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Discussion Starter · #1 · (Edited)
I've already wrote about those in another battery thread. I've got them to test real capacity from Gearbest. They choose to release coupon code to lower the price:

Black Iron Metal Technology Wire

2600mAh 8.4V 4 x 18650 Portable Rechargeable Water - resistant Battery Pack-12.07 and Free Shipping| GearBest.com
$10.59 with Coupon: 4Bpack

Cable Technology Wire Still life photography Circle

8.4V 3900mAh 6 x 18650 Portable Rechargeable Water - resistant Battery Pack-15.95 and Free Shipping| GearBest.com
$13.69 with Coupon: 6BPack

Funny I have realized today those are copies of Magishine MJ-6038 and MJ-6036S

OK, let start. Both are made from plastic and has standard Magischine type connector 5.5x2.1mm. Cable is flat and mid sized. Both packs has rubber straps to be mounted on the bicycle frame. Alli in all the look is good.

Teardown has been done with screwdriver prying edge between the top and the body. To get to that point you can move ruber band to the bottom. Inside was welded pack with foam on every side to prevent rattling:


It is good there is zip tye to prevent pulling cable out:


The cells are unknow (no markings) with small protection circuit:


Protection circuit:


After full charge and one day rest I discharged 2S2P pack with iCharger 106B+ at 2A down to 5.6V and I've measured only 2198mAh. Since the pack is very likely unbalanced I would give it bit more, but not much.
Here is the discharge graph:


Similar to the previous one the 6 cell pack has only 3273mAh. The voltage falls down so fast that protection trips in before charger realize it reached 5.6V. Discharge graph:


Discharge graph of 4cell pack showing each pair of cells. You can see one pair is fairly good (ie. it has smooth curve) and the other is having some trouble.



I've done the same for 6 cell pack..... After charging pack it is noticeably unbalanced with 4.24V and 4.13V for each set of 3cels.
6cell pack is also having some issues and quite some difference between 2 sets in series.


Gearbest has corrected their description of the capacity based on my test. Not exactly the same figures, but close enough.
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DIY PART

Q: why would one buy these quite limited capacity packs?

A: For anyone who have some soldering skills and can do some modifications those packs might be very usable. Imagine you would have 10000mAh battery pack for a very long rides or for very power hungry lights.
How much would that cost? See it at Action Led Lights or Magicshine. How about half of that price and having balancing feature included in the battery pack. Sounds to good to be true? I don't think so.

What parts would you need for self balancing 6cell pack:

1. Disassembled batery pack from the top of this post
2. Two pieces of Original Xiaomi Pocket 10000mAh Mobile Power Bank
3. Protective/Balancing circuit from Hunk Lee: 4A or 7A version
4. Soldering station and some tools, Kapton tape would be nice too
5. Optionaly some older 18650 cells to make Xiaomi power banks usable

How to do it? Luckily I've got 10000mAh Xiaomi power bank today. I've dissassebled it to see if the cells are the ones and YES they ARE Panasonic (Sanyo) NCR18650BF the 3350mAh cells. Dissassembling is described HERE.

So you have to use two power banks to get two sets of cells and make an 2S3P pack. Since they are already welded you need to do just few additional connections.
Will post pictures later on...

Protection/balancing circuit should be properly soldered and nicely put into the shell. You can imagine all those dirty details to do.

Actualy I haven't done that mod yet, but I've used an old laptop pack and salvaged 6 Panasonic 2900 cells from 3S3P pack where 3 cells are already welded, just like with power bank. I've soldered together two sets and put into the pack without protection. It works nicely and there is enough room for protection circuit. I'm not shure it can fit with smaller 2S2P pack. It might fit verticaly, but it remains to be seen....
Old Panasonic cells:


I will have to wait for another power bank and protection circuit to actualy finish this DIY. But idea is doable and you might want to repeat it.

Will continue with some correction of the pictures later on or at the end ....

Edit 9.9.2015:
I would need to add the PCM doesn't have to be neccessary balancing one. Anyway I would go with the higher current ones as they have less resistance and are more apropriate for the BT70 type of lights.
Hunk Lee has some - HERE. Take a look detailed description of each where you can see Maximal continuous Discharging current. Be aware of Over charge detection voltage, some are for 4.30V cells - like this.
 

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Discussion Starter · #4 ·
Archie, yes that could be nice so we can finaly build high quality battery packs. It would be fine to find similar cheap and quality 2 cell power bank with cells welded.
 

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Very good idea. So for around $50 you can get make a 6-cell 10Ah panasonic battery. That make is possible to run those 4 amp lightheads (bt70 turbo) for over 2.5 hours.


My only concern is how waterproof the pack is after you put it back together.
 

