I just bought on Ebay. I've been looking for years for something like this that met my requirements. I have not found anything until last week. It probably comes in many names but I'm pretty sure it is the same unit inside. It's THIS. This thing is awesome. It does everything automatically. You don't have to press any buttons or anything. You just plug in what ever you want and it just starts charging. Extremely cool front panel readout. Tells you two different amp readouts for the outputs on back. When you need to charge it you just plug it in, the little battery meters start moving up sequentially till its full when it just sits there with all 4 meters pegged. I popped 4 efest 3500's in it and charged my note 4 and the meter did not even move down when it was done. The price was right also. That particular seller shipped relatively quickly. So that's around 14,000mAh available when you need it. Oh, and it will run on any number of 18650's, does not need all 4. Not too bulky, I pack it around now in my man bag. Love it! Check it out.
Amazon has the same thing but named ‘TOMO usb battery bank’ listed at $18.89; YouTube has a review under ‘TOMO usb battery bank review’.
13.29$ at Gearbest 
Ordered one. Thanks 
The famous “TOMO DIY powerbank”… I bought one some time ago when it was on sale on GB, while it is easy to use and convenient if you have lots of 18650s lying around, the efficiency is mediocre at best. Using a single cell to power a 5V 1.5A output the total efficiency was under 70%, dropping quickly after the cell was below 3.8V. The low voltage cutout was too high for modern cells an the output wasn’t properly coded for fastest charge rate. This is due to the use of generic boost controller chips and low quality inductors.
I mention all these technical details and flaws because I have lots of other powerbanks to compare it with and some of them can achieve an impressive efficiency of 94% (YZXStudio 7th gen). But for a regular user this could be a handy device, if you want to use one cell at a time I recommend the Miller ML102, it can achieve 80%+ efficiency under optimal conditions.
Personally speaking I wouldn’t spend $13 on this powerbank host, you can get a xiaomi 10,000 powerbank at this price with already 3x LG F1 cells included and very good efficiency at 86%.
I ordered this board to build a big power bank out of old laptop cells. Do you think it will be any good?
Hard to say if it’s good or not by just looking at it and a test is always required. But the rule of thumb is that these DIY boards normally have low efficiency because of:
-High low cutoff voltage, often 3-3.3V which drastically reduces capacity for modern cells which can be safely discharge to 2.5V
-The use of generic or copy boost chips and low quality components.
-Incorrect output coding causing the device to not use all of the supplied power.
For £7,74 I would just spend a bit more get a cheap and reliable powerbank like the xiaomi 10ah and just use the circuit inside if you plan to upgrade the capacity, or use dedicated boost converters with dedicated high efficiency boost chips like this one: http://www.ebay.com/itm/121728774027 However this is not optimized for a powerbank because the output is not coded in anyway, there is only - & + output leads.
What I’m trying to say is the best way to DIY a powerbank is to use an existing circuit, it is actually cheaper and works better this way.
I could care less about how much energy it wastes. It works well for recharging your rechargeable devices. For me anyway. Apparently it is a piece of garbage by the quick reviews here. Again, it works really well for me and I like it and would recommend it.
I ordered one even though I have a couple of highly rated power banks from Anker and Xiaomi. I have plenty of 18650 laptop pulls laying around doing nothing. I might as well put some of them to good use. I’m with you. I don’t give a rat’s ass about efficiency.
This is the link where I first became aware of the YZXstudio Power Monitor.
The 8th gen is out, it has a even more powerful input chip capable of supplying 15A+ into the batteries where the 7th only does 4.5A. It comes with a color OLED display and a updated coulometer for more a more precise capacity readout. In the chongdiantou forum it is said this 8th gen can achieve 96.5% peak efficiency with a 5V 1A load. However its soldered battery design doesn’t allow quick cell replacement like the 7th gen. It is available here: https://yzxstudio.world.taobao.com/
A seller on ebay called “DZ-Studio” can have it shipped to you with some added cost, last time I checked with him he wanted $135 for the 28,000mAh 8x LG MJ1 version. Actually not so bad considering all the technology behind this device, the components are simply top-notch.
I also have the complete discharge results of my 7th gen, will find some time to post the review. The efficiency have actually dropped a bit to 93.5% at 5V1A because of me constantly discharging the cells to 2.5V (lowest possible LVP), I guess there is some capacity and performance loss.
These work great in an emergency if you need power and you are in a black out i guess. We all have so many lights so we have so many 18650s around.
They sound good will34 if you want mass storage that is semi portable have you thought about a small deep cycle battery?
Thank you will34 for the update on these products.
USB output is 5V on one side and QC 2.0 on the other, both adjustable +/- 0.3V, useful to compensate cable losses.
DC jack is for input and has 5-12V range, micro USB input can take up to 9V 2.3A before hitting the limit for the 4.5A charge current to the batteries.
No English UI, it did took me some time to figure everything out.
frankie tung at 99centhobbies ebay is where I try to purchase yzxstudio products. He can on request provide an English translation of instructions on some products.
Thanks for the product reviews. I can appreciate the benefits of higher efficiency.
The xiaomi 10,000 power banks seem to be closer to $30 than $13. At least on ebay. Where can they be had for $13 ?
Zebretta,
I do not know where one can be purchased for $13, but here is a price of $21.
http://www.gearbest.com/xiaomi-10,000-power-banks-\_gear/
Jerry
I saw this one on Amazon. Any info on it?
https://www.amazon.com/AUKEY-16000mAh-Portable-Charger-Samsung/dp/B01B2NWTGG/ref=sr_1_8?s=mobile-apps&ie=UTF8&qid=1483741889&sr=8-8&keywords=xiaomi-16%2C000-power-banks
Jerry
I got one of these from TMart for a review. It's under their own brand TLIFE.
I thought I recognized it from somewhere :)
Ok, I bought one of the Tomo Power Banks from Gearbeat for just under $13
What’s REALLY impressive is that GearBest got it to me in the 12 days advertised……from CHINA……during the Chinese New Year !! (That blew me away)