Power Bank ("emergency" battery pack) for USB-powered devices

If a company itself, translated into German, the name "Descending" is and then is not even capable of this without error to assume in the product description ("Decresent"), then they are attacking an ever slight doubts whether the 15 could not possibly set again in the sand for another cheap thingy from China.

But I can subsequent buyers mind at rest: the device works and fulfilled, albeit to a lesser extent as far as its purpose. Most users will want to use the Power Bank traveling as an emergency power source for mobile gadgets. I myself want to use it as a UPS for a Raspberry Pi. At its 2 USB-A output jacks, it can provide even 500mA and 1A lt once. Datasheet. Its outer dimensions are similar to those of a mobile 2.5 "hard drive.

The device comes with a cable with a USB-A connector and a barrel connector socket at the other end, at the latter come supplied plug adapter, including one for mini- and micro-USB, three special plug for common (?) Cell phones, a 30-pin dock connector for the penultimate generation of Apple gadgets and another two hollow plug, one of them in the format 3.8 x 1mm, the other is an extremely thin with 1.8mm outer diameter. With the mini-USB plug adapter to the included cable can also be employed to charge the Power Bank on the computer or USB power adapter. Come but please do not use the idea that cable as a USB data cable to want - yes it has no data wires.

However, a power adapter is not included. So I immediately ordered me to a USB power supply with 2.1A current capability. In retrospect, however, the latter presented as oversized out: the power consumption of the Power Bank when loading does not exceed 0.7A, so rich, most standard USB power supplies. However, this figure also means that the charging time would exceed the nominal operating time at full load by more than double.

Speaking of battery life: first interested me whether the advertised 5 Ah actually available. Here I was then faced with the first disappointment: A USB Gadget (Nano Wireless Router TL-WR702N) whose power consumption is 150 mA, was held by the fully charged Power Bank for ca 24h in operation. Unfortunately, this only corresponds to a capacity of 3.6 Ah.

ADDENDUM: >>> The reviewer uhu_S2 dismissed entirely correctly points out that the capacity of 5 Ah indication on the built-in battery itself, and thus to its immediate clamping voltage must relate. However, since the downstream electronics up sets the voltage of 3.7 to 5 volts, you have to the current yield Convert (in Ah) to the USB output by the energy conservation law yet, and lo and behold: the determined I value is in good agreement with the expected capacity agreement in watt-hours (Wh). I therefore raise my rating to 4 stars.
Now I was curious and have decided to open the device to bring possibly the nominal values ​​of the built-in battery experience. So hastily special tools unearthed from recent iPod battery change and trying to outwit the snap-in connections between the housing base and lid. Here on the one hand it turned out that the housing upper part is made in two parts - the outer, abgewölbte at the edges Fancy-cover is bonded by means of double-sided tape with an underlying surface. Andererseit occurs after carefully peeled off the fancy covers a surprisingly sank with four screws attached to cover days (so there's no snap-in connections). Although the plastic material of the housing parts is not shatterproof ABS, but probably polystyrene, yet sufficiently stable for this applied most slowly and with constant tension action. The removal of almost all-over adhesive layer afterwards (by rolling the thumb) has certainly lasted longer.

Under the screwed cover of bonded again in the housing base battery and the electronic circuit board will now be visible. Unfortunately, the battery on the top does not carry any information, and for fear of damaging the bottom of the housing very strong bonded film battery, I had to do without it, even to take his bottom yet inspected. After looking at the produced in tolerable quality SMT assembled board (I had only a few - Remove solder splashes - bequeathed to non-critical sites) I have assembled the device again. The chips carry partly no visible identification, so that I could not continue to analyze whether in fact two separate dimensioned voltage regulator for the two USB outputs are available. One has to rely on the manufacturer's therefore in this regard.

Then fall in operating the following oddities on:

The lying in the housing cover Power-on button to light up a blue glowing three-part bar display in the on state. Why, however, for each of the beams two LEDs have been used in the sense of a power-saving mode highly questionable (series connection of the LEDs is expected to retire at voliegenden supply voltage level). The blue light "pops" in addition particularly in the dark over the eye.

The supplied voltage is stable 5.1V in the ON state. In the off-state, the output voltage is, however, not entirely unexpectedly shut down, rather then the pure, "unboosted" LiPo battery voltage seems (about 3.7 to 4.2V, depending on the state of charge) to be due to the USB ports. I do not know whether this should be a feature or a bug of the booster circuit, I personally believe in the latter. After all, this has the advantage so that you, the availability of suitable measuring accessories *) provided that the battery can occasionally feel the tooth without having to open the device again. Disadvantage is quite clear that "off" means not just here "Off".

*) I have made this a measuring adapter for current and voltage for looping into a standard USB cable.