Eventually, all battery-powered mountain bike lights will die and need a recharge. The battery life or burn time of a light ultimately depends on the quality of the battery and light, the setting used, and the air temperature.
If you’re running a high-quality bike light at peak power, it will generally only stay on for between 90 and 150 minutes. At lower outputs, the same lights may be able to last for twice as long or longer. The mountain bike lights with the biggest and most powerful battery packs may be able to stay on at full output for up to 4 hours.
To get the most out of your light, we recommend always starting your ride at full charge.