My 16 year - old son's 640 Medtronic pump stopped working a month ago. The problem was the battery lid, so Medtronic sent me a new lid. However, we still had problems with the new batteries we used, because the pump rejected most of them. Finally, it worked but it started making rumbling sounds. Since I wasn't sure whether it worked or not, we started using our 11 year - old pump. I have been monitoring the 640 pump and I realised that there is no rumbling sound any more, the pump works normally (basal and boluses) but the batteries are out after 2 days, instead of 7 to 10 days that they used to work. Any ideas?