This is a much shorter time, but when combined with the 80ms of 4.2V, means that the attached device will be exposed to out of specification power for about a fifth of a second. The output voltage does have a loss because of the resistance of the MOSFETs in the power path as well.ĭoing the same but instead having the load on the USB-A port and the charger be on the USB-C port results in a slightly more favourable result of no output for about 125ms. The output power does return after this, but sits at around 4.8V as the system tries to “balance” the power going into the battery and out to the load without overloading the power adapter. This means that whatever load is connected will see its power out of spec for about a second during a charger plug-in event. The output voltage collapses to about 4.2V for 80ms, then down to absolutely nothing for 960ms. The above is the trace from a USB-C load attached to the power bank while a USB Micro-B charge cable is attached. The results are interesting to say the least. I used my ZMI zPower Trio USB charger to provide power to the BW-P12 while monitoring the output voltage using a Rohde & Schwarz RTM3004 oscilloscope (although FastLog would have been sufficient for this purpose as well). I enlisted my “on-loan” Rohde & Schwarz NGU401 SMU to act as a load on the output of the BW-P12, sinking a constant 500mA to simulate a moderately light load. It would seem that from the datasheet, unless explicitly disabled by the manufacturer, the controller would support pass-through charging capability.īut what does this mean in practice?The easiest way to know is to try it out. if input voltage drops due to the weak power supply of adapter, charge current will automatically fall down so the input voltage holds to 4.8V and supplies extern device in priority. In this situation, charger hold voltage is set to 4.8V. When two or three ports turn on, it only supports 5V input and output. When only one port turns on, it supports fast charge input and output. The SW6208 supports charging the battery and supplying extern device simultaneously, and this function can be disabled if not needing. Increasingly, products might occasionally state that they support pass-through charging, but that is not a universal practice and what that means in practice can affect certain applications.įor example, the Blitzwolf BW-P12 is a great example – the manufacturer’s website does not mention pass-through charging, but the iSmartware SW6208 datasheet states the following: When buying a power-bank, rarely do they say very much about whether they work as a UPS or not. If you want a simple answer, unfortunately, you’re usually out of luck. This is an excellent question and one I’ve always wanted to convey some of my thoughts about, so I decided that it deserved its very own post. On my recent review of the Blitzwolf BW-P12 10000mAh Power Bank, a reader commented asking whether that particular power bank could be used as a makeshift uninterruptible power supply (UPS) for USB-powered devices.
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