I don't consider a dead battery to be a failure as long as it is user replaceable. However, when the battery is only manufacturer replaceable AND the manual states explicitly that even with 0% remaining battery life you can still dive it, but then it fails with 38% remaining battery life indicated, THAT is a failure... especially on a long deco dive. That happened to me. Ever since then I have dived with two computers on my wrist and only buy ones with user replaceable batteries.
No actual failures of any of my computers though.
No actual failures of any of my computers though.