KMASHI 10000mAh MP816 (2.1Amp+1Amp Output,2Amp Input Fast Charging) Dual USB Portable External Extended Battery Pack Power Bank Backup Charger For iPhone 5S 5C 5 4S 4 iPad Air Retina Mini Samsung Galaxy S5 I9600 Neo S4 I9500 I9190 S3 I9300 S3 I8190 S2 Not

The price of this KMASHI 10000mAh MP816 Dual USB Power Bank is lower than most other power banks with half of its capacity. Previously I have good experiences with several KMASHI products (such as the KMAX-812 4400mAh Rechargeable Backup Battery Pack). That's why I decided to give this unit a try.

[Battery Capacity]
Most lesser-known battery packs tend to exaggerate their capacity ratings. So I conducted my own test to verify the claim of '10,000mAh'. I connected a 3.3 ohm power resistor to the 'OUT2' port (which is rated up to 2.1A max). The unit is able to supply 1.5A at 5V for 241 minutes, before shutdown. This means a total output energy of 30Wh (5V * 1.5A * 4hr). Assuming conversion efficiency of 80%, I can then estimate the internal battery to be about 10,000mAh (3.7V * 10Ah * 0.80 = ~30Wh). So the advertised capacity rating is accurate.

[Output Current]
During my testing, I discovered that OUT2 port is unable to sustain any load current greater than 1.8A, even though it is rated as '2.1A max'. The OUT1 port, on the other hand, is able to supply 1.1A, or slight higher than the rated '1.0A max'. This is disappointing since my main goal is to recharge my Barnes & Noble NOOK HD+ Tablet during long trips. The Nook has problems with most power banks I tested. It will try to draw 2A charging current initially. But if it can't, it will drop the current to 0.45A instead. In this case, the Nook can draw 1.1A from OUT1, but only 0.45A from OUT2.

[Status Light]
The MP816 has a 4-LED battery status indicator light. According to the instruction sheet, each LED is supposed to represent 25% of charge. My actual testing showed that the status light is highly non-linear:
4 LED = 61 to 100%
3 LED = 32 to 60%
2 LED = 19 to 31%
1 LED = 4 to 18%
blinking = under 3%
This is a common problem with most power bank units: you can't reliably tell the remaining battery capacity based on status lights. One exception I found is the PNY Dual-Port 2.4 Amp 7800mAh PowerPack. It has a digital status indicator that can report the battery status accurately - down to 1% according to my test. Sadly, the PNY unit is also unable to supply 2A for my Nook.

[Power Button]
One quirky thing I noticed about the power button: it needs a very short press to turn on. If I press and hold it for 1 sec, the power remains off. This behavior is opposite to that of most other power banks.

[Recharge Time]
During recharge, the MP816 draws up to 1.5A - as long as your USB power source can supply it. So it takes about 8 hours to fully recharge the internal 10Ah battery pack. But if your USB power source can only supply 0.5A, then it could take 20 hours! One drawback I discovered is that there is no pass-thru charging. That means while you are charging the internal battery of the MP816, you are unable to recharge anything else from OUT1 or OUT2 ports.

[Bottom Line]
Given its low cost and high capacity, I still consider this KMASHI unit a very good value. I just have to remember that the '1A' port actually charges my Nook faster than the '2.1A' port.

[Footnote]
I used the PortaPow USB Power Monitor to measure the unit's input and output currents. It is indispensible in testing charging rate of my USB devices. See my review on it for details:
http://www.amazon.com/review/RVRNRAC9JJYOP

[Update on Mar 18, 2015]
I have tested the Yoobao SP2 10000mAh Dual USB Port Power Bank and found it capable of charging my Nook HD+ at 2A. See my review on it for details:
http://www.amazon.com/review/R2NOFH93OIVY5C/

[Update on Jan 18, 2016]
In case you're looking for a high-capacity power bank that supports pass-thru charging, I recommend the MoKo 9000mAh Dual-Port Portable External Battery Charger. It is much better than the Kmashi MP816 because:
- It is more compact
- Comes with an LED flashlight
- Able to charge my Nook HD+ at 2A from any port
- It puts out nearly the same total energy (29.5Wh) as the MP816, despite lower advertised battery capacity (9000mAh vs. 10,000mAh)

Here is the lowdown. I bought this when it had just 1 review. The problem with that particular review is that it seems to be from someone from the seller or the manufacturer, considering a bulk of his reviews are of Kmashi products and all rated 5 stars. So I took a leap of faith as the price was very reasonable, and I could always return it to Amazon.

