For a one year old battery to be goosed it sounds to me like either the charge profile of your charging source is wrong for the chemistry of the battery or there is a fault with your charger.The battery is cooked. 11.8v last evening. Next step is to find a leisure battery in the Highlands. Any local knowledge? We are on our way to Aviemore passing by Inverness.
Why did a one year old battery cook? I will check charger jumper settings. Clearly I don’t want to fit a new battery to see it go down the same road. Is there anything I should be keeping an eye on to make sure it was not the charging system that was the battery killer.
Although saying that 2 years ago I had a 13 month old battery fail for no reason so it does happen.