Originally Posted by steelbikeguy

I don't keep up on the different technologies or chemistries, but I keep hoping that a good low temperature rechargeable battery shows up.
I've made some standlight circuits for my bikes, and they have used AA nicads. These don't mind (much) being recharged in very cold temperatures, and the 1.3V works well with my circuits.
Last year(?), I had one that died and I was looking for a good replacement. It turned out that I did have some untabbed AA nicads stashed, but I would like to find a good replacement.

I did check some of the lithium chemistries, and didn't find anything that I thought performed as good well as a nicad. .. oh... it seems that nicads are gone from the marketplace, so the next best option for that form factor is probably NiMH.

The best cold temp performance for a lithium was the fairly new lithium titanate. Nichicon was marketing something called the SLB12400L151. It could be charged down to -30C, according to the preliminary datasheet that I've got. Or maybe that's just the discharge temperature? It's a very brief datasheet. Unfortunately, the capacity is very poor. 150mAhr for a cylindrical cell that is 40mm x 12.5mm.

The lithium iron phosphate batteries are rated for discharge down to -20C, but only 0C for charging, which isn't sufficient for my standlight use.
Is there something suited for charging at -15C (around 5F)?
Just wondering if I need to convert my standlights to supercaps. I've got one headlight using a 100F supercap, and it's not bad. It's a rather bulky item to retrofit where a AA used to be, though!

Steve in Peoria