Opened up one bike light from china that charges via a USB port (5V, .5A) and inside, the rechargeable battery is a barely labeled "R6P AA size 1.5vols 0% mercury". besides that only engrish, brands and a warning "Do not dispose in fire, re-charge, put in backwards..."
I couldn't find anything from the R6P type, only alibaba.com (china wholesale ebay) sales. So i'm assuming it's an zinc-carbon AA-R6 for now.
If so, i used the bike light for almost a year with that battery inside it (not serviceable) recharging every week or so. what's the magic?
the control board has some ICs with black epoxy, i'm in the process of scrapping it.