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:
- high charging current
- noble look
- small dimensions
- very robust construction
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.
Chapter in this post:
- 1 disclaimer
- 2 power banks from Zendure at a glance
- 3 Technical data of the A2
- 4 durability
- 5 Appearance and operation
- 6 Practical: load-through feature
- 7 Charging current and measurement results
- 8 Why I prefer to use Wh instead of mAh ...
- 9 practical tests
- 10 My equipment for measurements and tests
- 11 Charging the Zendure A2 itself
- 12 Charging an iPhone 7 Plus
- 13 Charging an iPad Pro 9,7-inch
- 14 Complete discharge of the Zendure A2
- 15 Summary of the measurement results
- 16 Conclusion: a good companion for hikes
- 17 Similar posts
Because every now and then readers ask about it in test reports: The product mentioned here was made available to me by the manufacturer for a test. No money has flowed and I don't feel obliged to rate a product as good that I don't think is good.
Here I see myself more responsible for my readers to give an honest rating, because I'd rather annoy a manufacturer with a reasonably poor rating than many readers with a supposedly good rating for a lousy product.
However, if products are really bad, they usually don't get a platform on my blog. You can assume that the product (from my subjective point of view) is not total rubbish if I take the time to write about it. ;)
Zendure power banks at a glance
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.
Technical data of 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:
- Capacity: 6.700 mAh or 23,6 Wh
- Dimensions: 94 x 50 x 24 mm
- Weight: 140 grams
- Output current: 2,1 max Ampere (at 5 volts)
- Charging current: max. 1,5 amps
- Battery cells: 3,7 volt lithium-ion cells (super high density)
- Material: ABS-PC composite plastic
- Low self-discharge: after 6 months still 95% capacity
- Lifespan: at least 500 charge-discharge cycles
In addition to the power bank itself, the scope of delivery also includes a Micro-USB-Charging cable, a cloth 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 over your additional batteries in practice, you can assume that you will hardly break the Zendure A2 with "normal" use.
Optics and operation
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.
Practical: load-through feature
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
My iPad even says "Not charging" because it considers the current flow to be too low. Zendure still has potential for improvement here. In an emergency, however, this “emergency charging” function is enough for me. And if you are really more likely to use tablets, you can also switch to the larger Zendure models, as these are designed more for tablets.
Charging current and measurement results
Even during normal use when charging the iPhone and iPad, I noticed that the power bank charges both devices fairly 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 large "hunger for power", but if you just want to keep the iPad alive for a while, then it is the Zendure A2 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 current output" are terms that can mean anything and ultimately say little. That's why I've made it a habit to always measure a few things when testing power banks. Hopefully the examples will help to classify the technical specifications in everyday practice.
Why I prefer to use Wh instead of mAh ...
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.
My equipment for measurements and tests
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.
Charging the Zendure A2 itself
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.
Charging an iPhone 7 Plus
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.
Charging an iPad Pro 9,7 inch
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.
Complete discharge of the Zendure A2
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.
Summary of the measurement results
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.
|Measurement with the box||Value|
|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%|
Conclusion: good companion for hikes
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
4 comments on "In the test: Zendure A2 Powerbank - elegant, powerful and suitable for outdoor use"
thank you at this point for this great blog. Have you ever tested power banks that are operated with solar technology?
Hello Julia! So far I have not had any such power banks in operation. I am interested in them, but I have doubts whether they can actually be filled by the German sun again in an acceptable time. In practice, I might have had it on the windshield in the car or on a window sill in the apartment and then I don't know whether it's enough for one charge. But I am sure that such a solar power bank will arrive soon. Then I know more!
Hello Sir Apfelot,
thank you for the test. I would like to suggest that you always determine the minimum discharge current when testing a power bank. Due to the internal self-discharge protection, there is a threshold value below which no current is delivered. This is always a problem for powering smaller consumers (example: Bluetooth adapter).
Hello Mario! Thank you for the idea! I will definitely include that. I'm trying to do that for the power banks that are still here and add them to the table. I also noticed with the Zendure A8 that it likes to switch off my USB multimeter when its battery is full. So I'll be happy to take that into account! : D LG! Jens