Thanks - I had been pondering the Optima batteries but the smaller capacity put me off. At the moment I have a big-ass 160Ah truck battery, but these top out at around 50Ah. Given the benefit in technology though I may have to reconsider when this battery gives up on me (assuming it hasn't already
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I got the new cable through today (ouch copper is expensive) and it looks more up to the job so now I just have to find the time (and more importantly, the "get-up-and-go") to fiddle around out in the cold.