Norm - we have 5 cars in the family and they show that same kind of battery behaviour (slight drop in rest voltage after shutdown), and still start and run fine. I bet if you let the Honda sit for 24hrs, you'd see 12.6-12.8V at its terminals too.

If you find that the battery is noticeably slower to crank the engine after sitting for a day or three, suspect a bad battery. The place that sold it may be able to load test it for you. As for your charging system, if the battery voltage is 13.5V or greater at idle, all would seem to be well. Turn on high beams, blower fan, and rear demister and it should still hold up...maybe with a slight increase in RPM.

The current drawn by the clock indeed spikes with each 'tick' - as you've observed. Check your math - it draws 0.25W, not 2.5. Radio memory and maybe some other devices will also draw a tiny bit, but should have negligible impact on a good battery - even after several weeks.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and numerous old motorcycles)