> Even a zener clamp will keep a graphite cell <= 4V2 if
> properly designed. Would almost certainly be << 4V2 to
> ensure this in all cases so capacity will be down or even
> much down.

You have 1% zeners?  1: zeners have bad knees. 2: temperature.

> Low voltage cut-off can be arranged at extremely low cost
> with a bipolar switch and eg zener plus glue.

You need to draw really close to zero current after cutoff.

> If I chg << Ichgmax then should be OK as long as Vmax
> limited as above.

True, and you step the voltage down when current is < X (select for
cell ratings)


> Charge cutoff at end of charge taper seems the hardest at
> zero cost BUT if Vzener clamp or whatever is << 4V2 then it
> will sink ALL charge current as 4V2 approached so should
> have zero current below 4V2. A well sloped clamp curve would
> help.

Assuming the zener clamps at the right point, then it's dissipation
gets rather enormous, doesn't it?

Additionally, you could use a timer to terminate charge after a reasonable time.

Current limit isn't that hard to achieve with a couple of transistors,
if you don't mind some dissipation, and you've got a couple volts of
overhead to work with.


> The bad energy utilisation at low Vmax_allowed  may mean
> that NimH are superior in absolute terms.

Nimh are way more complicated to charge, if you're going to respect
all the rules.
Last time I did it, I filled a tiny-26 with assembler code.
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