fuse on positive battery terminal

[T5norm]

Hi. I have a volvo v70 D5 2008 R Design.

The car developed an unhealthy noise and I called out a mobile mechanic. A message came up on dash saying there was a charging failure service urgent. When he arrived the car would not start and he initially thought the engine had seized as he could not turn it over by hand, however he has diagnosed an alternator problem and we replaced the alternator with a new one. Still wouldn't start but engine moving freely by hand which it wasn't before.

After lots of testing why it wouldn't start we found that there was no voltage from the rear of the positive battery terminal. Basically there is a small fuse that has blown - when bypassed it starts and runs spot on. He hasn't come across this before but basically when the car is started then all works fine and current flows over the terminal but it will not start until it is bypassed.

Does anybody know anything about this please? What is it for and is it safe to bypass it. He has called Volvo and asked for a replacement fuse and they have said its not possible and the terminal connection needs replacing at a cost of £150 for the part.

Any and all advice really appreciated. Haven't yet received the bill but am sure the alternator isn't going to be cheap let alone the diagnostics.