My cars a 58 plate,and had problems with the battery.
Similar audible/visual dash warnings,coupled with the car just cutting out completely.
It turned out to be water ingress into the battery compartment (known fault for E92s apparently).
The fault which was caused by corroded terminals and cables was dealt with by goodwill by the dealer,with a 50% contribution from me for just the labour.
Worth checking NJ,although I would have thought you'd have seen signs of water when changing the battery.
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