David C. comments that:

>initially; states that: the green LED functions at 12.5 volts and above;
>the yellow below 12.5 volts and the red between 12.5 volts and 12 volts.
>So both Harmon and Derek are right: a battery below 12 volts is in danger
>of not being able to start the car, still it seems that 12.5 and above is
>sufficient and perhaps a little less would be ok...DC

Thanks for the clarification;  would it be reasonable then, that if a
battery (primary, or otherwise) appeared to be in good shape, had its
plates covered, had clean solid connections and was fully charged to 13+V,
yet dropped to, say, 12V after hooking up to the starter or fridge, is due
for replacement?  The assumption is that the charging system is also
functioning correctly, btw.  

Norman