The Princeton Tec Apex Rechargeable is one of the heavier headlamps in the Princeton Tec collection. The lamphead is itself can be well compared to the other headlamps of this brand, but the difference is that the lamp is powered by a separate lithium-ion battery. This ensures an extra long burn time and can be charged using the included USB-cable. A massive advantage of the lithium-ion battery is the fact that these do not have the so-called memory effect. This means that there is no harm in some additional charging. So you can always make sure you have a fully charged battery on hand.