Combined with a hard shutdown it can cause problems (pages SQL assumes written to disk never got there).
If the RAID array's battery is faulty, you must disable the write cache until it can be fixed.
Seriously, get someone to have a top-to-bottom, end-to-end look at that SAN, it really doesn't sound healthy
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability