In my country they sell these “2600”mAh powerbank for about $15 to rip people off, in the cheapest units the real capacity of these 18650 is less than 1200mAh measured with my hobby charger. This is the most generic form in power banks and countless of manufacturing plants in china makes them.
I have a friend in shenzhen, china, which most of the cellphone electronics are made, he told me these only cost about 5RMB to make, less than a US dollar. And you can order the quality you want, from 1200mAh to real 2600mAh. Medium quality power banks which are in the 10,000mAh that retails about $30 on amazon, use real capacity generic 2600mAh 18650 cells. Some of the better quality ones uses samsung cells.
But still, this is a very dirty business and has become very saturated in the past years. The worst thing is even in stores like amazon, many companies would pay reviewers for fake numbers, I have seen countless reviews where people said a 5600mAh power bank was able to charge their iphone 3 times, which is impossible. Normally people would assume 100% driver efficiency and batteries rated 5V, and they think they get the capacity they see.
I have to agree. I happen to buy a Samsung Galaxy S4 in Bangkok for such a very cheap price. It turned out to be an imitation (I should have known) and its lithium ion battery marked 2800 mAh won’t last 24 hours even when the phone is only on standby mode - no calls or text messages the whole day. And guess what, my powerbank (bought from BangGood) with a 2600 mAh Sanyo 18650 (genuine of course) in it can have the 2800 mAh battery fully charged three times. The ‘2800 mAh’ battery is of course made in China.
My first clue as to how bad Chinese cells are is when I ordered a replacement battery for my Panasonic camera. An authentic replacement cost $50, I found a Chinese battery on Amazon for $7. Trouble was the new replacement wasn’t even as good as the original I was trying to replace!
As for the included cell in this power bank, I already know that it is better than the typical UltraFire. I am now doing another charge - discharge test to be certain as to what the capacity really is.
My premise all along is that because this unit is in the mainstream retail chain, it is most probably of decent quality. No way a major retailer is knowingly going to put stuff in their stores that will have a 100% failure rate. Also, no Chinese company would want to take a chance with ruining a relationship with a large retailer on a faulty product line.
Secondly, I believe that ultimately, the mainstream retail chain can sell for less than any one - of EBay or internet reseller. Don’t forget, as texaspyro once stated, “uniformed couriers deliver my purchase right to my door” Even though it appears to be free, we are actually paying for that. Somebody does, who else do you think it could be? So that $7 replacement camera battery could be sold for much less, if it wasn’t for the “free” shipping. That should tell us how cheaply made it really is.
On the one hand, not all Chinese cells are total junk. HP has certified one to provide cells for some of their packs.
On the other hand, from my perspective, your assumptions are shakey. I think you put too much faith in the supply chain management of US retailers and consumer brands. They’ve shoveled a huge amount of crap in pretty wrappers in the last decade or so. Don’t get me wrong. I’m not one of those people who paint Chinese made products with the same broad brush dipped in “crap;” Some Chinese made products are great quality, its just that a lot of US companies have done a poor job of making the transition to Chinese manufacturing.
I also disagree that a mainstream retail chain can be expected to sell for less than EBAY or an Internet reseller. Sure, 2nd day shipping costs something, but so does carrying inventory, rent, depreciation on fixtures and other assets, labor during off hours, and lets not forget marketing expenses and multiple layers of management overhead. Ebay sellers and other internet retailers can avoid a lot of that overhead. Their costs of merchandise can be lower too, because they can buy overstock and clearance, etc, rather than worrying about keeping specific items in stock.
Finally, how critical is the average consumer going to be of these powerbanks? We’ve probably all seen the reviews on amazon for rechargable batteries and power banks. Some people are quite critical, but a lot of them are happy if it works. And what’s the criteria for a working powerbank? Something like: 1) Does it charge my phone in a pinch? 2) Does it charge it enough to be worth buying/carrying? 3) Do the size and price seem reasonable? 4) Does it do anything that concerns me, like get hot, or melt, or catch fire.
Well, I think you can tell I am pretty disgusted with online sales of most of the stuff we buy here.
Of those 3 power banks that I mentioned in the OP, one had the “bad” chip and was no good from the get go. The other 2 had the “good” chip, and even though they were initially OK, they too failed after about 3 charges. I threw them all away. Lost a good cell too due to that crap.
When we buy off EBay, or even from some of the retailers online, we never know what we are going to get. Time and time again, even when an item is decent, next time around when we order, some thing is changed. Almost always for the worse and to the point it no longer functions properly.
As one example where retail beats online check this link for “scientific calculator” http://www.ebay.com/sch/i.html?\_from=R40&\_sacat=0&\_nkw=scientific+calculator&\_sop=15
That calculator I mentioned in the OP comes up a lot, always at a total cost of $4 or more.
I have never bought a flashlight from a retailer that didn’t at least work. Many times I have gotten 5 of 5, or 4 of 6 come through DOA from internet vendors.
I charged and discharged the included cell in my OPUS 3 times.
The cell says 2000 mAh, the package claims 1800 mAh, but in reality the cell tests out at 1500 mAh.
I can accept that, it is better than I expected.
I will now re-install the cell and see how this unit performs. Charging my cell phone, how it limits the discharge of the included cell and a simple test of how it charges back up. No sophisticated equipment, nor charts. Just a Charger Doctor and a DMM.
