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64 of 68 people found the following review helpful
on 31 January 2012
This is, certainly, an amazing piece of kit. The amount of power it packs into a sleek case that will fit in the back pocket of your jeans is truly impressive, and for the price (under 35 pounds at time of writing) it's an absolute bargain.

However, I do have one niggle: It wont provide 12,000mAh.

Now, I have to say that I'm using this for a totally unsupported purpose; namely, to run a set of LED bike lights. Two sets, actually. The stock battery that came with each was a 6V / 2,400mAh unit of nearly the same size and weight as this TeckNet unit, so this will run twice as many lights for far longer without a weight penalty. Happily the 6V lights work perfectly on 5V or 5.5V, so a minor adaptation of a USB cable and hey presto, one of the best bike light batteries you could wish for.

This in turn led me to my findings about its usable capacity. The lights draw about 550mA according to my multimeter. A quick bit of maths should tell you then that a 12,000mAh battery should run the lights for about 22 hours between charges. In fact, the run time is about 14 hours (yes, I know, still longer than any night ride!), meaning about 7,700mAh of usable capacity.

I questioned this with the seller and very promptly they replied and reminded me about the inefficiencies of charging batteries; when you charge a battery it gets warm as, while most of the power charges the battery, 30-40% will be lost as heat. Which is fine, except, (a) I wasn't charging a battery, and (b) I was measuring the current flow from the battery to the load. What it did when it got to the load, I have no care (and neither does it), the point is that the battery put out 550mA for 14 hours before it became sufficiently discharged to turn itself off.

I suspect that the truth may have more to do with the clever electronics inside the unit. The instructions say that the output is shut off when the battery voltage drops below a certain value; my suspicion is that this value is reached significantly before the actual chemical cells are exhausted. In other words, the cells may well have a 12,000mAh capacity, but the electronics prevent you from getting much more than about 60% of that capacity out of them. On the plus side, those clever electronics keep the output voltage constant throughout the discharge, as is required for a USB supply; this means the lights stay on full brightness until they switch off.

I have no reason to believe this discrepancy is unique to this battery; it wouldn't surprise me one bit to learn that all similar batteries did the same, and, had I only ever used this to keep my phone charged when away from the mains for long periods, I'd probably never have discovered any of the above, and I'd have nothing but praise.

Speaking of which, I am buying a second one, for its advertised use this time, because despite the above niggle, the capacity/size/weight/price combination of this thing is still amazing - just be aware that the quoted capacity does not reflect the usable power while you're adding up what you want to charge or run from it.

*****
Later edit:

As some others have pointed out (below), the mAh rating applies to the chemical cells, which, being LiPo, output 3.7V. This gives a "true" output of 44.4Wh which is marked (in tiny writing) on the battery itself.

Convert the voltage to 5 or 5.5V for USB, and this power rating gives around 8,800 or 8,000mAh at the actual output voltage (minus whatever inefficiencies the voltage conversion introduce), in line with my findings above. It's a niggle / annoyance that this battery (and probably all similar LiPo USB-voltage packs) is sold quoting a mAh capacity that cannot be achieved at the supplied voltage. It's like saying my car can do 100mph and 100mpg - it can, but, not at the same time!

Still a great piece of kit and still highly recommended, just a shame batteries like this aren't sold quoting the Watt hours which would give a much more accurate customer expectation.

Sellers *please* take note!

:)
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5 of 5 people found the following review helpful
on 3 May 2012
I bought this battery bank for £33.98 on 31.Dec.2011, having decided to treat myself to a second model in addition to a Sanyo Eneloop KBC-L2B. I had bought the Sanyo for their excellent reputation in batteries; I opted for the TeckNet iEP392 for the lower price after reading favourable reviews on Amazon.

The battery bank arrived on 25.Jan.2012, slightly ahead of Amazon's estimate. A nice surprise - it looks better in reality than on the picture, made of black glossy plastic with a curved silver trim at one side of the top. Under the silver trim (which turned out to be semi-transparent) are four blue LED lights to indicate the level of remaining charge.

The iEP392 feels solid and well built. It is chunky and would be an overkill to carry around in your backpack in the city, but would be very useful for trips to regions without electricity, long flights with your iPad, or simply to be able to charge several USB-powered devices while traveling. It can charge two at a time.

The battery came in a fairly large box that contained also a UK mains charger, several different connectors and a nice cloth pouch. It was about 75% charged (three out of four indicators lit), so I topped it up to 100% before use. Then used it to charge my Blackberry twice over a week. Still four indicators lit! This thing appears to have some serious capacity, as it claims.

