How To Trouble Shoot If batteries Are Getting Charged

LynnandCarol wrote:
OP... The Problem is when I disconnect shore power, we have no 12V power. The battery voltage was tested on the battery terminals with nothing connected.

So, with meter connected across the battery terminals and trailer plugged in to shore power, you read 13 volts but as soon as you unplug, the reading drops to zero? If so, the batteries are not functioning at all.

If you do have 12 volts on the batteries when unplugged from shore power, but no power to the lights, check the battery isolator switch, usually near the trailer door.

Incidentally, I don't think anyone mentioned in this thread that batteries indicate a misleadingly high voltage for a few hours after any charging. With a voltmeter you can only read the approximate charge level after not charging for a few hours.

A test light is more valuable to a newbie than a DMM. Either it glows or it doesn't.

A test light test few know about...

Clamp the test light to the shiny connected negative post and touch a bright area of the rig with the lamp's needle tip. Got test light lit? Bad connection in the ground cable.

LynnandCarol wrote:
OP... The Problem is when I disconnect shore power, we have no 12V power. The battery voltage was tested on the battery terminals with nothing connected. The trailer wires were tested disconnected. This a TT and we are parked for the winter, so this will only be a problem for us in the short term if we loose park power which has happened in the past. We will get the batteries tested (they are over 2 years old) and pull and check the plastic auto type fuses above the circuit breakers. Thanks for the assistance and sorry if OP wasn't clearer!

You have an open circuit between the battery and the 12v panel.

If you want to dig into this.... all you do is check voltage along that positive wire from battery to the 12v panel. Most likely a fuse, switch or other connection. At some point you will find 12.6 volts on one side of something and zero volts on the other side. Clean, repair, replace, tighten, or adjust that item.

mkirsch wrote:
It's not the batteries.

Probably not but you can NOT say that absolutely.

It could even be something as simple as a loose or corroded connection at one of the main battery connections.

Even with no batteries in place you should have usable 12 V power when plugged into shore power.

It's not the batteries.

If it were the batteries, you'd get some 12V power, but it would fade quickly. For example, you'd turn on the lights and they would come on bright but get dimmer and dimmer over the course of a minute or so.

With zero, zip, zilch, no 12V power at all, something is disconnected, a fuse is blown, or a breaker has tripped and not reset.

It is probably the main breaker between the 12V batteries and the converter. Every RV has one. It is usually buried behind the batteries or in some out-of-the-way place. Follow the red wire off the + on the batteries, and you should find a black box with two terminals on it. That is the main breaker.

They often go bad, but sometimes they are trying to tell you that you have a major problem. If it has a reset, try resetting it. You could jumper it with a screwdriver for a short time just to see if you get power. You may need to replace the breaker.

OP... The Problem is when I disconnect shore power, we have no 12V power. The battery voltage was tested on the battery terminals with nothing connected. The trailer wires were tested disconnected. This a TT and we are parked for the winter, so this will only be a problem for us in the short term if we loose park power which has happened in the past. We will get the batteries tested (they are over 2 years old) and pull and check the plastic auto type fuses above the circuit breakers. Thanks for the assistance and sorry if OP wasn't clearer!

LynnandCarol wrote:
OP Update.. Tested my battery (2) both had 12.6 DCV. Then tested the trailer battery lines and got 13.5 DCV. Removed covering from junction box and no fuse or any other inline fuse on the external wiring. so not sure where to go from here??

13.5 would be a normal float. 12.6 is fully charged but not charging.

How many sets of batteries do you have? All batteries should be at 13.5 if you are plugged in. Measure on the actual battery terminals, not the wire, not the clamps, not the fuse.

Until now I had thought this was a motorhome....

Do you have a storage switch that was turned off?

This thread is on its 3rd page now, and we still don't know what the OP's actual problem is. All we know is they're somewhat technical and they're *sure* it's a battery charging problem.

I think you answered your question.
If you took the voltage reading at or near the batteries, then Yes, at 13.5, your batts are charging. And it appears your batteries are nearly full charged at 12.6......no charging.
But if you have a batt problem besides that, you may have to get the batts tested. If they test good, then start looking for poor connections in the battery 12v circuits.
You never did say what problem you were having, if any

LynnandCarol wrote:
OP Update.. Tested my battery (2) both had 12.6 DCV. Then tested the trailer battery lines and got 13.5 DCV. Removed covering from junction box and no fuse or any other inline fuse on the external wiring. so not sure where to go from here??

Some may understand what you are saying but most probably not.
You need to be a bit more specific.

Which two batteries did you test ?
What was running when you did the test....truck engine, generator or shore power ??
And where exactly did you test the "trailer battery lines" ??