RV batteries dead or not charging: converter, battery, or something else

Dead house batteries are the classic November call in Zephyrhills: a rig that sat on its space all summer, the owner arrives, the slide will not move, the jacks will not run, and the panel shows nothing. Some of those batteries are genuinely finished. A good number are fine and the converter stopped charging them months ago, often on the afternoon of a thunderstorm, which is a different repair with a different price.

Check this first (fifteen minutes, one multimeter)

1. Measure resting battery voltage with shore power unplugged and everything off. 12.6 volts or better is a healthy full charge. 12.2 is about half. Under 12.0 is deeply discharged, and a lead-acid battery left there for months has lost capacity permanently.
2. Plug in shore power and measure again at the battery terminals. A working converter should push the voltage up into the 13.2 to 14.4 range. If it reads the same as it did unplugged, the converter is not charging.
3. Check the pedestal and the GFCI. A tripped pedestal breaker or GFCI after a storm means the converter has had no power for however long it has been tripped, and the batteries have been carrying the rig’s parasitic loads alone. This is the most common reason a bank left “on shore power” for the summer comes back flat.
4. Check the battery disconnect. Many rigs have one, and it is frequently the answer. Also check the main fuse or breaker between the converter and the battery bank.
5. Look at the terminals. Corrosion at the posts creates enough resistance to stop charging entirely while still passing enough current to power a light. In this humidity the crust forms fast. Green or white growth means clean the terminals before diagnosing anything else.
6. Check the water level if the batteries are flooded lead-acid. Heat drives it off, and plates exposed to air are permanently damaged. Fill only with distilled water, and only after charging.

What is usually wrong

These sit inside the 12V electrical range on the pricing page, on top of the $75 to $150 trip fee and $125 to $190 hourly labor.

Why Florida is hard on RV batteries

Heat is the enemy of lead-acid chemistry. Self-discharge roughly doubles for every 18 degrees of temperature rise, and the sulfation that eventually kills a battery accelerates the same way. Zephyrhills summers run average highs around 90 degrees from July into September with nights that never cool much, so a battery bank sitting unattended from May to October is losing charge every day and hardening its plates as it goes.

Add the parasitic loads that never truly switch off, propane detectors, control boards, radio memory, and some slide controllers, and a bank left unattended through a summer here has no chance without a charger or a solar maintainer that actually stays powered.

Then there is lightning. Florida had more lightning per square mile than any other state in 2025, and the Tampa-to-Orlando corridor is the heart of it. The converter is the first thing on the park’s power line inside your rig, and it is a frequent surge casualty. A converter that dies in June leaves the bank to fend for itself until November. A surge protector at the pedestal is cheaper than a converter and far cheaper than a converter plus a set of batteries.

The practical version of that advice:

• Leave it on shore power with a working converter and a surge protector, or on a solar maintainer, if the park allows either. Have someone check the pedestal after big storms if you can.
• If it must sit unpowered, pull the batteries and keep them somewhere cooler, charged.
• Check water monthly on flooded batteries in summer if you are here. They drink.
• Do not trust the panel gauge. Those meters are approximate at best. A twenty dollar multimeter tells you more.

Converter, inverter, and what people confuse

A converter turns 120V shore power into 12V to run the coach and charge the batteries. An inverter does the opposite, turning battery power into 120V for outlets. Many rigs have both, sometimes in one box. When someone says “my inverter is not charging”, they nearly always mean the converter, and getting that straight on the phone saves a wasted trip.

Older converters are also often the wrong charger for the batteries in front of them. A single-stage converter from twenty years ago will boil a modern battery bank, and it is no charger at all for lithium. If the rig is old and the batteries keep dying early, that is worth looking at as a system.

What to expect on the call

Give us resting voltage, voltage with shore power connected, the battery type if you know it, and how long the rig has been sitting. That is enough to tell you whether you are buying batteries, a converter, or a terminal cleaning. We work on site at park spaces, storage lots, and driveways across Zephyrhills, Dade City, Wesley Chapel, Lutz, and Plant City, and the appliance and 12V repair page covers converters and the rest of the electrical side. If the dead bank showed up as a slide that will not move, start there.