"10-15 seconds" is the definition of the average Pakistani's standards of measurement. Which is it? 10 or 15? How big is the resistive load, is it sized correctly for the delivery capabilities of the battery, and is your measurement instrument calibrated correctly?
What meaning does "12V" hold when cranking voltages can drop far below that? Is a battery not good after cranking a starter for 10 seconds with an end voltage of 11.8V?
The real child's play is talking about "Magic Eye" as if it means anything at all. At most it indicates an idea of the state of a single cell. Plus, I was an actual child when I learned I=V/R. Good job explaining it!
Were these illustrations of colors also child's play? Great! We played together. 
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A battery's IR is not necessarily indicative of its progression along its service life, even if it does give a rough measurement to determine whether or not it is a serviceable battery.
A "magic eye" indicator is usually a very simple, low-cost hygrometer that shows a rough idea of the condition of the cell and the level of electrolyte, but only on the cell it is installed over.
A large number of 3-stage/4-stage "adaptive" or "smart" chargers available in the Pakistani market, especially with ridiculous ratings like 25A or 30A, are simple timer based circuits (or even a generic Chinese Pb charge IC with the board laid out exactly like the datasheet "example" application) with noisy SMPS components, poor ripple regulation, no actual CC-CV mode, no safety measures or charge termination logic, poor or nonexistent isolation between HV/LV sides, a float mode that sits at 14.4V (!), no temperature compensation, etc.
