2004 s80 runs for 30 to 40 min then electricaly shuts off

[fatherof4]

HI guys and gals, I am a new volvo owner, got a 2004 s80, and for 3 months, no issues. now suddenly, it will start acting funny. I have read many posts, but nothing fallows what problem i am having. So, here it goes. The car starts and runs great, perfect even for about 30 min sometimes way longer. then it starts, the transmission feels like it is slipping, and then the insturment pannel goes dead. no windows work, no messages on the screen, almost like it came unplugged. Oh, and it is stuck in whatever forward gear it was in. Today, 4th gear. that was fun trying to get back to the house. Atleast i am in Florida, flat land right. I get to a safe place, the house, and am able to shut it off with the key, and when i go and turn it back on, it goes right back to like nothing happend. Fuel econonmy is great. No messages get displayd untill today, says somehting about the srs system, all i can figure is there is something loose and I will be darned if i can find it. if you have any help, know of anything, i am a pretty good shade tree mechanic, but elelctrical problems throw me for a loop. Thanks

[JDS60R]

Sounds like a bad battery or a loose ground. Start with having the battery tested regardless of age. You may need to smack it while testing to see if a plate is loose. If possible just swap in a different battery. Also check the main positive and negative connections. If everything is tight and the grounds look clean and well connected you may have a computer issue.
Let us know if you have any OBD codes stored. Your car may have codes and not set a warning light or message.

[fatherof4]

i will give that a try. Last night, i work an overnight shift about 25 miles form the house, the volvo s80 worked flawlessly. maybe i have a ghost....kidding, however, i will have to jumble the batary around, cause it seems to do it in stop and go traffic.