powering the inverter are not connected to the converter/charger in any fashion, I can see no problem. You should take precautions, though, to make sure nobody decides to hook in a battery without your knowledge. I’m sure you will say “can’t happen”, but people often forget over time, or perhaps a buddy decides to help you out with a battery while you aren’t on hand to explain why you don’t have one there. Things like that do happen, so it’s best to make sure they won’t. A simple switch on the charger power source would do the trick” – GaryRVRoamer

  9. Larry keehne-la Verne says

    I like your idea of wiring a 30amp recepticale to the inverter out put. If i am using a inverter/charger will my batteries still charged? I think the answer is only when on shore power or generator.

    Do you have a brand preference?

    • says

      Hi Larry,

      Thanks for your question. This excerpt says it best from http://www.wind-sun.com/ForumVB/showthread.php?16719-Off-Grid-Inverter-Battery-Charging

      “Current either flows from the inverter to the batteries or from the batteries to the inverter. It can not do both at the same time over one set of wires. I’ve yet to see any inverter with separate wires for charging and discharging the batteries.

      Even with those inverters that can do load sharing/shedding they are either drawing from the batteries or sending to them. This may change form moment to moment depending on the load draws, but it is still a one-way street. While charging no power is being drawn from the batteries. If power is being drawn from the batteries no charging is occurring.

      Note that you can have a separate stand-alone charger for the batteries (as many do with inverters that have no built-in charger)”

      See our post How to choose the Best RV Inverter for our favorite brands.

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