Chapter in this post:
For a few weeks now I have been using the Zendure A2 additional battery for my iPhone as well as for the iPad and other USB-powered devices. Should you consider the special features of this power bank from Zendure (for Company homepage) summarize in short form, then I would highlight the following key points:
But that is far from describing the Zendure A2. The power bank has definitely risen to become one of my favorite power banks lately, and that's not just because of the look.
The Zendure A2 is one of five models offered by the manufacturer. In addition to the A2, there are also the A1, A3, A4, A5 and A8 QC models.
|Zendura A1||3.350 mAh|
|25 x 23 x 96 mm||68 g||In: 5V / 1,5A |
Out: 5V / 1,0A
|Zendura A2||6.700 mAh|
|94 x 50 x 24 mm||140 g||In: 5V / 1,5A |
Out: 5V / 2,1A
|Zendura A3||10.000 mAh|
|96 x 62 x 23 mm||200 g||In: 5V / 1,5A |
Out: 5V / 2,1A
|Zendura A4||13.400 mAh|
|108 x 72 x 24 mm||260 g||In: 5V / 1,5A |
Out: 5V / 2,1A
|Zendura A5||16.750 mAh|
|127 x 72 x 24 mm||320 g||In: 5V / 1,5A |
Out: 5V / 2,1A
|Zendure A8 QC||26.800 mAh|
|119 x 74 x 40 mm||482 g||In: 5V / 2A |
9V / 2A
12V / 1,5A
Out: 5V / 3A
9V / 2A
12V / 1,5A
Anyone who thinks they are with Audi is almost right, because the same applies to Zendure: the higher the number, the more power the battery has. And the A8 QC is, so to speak, the Audi Quattro of the Zendure Powerbanks, because the QC stands for Quick Charge, whereby the Powerbank supports the latest version QC 3.0. But I might take on the model at another point in time. At the moment it's about the second-smallest Zendure - namely the A2.
In order to look at the individual points in detail, let's first take a look at the technical specifications of the Zendure A2, which are in themselves quite okay:
In addition to the power bank itself, the scope of delivery also includes a micro-USB charging cable, a fabric cover for transport and instructions.
I can't say much about the durability of the power bank because I didn't subject it to specific drop tests according to military standards. The power bank always ends up unprotected in my backpack and has to cope with one or the other fall. Most power banks can withstand this if they are not made of sensitive plastic.
With the Zendure, however, you can tell even without explicit drop tests that it was developed to withstand high loads. The shell made of composite material is provided with small bars that not only stiffen the housing, but also protect the power button. A strip of rubber runs between the top and bottom of the power bank, which is supposed to absorb the energy in the event of a fall. How well the whole thing works can be seen in the manufacturer's video about the Zendure A series of power banks (from second 44).
I think that even if you rarely drive your car with your additional batteries in practice, you can assume that the Zendure A2 will hardly be broken with "normal" use.
When it comes to design, Zendure is definitely right, because the A-series power banks all look very appealing. I chose the silver version of my battery, but most models are also available in black and the A1 even in some trendy colors.
If you look at the Zendure A2 in silver, a comparison with an aluminum travel trolley is obvious. The strips in the housing and the rubber coating on the side ensure that the additional battery looks like it was planned for use on expeditions. But don't worry, it can just as easily be used in a wellness hotel. ;-)
The battery is charged as usual via a micro USB socket. During the charging process, 4 blue LEDs above the power button show the current charge status. The current draw works via a normal USB output, whereby the internal electronics of most devices automatically switch on the power when the device is connected. That works for me with both the iPhone and the iPad.
If you plug in a consumer that the power bank does not recognize (for example my USB load resistor), you can start the power supply manually using the power button.
The current charge status can also be queried using the button. If you press this briefly, the available capacity is displayed for a few seconds via the 4 LEDs. A review on Amazon criticized that this ad would be very inaccurate. For this reason, I looked at the consumption and the LEDs when discharging and found that the display gives quite good information about the state of charge. The penultimate LED, for example, only went out 170 mAh after the calculated end of its display. So you can assume (based on the almost 4.000 mAh of the available total capacity) of +/- 5% tolerance in the display, which I think is very passable.
A feature that I have already missed with some other power banks is the load-through function, which allows the power bank to be charged on a charger while a smartphone or other device is being charged via the USB output of the additional battery.
This is mostly asked on vacation when you come home in the evening and only one charger is available in the holiday apartment. However, there is one limitation with this feature, because the output voltage and current dropped sharply in my test, so that the iPhone and iPad were only charged with 3 W (4,6 V / 0,6 A).
You can still cope with that with the iPhone if it has time to fully charge itself overnight, because in order to go from 7% to 5% with the iPhone 100 Plus, we need approx. 15 Wh, which means that we can cope with the load -Through function should plan about 5 hours of charging time.
With the 9,7 inch iPad Pro, however, you have to calculate with a battery that is more than twice as large (> 7.000 mAh) and you would then have a charging time of at least 12 hours, which in my opinion is no longer practical
I even get the message "Not charging" on my iPad because it considers the current flow to be too low. Zendure still has potential for improvement here. In an emergency, however, this "emergency charge" function is sufficient for me. And if you are really more on the move with tablets, you can also switch to the larger Zendure models, as these are more designed for tablets.
