Black dot on Century battery?

what does it mean? its been on the charger for a few days now... still hasnt gone away, top'd up the water yesterday no change...?

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Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

dont know what it means... but i put it back in the moke and it started...?

at idle it sits at around 12.5v under load with lights on etc, it goes to 13.6v... seems a little low to me... any thoughts?

_________________
Here am I sitting in my tin can far above the Moon
Planet Earth is blue and there's nothing I can do...



“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

Dot should be green if all is well, black (or clear) dot not good. Had a bloke at the battery shop try to sell me one off the shelf with a black dot. Told him to test it under a load and it dropped its bundle. Its sulphated, wont accept charge properly any more.

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Over 1,000,000Km, but now my retirement restoration project