This is a keeper. I am not sure about the mAH rating, since I have no way to actually test it. I suspect it may be exaggerated. However I will tell you what my findings as an user are, and you can judge for yourself if this fit your needs.

The battery pack has a little heft to it. That is expected considering the size of the battery. Very well built, it feels solid and belies the price I actually paid. Quality feel. It can slip into your jeans pocket, but will make it's presence felt.

--- Getting this juiced up.
It takes over 14 hours with a 5V 1amp power source.
It takes a little over 7 hours with a 5V 2.1amp power source.
This does not come with power adapter. It only has a USB to Micro USB cable.

--- Charging devices

Charging iPhone 5.
Once the battery pack was fully charged, I could get 5 full charges with some juice to spare. I got the charge to 100% from the following phone battery charge state.

Twice from 20%
Twice from 15%
Once from 10%

Since these charges happened over a week without having to recharge the battery pack, it tells me that this product can be used with confidence, during travel.

Charging the iPad 2

This was a bit of a let down. But probably technically ok. I could only get partial charges from a full charge of the battery pack.

Once from empty to 86%
Once from 15% to 93%

So a full charge of the battery pack will not charge the ipad to 100%, if the ipad charge is below 20% or so. But my iPad is over 2 years old and the battery may not be as efficient.

My tests above should give you a fair idea as to what to expect in real world usage. I do not have other devices to test out.But based on the findings above, you could do some math and find out how this would serve your device based on your particular devices battery capacity.

I had to knock off one star because of two issues :

1) This will not charge any device while the pack itself is getting recharged. There are other battery packs which do that. However it was not a deal breaker for my needs, but would have been nice.

2) The charger needs a little kick in the pants, to charge upto 100%. For some reason my iPhone would stop getting charged at around 96%. I had to press the power button on the device once again to get the charge to 100%. It may be a particular quirk with my device.

I purchased this to use for Bonnaroo last month and it worked great... it would charge my iphone 5 about 4 or 5 times on a single charge. When I came home from the festival my wife used it a couple of times at work and while out shopping, then she went to go on a trip out of town last week took it with her. Before she left it was discharged (zero cubes filled) so I plugged it in overnight to charge it. In the morning it was still one cube away from a full charge, so I left it plugged in and I went to work and returned that evening and it was good to go, all charged up. I gave it to her that evening and she left for her trip the next day. On the following day (2 days after charging) she sent me a picture of the battery all melted and said she was looking for something in her purse and noticed it was all messed up. It only has a 30 day return window, luckily it was only $15 and I at least got that much use out of it and it didn't catch fire or ruin anything in her purse... I guess they're lithium ion so not as sketchy as lithium polymer but still not cool at all.

Kmashi charger-
Unboxing: the unit arrives is a sturdy cardboard box, with a manual translated into very good English, a warranty card in mostly Chinese, and a white micro USB cable about 20" in length. I was pleasantly surprised by the quality and rounded molding of the cable. The battery unit itself is shipped in anti-scratch plastic, and has a shape that slightly rounds in the long edges of the case, which I found made it easier to slip into a pocket without edges sticking out, nor being uncomfortable when sat on in back pocket. There are also long scalloped indentations along the edges to assist in grip. I couldn't quite see these details from the photos provided on the product page. The length of the USB cable allows for the battery pack in a back pocket while the phone is in the front easily, or to pull out and use without pulling on the battery pack, without being so long as to be obnoxious. Not quite long enough to hold phone to ear for me at 6' tall, but close!

The unit arrived partially charged, with two of the four blue LED charge indicators showing up to 50% charge, according to the manual. It took approximately 5 hours to reach full charge, with all four LEDs solidly lit, using a 2.1 amp iPad 2 charger. Using your average phone charger, which typically range from .5A to 1A, will obviously extend the charging time required.

The following informal tests were done using the 2.1 amp output.

Note that this unit will not charge from the USB output while being plugged in and charging itself, as I had hoped, and as some of the other battery packs are able to do, working as higher powered USB hubs. I did not see this mentioned in any other reviews, so I hope it is helpful.

I started charging my Nexus 4 with it at 32%, and it immediately showed progress, at almost 1%/minute. I was using (battery hog location-based game) Ingress, browsing, and video during charging as well as writing part of this review; it may be significantly faster if just charging alone. GPS was on, wifi was off. Also of note, my Nexus has a worn battery (2100 mAh), hence the purchase of this Kmashi external battery while waiting for a new internal Nexus battery to arrive.

