[rohrmann]

Don't know what brand or model of converter you have, but ours is the Progressive Dynamics that was installed in our Montana. It is possible that yours is also. If yours has the Charge Wizard, you will at times have different charge activity going to your batteries, which will cause your lights to brighten and dim slightly. This is copied from the manual for ours:

The Charge Wizard selects the best mode for your battery automatically. However, you can temporarily override the auto settings giving you the
freedom to change the way your battery charges. The Charge Wizard will be able to select between three very unique modes of battery charging.
BOOST, NORMAL, and STORAGE.
BOOST MODE: If the converter senses that the battery voltage has dropped below a preset level the output voltage is increased to approximately 14.4
volts DC to rapidly recharge the battery.
NORMAL MODE: Output voltage set at approximately 13.6 volts DC.
STORAGE MODE: When the converter senses that there has been no significant battery usage for 30 hours the output voltage is reduced to 13.2 volts
DC for minimal water usage. When in storage mode the microprocessor automatically increases the output voltage to 14.4 volts DC for 15 minutes
every 21 hours to help reduce sulfation of the battery plates.