whilst shortening the windlass cable run (by 7 metres ) I overtightened the battery post , which has a small /4 mm ? , bolt holding it to the battery body and it snapped , inside the battery lug . ah , problem ! how can the broken remainder of the bolt be extracted ? it seems a bit lightweight fitting a battery post to a big heavy battery using a little 4 mm bolt ? I would be grateful for any ideas ,please , grafozz .