This does not pertain to the original issue, but rechargeable lithium AAA and AA are now available. Their capacity is lower than NiMH, given the internal circuitry that takes space. However, they provide stable 1.5V voltage and are far less vulnerable to low temp than NiMH. I switched to those for the bike and do not look back.
Thanks for posting. I was unaware of such batteries. Did some internet searches and found that yes they are out there. Some on Amazon needed their own proprietary charger but one brand had what looked like a micro USB jack for charging each battery without a separate charger.
Since you are using these, do you find much warning before you run out of power? With disposable or NiMH AAA batteries in my taillight, it gets dim as a warning that the batteries are getting low. But if the Lithium ones provide full power until they shut off, I would be hesitant to use for a taillight where I might not be aware that I no longer had a light on.
Touring, I charge up my taillight batteries once a week, I do not wait for them to get dim. But for my many bikes that I use for riding around near home I do not keep track of how many hours of use I have on each taillight, I wait for them to get dimmer.
So, could you elaborate on whether or not there is any warning before the batteries stop functioning, and if so, what is that warning like?
Thanks.