RV batteries dead or not charging: what to check and what the repair costs

RV house batteries that are dead or will not charge in Sebring come down to three things in this order: a converter that is not charging (a surge, a fuse, or a failed unit), batteries that were cooked or sulfated over a summer, or a parasitic draw pulling them down faster than the charger fills them. Fixes run $150 to $900 on top of the trip fee, with converter replacement at the top of that range. Batteries are extra, and we tell you honestly whether yours are worth keeping.

Check this first (ten minutes with a multimeter)

Battery voltage with shore power off. 12.6 volts or more: charged. 12.2: half. Under 12.0: flat. Under 10.5: probably damaged.
Battery voltage with shore power on. After ten minutes it should climb to 13.2 to 14.4 volts. If it does, the converter is charging and the problem is the batteries or a draw. If it stays where it was, keep going.
Converter output. Find the converter (often under a dinette or in the basement, sometimes inside the 12V panel) and meter its output lugs with shore power on. 13.2 to 14.4: it works and something between it and the batteries is open. Zero or battery voltage: the converter is not putting out.
The converter’s own fuses. Most converters have output fuses on their face or in the panel next to it. A surge blows them. Look.
The 120V side. Is the converter’s breaker on? Is the GFCI outlet it may be plugged into tripped? A tripped GFCI after a storm is common and it silently disconnects the converter.
Water level in flooded batteries. Pull the caps. Plates showing above the electrolyte means the bank was cooked; that bank is likely done.
Disconnect switch and lugs. A battery disconnect in the off position, or a green, crusty terminal, is an open circuit no charger can push through.

What is usually wrong

What you observe	Likely cause	Fix and cost
Converter output zero after a storm	Converter killed by a surge	Converter replacement, $400 to $900
Converter output zero, no storm	Blown output fuse, tripped GFCI, or failed unit	Fuse $125; converter $400 to $900
Converter fine, batteries stay low	Corroded lug, open fuse, or disconnect switch	$125 to $250
Charges, then dead by morning	Parasitic draw, or a battery with a shorted cell	Trace draw $150 to $300; battery
Plates dry, water level low	Converter without float mode boiled the bank	Batteries, and a converter upgrade $400 to $900
Everything works, batteries just weak	Sulfated from sitting flat	Batteries
Dim lights, pump slow, converter humming loud	Converter failing under load	Converter $400 to $900

Same figures as the pricing page, with labor at $125 to $190/hr inside those ranges.

Why this happens here

Two Florida facts drive most of these calls.

The summer in storage. A rig stored from April to November in Highlands County sits through the hottest, wettest months of the year. If it is plugged in, an older single-stage converter holds the bank at a constant 13.6 volts for six months in a cabinet that is well over 100 degrees inside, and flooded batteries boil dry. If it is not plugged in, the bank sits and sulfates, and the parasitic draws that every modern rig has (the propane detector, the stereo memory, the fridge board) take it to zero by July. Either way the owner arrives in November to a dead bank and, often, a converter that was already marginal. The fix is a modern multi-stage converter with a float mode, and either a battery maintainer or a real disconnect for the summer.

Lightning. Florida recorded 305 lightning events per square mile in 2025, more than any other state, and averaged more than a million cloud-to-ground flashes a year over the previous decade. A strike near a park’s electrical service puts a spike through every pedestal on the loop, and the converter, a switching power supply sitting on the 120V line, is the first thing it kills. The batteries then run down over a day or two and the owner calls about dead batteries. The batteries are fine. The converter is gone. An EMS-style surge protector on the pedestal is cheaper than one converter.

What the repair involves

We meter the whole chain, shore power to converter to batteries to loads, before replacing anything, because a converter that reads dead is sometimes a converter on a tripped GFCI. If the converter is gone, we carry a replacement on the truck for the common sizes; it is a one-visit job. If the batteries are cooked, we tell you plainly and give you the options, including whether the converter that cooked them should be upgraded before new batteries go in, because putting a new bank on the converter that killed the old one is throwing money away.

When to call

Now if the rig has no 12V and you are living in it. In November on arrival if the rig sat through the summer; the arrival checklist starts with the battery voltage for a reason. After any big storm if the lights are dim. We do these on site across Sebring, Avon Park, Lake Placid, and out to Okeechobee, and the appliance and 12V page covers the rest of the electrical system.

Frequently Asked Questions

How much does it cost to fix an RV that will not charge its batteries?

$150 to $900 on top of the trip fee. A blown fuse or a corroded connection is at the bottom. A converter replacement, which is the most common real fix in this county after a lightning surge, is at the top. Batteries themselves are extra and we tell you honestly whether yours are worth keeping.

The rig is plugged in but the batteries are still flat. Why?

Either the converter is not putting out (a surge, a blown fuse, or a failed unit) or it is putting out and something between it and the batteries is open: a fuse on the converter output, a corroded lug, a disconnect switch. Meter the converter output and the battery terminals with shore power on; the two numbers tell the story.

My batteries were new in April. Why are they dead in November?

Six months on an older converter with no float mode boils flooded batteries dry in a Florida summer; six months on no charge at all lets them sulfate flat. Either way, a bank that sat through June to September untended is often not recoverable. Check the water level; dry plates are the sign.

Should I switch to lithium?

Sometimes. Lithium tolerates heat and partial charge far better than flooded batteries, but it needs a converter with a lithium charge profile, and an older converter will not charge it correctly. It is a real conversation, and the honest answer depends on how you use the rig.