Thats one dodgy battery cable! Thank god it didn't cause any more damage or worse!
Love the old school volvos, I miss my 940, would take anything I could throw at it, even battled on with a corroded cylinder head mating surface (when my sister in law had it). I had a spare cylinder head but it had been sat outside for years and was all oxidised. A quick scrub and pressure wash and it was useable (fortunately the mating surface was good), still going strong today