What is the make and model of your current converter?
If it is a Iota, look for what appears to be a phone jack on one of the sides. If it has the phone jack all you will need to do is purchase a Iota IQ4 Smart Charge Controller and plug it into the phone jack. The converter then becomes a multi-stage converter. In my experience it works well.
If you do not have the phone jack you will have to purchase another converter with the multi-stage charging feature.
Here is my experience with the IQ4 Smart charge Controller:
When I needed 4 new house batteries, I debated about getting 4 AGM batteries. But I decided to get another 4 Interstate U2200's.
However, at the same time I added the Iota IQ4 Smart Charge Controller ($36) that plugs into the Iota Converter. This has made a big difference in charging of the batteries. Prior to the Smart charger, I had to keep an eye on the battery fluid levels and deal with the out gassing associated with the charging of the batteries.
Now there is virtually no out gassing and I've not had to add any distilled water to any of the batteries during the last 6 months of continuous use.
This was alot less expensive solution than buying the AGM's.
Here's the IQ4: IQ Smart Charger for DLS Series Battery Chargers from IOTA Engineering
The IQ4 and converters can be purchased from one of the site sponsers, RVupgrades here: Electrical - Iota Converters