Review, teardown and analysis of Charging Essentials USB wall outlet

(UPDATE: March 2, 2015 – I’ve picked up a pair of the newer tamper-resistant versions of this wall outlet. A review and teardown on that unit is coming up; stay tuned!)
(UPDATE 2: May 29, 2016 – Scratch that on the first tamper-resistant model; it had the same performance as the one mentioned here. Also, Costco has released a 3.1A version of this outlet, and is currently under review.)

About a week ago I bought a set of wall outlets from Costco that integrate two USB charging ports into a standard Decora-type receptacle. It’s marketed to replace your traditional AC adapter, allowing other appliances to be plugged in while charging your portable electronics.

The outlet is made by Omee Electrical Company, but curiously enough this particular model, the OM-USBII, wasn’t listed on their site. The packaging itself bears the name Charging Essentials, with a logo that looks like a USB icon that’s had one Viagra too many. The packaging states that the outlet has:

  • “Two 5VDC 2.1A ports for more efficient charging in less time”
  • “Smarter USB charging with special chip designed to recognize and optimize the charging requirements of your device”
  • “Screw-free wall plate snaps into place for a more clean, modern appearance”

The second note is of particular importance to me. If it’s true, that means it might be using some USB charge port controller like TI’s TPS251x-series chips. But I’m not one to have blind faith in what’s written on the packaging. Let’s rip this sucker apart!

The outlet has a snap-on coverplate which may look sleek but could hamper removal of this outlet later on if needed. I was curious as to why one couldn’t just use a regular screw-on coverplate, and it turns out it’s because the mounting flange doesn’t have any tapped screw holes; you physically can’t use screws on this because the manufacturer didn’t want to go to the effort to make holes that can accept screws!

The casing is held together with four triangle-head screws in a weak attempt to prevent opening of the device. I had a security bit set on hand so this posed no hindrance to me. Upon removing the cover, the outlet seems rather well built. However, after removing the main outlet portion to reveal the AC-DC adapter inside, I quickly rescinded that thought.

The converter seems relatively well-built (at least relative to some crap Chinese power supplies out there). Some thought was put into the safe operation of this device, but there’s almost no isolation between the high and low voltage sides, and the DC side of this adapter is not grounded; the “ground” for the USB ports floats at 60 volts AC with respect to the mains earth pin. The Samxon brand caps are also pretty disappointing.

As for the USB portion of this device, I had to remove some hot glue holding the panel in place. After a few minutes of picking away at the rubbery blob, I was able to pull out the USB ports.

… and I found LIES! DIRTY LIES! There is no USB charge port controller, contrary to what the packaging claims. It just uses a set of voltage dividers to emulate the Apple charger standard, which could break compatibility with some smartphones. Ugh, well let’s put it back together and take a look at it from the performance side of things. At least the USB ports feel pretty solid…

To measure the voltage-current characteristic of the outlet, I rebuilt my bq27510-G3 Li-Ion gas gauge board so it had better handling of high current without affecting my current and voltage measurements. The reason I used this is because the gauge combines a voltmeter and ammeter in one chip, and by using the GaugeStudio software, I could create easy, breezy, beautiful V-I graphs.

Using a Re:load 2 constant-current load, I slowly ramped up the load current while logging the voltage and current data to a CSV file for analysis in Excel.

overall vi graphThis charger’s… okay. It has surprisingly good regulation up to 2.3 amps, but after that point the AC-DC converter basically brickwalls and the voltage plummets to 3 volts. That said, this also means that this outlet is not a set of “two 2.1A USB ports”. You can charge one tablet but you won’t be able to charge a tablet along with another device simultaneously.

Bah, I’ve had it with this wall outlet. Looks like this one’s gonna be returned to Costco in the next few days. This outlet may be adequate for some people, but for me it’s a disappointment.

Pros:

  • Solid USB ports
  • Good voltage stability (up to 2.3 amps, enough to charge ONE tablet)
  • Apple device compatibility

Cons:

  • Annoying coverplate design
  • Does not meet rated current output, will not charge 2 tablets or 1 tablet + another device
  • Does NOT have a “smart charging chip” despite being stated on packaging, some devices (eg. BlackBerry) will refuse to charge from these ports
  • Power supply for USB seems cheap
  • USB port is not grounded – if a short-circuit happens inside the power supply it can be a shock hazard to you
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A Temporary Hold: Creating Li-Ion battery holders with prototype boards and pin headers

As seen on Hackaday!

Lithium-ion batteries are great. They have high energy density, are lightweight, and in the case of many portable devices, they can be easily swapped in and out. One problem with prismatic (the types you often find on cell phones that have a set of flat contacts on one end of the battery) packs is that they’re all custom; the cell may be standardized but the pack it’s in is often proprietary to a certain make and model. Sure, there are “universal” holders out there, but they provide poor electrical contact at best. Since I need a secure electrical connection when using my battery fuel gauges, I sought to create a more sturdy holder for the batteries I have lying around.

The construction of the holder is pretty simple. A strip of female pin header (I used a single-pin-width header but a double-width one can be used for greater mechanical strength) is used as an end-stop for the battery, and a right-angle pin header is used to create contact with the battery’s terminals and to provide the physical “clamping” needed to create a good connection. The right-angle header can be bent and soldered into place to adjust the holder to the particular cell you’re using. Additionally, be sure to use some high-quality FR4-based boards as the brown-coloured paper/resin-based boards won’t have as good resilience and strength, and probably won’t be plated through either (this improves the structural integrity of the holder since the pin headers will be under a bit of physical stress).

For connections, I have a 2-pin header (physically a 3-pin header with one removed to denote polarity) and a set of screw terminals. These are wired up using a flat ribbon “wire” used to connect solar cells together as they can handle several amps and come pre-tinned with solder.

This sort of setup can be adapted to nearly any commercially available prismatic battery, provided it uses a flat contact area on the sides.

Mini-Ramble: Upcoming posts

In lieu of any recent posts, I’d at least post what I plan to write in the near future:

  • Failure analysis of KitchenAid KICU509XBL induction cooktop
  • Teardown/analysis of XtremeMac InCharge power bank
  • Teardown/analysis of Nexxtech Slim Power Bank (3000 mAh)
  • Shoehorning a Nokia BL-5C into a Samsung Galaxy S II
  • Review of the Texas Instruments Gauge Development Kit (GDK) – it’s a beauty!
  • Create a tiny stereo audio amp that’s efficient enough to run off a coin cell!
  • Adding fuel gauges to devices that normally don’t have one (or at least provide some way to track capacity remaining in the battery)
  • Creating a digital music player, using only 7400 logic, some EPROM or NOR flash, and an oscillator. (might even post this one on HackADay 🙂 )
  • Plans for making Li-Ion gauge boards on Tindie
  • More solar panels