I have had one 18v LXT die (from six) and one 36v Makita battery die. The rest have been fine, and I think the system is fantastic. I have a 18v circular saw, 36v chainsaw (which takes two 18v batteries on an adapter) and 36v strimmer/pruner/hedgetrimmer. They are all amazing, though I like the idea of finding a dealer who can test failed batteries. We did an article about boosting failed batteries. I wonder if it would work in this case.
Nick