I'm surprised that you trailer converter doesn't charge your battery more quickly. Unlike converters used in trailers years ago, which only provided minimal charging current, modern converters which are actually switch mode power supplies, make the entire converter output current available to the battery for charging. Additionally they provide multi-stage charging to avoid over charging if you keep your trailer plugged into shore power for long periods. One thing you will find us that you can actually run the entire trailer 12 volt system of the trailer from the converter. This was not possible with the simpler converters of yesteryear.