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
