Cheap Powerbank Logic And Teardown

A fixture on many British high streets are pound shops. You may have an equivalent wherever in the world you are reading this; shops in which everything on sale has the same low price. They may be called dollar stores, one-Euro stores, or similar. In this case a pound, wich translates today to a shade under $1.24.

Amid the slightly random selection of groceries and household products are a small range of electronic goods. FM radios, USB cables and hubs, headphones, and mobile phone accessories. It was one of these that caught [Julian Ilett]’s eye, a USB power bank. (Video embedded below.)

You don’t get much for a quid, and it shows in this product. A USB cable that gets warm at the slightest current, a claimed 800 mA of output at 5V from a claimed 1200 mAh capacity, and all from an 18650 Li-ion cell of indeterminate origin. The active component is an FM9833E SOIC-8 switching regulator and charger (220K PDF data sheet, in Chinese).

A straightforward teardown of a piece of near-junk consumer electronics would not normally be seen as something we’d tempt you with, but [Julian] goes on to have some rather pointless but entertaining fun with these devices. If you daisy-chain them, they can be shown to have the properties of rudimentary digital logic, and in the video we’ve put below the break it is this that he proceeds to demonstrate. We see a bistable latch, a set-reset latch, a very slow astable multivibrator, and finally he pulls out a load more power banks for a ring oscillator.

If only [MacGyver] had found himself trapped in a container of power banks somewhere from which only solving a complex mathematical conundrum could release him, perhaps he could have fashioned an entire computer! The best conclusion is the one given at the end of the video by [Julian] himself, in which he suggests (and we’re paraphrasing here) that if you feel the idea to be unworthy of merit, you can tell him so in the comments.

That you can buy all this in one product for so little is a minor miracle, so as you might expect this isn’t the first time those in our community have turned their attention to dollar store items. We’ve brought you a dollar store Bluetooth camera trigger giving up its secrets, and a pedometer turned into a voltmeter. Keep watching, there are sure to be more devices finding their way onto the shelves for not a lot.

We’ve featured [Julian] before, when he found a very cheap and very bright LED array.

43 thoughts on “Cheap Powerbank Logic And Teardown

  1. I have done my fair share of exploratory purchases and teardown from many suppliers, since having a reliable USB power bank to recommend is closely linked to the RGB Shades. What I’ve found has been pretty scary, some packs arriving with damaged internals, re-used laptop batteries, and some with zero safety protection at all (was able to draw 8 amps from a 1 amp rated pack). Fractions of advertised capacity. Disintegrating cases.

    My results: for the 2000mAh range USB power pack, don’t rely on Amazon reviews (almost all of them skewed by “I received this product for free” positive reviews). Stick with the better-known brands like Anker and Jackery. And one pretty reliable indicator is the price. I was not able to find a single-18650-cell power pack that met my safety or tested-capacity requirements for less than $9 retail, and I haven’t found a good source at wholesale for any less.

          1. Amazon US employee here. Jason is right about their popularity. I handle power banks, USB/lightning cables, and various other mobile accessories, of Anker brand, frequently throughout my shifts.
            They seem to be primarily sold online though (I’ve never seen them while at the supermarket), which might explain why you never heard of them.

          2. The Anker name inevitably pops up when you start asking people about USB accessories on a budget-conscious level. They are quite good on the quality-to-price ratio and have a pretty wide range of products. The Jackery name is more recent and fewer people have seen it, but it’s on the rise in the same market as Anker. Please note that those two brands are representative of quality levels you should not drop below; they’re not as high quality as Mophie products but you do get a good value. Below Anker and Jackery, you start to see the ugly junk shown in the video above.

    1. For power bank and other gizmo like phone chargers, I personally went for the Xiaomi or BlitzWolf products, the upper prices of “direct-from-China” on-line retailers. I saw Xiaomi mentioned in a video here on HaD (I think from WIRED mag.) about the electronic market in China. I had the feeling that they want to be a kind of locale Apple. For westerner ready to suffer the long delivery time, that give us access to better quality stuff without Apple-like pricing.
      Am I too naive?

  2. Dollar Stores – Dear God, I’m old enough to remember when these were called ‘Five-and-Dimes.” Regardless, it is true that these shops can be the source of quite a few inexpensive hackable components (or components for hacks) in any number of domains.

    1. I’m old enough to remember a five only store! Right now there are “5 and 10” stores, dollars that is. It’s getting rare to find anything for a dollar even that isn’t moldy old CD or DVD from 10 years old or some other old stock that doesn’t even sell on eBay.

  3. After searching for a little while, the closest I could come to that IC was some like an LTC4099.

    However, its ~$4.7 qty 1, has many more pins, and has more protection features. It looks like Linear used to produce something similar (LTC4160) with less features that is now out of production.

    I don’t think it will automatically switch between charging and supplying like this IC though. That’s kind of a nifty chip.

    1. I was wondering about that. There are a lot of these chargers of varying capacity, and presumably most of them have a single chip charger AND switching regulator. Which sounds useful, but I can’t find such a combination from most places… grr. (I wonder if you can get away with a microcontroller, a power transistor, and a few passive components…)

        1. Long time ago I had 6GB audio player – with 2,5″ harddisk from “Archos”. It used an A-A USB-cable. It was a shitty design running on 4 high-self-discharge Ni-MH cells, crashing frequently and suddenly locking the HD in a hardly documented ATA password protected mode.

        2. A cheap AVR programmer I bought from a “robotics” website uses an A-A cable.

          Works OK, but once I bootstrapped a 32U to be a programmer for me, I just put it away and never looked at it again. I suspect it’s PIC under the hood there. The entire thing is strange. It also used a non-standard header arrangement that was a pain in the ass.

          I also jave a couple of others but I have no clear where they’re from or what hardware it was for.

          1. Inside a crappy disposable printer (ink being more expensive than the unit itself) it has USB mini male-male cables between PCBs. But I don’t think they’re used for spec USB, rather because it’s an easily available surface mount connector and pre-made cable.

  4. An interesting possibility is that you can buy a charger/box WITHOUT a Li-Ion cell in it, and then use your favorite source of cells (whether that’s high-quality name-brand cells, or something YOU have harvested from a “dead” laptop battery.)
    (These also come with “boxes” designed to hold more than one cell, for increased capacity. Presumably, they’re simply connected in parallel.)

    1. Connected in parallel, the cell with a slightly higher voltage, from more charge, will try and charge the lower one. With something like dozens of amps. Fairly high blowup chance. You don’t generally put any sort of cell in parallel with another, they all have this problem. If it’s a high-current cell like lithium ion, or Nicad or NiMH, it’s pretty dangerous.

      For several cells, they could be in series, and the buck convertor would therefore draw less current from the higher voltage. Or maybe they have separate power circuits for each. I suppose you couldn’t put it past some defective Chinese manufacturer, but a large amount of them would pretty quickly explode, and surely you’d hear about that.

      ^^ this one looks like it’s dozen or so cells are in series, from the look of the metal connectors in the battery box.

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