Battery seeping fluid

[exdrocca]

Hi guys, so I took my truck on a 6 hour roadtrip to a family vacation. The truck drove well, except when I stopped for fuel after 3 hours in, my battery was dead trying to start back up. It smelled like battery acid also. The battery was like 2-3 years old. The acid fluid was seeping out of the top, looks like vent holes. I had AAA come with a brand new battery, and continued my journey. When I arrived at my destination, I noticed it was seeping fluid again, not a lot of fluid, but I noticed a wet stain area around the same location. It didn't smell though. I installed a new alternator and regulator the next day. Autozone tested it and it was low on output, so not overcharging it from what i understand. It's only when I drive. And never had this happen before. Anyways, still on vaca and heading home at the end if the week.
Any ideas of what can cause this? It only happened on this long drive. I drive it regularly.