williamwright wrote:
Could he simply use a torch bulb as a current limiter?

I don't know the resistance curve of a torch bulb, but I'd want to make sure
I never put more than 4.2V across the lithium cell. If the cell isn't
taking much charge current I'd expect the cell voltage to rise above 4.2V
which is likely to damage the cell (not in a fireworks kind of way if the
current is low, but in terms of reduced cycle life). The torch bulb also
won't back off the current as it reaches top-of-charge.

However, it's likely this cell has a protection circuit in it so you might
get away with it, but personally I'm not sure I'd want to risk it.

Theo