Well that's our replacement MaxG battery. Has given service for two seasons now, always in an old style McMurdo neoprene case. It hasn't been subjected to anything out of the usual but whilst giving it and the LJs a quick once over last week found it had split like that - definitely not waterproof anymore! Will see what they say.
Was having a look at it as Gotchidad is doing a floatplane rating in a couple of weeks and wanted to take it with him for that, fortunately it gives us a few weeks to sort it before the boating season starts. Will see what McMurdo have to say about it, their customer service has been excellent in the past.