The Battery Backup Unit measures and evaluates the battery pack temperature on a continuous basis. If the temperature is too high to operate, this message will be posted. You should check that there is enough airflow around the Battery Backup Unit. When this event happens, the Battery Backup Unit becomes not ready and is unable to backup the 3ware RAID controller. You must replace the battery pack if the temperature error persists. The use of a PCI card in the slot adjacent to the BBU is not recommended and may result in the battery temperature being exceeded.