How fast does a solar panel charge a phone?
In full sun with the panel perpendicular to the rays, the 18 W panel gives about 2 A from one port, the same as a wall charger, and charges a phone in 1.5-2 hours. The 9 W panel gives about 1.5 A, so a phone charges in 2-3 hours, the 6 W panel about 1 A and needs 3-4 hours, and the 3 W panel is for keeping earbuds, a smartwatch or a flashlight topped up. Under clouds and at an angle these times stretch several times over.
Why do the angle and direct sunlight matter so much?
Cells deliver their rated power only when the rays hit them perpendicular in full sun. A panel tilted 45 degrees loses about a third of its power, a panel lying flat in the morning or evening gives a fraction, and behind a window another 30-50 percent is lost. In shade and full overcast a few percent remain. So point the panel straight at the sun, prop it at an angle and reposition it every 1-2 hours.
The panel on my desk by the window shows charging, but the phone barely charges. Why?
The LED or charging icon lights up at a minimal current, while the glass, curtain and room shade take most of the energy, so the panel delivers a few percent of its power and the phone effectively stands still. This is normal behaviour, not a fault. Take the panel outside or onto the balcony, point it straight at the sun, and you will see the difference at once.
The phone keeps stopping and restarting charging from the panel. What should I do?
When a cloud covers the sun, the panel current drops below the threshold, the phone stops charging, and when the sun returns it negotiates from scratch, which in changeable weather means many interruptions and a poor result. Connect a power bank to the panel: it accepts any amount of energy without interruptions, and you charge the phone from the power bank in the evening, steadily and fast.
How long does it take to charge a power bank from a solar panel?
The 18 W panel in full sun feeds about 10 W into a power bank, so 10000 mAh charges in 4-5 hours and 20000 mAh (74 Wh) in one long sunny day. The 9 W panel needs about two days for 20000 mAh and the 6 W panel three. A power bank with a built-in 1-1.5 W panel charges from the sun for over a week and serves only as an emergency top-up, so for real charging in the field choose a separate panel.
Are the panels waterproof and how do I attach them?
The 3 W panel has a waterproof, flexible construction, and the foldable 6, 9 and 18 W panels are built for outdoor conditions; still protect the USB ports from water, never submerge any panel, and disconnect and dry a wet one before plugging in a device. Eyelets and carabiners let you hang the panel on a backpack while walking, on a tent or on a balcony railing, always with the cells facing the sun.
