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