Having a smaller backpack would be a better option, so you are not carrying as much on your back. A small daypack will be the best option for those who are doing strenuous activities such as running or cycling. These bags are lightweight, made with breathable mesh, and fit close to your body. Some come with hydration bladders and waterproofing. If you plan on doing long-distance hiking or camping, you'll need a large bag that can protect your devices from the elements. This may include waterproof material or built-in rain covers. Having a detachable solar panel is useful because you can tuck it away when you feel it may get damaged, or you can leave it out in the sun for charging.