Essential Guide to 120-Volt Power Converters for RVs

The power converter is an essential component in an RV’s electrical system. Typically, coaches have two essentially separate electrical systems; one that provides 120 volts AC to high-power consumption, high-wattage appliances such as coffee makers, microwave ovens, hair dryers, air conditioners, etc. The other, low-voltage part of the electrical system provides 12 volts DC to lights and other items which don’t have high current draws, and are sometimes powered by onboard batteries (which provide power when you’re not hooked up to an outside power source or generator).

Power Converter
Top left: Parallax Series 7300; top right: Iota Engineering DLS Model; bottom left: Progressive Dynamics Model PD9250c; bottom right: Xantrex Truecharge 2-40a

When you are connected to campground power or running off a generator, the power converter changes the 120 volt AC power to 12 volts DC, which is compatible with the low-voltage electrical system and batteries. This electricity supplied by the converter can take the place of the power from the batteries, and can also recharge them.

Many basic single-stage converters, typically found in older and lower-priced coaches, are still in use. They don’t have the sophisticated internal circuitry to properly charge and condition batteries. Some converter models supply only a fixed voltage of around 13.2 volts, which prevents batteries from reaching full charge and also shortens their service life. Modern multi-stage charging circuits typically include four operation modes: boost, normal, equalization and storage (or float).

Related article: RV Battery Basics: A Beginner’s Guide

Batteries have become quite expensive, and faulty charging by the converter can be both inconvenient due to loss of power, and costly in terms of ruining batteries. It’s likely that the majority of RV batteries succumb to sulfation, rather than actually being worn out, or dying of old age. Sulfation occurs when lead sulfate forms on the internal plates and reduces or even halts the battery’s ability to accept and hold a charge. When batteries are stored in a partially charged or discharged condition, and/or are improperly charged, sulfation occurs.

Batteries are sensitive to charging voltages and require multiple charging stages to get a full, proper charge. Multi-stage power converter/chargers that have an equalization stage are needed for effective battery charging.

One of the best things you can do for the life of your battery/ies is to familiarize yourself with the type of power converter you have in your coach. Many owners don’t even know where their converter is located. Typically it’s a metal box a little bigger than a large box of facial tissues and is situated adjacent to the fuse panel, near where the wiring comes into the coach. When it is powered up, it gives off a humming sound, which can help you locate it. Usually the make and model and power ratings are written on the case. You can also look up the ratings in the manuals that come with the RV.

Modern converters operate automatically and have become more efficient. Some newer models combine an inverter, which provides 120 volt AC power that’s produced electronically from 12 volt DC battery power, when the coach isn’t connected to an outside source of electricity. These add convenience and many owners upgrade to inverter-type power supplies when replacement time comes.

Troubleshooting Power Converters

If you have some DIY skills you can perform basic troubleshooting on your power converter. Power converters require sufficient voltage input to operate.

  • Begin by checking voltage at the outlet the RV is plugged into. Use a handheld multimeter to check voltage at the campground outlet. It should range between 108 and 130 volts, preferably 120.
  • Next, check to see if the circuit is protected by a ground fault circuit interrupter (GFCI). If so check if the GFCI is tripped, reset if needed.
  • Then check for power going into the converter inside the coach. See if it has fuses on it; replace burned out ones with exact replacements.
  • If everything checks out, listen; the unit should hum if it is operating.
  • After that, measure for DC voltage (which requires a different scale on the meter) where power comes from the converter into the 12-volt DC breaker box. It should be around 12 to 14 volts if it is operating properly, if it’s lower you may have a faulty power converter.

Converters also have a small fan which cools the internal components during operation. The cooling fan should go on and off during converter use, controlled by a temperature sensor. The fans usually run on 120 volts AC, so be careful when measuring voltage and use the 200 volt AC meter scale. Make sure voltage is getting through the temperature sensor to the fan motor before condemning the motor. If the fan motor is good, you should be able to jumper wire the sensor and get the fan to operate. In this case, replace the sensor.

