Many Insighters have the same misconception. the 12V is required for pulling in the HV contactor else the 144v pack will _never_ be engaged :!:
And there's still a complex and possible interaction between IMA load and the DC-DC converter. It uses some of the 144v generated in the IMA motor and drops it to 12v for the conventional electrics.
One possible scenairo is that a 12v near its demise drops low v enough that the BCM resets (effectively a manual recal) and your in a forced charge on start-up.
Another is if the 12v fails in an unusual fashion. Sometimes the internal resistance of a 12v can drop dangerously low. Plate bridging or heavy sulphation are two of the possible causes. Then the 12v charging system incorrectly "sees" the need for more current, drawing a heavier load in the IMA system. In a car with a conventional charging system the alternator frequently melts down.
But from the many reports in here the 12v is prematurely replaced. Sometimes the BCM can drift into the SoC doldrums for days - weeks at a time. A reset is all that's needed. Disconnect the 12v or
The IMA reset proceedure.
http://www.insightcentral.net/encyclope ... orage.html
Replacing the 12v effectively does the same.
And IMA batteries will eventually exibit a more fragile SoC and more frequent recals. Its just the normal part of their aging process. Their probably still "good" for many tens for thousands of miles. You'll just have to live with the lower MPG due to the more frequent forced charging or _choose_ to replace them prematurely. Warranty will only cover them at their predetermined point of failure as defined by an IMA code (the red IMA light on the dash comes on while driving).
HTH!
