12 volt

Keep an eye on this. Test your batteries and converter. Sounds like your converter is OK but your batteries are struggling/weak. If the batteries are week, they will continue to fail and faster ass they get weaker.

camp104 wrote:
First question. Why do my 12 volt lights get brighter when I plug into shore power? Next question is if I tap into my 12 volt reading light in the bedroom can I use those wires to run a pig tail to install a cigarette lighter plug so I can use my c-pap machine that runs on 12 volt?

First question: The battery, if fully charged, is 12.6 volts. The converter (Which charges the batteries when plugged into shore power) is 13.6 if in float mode. Higher if charging (usually) so that is what is making the lights brighten.

Second.. I have tapped into my bedside lights as you suggested and drawn quite a bit of power.. However the outlet was damage (I pulled that much) So makle sure you use a heavy duty outlet.. Second, The fuse and wire may or may not be up to the job so monitor the voltage when you try it, In my case the wires are good.. But as I said, 12 volt Accessory outlets are not that great.
3

camp104 wrote:
I changed all the lights to LED 6 months ago.

Excellent. And they're taking these voltages ok? I wasn't aware Leds would dim or brighten.

I changed all the lights to LED 6 months ago.

elwood58 wrote:
Keep in mind that the 20 amp fuse may be for a whole series of lights.

Which would be more than plenty for LEDs.

Keep in mind that the 20 amp fuse may be for a whole series of lights.

I traced the wire to a 20 amp fuse. C-pap only needs 6 amps so I should be good.

I'd run a #10 wire from the dc distribution panel usually there are a few extra spaces to allow additions.

My charging voltage, whether from the inverter/charger, or my alternator is about 14.4 volts. When the batteries are not being charged, they are a little over 12 volts.
When you plug in to shore power, and your batteries are discharged to the point where they need a charge, the voltage will increase, which makes your lights brighter.

Lights get stronger when you plug in because the battery charger is supplying your 12VDC, not the batteries. You probably have weak batteries or bad connections in the 12VDC side of things.