Battery not charging on AC power

Hey, sorry I'm new to campers. I've searched the forum and can't quite find a matching issue. My parents bought a Palamino tow behind camper and set it up at our place to visit but the battery keeps going dead from a full charge, even though it's plugged into AC from my house,within a few hours of running the furnace. I checked the fuses and panel that's under the sink area and there's power there. I pulled the battery and charged it, and checked the terminals from the camper and there is no power coming back to the battery. When they plug it into their running truck the 12V system powers right up. With the AC plugged in only the outlets seem to work and everything else seems to go off of the 12V battery. I'm hoping it's something simple I just overlooked and not a bad inverter/converter or something. I did see in an article among my searches that there may be a brake away box that should be unplugged when the camper is parked? Where should I be checking for that and what am I looking for?

Ok, here is the battery charge path

Assuming this is a trailer (if ti's a motor home)

House outlet {1} cord to (optional inlet and then automatic transfer switch) To power distrubition panel {also called breaker panel or box} {2} and from there a branch breaker {2} to the converter {3} to fuses or breakers or both {4} to the battery.

1: If the outlet is a GFCI (it should be) that has tripped or the breaker is tripped no power.. (To test make sure something 120 volt like the TV works).

2: WHen my Rig was new. and I mean new. I had some 120 volt issues. started trouble shooting at the breaker box. stopped there too. Had several loose screws (Many RVers have a few screws loose but the joke is not as funny when I tell which screws first) one took over three full turns. since then no problem. When I tighten them they stay tight.

3: after 12.5 years my converter failed  Took me a few days to pop in a new one.. but I now have a very nice smart charger for emergency use.

4: Obvious. note most converters have 1,2 or 3 30 amp fuses on them.. Right on the converter. Exception is integrated converter/power panel (The converter is right behind the fuse (12 volt) and breaker (120 volt) panel.. the fuse on these is normally on the right (May be left) will be 30 amp IF more than one fuse replace all at the same time.

Normally I'd include the battery disconnect.. but since the furnace works with a fill charge I will not it has to ber in the "USE/ON/Connected" position for the furnace to work.

Changing converters. IN my case it was 4 screws and pull the box out. 3 wires (Tape off one of 'em) and haul it to the factory. pick up a factory refurb and back. hook up 2 wires and plug it in (it is a plug in model)

I used a Progressive Dynamics 9100 series with my already existing Charge Wizard. same as OEM.
If yours is a stand alone I suggest teh 9200 line unless you already have the wizard as I did (Same wizard)

If yours is part of the power panel the 4600 series is suggested

Match the last two digits with your existing as close as possible

The 9180 Refurb was 230 something 6% tax included factory pickup.

The breakaway box is only for towing - it applies the trailer brakes if it should ever get disconnected from the tow vehicle on the highway.  Do NOT ever manually activate it except to test to verify it is working.  If it was accidentally activated, it would indeed place a large power draw on the battery, but even then the onboard converter/charger should be sufficient to keep up with it.

The symptoms you describe are either a malfunction of the converter/charger or lack of 120v power to the converter/charger.  You should see 13+ volts ate the battery terminals whenever the trailer is plugged to shore power.  Check to see if there is a major fuse, breaker, or a disconnect switch/relay in the wire between the converter/charger and the battery + terminal.  If not, or if present and working, you probably have a failed converter/charger.  It would help diagnose if you could identify the make & model of the converter/charger. It may be either a separate unit or integrated into the 120v power panel. If the same panel has both 120v breakers and 12vdc fuses, the charger is probably integrated with it. If the 12vdc fuses are separate from the 120v breakers, odds are the charger is a separate unit.

Welcome to the Forum

Another similar explanation:

Campers use BOTH 12VDC and 120VAC.  The 12V is provided by the battery and/or converter (when 120V is present)  The converter and battery are connected, so both provide 12V power through the main panel and fuses.  This powers almost all lights, control circuits for A/C, water heater, and fridge.  It also power the furnace, slide outs, power jacks, awnings, etc.

A fully charged battery should read about 12.6VDC.  If the converter is working, and plugged in, it will put out 13.5 V or more to maintain the batteries.  Measure the voltage at the batteries.  If it is 12.6V or less, the converter is NOT sending power to the battery.

This can be because  * Fuses on converter blown    * Converter breaker off or converter unplugged    *  Converter shot.

Short term fix:  Take car battery charger out to the camper.  Plug into working 120V plug on the camper and connect to the battery.

The 120V in the camper also provides power to the big users like the A/C, microwave, 120VAC plugs and water heater and fridge (optional)

Hope this helps.