Was reading in the RV the other night (that's another story) when the lights dimmed then came back bright. Did the same later. Today I turned on the main lights (10 bulbs) and they seemed dim. I turned off the charger and flipped the battery disconnect switch a couple of times...Voltage at the batteries - 12.4Voltage at the "charging plug" for phones and such - 12.4Voltage at the light fixture base - 10.5Any help would be appreciated.

You have resistance between the batteries and the loads.It could be a loose connection, corroded connection, too small a wire gauge to lights, etc. You need to find out where the voltage drop occurs between battery and lights.Be aware that 12.4 suggests that you are NOT on shore power with the converter or inverter/charger keeping the batteries charged. If you are plugged in with these readings, we need to dig deeper-- starting with what kind/number of batteries you have.

Here is what I did.I left the charger off. Had all the lights on for a while.Went back out and had 11.9 at the battery. OK.Pulled fuses at the panel for different lighting areas and verified 11.9 volts at the fuse base. But, at each bulb base, it was lower. Like the main lighting (10 bulbs) the light base socket showed 10.2 volts. Other areas with less lights showed slightly more, like 11.2 but still less than battery voltage.So I flipped the charger back on and all the lights brightened, as you would expect. Batteries showed 14.2 volts, as did the fuse bases. The light socket bases showed more voltage than before, but not a full 14.2. More like 12.9 on the main lighting bank.Is this normal. Less voltage because of the draw?Will see if batteries come up to a full charge and hold that charge.They are sealed batteries so I assume they can't be checked. Two group 24 batteriesI should add the trailer and batteries are 3 years old.Thanks in advance.

Look for a 12v lamp that is wet, like maybe in the shower or outside.

mabell wrote:Here is what I did.I left the charger off. Had all the lights on for a while.Went back out and had 11.9 at the battery. OK.OK, let's start with the root problem.11.9 is a COMPLETELY discharged 12 VDC battery. 12.2 is 50% discharged.Start by fully charging the battery(s).If wet cell, after charging, check SG (Specific Gravity). You can find them for under $10.

I was thinking maybe like the LED lights I put in the outside fixtures that have exposed circuit boards. But they are not on.Good thought though.

Low Voltage | Good Sam Community

16 Replies

mabell
Explorer
May 20, 2015
Sorry this took so long. Planning a trip in the next week or two and will have time to mess around with this some more. I will bring a long piece of wire as Harvey51 suggested to by-pass in house connections
THX
time2roll
Nomad
Apr 14, 2015
What is the voltage with the converter on? Is this a WFCO?
I am thinking more converter issue over a bad connection.
BFL13
Explorer II
Apr 14, 2015
Your battery is fine. As you see the trouble is in the lighting circuit itself from the fuse out to the lights. Somewhere along that circuit there is a high resistance spot you need to find and repair causing that low voltage.
mabell
Explorer
Apr 14, 2015
Charged the batteries all night.
Shut the charger off.
Voltage at batteries 13.6
At fuse base 13.6
At light bulb base 11.9 with 10 bulbs on.

I disconnected the batteries and will see what happens to the charge today.They are sealed batteries so I can't check gravity.
Also, they don't indicate warranty period. Marked C3 so I assume March 2012 - which is when I purchased the trailer.
To my limited knowledge, it seems to be a voltage drop issue.
Harvey51
Explorer
Apr 14, 2015
Check the voltage across the light switch. I bet it has most of the drop.
If not, get a long ground wire connected to battery negative and measure the voltage from ground to positive at the switch & compare with positive at a light. This tells you if the drop is on the positive wire and if it is between battery and switch or between switch and light. Check negative wire similarly with a long wire to battery positive.
Almot
Explorer III
Apr 14, 2015
MEXICOWANDERER wrote:
...
Then come back and report your readings...

... Also, before the test let it sit overnight with battery PHYSICALLY disconnected - i.e. red and black cables off. And make sure the trailer isn't plugged in shore power during the test.
Almot
Explorer III
Apr 14, 2015
You have too much voltage drop between the battery and bulbs. Something is wrong in wiring - probably a short. Could be a short on some connection or on some load like faulty bulb or socket.

11.9V at the battery is not fully discharged, in your case. It would've been fully discharged at 11.9 IF there were no loads and IF battery was at rest for several hours.
Turn the loads on - voltage drops, turn the loads off - voltage rebounds to its "true" level after some hours.
Turn the charger on - voltage goes up almost immediately, turn it off and don't turn the loads on - voltage returns to its "true" level after some hours.
MEXICOWANDERER
Explorer
Apr 14, 2015
Measure voltage at the battery

Then

Measure voltage at the ATO fuse panel

Then

Measure voltage at the light switch terminals

Then

Measure voltage at the light socket

Then come back and report your readings.

This is how the proessional technicians do it.
mabell
Explorer
Apr 14, 2015
OK. Thanks BFL13. I will remove them tomorrow. Easy to do.
BFL13
Explorer II
Apr 14, 2015
mabell wrote:
I was thinking maybe like the LED lights I put in the outside fixtures that have exposed circuit boards. But they are not on.
Good thought though.

They are not switched on, but may be "on" due to a short. For any trouble-shooting, the first suspect is the last thing you did to it.

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Low Voltage

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