Three months later, it has been to Morocco and back, but apart from that I have not used it heavily. After 4 charges of a Blackberry or an iPhone the remaining capacity was over 50%, so in theory it should manage about 8-10 charges of a smartphone.

I haven't done a proper test of the capacity, but came across another reviewer's comment that he measured it at 7700mAh. This will be correct if the quoted 12000mAh capacity applies to the actual lithium battery inside the device, which has nominal voltage of 3.7V and not to the 5V USB output. To provide a given current at the 5V USB output, you need to draw higher current from the 3.7V battery. Also, since the electronics that convert the voltage from 3.7V to 5V are not 100% efficient (more likely 85-90%, say 87%), the current drawn from the internal battery needs to be even a little higher. Simply put, it has to be 5/3.7/0.87 = 1.55 times higher at the battery than at the USB output. Divide 12000mAh by 1.55, this is about 7700mAh, therefore the observed capacity sounds about right. Still, this is a very high capacity for a portable power source.

The iEP392 is intended for indoor use, but I suspect that with some improvisation to keep it dry (watertight food box with a clip-on lid?) it could even be used outdoors. Just be very careful not to hit it hard or make it wet, ever. The electronics may fail, and lithium-ion batteries can ignite if short-circuited.

The risk of self-ignition of lithium-ion batteries is very low in normal use, but there have been a few such cases globally. That is why such batteries should be carried in the cabin baggage on a plane. Where you would need a mobile power source anyway.

Comparison with the 5000mAh Sanyo Eneloop Sanyo Mobile Booster KBC-L2B:

- The weight is proportional to the capacity: the Tecknet is 12Ah and weighs 300g, the Eneloop is 5Ah and weighs 140g;

- Both are solidly made with a nice design. The Tecknet is glossy black, the Eneloop is glossy white;

- The Eneloop's charge indicator is unnecessarily fiddly - you have to press the button for 2 seconds, after which the single blue LED flashes in a series to indicate the level of remaining charge. TeckNet's solution is simpler - press the button, one lit LED means about 25% charge, two - 50%, three - 75%, four - 100%;

- When left on without a load, the Eneloop shuts down after twenty seconds or so. The Tecknet is said to have a shut-down time of 1 hour. Most likely the electronics inside have low self-consumption without load, so this should not be an issue, especially given the high capacity;

- With the TeckNet iEP392, you get 2.4 times higher capacity at a slightly lower total price than an Eneloop KBC-L2B, which costs over £40. So, in terms of capacity per pound, the difference is nearly three-fold;

- iEP392's manual recommends to discharge and recharge the battery once every 5 months to prolong its life. I can't remember whether the Eneloop's manual contained similar advice (will check if I find it)

- Regarding durability - re-visit this review again in a few years!

The TeckNet iEP392 is now a permanent addition to my travel/emergency gadget pack along with a torch, a compass, etc., while the Eneloop KBC-L2B, being smaller and lighter (and white), is being carried around by my wife as a portable source for her power-hungry iPhone 4S.

Imagine your trans-ocean flight being delayed due to snow at Heathrow and you arriving hours or days later with a completely dead mobile phone, not being able to call whoever is meeting you. It may happen only once, but even for that reason alone it is worth to carry a small power pack, say 2-3000mAh. The iEP392 with its high capacity is fit for this purpose and many more, and offers excellent value for money. I hope it lasts, too.
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17 of 18 people found the following review helpful
on 18 June 2011
I ordered this TeckNet iEP390 battery pack a few days ago and I have to say it's a great travel tool! I have an iPad and I tried a couple of other battery packs but they all failed to properly charge it. None of the other batteries could provide enough power to the iPad and it would charge way too slowly. With the TeckNet iEP390 it charges really fast! I think it might charge even faster than from the wall outlet. Also, none of the others had even close to the same 11000mah capacity for the price. You definitely need the extra juice to charge a tablet. For phones, I was able to charge my iPhone several times over.

It comes with several tips so you can charge just about anything. My brother has the Galaxy tab and he said he had the same problem of other batteries not working. I used the included galaxy tab tip and his charged perfectly.

The size is not bad either. It's a bit heavy, but only a bit bulkier than an iPhone. People always ask me what it is since it looks so shiny.

