RV Generator and Battery Issues on the Road

You are at a rest area, it is 96 degrees, and you go to fire up the generator so the dog is not sitting in a hot box. It cranks and does nothing. Or you boondock one night at a Walmart, and by morning the lights are brown and the water pump will not prime.

These are the two most common RV power calls, and they usually share a root cause: the rig sat, and nothing got exercised or charged while it did.

Two batteries, two completely different jobs

A motorhome has a chassis battery and a house battery bank. They look similar and they are not interchangeable.

A chassis or starting battery is built to dump a huge amount of current for a few seconds to spin an engine, then get recharged right away. It hates being deeply discharged, and a handful of deep discharges will ruin it.

A house or deep-cycle battery is built the opposite way, with thicker plates, to deliver modest current for hours and tolerate being drained and recharged over and over. It runs the lights, pump, furnace fan, slides, and jacks.

A travel trailer or fifth-wheel has no chassis battery, just the house bank plus whatever charge the tow vehicle trickles down the seven-way while you drive, which is not much.

Using a starting battery as a house battery is a common and expensive mistake. It works for a while, and then it is dead permanently.

Why house batteries die in year two

Lead-acid batteries, flooded and AGM alike, are killed by two things: being discharged too deeply, and being left sitting discharged.

The rule of thumb is that you do not take a lead-acid deep-cycle bank below about 50 percent state of charge, which is roughly 12.0 volts at rest. Every trip below that shortens its life.

Then there is sulfation. A lead-acid battery that sits partially discharged grows hard sulfate crystals on the plates, and they do not come back off. Capacity is gone for good. That is exactly what happens to a snowbird rig parked in April with the batteries half down and left in the heat until October. Come fall they show a decent voltage and then collapse the moment you ask for anything.

• Keep the batteries fully charged in storage, on shore power with a working converter or on a maintainer, and check on them.
• On flooded batteries, keep the water topped off with distilled water only. Plates exposed to air are already damaged.
• Clean the terminals. Corrosion adds resistance, and resistance means the bank never actually reaches full charge.
• Use the battery disconnect during storage, but understand it only slows the bleed. It does not charge anything.
• Replace the whole bank at once. Mixing an old battery with a new one drags the new one down to the old one's level.

Parasitic draws: the slow leak

An RV never really turns off. Parked and dark, it is still pulling current for the propane and carbon monoxide detector, the fridge control board, the stereo memory, the leveling controller, the slide controller, and usually a couple of things nobody can identify. Individually those are small. Together they flatten a house bank over a few weeks, and then the bank sits flat and sulfates. That is the most common way RV batteries get killed, and the owner is a thousand miles away when it happens.

If your batteries keep dying in storage with the disconnect off, something is wired ahead of the disconnect. That is worth chasing with a meter rather than buying another set of batteries.

When the generator will not start

Work these in order. The answer is almost always near the top.

1. 1Fuel level. Most RV generators draw from the engine's tank, but the pickup tube is deliberately set high, usually around the quarter mark, so a running generator cannot strand you with an empty tank. That means the generator quits dead at a quarter tank while your gauge still shows fuel. This surprises people every season.
2. 2Oil level. Generators have a low-oil shutdown and will refuse to start rather than destroy themselves.
3. 3The start battery. If it will not crank, or cranks slow, you may have a battery or connection problem rather than a generator problem.
4. 4Stale fuel. A gas generator that sat eight months with ethanol fuel in the carburetor very often will not run. Ethanol attracts water and leaves varnish behind. That is a carburetor cleaning, not a mystery.
5. 5The air filter. Generators live in a compartment full of road dust and they get choked.
6. 6The breaker or the transfer switch. Many generators have their own breaker separate from the coach panel. If the generator runs but nothing inside works, look there.

Exercise it or lose it

A generator that never runs will not run when you need it. Fuel goes stale, seals dry out, contacts corrode, and the carburetor gums up.

General manufacturer guidance is to run it about two hours a month under a real load. Load matters. Idling it with nothing turned on does little. Run the air conditioning and the microwave and make it work. That gets the engine up to temperature and burns off moisture.

Carbon monoxide is the part nobody thinks about

A generator makes carbon monoxide. It is colorless, odorless, and it kills people every year in RVs. The classic setup is running the generator overnight with the wind pushing exhaust back along the rig, or an exhaust leak in the generator compartment, or parking with the exhaust outlet near an open window or a slide seal. Never point that exhaust at another rig or into a wall that bounces it back at you.

RV carbon monoxide detectors have a service life, typically five to seven years, and there is a manufacture date printed on the back. An expired detector still lights up and still looks fine. It just does not protect you. Go read the date on yours.

Lithium changes some of the rules

If you have upgraded to lithium iron phosphate house batteries, the sulfation and 50 percent rules largely go away. Lithium runs much further down, holds voltage under load, and does not mind sitting at a partial charge.

It brings its own rules, though. Most lithium batteries will not accept a charge below freezing without an internal heater, which matters on the trip north in February. They need a charger with a lithium profile, and an old converter may never fully charge them. And their battery management system can disconnect the whole bank to protect itself, which looks exactly like a dead battery until you know what happened.

Dead batteries and a generator that will not start are two of the most common reasons an RV sits when it should be moving, and both are usually fixable right where the rig is parked. Duckett Roadside Repair handles RV electrical, batteries, jump-starts, and charging problems across Milton, Pace, Bagdad, Pensacola, Gulf Breeze, Navarre, Crestview, and the I-10 corridor. Call (850) 495-0366. Dispatch is answered 24 hours a day, seven days a week, so it does not matter what time your power quit.