Mod #10: Power Inverter

Mod #10: Power Inverter

Submitted on: 06/14/08

     Category: electrical, featured
Mod Rating: 12345

(22 ratings)

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Mod Description:

This mod often stirs spirited debate in the RV community on the “bang for the buck” argument. Oftentimes, the question will arise on how to run a coffee pot or a microwave without a generator or other 110 VAC power source to the RV. On the one side, you have those who prefer to just use a good old coffee percolator over an open flame. On the other side, there are those who would prefer some of the conveniences of home when camping, i.e., running the microwave. On the third side, there are those who just want to run a TV/DVD or charge their 2-way radios. Whatever the case may be, there are a multitude of ways (and costs) to accomplish what you want. Since inverters come in all shapes, sizes, and efficiencies, choosing and installing the right one can be a daunting experience. So let’s start with a few of the basics and work up to some examples.

Mod Difficulty:

A power inverter uses direct current (DC) power to produce alternating current (AC) power, like in your home. In an RV, an inverter is connected to the battery and provides 110 VAC for running appliances, like a coffee pot, microwave, or electronics like a TV, satellite receiver, computer, or cell phone charger.

Depending on what you want to power, there are many sizes available, from 50 watts all the way up to 5000 watts. These sizes, or ratings, determine how much power can be supplied by the inverter. For example, if you want to power a typical 4-cup coffee maker which has a power consumption rating of 800 watts, then an inverter rated for 1000 watts is a good choice. Another example is an LCD flat panel TV/DVD combination, which has a very low power consumption rating of around 100 watts for a 19 inch size. You only need a low-power inverter of around 150 watts if this is all you want to run.

Inverters use 2 differing ways to generate AC power: modified sine wave and pure sine wave. The former, for the same power rating, is generally much less expensive than the latter. If you want to power sensitive electronic gear, like a laser printer (don’t laugh, some full-timers do it on the road!), or even a microwave, the pure sine wave inverter is the proper choice. Most other devices and appliances will work well with a modified sine wave inverter but there are some that are very finnicky or don’t work at all, like the digital control on an electric blanket or mattress warmer.

Inverters also can be packaged with a battery charger and automatic transfer switch built in, though these types are quite expensive and are generally reserved for the mid-to-high level trailers and motorhomes requiring high power delivery. This is very convenient way to have many components packaged into one form factor, eliminating some of the wiring work required when using separate components.

So now that you have a little background on inverters, let’s take a look at a few example installations. First up is the low-power install (see image) meant to power an LCD TV. Simply plug the inverter in to the 12-volt receptacle (typically found near where the TV is mounted) and plug the TV in to the inverter. Yup. That’s it. Since the power requirements are less than 150 watts, the 12-volt receptacle has adequate wiring to carry the power required.

Next up is a mid-power inverter powering a coffee pot (or anything else less than 1000 watts). This type of installation is a little more detailed. Because of the high input current requirements (nearly 100 amps!) to produce 1000 watts of AC power, the inverter must be directly wired to the battery, rather than through the 12-volt receptacle as described above. Typically, this means that the inverter should be placed within 5 feet of the battery (but not in the same compartment) to avoid voltage drop from the battery to the inverter, resulting in poor inverter performance. Large gauge cables, 4 gauge in this case, should be used for DC connections to the inverter through a 150 amp fuse.

AC wiring is as simple as plugging the shore power cord in to the inverter. This will power the entire RV so it is essential that the converter, refrigerator, air conditioner, and electric water heater breakers are all turned off at the AC distribution panel, especially the converter. The converter, when supplied AC power, will begin charging the battery. This will in turn deplete the battery supplying power to the inverter, which is supplying power to the converter to charge the battery. It becomes an endless loop and will run the battery dead in no time.

There are other AC wiring options so you don’t have to remember to turn off certain breakers. It involves wiring in a sub-panel, which is a panel of AC breakers separate from the main AC distribution panel, that is dedicated to circuits in the RV you want to power. A transfer switch, which ensures that no 2 AC power sources can be connected to the RV at the same time, is required as well since the inverter will be “hard-wired” to the AC distribution panel. This type of installation isn’t for the faint of heart. If you don’t have the skills required, have a certified electrician assist or do the job for you.

Finally, there is the whiz-bang super duper high-power inverter/charger/transfer switch combination installation. This is the creme of the crop and is typically found in either higher-end motorhomes or in RVs whose owners can afford to not have to worry about powering anything. Inverters in the 2000 to 3000 watt range are used to power anything from a convection microwave oven to a washer and dryer. Some are even wired to run the air conditioner in a pinch, though not for very long.

The type of inverter described above will have a remote control panel to manage and monitor many electrical parameters, such as battery status, AC information, inverter mode, charger mode, and overall system information. These can be adjusted to meet the demands of your particular installation, particularly battery charging. Adjustments can be made for battery types, charging times, and temperature-compensated charging.

