Top critical review
3.0 out of 5 starsOnly has 50-60% rated capacity
Reviewed in the United States on February 2, 2024
TL;DR - You're getting around 12,000 total mah for the 18$ cost based on my measurments of 6 samples. Not a bad bargain still but just be aware it seems statistically unlikely you'll get a full 20kmah. YMMV or rather YWMV (your wattage may vary).
I have 6 of these, 3x2 pairs, going back to 2021. 2 for $15-20 right for 20,000mah? With 10's of thousands of reviews and 4+ stars? Seems like a no brainer.
BUT....
I saw Project Farm's power bank review posted Jan 2024 and the results were so bad I thought I had to test for myself.
So I picked up a usb power tester, it's like a kil-o-watt, you plug power into one side and draw in the other and it sits in the middle and records the power as it flows, watts, amps, volts. They're sold here in fact, just search for usb power tester. The one I have is the + shaped one for $16 at the time of this review. (so $20 this time next year due to profiteering and customer gouging, I mean inflation)
All 6 of mine topped out between 10 and 11 watts of charging power with two draws. That's 2.2 amps at 5 volts.
All 6 I brought up to a full charge (4 lights) and then sitting on the chargers another 24 hours just be certain.
I plugged a string of 5v LED lights into the power tester which pulls 2 amps at full brightness (1.99 amps technically) and then plugged the tester into each of the 6 one by one until the powerbank shut down. Took 3 days to work through.
The oldest 2 died at 5000 mah and 5400 mah.
The middle 2 died at 6200 mah and 6300 mah.
The newest two purchased in October died at 6800 mah and 6100 mah.
It's interesting to note that the LED's seem to be calibrated to rated capacity (10,000mah), i.e. each light count as 2500 mah and has nothing to do with the capacity in the batteries.. But the reality is it takes awhile to drop from 4 to 3 but then it's a rocket ship to 1 light and shutdown.
Those capacities I also tested to use an alternate method by charging a cell phone with a dead battery, rated and measured at 5010mah, from 0% to 100%, started a game and let it burn the battery back 0, then put it back on the same power bank which took it from 0% to around 12% at which point the power bank shut off.