Maybe, but probably not that well.

Charging battery packs from a solar panel isn’t as straightforward as you think – even if the solar panel output is regulated. We recently tested 10 different battery packs and 6 had serious problems with solar charging, while 2 more had minor problems. Only 2 performed well enough that you probably wouldn’t be able to notice any significant issues. If you pair your battery pack (Anker and Mophie are two common choices) with our solar panels, what will happen?

Common Issues Charging Battery Packs from Solar

  • Narrow Voltage Range: Most batteries won’t accept a charge voltage outside of 4.8-5.2V, so they won’t charge from our 6V Solar Panels
  • Minimum Charge Rate: The battery will not accept any input power if what’s coming from the panel is less than a pre-determined limit (such as when the panel is too small or in non-ideal conditions) 
  • Maximum Charge Rate: If the maximum charge rate of the battery is set too low (typically 1A), potential power from the panel can be wasted
  • No Cloud Recovery: If the solar panel is shaded by a cloud or shadow, even after the cloud goes away the battery will not resume charging at the fastest available rate
  • Low Voltage: The battery will pull the voltage of the solar panel down so low that extra power is unnecessarily lost
  • Simultaneous Charge and Discharge: Many batteries cannot charge and discharge at the same time at a fast rate, and others cannot do this at all

Performance Testing Power Banks With Solar

The good news is that there are some simple tests you can do on your own to see how well your battery and solar panel work together. You will need a USB multimeter. There are lots on Amazon to choose from.

Step 1. Charge Rate

Go outside on a sunny, clear day. Connect the panel to the USB multimeter and the USB multimeter to the battery. You should see 70-80% of the rated power of the panel flowing into the battery (Volts x Amps = Power).

Is the battery charging at all? If so, angle the panel away from the sun. You should see the power decrease, but not straight to zero. The battery pack should be able to smoothly accept any small input amps, even as low as 20mA.

Here are two batteries charging from our Arc 10W in similar conditions (slight haze, sun low in the clouds), but with very different amounts of power.

solar panel and battery

solar panel and power bank

Beware the LED charge indicators: Most battery packs on the market will turn on their LED charge indicators to imply the battery is charging even if no amps are flowing into the battery as long as a positive voltage is detected from the solar panel. This is why you need a multimeter to see exactly how many amps are flowing into the battery.

Step 2. Charge Recovery

Point the panel at the sun and observe the charge rate (volts and mA). Angle the panel away from the sun or cast a shadow over the panel to see the output power drop (potentially all the way to zero amps while an input voltage from the panel is still available). Remove shadow or point the panel back at the sun and observe if the charge rate increases to the previous rate.

Step 3. Charge & Discharge

Put the USB multimeter between the battery and your phone or tablet to observe how fast your devices normally charge (will most likely be 1-2A). Do this test when your phone or tablet’s battery is less than 90% full, that way it will charge at it’s maximum charge rate.

Connect the solar panel to the battery. Confirm that the charge rate to your device stays the same. The charge rate to your device might decrease to a slow rate, cycle between a fast rate and a slow rate, or stop charging altogether. Unplug and replug the solar panel cable while your device is charging from the battery, and unplug and replug your device while the battery is charging from the solar panel in case there is any difference in charge rate between those two scenarios.

Additionally, you can place the multimeter between the solar panel and the battery while the battery is charging your device. Some batteries will limit the output power to your device while other batteries will limit the input power from the solar panel, so it’s important to test both.

If your battery fails any of these tests, it will not be a reliable solution for you on your next trip. You can experiment with other batteries on Amazon, or purchase on of our solar batteries that we’ve specifically designed for charging from a solar panel.




About The Author

One Response

  1. Andrea Poma

    Hi there,
    I have a sunpower 4.4v 4.4w 1A panel.
    The output is 5.2v and 0,7/0,8A.
    I attach a lipo 3.7v 2.4A battery and a pcb usb.
    Everything seems working fine when I’m trying to chage a standard smartphone and after few hours the phone is full, only the battery is lasting much less compared with wall charger (-50%).
    Do you know if could be related to the low voltage of the panel, the isolation of wires(panel is using tab wires I solder to the pcb and the battery), or the quality of the pcb (consider I have tried with several ready-made pcb with same results) or it is normal the charge quality is so bad when using 3.7v battery?
    Thanks in advance for your help


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