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Do those Hunk Lee circuits actually provide balancing? How can they if they simply connect to positive and negative of the assembled pack?

Awaiting pics. Tempted to pick up two of those power banks!

-Garry
 

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Discussion Starter · #8 · (Edited)
varider, I think you even not need to glue it back if you don't want. You can use just some duct tape. Or if glued maybe add some sealant and you are done. I would do it also at the bottom if you want perfectly waterproofed pack.
 

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Discussion Starter · #9 · (Edited)
Garry, in specifications says: "Balance current for single cell 70mA" and you can see it is differently constructed if you compare it with any other PCM.

Circuit component Electronic component Technology Electronics Electronic engineering


You won't see the pictures of complete DIY from my side very soon since it takes much more time to get anything from China than you do in US. This PCM has just been sent. So 3 weeks at best until it arrives.
 

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If Original 16000mAh Xiaomi Mobile Power Bank Aluminium Alloy Material for Samsung S6 HTC ONE M9 Tablet PC Smart Phone etc-23.99 and Free Shipping| GearBest.com would be cheaper then you could get 2S2P + 2S3P cells out of two devices. There are LG 3200 cells installed. So we could make nice 6400 and 9600mAh packs.
OR...if you wanted you could just buy a Hunk Lee battery pack of your choice and fit it inside the case. Heck, since they're both coming from China why not?

Anyway, thanks for the review ledo. Didn't surprise me that the cells in these things were crap. ...And speaking of crap; I would of crapped myself if you'd of said these were built with Samsung, Panasonic/Sanyo or BAK cells. ;)
 

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Discussion Starter · #12 ·
Just finished discharge test of a 3P cells in the Xiaomi Power bank and got 9690mAh down to 2.8V at 3A load (1A per cell). Since the cells are declared down to 2.5V I can conclude they are true 3350mAh (on average) cells. I think it's hardly you get better price elsewhere for those cells and power bank shell as a bonus.
 

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Just finished discharge test of a 3P cells in the Xiaomi Power bank and got 9690mAh down to 2.8V at 3A load (1A per cell). Since the cells are declared down to 2.5V I can conclude they are true 3350mAh (on average) cells. I think it's hardly you get better price elsewhere for those cells and power bank shell as a bonus.
Okay, I'm a little confused. This power bank, this is something used to charge cell phones right? Usually these kinds of power banks are limited to a certain current output. I've never seen one more than 2A. I looked at the output rating for the Xiaomi Power bank 16000 and supposedly it is rated to 2.1A maximum current output.

Anyway, LG is a good make of cell. Should make a fine battery pack. Yeah, a Hunk Lee battery might be a little more money but then again it's all wired up with a protection board already in place. All you would have to do is cut and splice the power leads to the connector on the case, put some foam around the cells to keep them from rattling and you should be set. ( not to mention you get to choose the brand cells you want it built with ). I'm not knocking your DIY idea just pointing out an easier option for people who wouldn't want to wire up a board and do all the soldering.
 

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Discussion Starter · #14 ·
Cat, of course I've tested bare cells not the power bank circuit since we are interested in the cells, right? Device was dissassembeld to get to the cells. I've connected them with aligator clips directly to my iCharger 106B+ which was set to 3A discharge and Li-lo limit at 2.8V. So again I can confirm in the 10000mAh power bank there are geniue Panasonic NCR18650BF cells.

LG cells are supposed to be in a 16000mAh power bank.

I agree Hunk's packs are more or less ready to go, but the main goal here (besides cells itselfs) is the balancing circuit. So no more worries the cells are out of balance. Hunk says he doesn't use balancing type of circuits in his packs. He is using only protection features.
 

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EDIT - Sorry, ledoman beat me to it.

Cat, ledoman has removed the cells from the power bank and tested them on a hobby charger. The power bank circuitry has no effect.

I still don't get how you're ending up with balancing with only two battery connections. Hopefully it will be clearer once you finish the DIY build posts.

-Garry
 

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Discussion Starter · #17 ·
Garry, where did you get "only two battery connections"? I see ordinary 5 connection points, 2 external (P+/-) and 3 internal (B+/-, MB).

Photograph Colorfulness Line Monochrome Black-and-white


See all the pictures from the link on the picture above.
 

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Typically with those protection boards, B+ and B- is where you hook up the + and - ends of a 2S pack and MB would be the center tap of the pack. P+ and P- is for the load, so that's for the cable that goes off to the light.
 

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Ok, so having that "MB" connected between the two sets of parallel cells (two sets of parallel cells then connected in series) provides the balancing? So it's not providing balancing to each individual cell, but to each parallel bank of cells? This makes sense to me.

-Garry
 
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