FlexSolar 8.5W Solar Charger Review

Categories Battery Banks



Build Quality


Charge Speed (Direct Sun)


Charge Speed (Indirect Sun)


Charge Jitter




Ease of Use




The Good

  • Can output 1A in full direct sun
  • Easy to use
  • Great build quality

The Bad

  • Charge controller makes a loud whine
  • Charge controller does not shut off when voltage drops
  • Will not charge devices in the shade
  • Charge controller may damage your device

Update: After further testing, this charger is unreliable and may even damage your device. It is not recommended to purchase under any circumstances. Above links have been updated to a more reliable charger instead.

My recommendation with a solar panel like this is to buy a battery bank and charge them together instead of directly charging a mobile phone or device. The reason for this is sunlight fluctuates, and phones are not as well equipped as battery banks to handle the drops and jumps in current. From my experience with this panel, in bright full sunlight, I got at best just under 1.3A of charging, with an average of around 1000mAh. Given the solar panels rating of 8.5W, this is expected. The panel is rated for a peak output of 1.7A and there will be some loss in circuitry, sunlight intensity, heat, etc. The one issue I noted with this panel is at lower outputs (in the shade particularly), the charge controller makes a quiet high pitched whine when there is not enough light. I also encountered a small voltage drop before the controller decided to stop trying to charge in low light but it wasn’t enough that it would damage my devices – just something I wanted to point out.

In non-technical terms, in direct sunlight it will take approx. 3 hours to charge a smartphone. This panel does not store energy on its own – it will only charge other devices in sunlight. Things like clouds blowing past, a window or intense heat can push charging time a little longer. Since it’s inconvenient to be connected to a solar panel for several hours in a row, I recommend buying an external battery bank with the panel, despite the fact that they take longer to charge. For example, a 10,000 mAh battery bank will take about 10 hours to charge with this panel in direct sunlight. However, charging a battery bank means your phone is not constantly tethered to the panel and you can move freely with it. It is also better for the phone, because this panel does not charge much in the shade, and phones need a consistent amount of power to charge properly. If you want to charge multiple devices at once, or charge better in mixed sun/shade you will need a higher wattage panel.

Where to Buy

Get this RAVpower Solar Panel instead. The Flexsolar may damage your device.


This is listed as an 8.5W solar panel online, but the specs say 10.6W. Little solar panels like this can be alright in direct sunlight but I’d advise, for most cases, to buy something a bit bigger otherwise you’ll just get 1A (standard speed charge) max. That’s not taking into account light fluctuations and whatnot that happen with the sun. This one also made an audible whine at lower current outputs. But otherwise it seems to work fine in direct sun. This power bank does not store power, so a separate USB battery bank would be required if you want to keep energy overnight.

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