A few weeks back, on a whim, I picked up a little LED string in Lidl, being sold off at 99c, complete with a pair of AA cells.
I've been running them on a pair of rechargeable AAs, as a test.
Apart from On and Off, there is a third switch setting that has them on for six hours, then off for eighteen and repeating daily, whilst the power source lasts - they are currently on the sixteenth cycle of that now, which is rather longer that I thought they might run on rechargeable AAs.
Today, I drilled a hole in a bottle and threaded them in, for a super-trendy light display.
View attachment 12021
The bottle was free (even when it was full) and so, for 99c and ten minutes work, I have this - and I still also have the 'real' batteries that came with it.
Fully prepared for next Christmas.