Even in normal use when charging the iPhone and iPad, I noticed that the power bank charges the two devices pretty quickly. Of course, due to its capacity of "only" 2 mAh, the Zendure A6.700 battery is more suitable for smartphones such as the iPhone and less for tablets with a high "power hunger", but if you just want to keep the iPad alive a bit, then is the Zendure A2 is quite practical.
Due to the high current output of 2,1 amperes maximum, the iPad battery is also charged during use if the Zendure A2 additional battery is connected. Many models from other manufacturers that I've tested fail to do this.
But let's get to the facts. "Fast charging" and "high power output" are terms that can mean anything and ultimately mean little. Because of this, I've gotten into the habit of measuring a few things every time I test power banks. The examples will hopefully help to classify the technical specifications in everyday practice.
When I take measurements, I usually do it with both mAh and Wh. The best way to compare with other power banks is to measure in Wh (i.e. watt hours), as this is the physically correct indication of the amount of energy. This is calculated from the current and voltage output in connection with the time: Current * voltage * time result in the watt hours.
The unit mAh is used by the manufacturers of the power banks, but is practically not exact when it comes to the specification of the amount of energy, since the specification of the voltage is missing. You assume about 5 V, but it makes a difference whether a power bank charges a device with 5,1 V or 4,7 V. The specification of the power in watt hours takes this into account.
Incidentally, the indication of the mAh, which can be found on power banks, refers to the capacity indication of the built-in batteries and does not provide any information about the actual amount of electricity that can be obtained for charging devices. However, this is not a marketing trick, but the only possibility for the manufacturer to name a capacity, because only the specification of the built-in batteries is known.
I have the flow of energy away from the power bank (discharging) and towards it (charging) with the help of a PortaPow USB multimeters supervised. It was loaded with the tizi gas station and the supplied micro USB cable of the Zendure power bank. I have the burden of one electronic constant current resistor from Yeeco simulated. So much for the equipment ... but now the results of the tests.
The charging current was about 1,9 amps for more than an hour, which in connection with the voltage supplied corresponds to about 9,8 watts. That is significantly more than the 7,5 watts promised by the manufacturer. After about 1,5 hours, the charging current slowly drops and the power bank is fully charged after a total of 3,5 hours. Until then, the process had required 27,1 Wh of power and a good 5.440 mAh.
The next practical test is charging my iPhone 7 Plus, which I hung on the power bank for 10 minutes. It was charged with 5,5 to 6,5 W and the battery level increased by 73% from 80% to 7%. During this time, the power bank delivered 1,16 Wh. The values are of course dependent on the connected device, because an iPad consumes significantly more electricity. But it gives you an idea of how long it takes to pump a few percent more battery into the iPhone.
To see how often you could actually fully charge an iPhone 7 Plus, I once ran my iPhone down to 5% and then attached the fully charged Zendure. For the first few minutes, she charged the iPhone to an impressive 1,8 amps, but the current gradually drops. After a good 2 hours the iPhone was at 92% and after approx. 3 hours at 100%. The last percent up to 100% always takes a lot of time, which is quite normal. After fully charging, around 15 Wh of the total of 20 Wh that the A2 delivers were used up. So you won't be able to charge the iPhone 7 Plus twice, but 1,3x is quite realistic.
Now I have repeated the same test with my iPad. 10 minutes of charging brought the battery from 80% to 82%. The power bank delivered 1,4 Wh. The power was around 8 watts.
In order to check how much mWh the Zendure A2 emits in total before the circuit breaker switches off the power bank, I loaded it with a load resistor that has constantly drawn about 1 ampere of current. I measured the energy output again with the USB multimeter.
The complete discharge delivered a total of 3.983 mAh and the amount of energy was 20 Wh. This results in a mathematical efficiency of 73% if you put the amount of energy for the charge in relation to the amount of energy that you ultimately get out again.
I have summarized everything that I measured and that could somehow be poured into a table. Personally, I think the values in relation to the size of the power bank are very good, but I think you can also see that the power bank is more for smartphones. If you do a lot with tablets and want to have more than just a few percentage points of charge, you should go for the models Zendura A5 and Zendure A8 QC to tend.
|IPhone 7 Plus charging performance||approx. 5 - 7 W.|
|IPad Pro 9,7-inch charging performance||approx. 8 W.|
|Amount of energy for fully charging the power bank||27,1 Wh (5.440 mAh)|
|Amount of energy when the power bank is completely discharged||20,0 Wh (3.983 mAh)|
|Maximum current without voltage drop below 5,0 volts||A 1,47|
|Maximum current until the power bank is switched off (protection)||2,5 A (at 4,79 V)|
|Maximum charging current for Phone 7 Plus with battery level ≤ 20%||A 1,8|
|Maximum charging current for iPad Pro 9,7 '' with battery level ≤ 20%||A 1,9|
|Efficiency in relation to Wh IN / OUT||74%|
The Zendure A2 very often ends up in my backpack when I go on tour. The robust construction and the possibility of supplying the iPhone with a few percent additional energy with a short connection to the power bank make the Zendure A2, in conjunction with its low weight and small dimensions, a welcome companion.
If you accidentally fall out of your backpack and hit a rock, you don't have to worry. The composite construction absorbs these bumps well and prevents damage that would impair the function of the power bank. And although this has happened to me one time or another, it still looks almost perfect.
If you're interested in the Zendure A2, you'll find it here at Amazon or go through this product box:
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.
The page contains affiliate links / images: Amazon.de