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Battery update...
Mar. 28th, 2013 04:56 pmAfter putting four of the N cells out into the sunlight to charge, I took a stab at inserting three other batteries into my HP-28C, and the unit started right up (though not with the oomph! I would have expected, in terms of screen brightness). I put the calculator away, and then recovered the charger, removed the batteries, and threw them into a plastic box along with one other cell.
On a whim, I broke out my pocket voltmeter this morning to see if there was any discernable difference in voltage between the batteries that were charged and the one that wasn't. My curiosity was triggered by yesterday's indication on my charging unit when I first set the batteries out, to the effect that they were already fully charged.
There was a difference. Four of the five batteries in the box came in at 1.36 V; the fifth had a voltage of 1.17 V. I quickly broke out the remaining batteries, and their voltages varied between a low of 1.16 V and a hight of 1.21 V.
I put four of the low-voltage cells out today (not a great day for solar charging, as there were a lot of clouds in the sky) and after 5 hours, they all exhibited voltages of 1.37 V or more.
It occurs to me that I might get a better handle on the behavior of these units if I periodically measure their voltage, although from what I've read of NiCd batteries, they tend to retain their voltage as they deliver power, so this idea may not work out.
But I won't know until I try, will I?
On a whim, I broke out my pocket voltmeter this morning to see if there was any discernable difference in voltage between the batteries that were charged and the one that wasn't. My curiosity was triggered by yesterday's indication on my charging unit when I first set the batteries out, to the effect that they were already fully charged.
There was a difference. Four of the five batteries in the box came in at 1.36 V; the fifth had a voltage of 1.17 V. I quickly broke out the remaining batteries, and their voltages varied between a low of 1.16 V and a hight of 1.21 V.
I put four of the low-voltage cells out today (not a great day for solar charging, as there were a lot of clouds in the sky) and after 5 hours, they all exhibited voltages of 1.37 V or more.
It occurs to me that I might get a better handle on the behavior of these units if I periodically measure their voltage, although from what I've read of NiCd batteries, they tend to retain their voltage as they deliver power, so this idea may not work out.
But I won't know until I try, will I?
