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Review: 4 (2S2P) and 6 cell (2S3P) hardshell waterproof bicycle battery packs from GB

38K views 231 replies 15 participants last post by  bianchifan 
#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.
----------------------------------------------------------------------------------------

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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#64 ·
For indicator leds I thought I would just drill small (1.5-2 mm) holes in the top part of the case, fill them with hot glue and then just smooth out top and bottom part, that should work (also I hate riding when its raining so waterproofness should not be that big problem), for button I have small rubber boots for maglite flashlights and a set of tact switches with different stem lengths bought long time ago...
 
#65 ·
It would be nice if you can find out if your indicator circuit drains battery on it's own. Ie. it has parasitic drain. It is just we would be aware about it. If you can measure the current it would be perfect.

Otherwise it would be nice to see final result in a case.
 
#70 ·
I like doing business with GB because they provide so many good deals and its easy to comunicate with then, but today they were too slow :p
Woke up this morning, powered on my computer and first thing I see in my emails is BG promo: "1st Round of XiaoMi Week!" (I am telling you, they read ths forum, BLF as well :) ) I missed the last deal so I had to be quick this time, first this I did, before going to toilet, was to buy those 2 banks :D then breakfast and then off to work... :p
 
#71 ·
Yup, at the moment GB has the best price. I would suggest anyone interested to buy now. I don't think the price would be any lower in the future since the Panasonic cells alone would cost you more elsewhere. And there is high possibilty to fake ones will apear in a short time as can be seen with 10500mAh version -> see on Youtube .
 
#79 ·
I've just got the Hunk Lee balancing PCM. For testing purposes I've soldered it to the unbalanced 2S3P pack with cells taken from 6cell case described in the first post. Curently voltages are 3.76V and 3.90V for each set in series. After soldering it needed reset ie. few seconds of power from charger in order to give output to the light.

Will leave it over the night and see if the cells gets balanced. If not, balancing probably works only during charging, Will see.....
 
#80 ·
So I just riped the two powerbanks appart I've got.
I fully charged both of them overnight.
Fully charged the pack has a voltage of 4.26V, seems like too much imo. I charged two phones with the packs to get them down to 4.18V.
Sadly I destroyed one of the PCBs while tearing the pack apart (screwdriver slipped off into some small SMD component and ripped it off)
Don't try to tear the welded contacts off of the PCB, just cut them >_>

Lets see what I can find to make a waterproof battery pack of these, ordered this cable to use it with the Nitefighter BT70: Cheap 5.4mm Male to Female Extension Cable for SKU 29489/30864 (100cm)
Hopefully the wire used in it is thick enough.
 
#81 ·
The wire from DX is about 20AWG and is thick enough even for higher currents.

4.26V is just on the top of alowed limits, no big problem, except regular charging to that level would shorten litefetime/capacity. On the other hand power bank circuit consumes some power (parasitic drain) so the voltage would get lower anyway.

To report about Hunk Lee PCM. Over the night cells didn't balance itself. Voltages have been 3.77V and 3.89V. Difference 0.01V to previous reading could be difference in the measurments and/or due pure cells I'm using for this test.
Now I'm charging the pack to see what happens during that process.
 
#83 · (Edited)
EDIT: Some more explanations from post #107 onward. I might be wrong at some points, so not all below is correct. At least it's NOT total CRAP.

I've been trying Hunk Lee balancing protection module (PCM) last few days and can tell it's A JOKE, CRAP, whatever you like in regarding balancing feature. Totaly wrongly designed. Did not test other functions except overcharging kicks in at 4.29V on any set in series.

I've been discussing with Hunk and he doesn't want to admit balancing feature in this PCM is useless. He is taking some reasons for it's usenes which should never happen. Here is his description of balancing feature:

"If the voltage of one set of battery is lower (A), the other one is higher (B) during charging, when charging voltage up to 8.5V(4.25V each) around, the circuit over-charging action and stop charging, balance function begin to work, first the battery B discharging , if the whole voltage low than 8.5V, over-charging switch off and begin to charging whole battery again. Re-stop when the voltage up to over-charging voltage, then the battery B re-discharging.
Need much more cycling to get same voltage, not in one cycle in charging and discharging.
"

In the first place proper charger should never charge as high as 8.5V so the balancing function would NEVER happen and indeed it does not. I have tested situation with set A of cells at 4.19V and the other name it B at 4.00V before start charging, so 8.2V for the whole pack. After charging some time, set A reaches 4.29V and PCM cut off the whole charging which never restarts.

Since Hunk Lee also writes:

"First, balance function is only apply to small voltage tolerance between two sets of battery. As the balance current is very small, higher tolerance voltage need more cycle charging and discharging to get same voltage."

I've tried it with small difference. Again with good charger the whole voltage of the pack couldn't reach 8.5V so as expected balancing didn't take the place.

Then Hunk says:

"What you said is correct, the professional charger is no more than 8.4V, like the chargers in our stock.
So not only PCM but also charger protect Lithium battery, more safe.
But someone may use 9V charger to charge battery as they haven't the knowledge of battery and charger.
"

So if one not knowing is using bad charger (ie voltages from 8.5V to 9V) might experience balancing while the others using proper charger can't. WTF.

Will see what Hunk have to say next as we are all using good chargers.
 
#87 ·
Well, protection features should work, but this PCM is to expensive for that only. Archie might help us with some ideas. Maybe resistor mod or something. If we lower the trigger when "balancing" (ie discharging) starts we might get out the working stuff.

Of course I'll continue discussion with Hunk to see what he can do. I've got feeling he has low attitue on this issue.
 
#90 ·
Oh wow! Didn't expect to hear it's crap! At least I only bought one!
@Garry, so far it looks only balancing feature is a crap, but this is why we've bought this PCM, isn't it?
I didn't expect to work like this either. Actulay I was trying to get some info from Hunk before, but couldn't get anything usable until I bought a pair and starts testing and complaining. Then he has answered as I wrote above.

@sirius. If you look closer you would see balancing feature in all hobby chargers works in the similar way ie. discharging single set of cells after charging all. Hobby chargers charge over the main port and check and discharge over balancing port when using balance charge mode. This is done until all cells (or set of cells) in series reach 4.20V (or whatever you have set). Of course this is not the most efficient way of charging. It would be better to work like in the multibay chargers. But can it be done so once they are assembled into the pack? Multibay chargers use common negative side while hobby chargers can't and so can't this Hunk Lee PCM.

I'm not EE but Achie might hopefuly explain the situation and possible solutions. The only thing I can think of is using big capacitor and temporary store energy from higher cell in it, switch to another cell and release energy from the capacitor to it. Not shure electricaly this can be done. I'm imaging this like you have two barrels of watter and use tiny coffe cup to equalize their levels.
 
#89 ·
Generally even if you use balance charger like accucell 6 balancing works kind of funky: first it charges all cells and when it detects overcharging of one side of the pack (let's say it's 2S2P pack and one side of the pack is at 8.2V and the other side is at 8.5V) then it stops charging both sides, start discharging overcharged side until they are both at 8.2V, then starts charging again both sides and so on, very time consuming process because of quite low charging current in balancing regime.

I think you mentioned this but I was also thinking the same thing/idea for a long time: making each cell as a independent unit. Each cell would be equipped with its own charging/discharging control unit so battery packs would be highly modular and scalable systems, just plug couple more cells to get desired capacity or reconfigure their connection to get desired voltage. Something similar as if you were to use protected cells except kicking off protection on one cell would not power down entire pack..
 
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