22 Dec
2022
22 Dec
'22
10:34 p.m.
On 12/22/22 13:50, Paul Koning wrote:
Yes, that looks similar to what I read. One
interesting point in the
discussion I saw is that it said slow charging is not recommended for
NiMH because the right way to detect end of charge is by voltage drop,
and that drop is even smaller if the charge rate is low. So to have
reliable detection of "fully charged" you need to go reasonably fast.
Interesting.
What I gathered was that once a cell is fully charged, anything beyond
that is converted into heat. It also mentions that simply sticking a
thermistor in the battery compartment is not a reliable way of gauging
end-of-charge.
So charging at a very low rate (say, 0.01C) will probably not cause
much in the way of heating, but will take forever, which explains my
driveway lights--they charge during daylight hours and only discharge at
night at a low rate (there's an interesting circuit there that boosts
the 1.2V and blinks 3 high-intensity LEDs about once per second.
Clearly, the little PV cells can't supply much current.
The problem that I have with NiMH cells is that they do occasionally
spring a leak, with a nasty cleanup job afterwards. I've not run across
a leaky Li-ion cell yet (knock on wood).
That's not to say that Li-ion cells are without their quirks. I
recently almost discarded a AA-sized 14500 cell because the output
voltage had suddenly dropped to the point where none of my chargers
would even see it. So I put it on a corner of my workbench against the
time when I had accumulated several and could turn them in for
disposal. A couple of days ago, I picked up the cell and checked it
with my voltmeter and it read 3.5V. Put it in the charger, and slowly
charged to capacity. What happened during the month or so that it sat
on my workbench, I cannot say.
--Chuck