A power bank boasting a massive capacity of 9 million milliamp hours (mAh) that fits in the palm of your hand, all for just a little over$10, sounds too good to be true, doesn't it? Well, you know what they say.

A reader brought this listing to my attention, questioning the validity of such bold claims. Although I harbored significant doubts, I decided to investigate further. All in the name of science, of course.

Also: The best iPhone power banks you can buy: Expert tested

First, let's put that claim of 9 million mAh into perspective. TheAnker PowerCore 24K has a capacity of 24,000 mAh, and it's quite a sizable power bank, weighing in at 1.3 pounds. To achieve a capacity of 9 million mAh, I'd need to spend over$35,000 on 375 PowerCore 24K power banks, and that's certainly not something I'd want to carry around-nor would it fit in the palm of my hand.

So, I went ahead and ordered one of these purportedly massive-capacity power banks and waited a few days for it to be delivered.

Here's what I received: 

Surprisingly, the packaging lacked any bold claims about the promised, yet unrealistic, capacity. Additionally, the plethora of typos on the package didn't inspire confidence in the product.

The power bank being dead on arrival also didn't improve my first impressions. Even worse, despite my attempts to charge it, nothing worked. It was completely unresponsive out of the box.

Maybe I could fall back on the "warranty." I doubt it. 

It was time to roll the dice and take it apart to see what was inside. At this point, my money was on even more disappointment. Since I was prying into a power bank, I didn't want to use mytrusty metal spudger , so instead turned to asafer plastic tool .

Then, to both my surprise and shock, the power bank blinked into life for a few seconds while I was poking inside it.

After a little bit of force -- sometimes an unreasonable amount -- the case popped open and I could see what the problem was. One of the wires from the battery was disconnected. Not only does this account for why it wasn't working, but it also presented a danger of short-circuiting and even fire.

Also: The best power banks you can buy: Expert tested

I took a closer look at the batteries. 

They were all no-name 18650 lithium ion cells, and I measured the capacity to be about 2,000 mAh. I suspect these may be old "recycled" cells or possibly seconds, as I'd expect the capacity of even a cheap 18650 cell to be about 2,300 mAh.Thismeans the entire pack had a capacity of 6,000 mAh, a far cry indeed from the 9,000,000 mAh that it advertised.

Now, to be honest, this is ultimately what I was expecting. 

Exaggerated claims are being used to dupe buyers into buying poor quality power banks built poorly from cheap parts. If you're looking for a cheap power bank, I'd say throw an extra ten bucks into the purchase and get yourself thisBaseus 10000mAh for$20 . That way, you're getting a good quality power bank that delivers what it promises, will give you several years of service, and won't be a potential fire hazard.

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