22 Dec
2022
22 Dec
'22
8:33 p.m.
On 12/22/22 11:42, Paul Koning wrote:
I just read the battery chapter of the ARRL Amateur
Radio Handboo, which discusses this particular point at some length.
Among many other points it says (a) you can trickle charge a NiCd but not a NiMH, and (b)
NiMH requires a more complex charging algorithm than NiCd, so that NiMH chargers are also
capable of charging NiCd batteries safely, but NiCd chargers cannot charge NiMH cells
without the risk of damage.
I suspect NiMH charger circuits can be found. Buying $3 Chinese ones may work, or not; I
keep remembering that China disallows selling unsafe equipment within the country but
doesn't have any rules against exporting such things.
I've done a little reading on the subject of NiMH charging. The nub of
it appears to be that slow charge is best and should be discontinued
when the cell voltage reaches 1.55V--the idea being to limit the
temperature rise within the cell. I've seen circuits using discrete
components (transistors) and those adapting voltage regulators and even
microcontrollers. I haven't run across a single IC dedicated to the
process yet--I suspect there must be one out there somewhere. My
driveway blinking beacon lights seem to do quite well charging them from
a plain old PV solar cell--they've lasted for years.
All of this is child's play when compared to the problem of charging
Li-ion cells. There, ICs like the TP4056 appear to reign supreme.
FWIW,
--Chuck