Q. I live in a large 5th wheel full time and I am plugged in at all times. I heard the battery charger kicking in from time to time and the humming of the converter. Do I have to have the converter on all the time? Is it on only to charge the batteries? The manuals are the pits and I am really trying to know all about converters. The more questions I ask from different sources the more answers I get. I read your web site you do explain well. Thank you.
Mark Says: The converter in your RV basically does two jobs.
1) When you are plugged into electricity it converts a portion of the 120 volts coming into the RV down to 12 volts so all of the 12 volt devices like overhead lights and fan motors will operate without draining the RV battery.
2) It has a battery charger built in the converter to keep the RV battery charged (topped off).
The noise you are hearing is most likely the fan on the converter. The converter gets warm when it is on so the manufacturer adds a fan to help keep it cool. Some are very noisy.
You do need the converter on when you are plugged in. If the converter wasn't on, or wasn't operating properly you would run the RV battery down because you are using the 12 volt appliances and devices.
Some older RV converters charge the batteries at a constant rate and will continue to charge the batteries when they are fully charged. This can result in the battery or batteries losing water, so battery maintenance and inspections are important when you have the RV plugged in for long periods of time. Newer converters have 3 stage chargers that know when the battery is fully charged and at that point in time only provide a float charge (less charge) to prevent overcharging conditions.
Read this article I wrote on converters that might help explain it in more detail. http://www.rvuniversity.com/article.php/20080107175732307