No Power in Your RV: Battery, Converter, or Inverter?

RV electrical confuses people because there are two separate systems sharing one rig, and the parts that connect them have similar names. Let's sort it out, because knowing which box failed saves you a diagnostic fee.

The two systems

12-volt DC runs off your battery. Interior lights, water pump, furnace fan and control board, slide motors, jacks, the fridge control board, vent fans, USB ports.

120-volt AC is house current. Comes from shore power or the generator. Runs the air conditioner, microwave, outlets, TV, and the water heater on electric.

The converter turns 120V AC into 12V DC. It's what charges your battery and runs your 12V loads while you're plugged in.

The inverter goes the other way — 12V DC out of the battery into 120V AC — so you can run outlets without shore power. Not every RV has one.

Same word, opposite jobs. That's the whole confusion.

Diagnosing by symptom

Nothing works at all, plugged in or not. Check the battery disconnect switch first. Then battery terminals — corrosion is the single most common cause of total no-power. Then the main fuse between the battery and the panel.

12V works on shore power but dies quickly unplugged. Your battery isn't holding charge, or it isn't getting charged. Test it: a healthy 12V battery at rest reads about 12.6 volts. Under 12.0 is deeply discharged. Under 11.5 is likely finished.

12V doesn't work even plugged in, but outlets do. That points at the converter. It's not making DC. Check its fuses and its dedicated breaker first — converters have their own, and it's often the failure.

Battery never fully charges, or lights dim when plugged in. Converter is failing or underrated for the load.

Outlets dead, everything else fine, on shore power. GFCI first. There's one outlet — usually in the bathroom or the kitchen — protecting a whole string of others, and it's often behind a panel or under a bed where nobody looks. Reset it before you do anything else. Then breakers, then the pedestal.

Outlets dead only when unplugged, working on shore power. That's the inverter. Check its own switch, its remote panel, and the large fuse on its DC input.

Everything is weak and dim on shore power. Low park voltage, or a bad connection at the pedestal or in your cord. Read the actual voltage.

Things worth knowing

A battery that starts your tow vehicle is not a house battery. Starting batteries and deep-cycle batteries are built differently, and using the wrong one gets you a short life and poor performance.

Converters have a service life. Original equipment converters in older rigs are often undersized and slow-charging, and upgrading is a real improvement rather than just a repair.

Corrosion on a ground connection produces the strangest symptoms in an RV — things that half-work, work intermittently, or work only when something else is on. If your problem is weird, suspect a ground.

Lithium conversions usually need a converter or charge profile change. Dropping a lithium battery into a system built for lead-acid without addressing charging is a common and expensive mistake.

When to call

Call when you've checked the obvious and it doesn't add up, when you smell anything hot, when a breaker trips repeatedly, or when you'd rather someone with a meter chase it than guess at parts. Electrical faults hide, and buying a converter that wasn't the problem is a costly way to diagnose.

We troubleshoot RV electrical as mobile service throughout our area — batteries, converters, inverters, generators, and the wiring between them.