How can this powerbank be so cheap?

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Forums › Finance and wealth management › How can this powerbank be so cheap?

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jbard

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#1767885 20-Apr-2017 13:21

Thanks for all the replies guys, makes more sense to me now how they can offer it for $30.

I had no idea you could get an Anker powerbank for so cheap from ebay, I have purchased a couple of those instead as they are easily worth the extra $10.

tripper1000

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#1767897 20-Apr-2017 13:40

This is one way to make power banks cheap.

I have seen this in person. A young fella in my workshop bought one of the linked power banks from trademe and when I expressed great doubt that it was actually 120,000 mAHr and showed him the above link, he cracked it open and found one cell and a bag of sand.

Anyone game to crack open one of the Warehouse jobbies?

A more recent link to a new version of the same kind of scam.

CassidyMed

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#1768623 21-Apr-2017 21:21

betterdon't buy a cheap powerbank 'cause one my friend got one and it exploded in her bag

Jase2985

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#1768669 22-Apr-2017 06:18

Can get a 10400mah anker one for about $50 from a nz/australian outfit delivered to your door.

BTR

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#1769505 24-Apr-2017 09:03

If you are interested in electronics checkout the YT channel bigclivedotcom he's an electrical engineer for dissects cheap Chinese electronics and test them for output, capacity and safety. Some of the things he has tested will make you think twice about buying from china.

The worst I've seen was a 12V rechargeable camping light which when plugged into power to charge meant 240V was then going through the USB charger port that was built into the lamp.

Back to OP, as others have said it probably no where near capable of its advertised capacity.

tripper1000

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#1771512 27-Apr-2017 20:25

Hi guys, rather than just slag this unit off without any concrete evidence, I decided to try test one out.

First I left it to change for 12 hours after the 4 battery level LED's indicated that it was full.

Did a discharge testing using a Turnigy Accucel 6 battery charger/discharge which has a max discharge rate of 1amp. Test was set to finish once output voltage sagged to 4 volts.

First discharge test at 1 amp on the 2.1 amp output port produced a 5v capacity of 6474 mA/Hr.

2nd discharge test at 1 amp on the 1 amp output port produced a 5v capacity of 5948 mA/Hr. I only let this charge for a few hours after the LED's indicated full.

Voltage regulation was good and did not sag below 5 volts when loaded at 1 amp, measured at the back of the sockets, however my cheap USB leads were dropping about 0.4 volts - that isn't the battery banks fault though.

The unit has 4x 18650 cells in parallel.

The 2 output port are independent from each other - when only one was in use, the other was 0volts.

The D+ and D- pins are open circuit which will leave BC1.2 compliant devices confused as the the output ability of the power pack. These pins should have combinations of resistors and short circuits to signal the instantaneous output rating of the power bank. Ref this link. I checked 5 other devices I had laying around and 3 had shorted d- and D+ pins indicating 1.5amp output or more and 1 had resistors indicating 500 mA output. 1 had nothing.

The unit uses some kind of electronic detection to determine when something is plugged in and power up the 5 volt output. It doesn't have any kind of mechanical switch to detect when there is a lead plugged in like some power banks do.

From here I intend to repeat the tests at 0.5 amps discharge rate and also do a discharge test of the 18560 cells directly to see if they are close to the 10500 mA/hr rating on the case. I will also hook a 2 amp load up to ensure the 2.1 amp output is up to spec.

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Oblivian

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#1771517 27-Apr-2017 20:36

In the name of science! I commend ye

tripper1000

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#1771526 27-Apr-2017 20:45

Actually, I should qualify not being BC1.2 compliant: It wasn't obvious that it had basic compliance from the resistances across D- and D+, however it is possibly that it has an auto detection and self configuration system in it as there were queer voltages (1.74 to 2.2v) across D- and D+ once powered up.

tripper1000

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#1777867 8-May-2017 15:21

Ok, so I have done some more testing:

1) 6449 mA/hr at 500 mA discharge rate on 1amp outlet

2) 6655 mA/hr at 500 mA discharge rate on 2.1amp outlet

3) Bare cells (3.7v) directly discharged: 10,071 mA/hr.

4) The difference between the 3.7v cell capacity and 5v output gives and theoretical conversion efficiency (3.7 volts up to 5 volts) of 89%. (10071mA/hr @ 3.7v = 37.262 watt/hr, 6655 mA/hr @ 5v = 33.272 watt/hr)

I tested a friends similar 4 cell power bank that is about 2 years old, and it had a capacity of 4798 mA/hr and 5130 mA/hr over 2 cycles at 5 volts.

tchart

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#1777904 8-May-2017 15:39

tripper1000:

Ok, so I have done some more testing:

1) 6449 mA/hr at 500 mA discharge rate on 1amp outlet

2) 6655 mA/hr at 500 mA discharge rate on 2.1amp outlet

3) Bare cells (3.7v) directly discharged: 10,071 mA/hr.

4) The difference between the 3.7v cell capacity and 5v output gives and theoretical conversion efficiency (3.7 volts up to 5 volts) of 89%. (10071mA/hr @ 3.7v = 37.262 watt/hr, 6655 mA/hr @ 5v = 33.272 watt/hr)

I tested a friends similar 4 cell power bank that is about 2 years old, and it had a capacity of 4798 mA/hr and 5130 mA/hr over 2 cycles at 5 volts.

@tripper1000 thanks heaps for sharing. Like I said the Warehouse power banks have been way better than others I have had over the years.

Nil Einne

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#1777929 8-May-2017 16:10

Thanks for your testing etc. While I'm not personally interested in the power bank, I think it's good to know it's not that bad. As others have said, one thing people tend to forget is how insanely expensive power banks are here in NZ. eBay etc obviously help a great deal with that provided you're careful. And while it's true there's a lot of total junk coming from China, we aren't talking about buying something from AliExpress here but the Warehouse. One of the reason's we're paying a big markup (and yes even at this price it's still a big markup) is because they're supposed to be at least making sure the devices are generally fairly safe and don't have crap like sand instead of cells.