Joined: Aug 2010
Posts: 12,728
Likes: 2,106
From: Madison, WI
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Some Lithium Ion batteries or devices have a protection circuit so that if the battery is discharged too low, it is prevented from charging. That is a safety feature, as discharging a battery too low and then charging can cause it to become a fire hazard.
I use taillights that take AAA batteries, I use rechargeable NiMH AAA batteries. I have lights that are 10 years old that still work great, although the NiMH batteries that I used a decade ago have been recycled. That said, good AA or AAA powered headlamps are quite rare. I got a B&M one to carry as a backup on brevets, I do not recall the model name and it is not super bright.