How about some details on your set up? What are the battery voltages on charge and at rest? Is the converter on? Definitely sounds like over charging so be VERY careful around the batteries. I think I would make sure the converter is turned off, and disconnect the solar until you check out the batteries. Overcharged batteries can and do explode. After the batteries are disconnected from the system, check the fluid in them. It's likely that its low. If so, add only distilled water, but don't overfill.
Lots of help here, we just need some information.
2000 Cherokee 29BH with 6V batteries, LED lights & 400 watts of solar power, flipped axles and raised. 2007 Tundra 5.7L DC-LB with lots of mods. C-co, 8/158th AVN Maint.