Battery won't charge

X2 on the voltmeter (multimeter set on a 20 volt DC range). As described, measure the voltage red lead to positive battery Post and black to negative post. When a battery charger is connected and turned on or the motorhome is plugged in to AC power, the voltage on the battery should rise to 13.5 volts at least to do any charging at all. Overnight charging will need more like 14 volts.

The same applies to engine charging. Disconnected from AC shore power with engine running battery voltage should go well over 13 volts. Engines try to be smart chargers but they adjust their voltage mostly based on the charge the engine battery has. In many cases poor connections, too small wires to the house batteries or relay trouble reduce the voltage, slowing the rate of charging.

The per cent of full charge can be estimated from a voltage reading a few hours after all charging has stopped. 12 volts means half charged (as low as you can go without battery damage). 12.6 volts indicates fully charged.

Old RVs have converters that charge the batteries at about 13.5 volts which probably takes forever to fully charge so you end up with a chronically undercharged battery that doesn't work very well. The solution is to have a modern converter installed or use a separate battery charger, preferably a smart one that provides well over 14 volts for some time, then stops or drops to around 13.5 volts to avoid overcharging when it deduces that the charge is nearly 100%.

Sorry to complicate this even more but I want to give you the whole story. Rather than spending money on a converter or charger you might be better off buying a solar panel or two. We are modest users of electricity so one 100 watt solar panel easily provides all our 12 volt power; we never use a charger or shore power.

You may save time by having converter/charger and house batteries plus house battery disconnect switches and solenoid relay checked by a trusted RV service. It would be good to get a cheap digital multi-meter and learn how to check house battery voltage with and without shore power connected. The converter charger operates on 110vac power to charge the house battery when RV is connected to shore power. The house battery disconnect switch operates a solenoid switch that connect/disconnects your house battery to/from the converter charger. It must be set to "on" for battery to be charged by the converter/charger. If house battery is near dead ( 12.2 volts) the disconnect switch may not operate the solenoid relay and converter/charger may not charge the battery. Have the RV service explain how test and maintain your house batteries, keeping connections clean, and keeping electrolyte levels up adding distilled water as needed. It is likely that you need new house batter(s)if converter charger is working.

While AC runs on 120vac. AC with wall mounted thermostats get their voltage from furnace. Most Class C furnaces need 12vdc to operate.

The air conditioner works off of 117VAC. If plugged into shore power the air conditioner should work. If it does not that means you have to find out why the rig has no 117VAC power coming to it. The connector you plug your rig into for AC power (shore power) may have blown a fuse or tripped a breaker in the house or garage electrical panel. If those are good find the rigs power panel inside of the rig and push the 30A breaker lever firmly to off. Then push it firmly to on. The air conditioner should now turn on. If it does you should have lights and the fridge will be happy. If you do not have lights that would point to a bad converter/battery charger. I know on my Chateau I have lights when plugged into shore power without the house batteries connected.

Everyone should have and learn how to use a cheap digital volt meter. They are from $15 to $20ish and sold even at Walmart. They have an on/off button to turn them on. They have two leads. The black one goes into the COM connector and the red into the V/Omega connector on the meter. There is a rotary knob you turn to the 20VDC setting (read manual). At this point you put the red lead on the battery positive terminal and the black lead on the negative terminal. The meter will read the volts your battery is charged to. If it reads 13 or more volts your converter is trying to charge you battery. If it reads 12.2volts your battery has no charge and the converter is not working. Well, on my Chateau the converter charges the battery even with the salesman switch off. So plugged into shore power the batteries will measure around 13VDC.

If the above looks good and you do not have lights when unplugged from shore power. You may have my problem. I have had an issue with the salesman switch on my rig. It likes to blow a 5 fuse on the 12VDC transfer relay every year. On my rig that is under the forward seat of the dinette. That seat has all the electrical breakers and fuses for the rig. There is a panel under where your legs would be while eating. I just replace the fuse every year. I paid to have it fix, NOT. Fuses are cheap. There are two 5A fuses physically on that switch (the switch looks like a small volcano just sitting behind the fuse/ breaker panel) and one blows every year.

Most steps, and many slides, are powered from the CHASSIS battery and electrical system, and not the coach systems. This is to insure that even if you killed the coach batteries boondocking, you can easily get the steps retracted and the slide in when you start the engine.

Does your engine start? If you have a volt meter (even a free one from Harbor Freight) you can check the voltage of the CHASSIS battery with the engine running, should be about 13.8 up to 14.2

If the house batteries are not being charged from the engine's alternator, you probably have a bad relay. Quite common for them to burn up, as the manufacturers use the cheap 85 amp version rather than the much better 200 amp one. 200 amp has heavier contacxt plate which is tungsten silver plated, vs plain copper on the cheap one. Contacts burn up and no current gets to the coach batteries.

Also make sure the parking brake is set, asmy slide and I suspect most, require the brake to be set to operate the slide.

You should see similar voltages at the COACH batteries with the engine running.... this is without the shore power or generator.

If this is OK, then with every off, everything unplugged, etc, Measure the voltage of the COACH batteries, should be 12.3 or so if properly charged. plug in shore power and see if it rises to mid to high 13's. If not, you need to check the two big 30 amp pull out car type fuses in the 12 v fuse panel. If one or both are blown, this can be due to batteries being hooked up backwards momentarily.

Charles

pauldub wrote:
If the air conditioner stopped running, you lost 120 AC power, maybe you tripped a circuit breaker in your house?

But maybe not too.

Some thermostats need 12 V to operate......and they don't get it from the AC unit itself like home units do.....but get it from the battery.

If the air conditioner stopped running, you lost 120 AC power, maybe you tripped a circuit breaker in your house?

I assume that you were plugged into electricity at the time as you were running the air conditioner. The air conditioner will not work on battery. Check the 22 volt fuses usually found in the converter/inverter when you open the cover. As noted before remove wires to the battery (one at a time and clean the post and the end of the wire. Replace wire and then do the same for the other wire.) Check that the battery disconnect switch is on. The switch is usually near the door on the wall.

pr41cl wrote:
Yes charger ( external one ) properly connected to the correct terminals, Lights worked at first then went dead.

The lights work when plugged into external outlet did not try using the 12V when all this started

That first sentence tends to indicate that your external charger failed.

IF.....the 12 V stuff works when plugged into shore power, that indicates that the onboard converter/charger is working and you need to leave it plugged into external power for about 48 hours to charge the batterie(s). An external charger should not be needed.

pr41cl wrote:
Had the charger on for 24 hours no charging happened.

What exactly is "the charger" that you had on for 24 hours ?

YOU NEED A MULTI-METER TO CHECK VOLTAGES.

Or you need to take the whole thing into an RV shop so they can look at it.

There really are only 3 possibilities here:
1) The charger (converter) has failed.
2) The batteries really are NOT good.
3) there is a problem in the wiring connections or a blown fuse.