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Customer Review

5 of 5 people found the following review helpful
5.0 out of 5 stars TeckNet iEP392 Li-Ion battery bank, 3 May 2012
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This review is from: TeckNet® iEP392 12000mAH Heavy Duty 2.1A/1A Dual USB Ports External Battery Pack for the new iPad 3, new iPad mini, iPad2, iPhone 5, iPhone 4S/4/3Gs/3G, iPod Touch all versions; Samsung Galaxy Note/Nexus/S3/S2/S; HTC Titan, Sensation, ONE S/V/X, EVO Thunderbolt, Desire; LG Optimus series; Blackberry Bold, Curve, Torch; Motorola Razr HD/MAXX & Bionic, Atrix/2; Nokia Lumia 700/800/900 and GoPro (iEP392 Heavy Duty 5V/2.1A/1A high speed charger) (Camera)
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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