Well at least the package didn’t say 2600mAh like most of the power bank this kind does!
I believe 1500mAh will deliver between 1000mAh-1200mAh charge, taking into consideration driver loss and phone’s charging circuity loss. My iPhone 5 has a 1450mAh battery, but it takes 1700mAh to fully charge, measured with the portapow premium usb dc monitor.
I talked to some colleagues about those powerbanks yesterday, the average opinion was, if this thing is able to charge my iphone up to 50% I will be happy, becaue this helps me to get thru the day (the example of sitting in an airport check-in area came up quite often).
I tested my powerbank with the iphone of my so last night.
It was able to bring the iphone5s from 3% to 61% charge before turning itself off.
So I guess, the real capacity of the cell is around 1000mah ?
I’m a bit disapointed, I had hoped that it will hold enough juice to fully load a smartphone, but this also explains the short period of time needed to charge the powerbank.
Still watching, very interesting !
All the posts in this thread proves the opinion I’ve had in the past —-> buy an empty powerbank with easy access on the cells and feed it with the cells you prefer.
The Charge Booster/USB wrapper adapter I am working on (and the Dedicated Charger adapter/USB Wrapper) making (initial prototype had some issues) allows people to use unknown charge ports at airports w/o sacrificing security as it removes the data sync of the device but still allows it to charge…with that said even boosting a phone that is critically low to approx 50% is still a good thing.
No argument from me about the inconsistent quality from online sellers on ebay, and on various chinese sites. Given the way Amazon is these days, you can’t even buy from/through them without the risk that you’ll get some shady knockoff, while the listing and reviews are all for a name-brand item.
It’s just don’t put much more faith in retail either. I guess the one upside is that if you get something and it checks out, chances are the remaining stock will be from the same batch, but when that runs out, all bets are off. Also, you have a place to return/exchange it.
Sounds about like what I’d expect. People who rely on these things constantly will be more critical than those who get one because they run out of juice every once in a while, and even then, the assessment isn’t rigorously quantitative. As a result, retailers don’t have to worry too much if things don’t deliver on their claims.
Keep in mind the conversions, and the losses. The power from the cell gets boosted from ~3.7v to ~5v, to do so, it has to draw at least ~1.35x more current than it delivers, so to deliver 1000mAh, it needs to draw 1350mAh from the cell.
That assumes 100% efficiency, which isn’t going to happen. As I recall, a reasonably well designed boost converter can see ~90% efficiency, which means 1500mAh required. And then there are other losses as well, int he cable, and the phone.
Observations and theory seem to align
I’ve been looking for an inexpensive, good single-cell DIY powerbank. Seems like our choices aren’t great, and there is a lot of variation.
For what its worth this unit with included battery does pretty well. In my rough tests, capacity seems to be as claimed. Also, it can deliver 1.8A while maintaining voltage within USB spec (it drops to 4.75v at max current), not quite up to the power bank’s claimed spec, but not bad for a single cell powerbank (though not necessarily good for the cell). I haven’t been able to get the case open, so I don’t know whats inside.
When using the power bank to charge my iPhone 3G with it’s old and worn out battery, it charges it at a rate of 0.80A. As the iPhone charges up the charging current diminishes to zero. As the charge progresses, The Charger Doctor reports an output voltage of 5.17V throughout the whole process.
When I attempted to charge my iPad, The Charger Doctor reported a charging current of 0.90A. That is not really enough to charge an iPad, and I really didn’t expect it to be able to charge it. It doesn’t.
I also wanted to see how this unit handled itself as its internal cell ran down. I measured the voltage across the terminals of the cell as the depleted cell continues to try and charge my iPhone. At about 2.80V the iPhone complained that it was no longer attached to an authentic charging device even though the Charger Doctor was reporting a 0.20A draw. Shortly afterword all charging stopped and the display on the Charger Doctor went out. This means that the unit had disconnected and was no longer on. At that point the voltage across the internal cell was about 2.50V.
I was impressed that this unit always put out a constant 5.17V all the way to the end, right up until it shut off.
My simple conclusion is that this unit works, it will charge up devices that requite less than 1A charging. It doesn’t seem to overcharge devices, and i doesn’t over discharge itself as the internal cell runs down. I suppose any 1 cell power box is under powered and the included cell is only average, but this unit will do what most people would want it to do, give them a little more run time on their device in an emergency.
What remains for me to discern, is how long this unit will last. I hope I can get more than a few uses out of before it burns out as the ones I received from BuyInCoins did. This unit is WAY better than those.
FWIW, iPads that display “Not Charging” will charge, albeit more slowly, when the display/backlight shuts off. That backlight draws a lot of juice, and accounts for a majority of the power budget on iPads (and probably other ARM tablets). You figure they can charge in, what, 5 hours, at 2A, and once charged can get ~10h of runtime, so, the operating current draw is ~1A.
Just received my Miller ML-102 with V7.1 board, wanted to share with you the readings.
It puts out an incredible 1.8A without dropping from 5V. Not sure for how long it can perform like this. Only tested for 3 minutes, got a bit warm.
It charges @1.12A, but sends 1.25A to the battery (3.8V 18650BD). Charge controller instead of a linear regulator? Nice.
And most importantly, standby current with nothing plugged in is 0.2mA. IMO this is far better than any other single cell power bank. Definitely worth the $5. HKJ reviewed an earlier version of the ML-102 and I believe it has been drastically improved now.