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4688 posts

Uber Geek
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Topic # 42616 7-Oct-2009 18:41
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I am resurrecting a very old notebook for a friend. For some bizarre reason known only to Sony, this particular model uses a 7.2 volt rechargeable NiMh for the cmos. This particular battery can no longer be found and anything even close to equivalent is both way too big and way too expensive.

Unable to replace the original, I had the bright idea of substituting two 3.6 volt lithium buttons in its place. Yes, I know lithium cells tend to explode when recharged, so I put a diode in the circuit to isolate the cells from the charging voltage while still allowing them to keep the cmos alive when the power is off. My thinking is if a lithium button can keep a pc cmos going for years, why not this one? I don't really see the reason for making that battery rechargeable in the first place.

I have tested the solution and it seems to be working perfectly. Before I return the notebook to its owner, can anyone who knows more about this than I do give me a reason why it might not be such a brilliant idea after all?

Thanks for reading.

I reject your reality and substitute my own. - Adam Savage

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71 posts

Master Geek

  Reply # 263252 11-Oct-2009 11:52
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I say good job, that's from ten years as an electronics engineer

4688 posts

Uber Geek
+1 received by user: 2100


  Reply # 263446 12-Oct-2009 11:09
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Thanks for the reassurance. I thought it should be okay but I wanted to make sure.

I reject your reality and substitute my own. - Adam Savage

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