The only people who might have the best guesstimate of the total number, is Chord support - but from reading this thread, not all owners with failed batteries do bother to contact Chord, so even they do not have the full picture. To me it feels like at most there have been a few dozen reports in this thread of swollen batteries - maybe I accidently underestimate so let's say the total for this thread is 100. That means a failure rate of 100 in 100,000 shipped units = 0.1% This 100 does not include owners on head-fi who do not post about failures, or owners who never visit head-fi, so for arguments sake, lets introduce a contingency and multiply the 100 * 10 to include them. That means a failure rate of 1000 in 100,000 shipped units = 1%, so 99% of the shipped batteries are still OK Even if that 1000 failures is still an underestimate by a further factor of 5, so that the real failure rate is 5000 in 100,000 shipped units = 5%, the vast majority of shipped batteries are still OK. I think it was reported that the head-fi forum contains the most active discussion threads relating to Chord, so they probably do contain a high percentage of the reported battery failures. Overall this explains the rationale behind my earlier comment 'the current percentage failure rate will still be low' - if for every failed battery reported in this thread, there are another 49 failed batteries worldwide, you will still only have a worst case failure rate of only 5%. I honestly believe that 49 is a large overestimate. Unfortunately when some owners experience failed batteries, they understandably get frustrated and emotive, and then sometimes write posts implying that most (ie over 50%) owners experience battery issues - which just then scares other owners, or potential owners. Hope this explains where I am coming from with my thoughts.