Reading the fine print on the Anker USB battery power units as sold by Amazon I note that 4 out of 5 I have looked at have greatly exaggerated capacities. Reading the small print on each unit, they state that the listed capacity is at 3.7V. As the USB power out is 5V nominal the useful capacity for recharging USB devices is only about 75% of the claimed capacity and this is BEFORE the additional losses involved in stepping up the battery voltage to 5V for actual output.
To me this is false advertising as Amazon listings for the devices do not mention the capacity listing is battery capacity at 3.7V nominal rather than output capacity at 5V. Until you have the unit in hand and read the fine print on the device this is not noted any where that I have seen.
This is crucial information and everybody should be aware, but honestly it is very difficult to explain it to someone with little knowledge in electronics.
They (not only anker) have always been doing this, fooling the customer by giving them both Phone batteryâs capacity and the power bank internal battery capacity, so they automatically assume if the power bank has double the capacity it means 2 full charges. Of all of the power banks I own only one has batteries wired in series, it uses 3,500mAh lipo in 2S and it claims 7,000mAh. False advertising a itâs finest. All the other have it wired parallel and most donât state nominal voltage.
Looking at another brand of USB Battery power unit this listing of capacity at 3.7V appears to possibly be âIndustry Standardâ but to me is so much bovine excreta. Thought up by some advertising type with a hemorroidal outlook on his/her customers intelligence. To me this automatically means that most of these battery boxes should have their claimed capacity multiplied by .75 or less to get any where close to the actual useful capacity for recharging external devices. And this is best case as it does not account for losses in the step-up circuitry between batteries and output port or exaggerated battery capacity claims.
At least the Anker units that bother to list them claim to use LG batteries so they should be close to claimed capacity (at 3.7V) |(
This is the efficiency of the boost circuit, in the review he compensates the delivered capacity from 5V back to 3.7V, the average consumer wonât do so and they are lead to believe the stated capacity is the same as the delivered one, when in real world use it only translates to ~60%.
Per the photos the unit you linked to is listed as 10,400 mAh at 3.6V. At best then it can output 7.5 mAh at 5V at 100% efficiency unless the batteries in the unit are under rated. Even with the high conversion efficiency to 5V the unit is not going to put out what many people would expect based on the claimed 10,400 mAh capacity unless they are quite knowledgeable about electronics, as will34 noted in his first post. 10,400 Mah in huge numbers and â3.6V/10400 mAh (37.44WH)â in much smaller print. At least the print is larger than on the Anker units.
I may be a naive old fart but I get very tired of ridiculous and to me deceptive advertising claims.
Itâs sad but this is how all the powerbanks state their capacity.
Worse are the manufacturers that claim XmAh so if your phone is only half of X you can charge it twice! While you might be lucky to get 1 charge if the circuitry is very inefficient.
At least with quality brands you get quality batteries and really the stated capacity in the batteries.
Low quality/cheap chinese knockoffs might give only 20% of what they claim.
Yeah, because Chinese companies are the only ones who fudge and misdirect.
Anker is an American company, manufacturing in China (like almost every other consumer electronics company), but with HQ, marketing, and its main market in the US.
Meanwhile, Xiaomi, which is a Chinese company, with a Chinese HQ, and whose home market is China, is one of the few sellers of powerbanks that actually include a number of mAh at the 5v output, taking into account both the trade of amps for volts in the boost circuit, and the thermal losses that accompany the conversion.
Yeah, these numbers are misleading, unfortunately they seem to be the norm, even among otherwise reputable manufactuers/sellers. At least though they are consistent.
Keep in mind these banks are typically used to recharge other li ion batteries, so 2000mAh bank should add 2000mAh to your cell phone. However the losses from the boost circuit and the buck (or linear) circuit in your phone kills this, so i wish it was mandatory for the bank to list their boost efficiency, and phones listed this charging efficiency.