After 1 hour, the phone was at 58%, and all four LEDs were still showing, meaning I still had at least 76% charge left, if not more.
At an hour and a quarter, the phone was at 63%, and all four LEDs were still lit.
At two and a half hours, the battery was completely full, and all four LEDs were still lit.

I then plugged the battery pack into my iPad 2, which was at 63% charged. I was not actively using the iPad, but WiFi, GPS, and Bluetooth were enabled. Cellular data/radio was turned off during this time.
At 2 hours, the iPad 2 was at 90%, and three LEDs were lit on the Kmashi.
At 3 hours, the iPad 2 was at 100%, and two LEDs were still lit on the battery pack. It may have been slightly less than 3 hours to reach full, but this gives you an idea of the charging ability for a tablet the size and battery capacity of the iPad.

Next, I plugged in my iPhone 4 at 38% charged. I was not using it at the time, but WiFi, GPS, and Bluetooth were enabled in addition to 3G cellular radio.
20 minutes brought it up to 55%, with 2 LEDs still lit on the battery pack.
At 1 hour, the iPhone read 88%, and battery pack was finally down to 1 LED.

I then plugged the Nexus 4 back in with it at 52%, and charged the phone while running errands on my commute home, approximately an hour of plugged in time. Upon arrival home, I plugged in not only the Nexus 4, but an old Droid X that I use as a dash cam, with the Droid going into the 1 amp output. The Kmashi battery pack had slowed its rate of charge slightly, but continued for a further 45 minutes, at which point the last LED began blinking. The battery pack continued charging both phones, however, for a further 10 minutes or so before shutting down, having served 4 devices valiantly all day long!
I know this test is far from scientific, with none of the readings and math I enjoyed reading in other reviews. Rather, it's a real-world report and review on what to expect from the Kmashi 10,000mAh external battery pack. Being one of the lower-priced options, I had moderate expectations that were actually surpassed so far. I understand that a few more charge/drain cycles should improve performance even more.

Despite the lack of science, if this review has been at all helpful, please click so below. Thanks!

Notes:
Have not noticed any increase in temperature of the unit while charging itself, or using it to charge other devices, indicating to me efficiency of operation as opposed to energy lost through heat.
I've also noticed that this pack will shut itself off once the device is it is charging has reached full capacity, indicating IC's that are providing smart functions not mentioned in the manual.
You do have to press the power button, located next to the level LEDs on the side, to begin charging. I've seen this be an issue for some reviewers of other battery packs, and I've forgotten once or twice so far, but don't find it to be an issue. Holding the button down for 2 seconds turns the unit off, or it will shut down automatically as noted above. The button has a solid feel with a firm but quiet click.

I would definitely recommend this battery pack so far as an option to the fancier and higher-priced aluminum clad, oled screen equipped alternatives. Solid build, design and performance. I was NOT provided a sample by anyone- I bought the dang thing myself like most everyone here does. ;-)

OK so i got this in today and decided to put it right to the test, i made sure it was fully charged then threw my ipad mini which was at 30% on to charge as i went out about my afternoon meetings. I also threw on my Nexus 6 on port 2 which is the 2.1 amp while my ipad was on port 1 the 1 amp port, my Nexus 6 seem to get fully charged up in about an hour and half mind you it was at 60% when i threw it on. The ipad was fully charged at about 7pm and i threw but device on at about 4:30pm today, the battery bank still shows three bars on the side so i have it in the battery pack pouch on my bag and will see how many charges it has left before it is finally dead and needs a recharge. So the next device i will charge on it will be my ipod since it's always in my bag along with my beat head phones, the only thing this bank wouldn't charge was my PS4 controller. The one device that dies on me the most and i would have loved if it could have charged the controller too. So far so good, let's see how this battery bank does through out the weekend, i have multiple battery banks that i use due to my day to day activities that keep me jumping from place to place so far it's out performed two of the 4 i have.

( UPDATE 9/11/16 )

OK so this battery bank finally died on me while charging my Nexus 6 this morning, so I'm very impressed with how it held up to charging all my devices. So i was able to get a full charge on my ipad mini, 2X on my Nexus 6, Nexus 5 and ipod before it died and needed to be recharged, but also i was able to power my USB desk light with this device last night so i'm pretty sure i could of got another charge out of it on a device if i hadn't used it to power my USB light for a few hours. So for the price it's a great battery bank to have, now mind you it's not an Anker butlike i said for the price it's a pretty decent power bank and will be seeing a lot of use in my tech bag.