Replacing a Converter

Power converters are available in various amperage output ratings, designed to meet the RV’s 12-volt DC system demands. The larger and more amenity-filled the coach, the higher the power requirement. Converter 12-volt power output ratings generally range from about 20 to 100 amperes (amps), although small campers may have less. Usually the original unit is sufficient for the electrical loads of the RV as it came from the factory, but if you have added 12-volt electrical lights or other items, and find that there’s sometimes not enough “juice” you may need an upgrade.

A major reason owners upgrade is to get more modern multi-stage charging features with an equalization mode, to improve charging and extend battery life. Batteries are also sensitive to extreme temperatures; they lose power at low temperatures and outgas and give off more water during charging at higher temperatures. Some converter manufacturers offer models which have temperature compensation circuitry, which adjusts voltage and charge rates according to temperature. This feature is not only convenient, but extends battery life.

Some folks always have their RV connected to shore power, and find it a nuisance to have to install, maintain, and replace batteries. With many power converters, the 12 volt DC current they provide is not smooth and free of AC “ripples” and voltage variations which cause problems with some sensitive DC electronics. Batteries soak up ripples and small voltage spikes to protect these devices. However, Iota Engineering has a DLS converter series which produces smooth DC power that’s compatible with sensitive electronic circuits and can therefore be used without a battery in the system. Iota also offers the IQ4 Smart Charge Controller which adds multi-stage battery charging capability if you do decide to run batteries.

When it comes time up update your converter, take your time shopping. There are many useful features, and some models can be upgraded rather than being replaced. With all of the models available, you can tailor your power supply to your RVing needs.

You might also be interested in this free video RV Power Converter Troubleshooting:

Popular Sources

Iota Engineering

Parallax Power Supply

Progressive Dynamics


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102 Responses to “Essential Guide to 120-Volt Power Converters for RVs”

  1. Michael Lopez

    Fridge is not powering with gas usage from propane Hello Michael, Great question! The ‘Ask an Expert’ section is currently for members of our online community. By becoming a member, you will have access to our expert knowledge. With your membership you will also receive discounts on products and hundreds of hours of Premium content. If you are interested in becoming a member, please click on the offer below:{{SubKeyHash}} Thanks!

  2. Stan

    Converter is bad and bought a series 4600 but the new dc board has more spaces for fuses and wiring and all of the wiring from old DC board are purple and have no idea what wire goes where . Old converter had blue,red,white coming from right side and only white and black from left side, new converter has white,black,green from left side and only white and black on right side , behind old DC board there's a green wire and a large black wire and all the smaller wires than went to fuse area are all purple . Have no clue where to hook all them wires to on DC board , old board only has enough spots for the wires that are there , new board has way more .

  3. Kirby Doiron

    Looking to replace a 12 volt power distribution center part number 111979a

  4. Gary michael Rice


  5. John Sidock

    I need a 30 amp Invertor converter pic u have shows 7300 parellax series

  6. Gary Gernstein

    Problem - no power getting to my ignition switch, slide-outs, radio, etc. The battery shows a good charge. Could I have shorted out an inverter or relay? The fuses all look good. Where should I start looking? Replaced the coach and chassis rocker switches as well.

  7. Bobbie

    How and where can I get a power compasitator in the power supply box?

  8. Ray

    My RV is permanently parked with shore power and a backup generator. I am tired of having to replace the deep cycle batteries at over $100 ! Can I just get a converter without a charger? Can I run my Intel without the battery? I have been looking for a converter without a charge but can’t find one Help

  9. George

    My camper sits powered up in a remote location for several years at a time. A couple days ago when we were on-site, the lights started flickering and, from near the power panel, a clicking sound was being made, sounding like a relay chattering. When I turn off the breaker powering the voltage converter, the flickering and chatter noise stopped, leading me to believe I have an issue in the voltage converter. During troubleshooting, when shore power is turned off, the coach lights don't work. Although I haven't checked my battery I think it's probably dead and needs replacement. My question is, will the dead battery cause the light flickering and noise on its own? I'm going back to location next week and will measure battery voltage and inspect the coach power panel & its fan as a start. Any assistance is appreciated. Per owners info packet, it appears that the existing (original) converter is an IOTA Engineering unit, Model ILC 3045, S/N 36405.

  10. Kurtis smith

    I have a rv electric outlet I would like to be able to plug in standard 120 outlet does anyone know of a adapter or do I have to get electrician