Interestingly, the most inefficient part of the system is the phone itself, my Samsung S3 with 3.7V 2100mAh battery requires almost 16 watt hours to fully charge and the phone is warm the whole time. I think there should be a sticky about power banks so people will know they should only expect about 65% (or even less) of the claimed capacity to be actually delivered.
The iPhone 6 in the other hand is very efficient and the 1820mAh battery only takes 8.5 watt hours to fully charge.
Interesting! So you are saying that the recharging circuitry in devices varies so greatly in efficiency that predicting the number of charges available from a power bank will vary tremendously, even recharging devices that have almost the same battery capacity. Combine that with varying efficiency of the boost circuit used in the output of the power bank and predicting the size of power bank needed becomes pretty much a guessing game. What do we use for making a purchase decision, an Ouija board?
I used the portapow premium usb meter and after several runs, I confirmed the amount of energy required to fully charge my S3 is ~15Wh. It does get warm which I donât think is normal so perhaps the charging circuity is damaged somehow. It draws 0.98A for 2.5 hours and then steadily decreases as it enters CV. Using a AC watt-meter would not give the correct numbers because the AC charger is quite inefficient (gets very hot). Also 15Wh canât be from measuring the battery because it is just 2100mAh.
These are part of my âcollectionâ of several brands of power bank, some of them are samples sent to me by the dealer (I work in a cellphone shop), even though they are mostly chinese brands there are few units that are really really good. Some have a sticker and marked with the amount of Wh (I just wrote W), measured by giving an iPad3 a full charge. The one with highest efficiency is the one on top left, 10,400mAh with 4x purple samsung cells. It delivers 34.7Wh when using 1A port and 29Wh when using 2A port.
In the bottom right is the tester used for all measurements. The ENB, ruinovo and evertones (unbranded white square) unit you see are from fasttech and GB, they use user replaceable cells but I found they discharge the batteries one by one and not at the same time, lowering the voltage and effiiciency. When the power bank is depleted the batteries are not all discharged equal, they vary from 2.7-3.4V, strange behavior. Iâve been using and handling all sorts of power banks pretty much since they started to massively appear on the market, many of them even those from the âbig brandsâ often use the same circuits and components from cheaper units, they just charge extra because of better advertising. Paying Premium does not always give you a better product!
Interesting. I know Apple has been using switch-mode charging ICs for at least a few generations. I donât know about other vendors, but it sounds like Samsung didnât for the Galaxy S3. Linear charger chips are cheaper, and I doubt device designers are particularly concerned with efficiency for its own sake, since the typical charging scenario is a AC adapter or a car adapter. Efficiency becomes important though when managing heat. All things equal, the less heat generated by the charger circuitry, the faster you can charge the battery without overheating it.
My experience with may different power banks confirm what user gauss163 stated with his calculations. I went a step further to find the efficiency (eta) of the DC-DC step-up converters to be up to 90 percent for the power banks using a syncronous rectifier and ceramic filter capacitors, and ranging between 60-70 percent for units using a single Schotty diode and electrolityc capacitor. Cheaper banks do not even have the output mosfet switch, so they have 3.5 V output (Battery voltage minus forward drop of the diode) when OFF, and 5 Volts when ON. No-name power banks on eBay and Amazon, with capacities declared between 12K-20K mAh, usually have installed 1 Ah 18650 cells, so a 12000 mAh rated power bank is 4000 mAh in reality. Anker (and very few other brand names) uses 2600 mAh Samsung pink cells (hybrid). I once bought, for 10 pounds, a no name power banks with 4 blue generic 18650 1 Ah cells, described as 12000 mAh. As it had digital display, sync rectfier with ceramic filters, in and out mosfet switches and foldback current protection at 3.2 A, I bought two more of them, since I were DiY and replacing the cells with Panasonic NCR18650Bs. Well. The two additional power banks I received (same price of the first) had the same case, display and crappy blue cells, but a totally different electronic board, reduced to barebone. Simple switcher with no ancillary circuits, I had to chuck them because they were noisy and dangerous. After that, I only buy DiY power banks with prime electronics, and I provide the cells.