At this power level, a large battery bank is required, typically consisting of 6 to 8 6-volt golf cart deep cycle batteries. As detailed above, the inverter must be very close to the battery bank and have cabling of sufficient size to handle the input current requirements. 4/0, or “four-ought”, which is over a 1/2″ thick, should be used at this power level, along with a 300 to 400 amp inline fuse in the positive cable. A competent RV electrician or very knowledgeable RV enthusiast should be consulted to provide the design and installation.

Warning: Always follow the inverter manufacturer’s installation guidelines, paying close attention to proper wire sizing. Installing an inverter requires understanding of safe electrical practices and electrical safety code. If you don’t have the necessary skills, get a qualified electrician to do the wiring. Don’t take chances with safety! I guess I cannot emphasize this enough having cooked one inverter myself.

ModMyRV recommends these parts for this mod:

Power Inverters
XANTREX XM1000 Pro Series Iinverter 1000 Watt
Go Power! GP-SW1500-12 1500-Watt Pure Sine Wave Inverter
2000W Inverter/charger High-efficiency - 12V Dc Input; 120V Ac Hardwired Input
Go Power! 50 Amp Transfer Switch
Go Power! TS-30 30 Amp Automatic Transfer Switch
Power Bright 0-AWG6 Power Cables for Inverter
Power Bright 0-AWG3 Power Cables for Inverter

General Reference
The 12-volt Side of Life

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19 Comments For This Mod

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  1. Bob Vaughn

    I did this mod to our TT so that when the hurricanes knock out the power to the big house I can go to the TT and get weather reports on the TV in the camper…..On the surface it seemed like a pretty easy installation but it turned out to be labor intensive….of course it may have been where I chose to install it to take up less space…

  2. ModMyRV

    What type of inverter did you install? And where did you install it? My install was pretty labor intensive as well. But I took my time, doing the mod over a couple of days. I’m kind of a stickler for neat wiring so that took the majority of time. I also wired in a sub-panel as well. Did you go that route too?

  3. Bob Vaughn

    I installed mine in the cabinet underneath the TV…
    http://community.webshots.com/album/570449413Sovoyq

  4. Bob Vaughn

    I also bought a small inverter to plug my wife’s lap top computer into in the tow vehicle…..

  5. ModMyRV

    I just did this too. I bought a 75 watt version and a AC to USB adapter so I can also charge USB devices, like my iPhone and BlueTooth ear piece. Works great!

  6. mhotchkiss

    Check truck stops for 12 volt toys to avoid the need. Also they have huge supply of inverters at the best prices.

  7. ModMyRV

    Good advice! I’ve been to a few truck stops during my camping travels and have seen the huge supply of 12-volt goodies. My DW always has to drag me away from that area of the store…

  8. blacknugget

    I’ve done this one, but did not hard wire it. I purchased a 1000w pure sine inverter, and built some cables with jumper clamps. When we dry camp, I always take along a spare 12v marine battery, besides the 2 6v batts in the camper. This way I can hook up the inverter to the spare batt and plug in the 20″ lcd outside. Good for powering up our string of lcd lights for the awning too.

  9. partero

    When I decided to replace my RV’s original Battery charger, I selected the Tripp-lite 750 watt model, as it seemed to be the best choice for the loads that exist in my motor home. 165 watts for my 42″ TV/monitor & 135 for my computer are the only directly connected loads, so that would leave plenty of power for any occasional loads such as a drill motor, etc. The beauty of this model is that it is a true UPS, loads connected to it do not see virtually any “off” time when the 120 VAC fails and this unit switches silently and instantly to making AC from your house batteries, so if your Computer is running, it does NOT reset!
    Plus this unit has 3 step charging, equalizing option, 200% output for 1 minute, an optional remote control, and many dip switch settable options. Lists for +$500, but if you shop around, you can get it for a bit under $350. Mine has been on line 24/7 for about a year, without any problems.

  10. Splitshaft

    We have had a 3,000W modified sinewave inverter installed in our 24′ TT for 8-years. We leave it running constantly to power all of our AC appliances and devices when dry camping, other than running the refrigerator which we set to gas. Depending on the state of charge of the batteries, it can run the air conditioner to cool down and keep the trailer cool at night. If the battery charge is good, it will run both the roof AC and microwave at the same time. What is amazing is the microwave clock keeps perfect time when running on the inverter, just like plugged into shore power. The longest we have run on inverter power without plugging into shore power was two weeks. Depending on power consumption, the batteries must be charged daily or every other day using a generator and high output 3-stage battery charger. Fuel consumption averages about half gallon per day using a Honda 2,000ia if using the AC sparingly at night.

  11. ON-A-ROAD

    I went with the GP300 Watt pure sine wave. http://www.outsidesupply.com/go-power-300-watt-pure-sine-inverter-12-volt.aspx . I bought it from this site, (cheapest I found). We have a Onan LP 5500 Generator for serious power, so I went with the smaller watt Go Power inverter.

    I did a lot of research before I bought this inverter. It’s one of the best ones out there. Ours is over 2 years old now and have gave me no problems at all. (don’t buy cheap inverters, your new age electronics can be destroyed).

