[clickman]

Checked battery electrolyte level, and it was way low.

Filled it with distilled water and put it back on the CTEK. Will check it over the next 3 days to see if it switches from "charge" to "maintain".

I checked the electrolyte level last fall before putting the battery on the maintainer, and it was a bit low, and I topped it up then.

Is it normal to lose so much fluid in one driving season, or is there another problem, like the alternator?

(I was really dumb and had the battery connected up backwards last winter for a few minutes. No codes and the battery voltage checked ok afterwards, like the alternator was still charging ok.)