12volt system will not work unless connected to AC

I have tested the battery and it is fully charged. I cannot turn on lights or extend slides. If I connect to AC (I'm still at home--just getting ready to leave this week) everything works fine. My surge protector shows it pulling 7 amps when extending the slide. Where do I start to find the issue? Could it be that a creature chewed through a wire near the battery? It's always something, huh?!

What was the voltage of the battery? How did you check the battery? Did you just put a voltmeter on the battery posts while the battery cables were still hooked up?  If you did, what you were actually reading was the output of the converter. You need to disconnect one of the cables (preferably the ground) then check the voltage of the battery. Or you can do it without disconnecting the cable as long as you're not hooked up to shore power.

I tested the battery with a volt meter and it read 13.6.  I was not connected to AC when testing.

Standard install looks someting like this

Battery---Fuse--Switch (Master disconnect)---All the stuff that uses or charges the battery

NOTE: some stuff (like the explosive gas detector) may be hooked to the Battery side of the switch

Possible suspects:
Negative cable, not connected well to battery or chassis

Positive not connected well to battery,  Fuse blown (or breaker triped) Switch off

Testing: using a TEST LIGHT (NOTE: there are 3 ways to test.. I usually use an automotive test light, get it at Wal*mart or any auto parts place.. But a 100 watt 12 volt "Trouble" light is an even better test.. I have one but avoid using it due to digging it out.. a Voltmeter is not a good test but can be used in a pinch)

Touch one clip to battery - (The actual battery) Tip to +  Bright light = GOOD
Move clip to any unpainted chassis part,  Still bright = Good

Follow the biggest cable from the Positive (if more than one) and touch first the cable lug at the battery, then the lug at the other end.. Bright-Bright = Good. whatever it's connected to touch the other big lug..

And continue out along that wire (not plugged in of course) till you get DARK.. problem exists between BRIGHT and DARK

But first;;;; Make sure the switch is not in STORE/DISCONNET/OFF (Aux battery may be the lable)


One final note: As you move out along the positive wire.. You will, from time to time, need to move the ground clip.. When you do this you should test with a known good 12 volt point to insure you have a good ground.. Another option is to "Bring the ground with you" (I have long coils of wire I can use for that)

Odds are your batteries are offline for some reason, often just the battery disconnect switch got turned off. The shore system still powers the converter, so you have power that way. You didn't tell us anything about your RV or its power system (make/model, converter type, etc), so we are mostly guessing.

I have a 2013 Winnebago lite 5 (fifth wheel). I've had it for 3 years and never had a problem of this nature. I'm headed out to check on disconnect switch--I have no idea about it as the only thing I have ever done with the battery is make sure it has water. I replaced the battery last year with a sealed battery. I'll ask my brother to try John's suggestion as it is Greek to me. Electrical systems scare me! I just want to be able to extend the slide a bit (so I can get to the bed without too many gymnastics) while I'm traveling to my hookup site. Thanks for all suggestions. I'm learning this as I go. I've learned a few things the hard way! Oy!

YOu will note the ONLY tool I suggested was a 12 volt tester.. I will describe it for you so you won't be scared of it.

It is an ice pick, in fact it can be used as an ice pick, the handle is either clear plastic or translucent (Light shines through it) ther eis a light bulb in side the handle and a wire with a clip on it that comes out of the handle.

Basically it's a light bulb in a holder.. that's all  It is bright (Good) Dim (Bad connection or low battery) or dark (NO power) you only touch plastic when using it save for when you clip the clip onto something conductive.

Not something you should be afraid of.. When I can't find mine I grap a light bulb and attach wires to it, Not that.. Is i a bit advanced,,, But the ones in the stores are actually easy to use.

NOTE: so long as you are NOT plugged into shore power.. and take care to touch the point to only one thing at a time (And in the world of 12 volts that's easy) it is about as close to fool proof as it gets.

Harbor Freight Tools has a nice 12 volt tester like John describes - available either online or in one of their stores.

https://www.harborfreight.com/circuit-tester-30779.html

It does sound like a battery disconnect switch, but I'm a bit confused by the voltage indication. The OP said she tested the battery with a volt meter while not connected to AC power, and the battery indicated 13.6 volts. Either the volt meter was indicating inaccurately, she mis-read it or she was connected to AC power.

Kev

If I hit my battery disconnect switch, nothing in the coach will operate unless I am connected to 120V power. My barreries will still read 12.5volts at the battery terminals.

I basically run into this every year when I pull my unit out of storage. The "Battery Disconnect/Store,In-Use" switch will not work. The actual switch itself is fine, but the actual "switching mechanism"-- (Sorry I am not e technician--- but I believe it may be called a Solenoid), simply gets sticky after sitting all winter.
Here is what I do: I bring MH out of storage and make sure the batteries are charged up. I have my wife "flip the switch", while I gently tap on what I believe is a Solenoid with the wooden handle of an old screwdriver. All I know is it works every year. You will her a slight "click" when it switches over. I am also pretty sure this is not the proper way of doing things.

As it turns out, it was corrosion--it didn't look bad but we decided to take the battery out to check and after a good cleaning, everything works as it should!! Yay! One less stress this week. Now if packing were that easy...

Thanks for all the help!

Smpsmpsmp said "It's always something, huh?!"

Always!!!!!!! I swear it never ends.

Had that problem myself yesterday.. More in a sec.. That's why I said to use the light (IT load tests so corrosion shows up) and touch the actual battery posts.> THEN the lugs on the cable. .The light will dim or not light i9f the connection to the battery needs attention.

My problem was the chassis battery, and it's a recurring one so I knew just what to do.. Went to start and nothing.. I mean nothign, Steps would not extend, seat would not move. Phone would not charge.

Hit the Emergency start button and made my trip

Got to Beaverdam, where I'm parked on a nic e solid surface (Concrete or ashphault) and cralled under with a Chicago dual meter plus dial load tester and wrenches... Unhooked negative cable.. Hooked up load tester and noted vooltage (Good) cranked up the amps (250 for that battery) and when it beeped.. Still in the green..  Unhooked positive cable and cleaned well (both battery and cable) re-connected,  cleaned and re-connected Negative.

First thing I( noticed was the steps extending.

Have not started the RV yet.. but I have no doubt.. DID use chassis battery to aid generator start at 5am this AM (I'm parked in a Flying-J/Denny's so nobody cares about noise)