    It has an auto shut off if your batteries run to low, saving your batteries from damage. VERY easy to install and VERY, VERY easy to install remote port. I install the inverter under the front storage of our 5th wheel next to the batteries, and wired the remote up into the bed area inside our 5er.

    We can run our Satellite receiver, TV, or DVD movie, run a 60 watt lamp, and wife has her heating pad while boondocking NOT running the generator. Installing an inverter and 6 volt batteries, is one of the best upgrades you can do to your RV. (if you dry camp).

  12. lucy6194

    We have a 5th wheel 28ft Coachman. 2 12 volt deep cell batteries, a solar panel on the roof and 2000 watt Honda generator. Planning on purchasing 2nd so we can run AC when not hooked up) I want to be able to run TV DVD Direct TV box while boondocking. inverter has been suggested. Hubby wants to connect to one of the batteries of our F350 thinks would give us additional souce of power. I think best to hook to 5Th wheel batteries. We are pretty new to RVing. Spent July in maritime provinces and planning 6 month trip across USA and on to Alaska. Any suggestions that could possibly save an arguement!!!

  13. ModMyRV

    lucy6194, while the F350 battery(s) would seem like a good source of 12-volt power, I would suggest not using them to power anything in the RV except in an emergency. Automotive batteries are not designed to provide long-term power at medium to high current demands. And besides, if you inadvertently run down the F350 battery(s), you won’t be able to start the truck! Probably not something you want to happen while exploring Alaska.

    With the generator and solar panel, you are in a great position to provide both AC power and recharging of the RV batteries. A small inverter would work very well for times you are not running the generator or have hook-ups.

  14. photog101

    I did a mod like this in my last Class “A”. I put the 1200/3600W (Harbor Freight) inverter in the basement along with 4 T-115 Batteries (house side). I ran one line for the under cabinet coffee maker and the microwave. I re-routed the receptacles for those two items next to a single receptacle from the inverter. All I had to do was unplug either the micro or the coffee maker and plug them into the inverter, one at a time. This way I could make coffee or heat something in the early hours without waking other campers.

    I also ran another line to the dinette, but I rarely used it … but it was there.

    I also changed the original Magnetec converter (30A) to a Power solutions 60A with a Charge Wizard, which kept the T-115 batteries up to snuff.

  15. rt700

    I did this mod a year ago. I used a xantrex sw3000 pure sine wave inverter, an automatic transfer switch and used a Marinco ac receptacle - all with four 6 volt interstate batteries. It was a real job because there are so many things to think about. Make sure you understand what your appliances are using for power, especially if you are using a smaller inverter. You may want to use a sub-panel. Xantrex makes an awesome display panel for this unit and it tells you a lot about what’s going on with the system. In addition, I installed a xantrex link-pro so that I know all I can about the system. The sw3000 has a 150amp, 3 stage charger in it as well. Simply a great set-up. One final thought, if you aren’t 100% sure you know what you are doing, have an electrician do the wiring and hook ups. It’s too much money to waste if you wire it wrong and fry the system!

  16. Rae

    Thank you for this post! I had a sneaking suspicion that just plugging my RV into my inverter was way too easy. Thanks to this post, I now know that I need to turn off some breakers before plugging in.

  17. Stephen

    So plugging the inverter into my shore power cord I get but turning off all the breakers to avoid the loop…won’t that cut power going to everything or am I missing something…?

  18. RoadToad

    @Stephen….You are correct…The Breakers that you want to turn off are the ones that would overload the Inverter and the one that feeds the Converter (the “Loop” issue).

    Think of it as the Breakers are just switches to disarm any appliances that would harm the Inverter.
    Meaning, any high current loads (e.g. A/C, Microwave,) that exceed the inverters capacity.

    As a guide, be aware that every Amp out at 120V is (roughly)10 Amps load on the inverter input Batteries. Read the Load wattage of the Appliance and divide that number by 12 and you will have the current draw on the Batteries for Inverter input.

    Example; 800 Watt coffee pot load = 67 Amp input to Inverter.
    VASTLY IMPORTANT is the wire sizing to handle this amount of Current. Google for wire sizing for 12 Volt circuits.

    You must manage the loading of the Inverter by using your breakers.

  19. Marty Santic

    TS-30 Installation.

    Have looked at a number of websites but no one has suggested a solution so the battery charger in the installed coach converter does not charge the battery when the inverter is supplying 120 VAC to the rig. Pondered for a bit and decided to install a solid state relay. The small relay mounts very well in the TS-30 automatic transfer switch case. The relay I picked is small, requires very little power.

    See http://www.amazon.com/dp/B0058UX17G/ref=pe_385040_30332200_pe_309540_26725410_item

    Mount the relay inside the TS-30 and connect the coil side of the relay to the shore power side. Run some ROMEX to the installed converter and connect this ROMEX to the relay contacts in the TS-30. Break and connect the wire between the charger breaker and the charger. This wire pair will either connect or interrupt the power to the charger.

    The battery charger will then ONLY be enabled when shore power is present.

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