Originally Posted by
unterhausen
most of my rear lights, I can tell just by looking down. I had trouble with my rechargeable lights dying on my fatbike in really cold weather, so now that bike has a dyno system. It was the last holdout because it costs so much. I really hated realizing I didn't have a rear light.
Good reason to have a second rear light and also a rear reflector. Note that using a dyno as the power source only eliminates one source of failure (the battery) and adds some wiring as an additional one. Still a good idea to have some redundancy since there are quite a few ways in which lights can fail.