I would highly recommend for anyone who needs power while traveling. Good to charge anything I could throw at it.
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6 of 6 people found the following review helpful
on 22 April 2012
I purchased the unit two weeks ago and noticed that the port markings were upside down making the tablet and phone ports opposite to what they should be. After many emails to TeckNet I was told that the whole batch was wrongly marked but the battery was functional regardless. I decided to keep the battery as to return it was at my expense.
The battery, I found, delivers about 70 percent charge for the new iPad so not bad. I have had many purchases from TeckNet and always found them good quality, time will tell on this battery.
Make sure the price quoted is what you pay.
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3 of 3 people found the following review helpful
on 5 March 2012
Great charger, feels solid and built to last. Bought for my PS Vita as the Sony battery extender for the Vita is only around 2000mAh for a similar price to this one. A word of caution - this one does not work out of the box for the Vita. It is necessary to buy a usb lead Male A to Female A and short the data wires at the female end to fool the vita into thinking it is attached to a "clever" power supply. Any trouble do a google search for "Nokia N900 dumb usb" as that device had the same problem as the Vita.
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3 of 3 people found the following review helpful
on 25 February 2012
Excellent device - comes with most connectors for nearly all devices apart from Sony Ericson phones.

Tried it with IPAD 2 and HTC phone which works well. It came partially charged upto 2 leds so you can use straight away without having to charge to full capacity when you unpack it.

It even comes with a nice pouch to keep it in and delivery was quick aswell - it said a month or two for delivery but received it within a few days of ordering so excellent service there.
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1 of 1 people found the following review helpful
I already own the TeckNet iEP386 6,600mAh version of this external, rechargeable battery pack and I was so impressed with its performance that I purchased its much more powerful brother.

I have only had the 12,000mAh battery pack for a couple of days but long enough to give it a full charge. Like its lower capacity sibling, its build quality, look & feel is impressive and I have no doubt will perform just as well.

Unlike the 6,600mAh pack, the 'Heavy Duty' power pack/charger is claimed to provide over 2A from USB port #1 and 1A from port #2. It is unclear it these currents can be supplied simultaneously but my guess is that it can. The larger current source (2.1A) is intended to power/charge iPads and larger tablets provided they can operate from 5.5V. The lower current source (1A) is intended to power/charge iPods and mobile phones, including smart phones. There are some devices this Heavy Duty power pack cannot power/charge, so check for buying.

The iEP392 is supplied with its own 2A charger which gives a charging time of around 7 hours from flat. There are 4 blue 'cool' LEDs which indicate both the charging status and the amount of charge remaining. These LEDs 'cycle' whilst the battery is being charged and remain on when fully charged. The number of LEDs on indicates the state of charge when the battery is powering external equipment, There is a circular, soft-touch button used to 'wake-up' the battery, which if not used for several minutes will turn the battery off to preserve power. The battery, like its little brother, comes with a soft case and a collection of adapters and a cable to connect them to the battery pack.

I have yet to put this battery pack to the test but I have no doubt it will comply with its design specification.

If you need the ultimate in portable power, the TeckNet iEP392 has a lot to offer.
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8 of 9 people found the following review helpful
on 5 February 2012
Plus points:
* Very good capacity - I fully charged this unit, then got about 4 full charges of my Samsung Galaxy S2 from it, after running the S2 down to about 15% each time.
* Seems to charge reasonably quickly.

Negative points:
* A little on the bulky side. If you want something you can carry around in a pocket, then go for one of the smaller, lower capacity models.
* Battery level status indicator doesn't really work. After I'd charged my phone 3 times, the status indicator was still showing 3 LEDs (50% - 75% according to the manual). After the 4th charge, it was down to 1 flashing LED and wouldn't give out any more power.
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2 of 2 people found the following review helpful
on 17 March 2012
This is a wonderful product.

I hesitated to give it 4 stars since the iphone / ipad plug end disintegrated after only a few hours use (although the charger was in a rucksack and the phone was in my jacket pocket, connected, while I was hiking).

I just use the original iphone USB cable and it's great. This device charges my phone about 4 times before running out of juice, although I've only emptied it once (hiking weekend).

Highly recommended.
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1 of 1 people found the following review helpful
on 24 March 2014
I bought this to power a Raspberry Pi and Nokia 6301 as they are used together in an embedded project. It's fine for the RPi, but the Nokia states it's not supported and doesn't charge. When plugged into the Nokia it appears to work and charge - some time later, between 1 and 30 seconds it stops charging and displays the error. I checked the output of the original Nokia charger and its about 7V, the iEP392 only outputs 5.3V even though the spec states 5.5V. I'm not sure why this does not charge the Nokia properly - although the adapter seems a bit long and doesn't click home like the original one does, or it could be the lower voltage. I was planning on having a single power source for the Pi and the Nokia, which are not easily accessible, it now means I have to sort something else out to charge the Nokia.

Note: you can use it's output and charge it at the same time, which is good.
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