The trickle charge did very little to bring the battery to a full state of charge.  Delco batteries prefer to be charged hot and heavy. The black usually returns after a good solid charge of about  2-3 hours.  I usually don’t worry too much about the eye, it only tells you the state of charge in that one cell.


I had an AC Delco battery for my 88 Dodge aries and the green hydrometer eye died out too (well, it wasnt green anymore, just black) and I too see the green come up slightly when you shake the battery. However, the battery is unfortunately dead. Not entirely dead, but from what I experienced, it was at first less than 5% of power but the car still
started (very very slowly), and after charging, running the car, etc.. all I could get was 65% – 75% of power. Which eventually went down to 5% again. So I just went out and got a new battery. I have just taken my 1979 Corvette out of heated winter storage (5 months). The AC Delco battery was new last August and the car stored in November. The battery was disconnected in storage and not charged during the five months. I put it on trickle charge this week for about 12 hours as a precaution. All seems fine after about 50 miles of driving: good cranking, lights etc. However, the hydrometer “eye” is black, not green as it should be. Will the green come back or is this terribly important to begin with? Back to dealer for check under Delco warranty? If I nudge the battery gently, the green eye appears for several seconds, then goes away. I have had this car for 14 years and through a number of batteries but have not seen this situation before. Would appreciate thoughts/advice. No wait, it’s not a piece of plexiglass or a mini-hygrometer, the
famous Delco ‘Green Eye’ is actually a miniature satellite transponder linked directly to the Delco ‘Charge Center’ in Anderson, Indiana.

The transponder has sensors that monitor the precise chemical reaction taking place in your battery….that information is beamed over a Microwave link to the Delco ‘Charge Center’.  There a team of electrochemical engineers analyze the data and then shout out: “Black!” “Yellow!” or “Green!” to the ‘Charge Command Center’.

The Command Center then transmits the appropriate signal to the Green Eye transponder and it emits the correct color. This process is repeated once an hour.  Thus you assume that your Delco battery is just sitting there under your hood …..when in-fact it’s being constantly monitored by a team of Nobel-Prize winning scientists.

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