Foldable Solar Charger, Cloud-Restart Test - ALLPOWERS 20W (AP-SP5V21W)

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Foldable Solar Charger, Cloud-Restart Test - ALLPOWERS 20W (AP-SP5V21W)

I recently purchased too many of these fold-able type solar chargers.  Some of them have many reviews, and some have very few, but almost no reviews discuss how the panel deals with shady interruptions like clouds.

NOTE: This is only a test of one aspect of this charger, not a full review.

Charge Restart Feature


These solar chargers are marketed toward backpackers, campers, and/or emergency situations.  In my opinion it makes sense to charge a battery bank with one of these, and then charge your mobile phone with the battery bank later on (after dark?).  These chargers can also work directly with your mobile phones, but that is a tricky endeavor. 

Many mobile phones (and some battery banks) will not adapt to the changing power provided by a solar charger.  For example, current generation apple devices will start charging at full power, but if a cloud reduces the output temporarily, the apple device will not resume charging at full power. 

In response to this, some solar chargers have begun adding charge-restart features to their circuitry.  The theory is nice, the panel detects an interruption in solar energy, and briefly cuts power to the usb ports.  This should trigger an apple device to automatically resume charging at full power.


Depending on how the charge-restart feature is implemented, there could be some serious drawbacks.  Ideally the solar charger would reset the usb ports only once, after the cloud has passed.  That means the charger has to notice a sudden increase in sunlight, and reset the device.

Some solar chargers are taking the easy way out, and just cutting the ports off when the output voltage drops below a certain threshold, say 4.4v.  This method means that when a cloud obstructs the sun, power is cycled immediately.  But as soon as your device begins charging, the voltage will drop again, and power will be cycled again.  This will repeat until the obstacle passes.  This method could be very bad for your device.  This method also makes it impossible to trickle-charge your device.

In this test I will try to determine if these solar chargers have a 'charge restart' feature, and if so how well it works.


The ALLPOWERS 20W (AP-SP5V21W, purchased on amazon, Sept 25, 2016)

Some Pictures




The Test

In my test, I tried to obscure the sun as much as possible without cutting power to the device being charged.  For this charger, I closed the third panel over the second panel, leaving only the first panel exposed to sunlight.  Then I used a semi-transparent piece of plastic over the last panel to further reduce the output.  I monitored the charge rate with a simple USB charging meter.

After the charge rate slowed to almost nothing, I removed the plastic and opened the panels back up.  Here are the results:

Looks like the ALLPOWERS 20W (AP-SP5V21W) has solar monitoring charge restart technology.  (not sure what to call it really)  This solar charger resets the USB port after it detects that an obstruction has just been cleared.  In my opinion, this is the best way to reset the charging.  This is because it doesn't start resetting the ports as soon as power is reduced from an obstacle, allowing trickle charging to continue.  The charger can tell when the obstacle has cleared, and it will reset the usb ports one time.  Very nice.


The Specifics

Resting Voltage
3 panels exposed
Charging Tesa PB
3 panels exposed

Charging Tesa PB

1 panel exposed

Charging Tesa PB
1 Panel with Plastic Cloud

5.29v 4.85v/1.60a 4.39v/0.61a 4.13v/0.06a

 Notice how this charger can continue providing small amounts of power even while being obstructed, while none of the other chargers I've tested with reset capabilities can do this.



In my opinion, this charger uses a very good method of charge restart technology.  In my testing, the port gets reset only once per obstruction, which is ideal in many ways.  It allows trickle charging to continue while the obstacle is in place.  The after the obstacle moves on, the port will be reset allowing apple devices to resume charging at their maximum rate.

I always recommend you fully test your setup in varying conditions before you rely on it.


 EDIT: typos

Edited by: netprince on 02/15/2019 - 12:40
sac02's picture
Last seen: 8 months 2 days ago
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Location: TX

Thanks for doing all these tests, this is good info.

will34's picture
Last seen: 1 day 8 hours ago
Joined: 12/18/2012 - 00:12
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Thanks for the test!

The Miller
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Thanks looks like a winner in real life use!
Can you link it up?

Last seen: 11 hours 39 min ago
Joined: 06/14/2012 - 13:48
Posts: 647
Location: Virginia

Sure, here is the amazon link:

MRsDNF's picture
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Location: A light beam away from the missus in the land of Aus.

Thanks for the review. Interesting info. Thumbs Up


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