Just realised this:
i know that many people recommend it for D2 but IMO those have too little knowledge about these things, red tops are AGM batteries and AGM needs a different kind of charging system which can deliver higher voltage, the D2's rudimentary alternator was conceived for SLA not AGM batteries and it's possible that it ruined your expensive battery which didnt get proper charging over time, that's the result of relying on all kind of forumists without making serious scientific research to make sure it's not b0ll0x. In a nutshell:
https://vehiclefreak.com/std-vs-agm-battery-charging-whats-the-difference/ , there are many articles about that, some more explicit... the fact that somebody fitted AGM battery to a D2 or other vehicle with "classic" alternator and he states it's OK doesnt mean it is from technical point of view too.