Based on your question I am going to assume that the two batteries that you removed were 6 Volt Deep Cycle Batteries and that you replaced them with a one 12 Volt Deep Cycle Marine/RV Battery and not a standard 12 Volt Engine Starting Battery.
If all of the above is true then the answer to your question is yes a properly wired and properly charged 12 Volt Marine/RV Deep Cycle Battery should be sufficient to operate the tip-outs on your 5th Wheel Trailer.
So the problem you are experiencing may end up being a battery wiring issue or a blown fuse. If you have already checked for those problems you may have to take your RV in and have a Certified RV Technician track down the problem with your tip out system.
I hope this helps.
Do you have any suggestions or comments on this topic? You can add them to this page by clicking on the "Click Here To Post Comments" link located near the bottom of this page.
Everything-About-RVing.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.