Battery Cable problems of the 2006 Volvo XC90

I drove home from work and messages started to appear warning me of the engine not working properly, low beams not working. Drove it home. Turned it off & wipers would not stop. We unhooked the battery cable using the manual. Took it to have battery tested, bad cell. Replaced battery & wipers quit working, air bag light warning came on. Took to mechanic to have wiper motor tested, it was fine. Took to Volvo, they wanted to replace wiper motor, told them that was not the only problem. Took to different Volvo and they diagnosed, after three hours, the cem was corroded due to a crack in the box that houses it. Wanted $3500 for the repair. I left without it and started to research it. Found out Volvo acknowledged a fault in the seal in a traffic safety report. Contacted Volvo about the repair, started discussions about a good will repair, three weeks later I received a call stating they would not cover any part of it. The Volvo looses power and could be unsafe at any time. There are many discussions of this on different Volvo. I don't understand how Volvo says it is a fault of the part and then refuses to replace it. I am driving it at this time, while I figure out a more economical route.