Replaced the old battery with a fresh new battery. Decided to mount a larger type, as the S80 has room for it.
See the big difference in size, which should account for a little bit more performance and safety as it has a lot more power.
Link to product: https://www.ebay.com/itm/252638760566
Chose a Powerline with the following specifications:
|Capaciteit (C20)||82 Ah|
|Capaciteit (C100)||90 Ah|
|Koude start Amps (EN)||680 A|
|Koude start Amps (SAE)||730 A|