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

Dead house batteries are the classic October call in the East Valley: a rig comes out of summer storage, 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, which is a different repair with a different price.

Check this first (fifteen minutes, one multimeter)

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.
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.
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.
Look at the terminals. Corrosion at the posts creates enough resistance to stop charging entirely while still passing enough current to power a light. Green or white crust means clean the terminals before diagnosing anything else.
Check the water level if the batteries are flooded lead-acid. In Arizona heat they consume water fast, and plates exposed to air are permanently damaged. Fill only with distilled water, and only after charging.

What is usually wrong

What you measure	Likely cause	Fix and cost
12.6 resting, 13.6 on shore power	System is healthy	Nothing
Under 12.0 resting, comes up on charge, dies fast	Batteries have lost capacity	Battery replacement, parts plus labour
No change when shore power is connected	Converter not charging	$300–$900
Voltage good at converter, nothing at battery	Fuse, disconnect, or corroded connection	$150–$350
Batteries boil or get hot on charge	Converter stuck in bulk, or a shorted cell	Diagnose before replacing anything
Everything dead after storage	Parasitic draw plus heat	Often batteries, sometimes a draw to trace
12V works, nothing on 120V	Not a battery problem at all, check the pedestal and the breaker	Varies

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

Why Arizona is hard on RV batteries

Heat is the enemy of lead-acid chemistry. Rate of self-discharge roughly doubles for every 18 degrees of temperature rise, and the internal corrosion that eventually kills a battery accelerates the same way. A battery bank that would sit happily for six months in a Minnesota storage lot can be flat and sulphated in eight weeks in an uncovered Mesa lot in July.

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

The practical version of that advice:

Leave it on shore power with a working converter, or on a solar maintainer, if the storage lot allows either.
If it must sit unpowered, pull the batteries and keep them somewhere cooler, charged.
Check water monthly on flooded batteries in summer. 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

Send 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. Battery and charging calls are done at resort spaces, storage lots, and driveways across Mesa, Apache Junction, Gilbert, Tempe, and Gold Canyon.

Frequently Asked Questions

My RV batteries died over the summer in storage. Are they finished?

Often, yes. Lead-acid batteries lose capacity fast in heat, and a battery sitting at partial charge in a 115-degree Arizona storage lot for five months is being destroyed twice over. A battery that will not hold above about 12.2 volts after a full charge is generally done.

How do I tell whether it is the battery or the converter?

Measure voltage at the battery with shore power connected and the battery disconnect on. Expect roughly 13.2 to 14.4 volts from a converter that is working, with the exact figure set by which charge stage it is in. If you see 12.4 volts or less while plugged in, the converter is not charging, and the battery may be innocent.

What does this cost to fix?

12V electrical work runs $150–$900 on the pricing page, with converter replacement at the top of that range. Batteries themselves are parts: a pair of flooded 6V golf-cart batteries is a few hundred dollars, and lithium is a much larger conversation.

Should I switch to lithium?

It is worth considering if you dry camp or run a compressor fridge, and it is often not worth it if the rig lives on shore power at a resort. Lithium also needs a charger profile that suits it, so it is a system conversation rather than a drop-in swap on many older rigs. Work out which camp you are in before buying.