3.0V from 2 x 1.5V is borderline for any Mac that needs a 3.6V battery. 3.3V should be the think-twice point, and 2.8V is already the chuckaway point. There are Macs that boot better without any battery at all rather than a sick battery. Others will not boot at all when the battery is in the range 2.8 to 0.0V. Amongst other things, it depends which parameters are stored in the PRAM of the Mac in question, and how critical they are for startup. 3.6V batteries can be had for USD4 each, plus postage, from the eBay seller ronaldo101. Why muck about with anything else?

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