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
