On Fri, 20 Nov 2020 14:19:41 +0000, bert wrote:

snip

My (very old) charger from jessops (remember them?)

I do. My Dad used to use them quite a lot.

Charges AAs @ 150mA and AAAs @ 50mA singles or pairs x 2

NiMh and Nicad?

PP3 @ 16mA single or pair

Ok.

Max Charging time 15 hrs by Timer Control.

Yeah, that's the thing, if you drop the current down you can safely
charge for a fixed time with little chance of overcharge and from the
link Pamela provided, might be safer than trying to detect the -dV

More is not always better.

Oh indeed.

The first electric RC cars we raced at Ally Pally came with a wire
wound resistor fixed to a small ally plate to limit the charge current
to the 4 x SubC 1.2Ah Nicads. Inevitably someone would 'forget' they
had left their batteries on charge and they would overheat, split
their cases, melt the plastic / ABS top and bottom trays they sat in
before one cell would explode. ;-(

So, I got a folded ally project case, fitted the resistor inside and a
clockwork timer (with built in switch) on the top. Connect to a car
battery, connect the output to the RC car battery, twist the timer to
20 mins and I didn't have to worry I would 1) burn myself / melt
something with the resistor and 2) overcharge the batteries. ;-)

Cheers, T i m