how to safely remove battery cells from powerbank?

[Paingamesyt]

I have old powerbank from Xiaomi (16,000mAh) but it's broken charge port and now i cant even use it. I want to remove battery cells and use it on something else. 

 

Now how do i safely remove them without damaging battery cells or worse, catch them on fire  

 

Here is the battery that i have and plan to remove battery cells: 

 

[limewire]

I'm gonna be honest, if this is a question that you're asking I'd honestly leave it alone if I were you.

 

New 18650s aren't that expensive, but you have to consider charging and battery management if you want to use them in some DIY electronics project.

 

[manikyath]

cut off the + wire, then cut off the - wire, and make sure they dont touch.

 

lithium batteries arent some ticking timebomb, just make absolute fcking sure to not:

- short circuit

- overcharge

- overdischarge

- poke holes in them

[TempestCatto]

Unless you really want to dive in and learn and do a fun diy project, I'd sooner recycle the current bank and get yourself a newer much more powerful one. Just my two Canadian cents.

[limewire]

3 minutes ago, manikyath said:

cut off the + wire, then cut off the - wire, and make sure they dont touch.

 

Actually, you do the opposite of this, as if you snip a positive lead while it is still part of a complete circuit it is likely to spark/heat up the cells as they try to dump power through a point of high resistance (your flush cutters, scissors, etc which are probably conductive and completing the circuit while the conductor is cut)

 

If you snip a negative first it makes the circuit incomplete and much safer to work with.

[manikyath]

5 minutes ago, limewire said:

Actually, you do the opposite of this, as if you snip a positive lead while it is still part of a complete circuit it is likely to spark/heat up the cells as they try to dump power through a point of high resistance (your flush cutters, scissors, etc which are probably conductive and completing the circuit while the conductor is cut)

 

If you snip a negative first it makes the circuit incomplete and much safer to work with.

false.

 

the direction doesnt matter anything, because there is no ground reference. the circuit is the exact same seeing the + as your ground or the - as your ground (when the battery + is ground, the - would be seen as a "negative voltage source"), and no matter where in the chain you cut you will introduce essentially the same amount of resistance doing the cut. a circuit requires a complete loop, and no matter where in that loop you cut, the result is the same.

 

also - at work (i'm a battery repair technician by the way..) we sort of have a habit that if a battery pack has a wire between different cells in series (we see anywhere between 7S all the way up to 20S regularly), we cut that wire first so that the potential total voltage is already halved while we do the rest.

 

on that note.. if anyone's gonna pop in and talk about an electrocution hazard, 4.2 volts isnt enough to properly pierce the human skin, let alone drive propper current trough the human body. i'm well aware that cell pack can probably do upwards of 10A, but that will never happen by a human fingering battery terminals. we handle up to 10S bare hand at work, because it's just safer to feel what you're doing. (and to be honest.. we handle 20S bare hand too, we just take precautions not to grab the pack *across* the end terminals with 74 volts on it, because that does give a nice tingle.)

[limewire]

Just now, manikyath said:

because there is no ground reference

okay yeah actually that makes sense, i'm used to auto electronics which uses the vehicle chassis as a ground so i guess that sort of tracks

[Agall]

53 minutes ago, limewire said:

okay yeah actually that makes sense, i'm used to auto electronics which uses the vehicle chassis as a ground so i guess that sort of tracks

Technically electron flow is from negative to positive. Overall if you're not creating a circuit from whatever through yourself or tools, then either side will work. I personally stick to always connecting+disconnecting the negative first since its generally the grounding connection. I'd rather ground it first in case there's any residual voltage, so less surge when completing the circuit in theory (also how I was trained).

[Agall]

1 hour ago, manikyath said:

false.

 

the direction doesnt matter anything, because there is no ground reference. the circuit is the exact same seeing the + as your ground or the - as your ground (when the battery + is ground, the - would be seen as a "negative voltage source"), and no matter where in the chain you cut you will introduce essentially the same amount of resistance doing the cut. a circuit requires a complete loop, and no matter where in that loop you cut, the result is the same.

 

also - at work (i'm a battery repair technician by the way..) we sort of have a habit that if a battery pack has a wire between different cells in series (we see anywhere between 7S all the way up to 20S regularly), we cut that wire first so that the potential total voltage is already halved while we do the rest.

 

on that note.. if anyone's gonna pop in and talk about an electrocution hazard, 4.2 volts isnt enough to properly pierce the human skin, let alone drive propper current trough the human body. i'm well aware that cell pack can probably do upwards of 10A, but that will never happen by a human fingering battery terminals. we handle up to 10S bare hand at work, because it's just safer to feel what you're doing. (and to be honest.. we handle 20S bare hand too, we just take precautions not to grab the pack *across* the end terminals with 74 volts on it, because that does give a nice tingle.)

Metrics we would use is the 1, 10, 100 mA rule, but that was with higher wattage/voltage circuitry. 

 

1mA and you'll notice, 10mA and you'll REALLY notice, 100mA and it might stop your heart. This is also assuming you're receiving it for a couple of seconds and there's a low enough skin resistance due to perspiration or cuts and that its across the heart, so from hand to hand. Although, If you stabbed two metal spikes into each thumb close enough to a nerve on both sides and connected it to a 9V battery, your heart might stop from it.

[manikyath]

3 minutes ago, Agall said:

Technically electron flow is from negative to positive. Overall if you're not creating a circuit from whatever through yourself or tools, then either side will work. I personally stick to always connecting+disconnecting the negative first since its generally the grounding connection. I'd rather ground it first in case there's any residual voltage, so less surge when completing the circuit in theory (also how I was trained).

but if there is no reference, the surge is exactly the same with connecting positive first as negative first. (except in automotive, because weird tings with grounding there)

 

having that said.. 'disconnecting from high to low' and 'connecting from low to high' is sort of how most stuff around li-ion batteries is designed. irrelevant here because it's literally two wires, so there is no circuit until everything is connected.

1 minute ago, Agall said:

assuming there's a low enough skin resistance due to perspiration or cuts and that its across the heart

if this is a problem with 4.2 volts, i should have died last time i groped 84 volts.

 

you would have to actually poke two probes nice and deep in your flesh to get anything low enough to get enough conductivity that you get 100mA trough your heart.

[Agall]

2 minutes ago, manikyath said:

 

you would have to actually poke two probes nice and deep in your flesh to get anything low enough to get enough conductivity that you get 100mA trough your heart.

Back in the Navy there was a sea story about someone doing this with a Fluke 189 by deeply stabbing their thumbs with the leads and dying  Obviously not true (hopefully) but is potentially a scenario where you could get that 100mA across the heart for a couple seconds.

[Paingamesyt]

2 hours ago, limewire said:

I'm gonna be honest, if this is a question that you're asking I'd honestly leave it alone if I were you.

 

New 18650s aren't that expensive, but you have to consider charging and battery management if you want to use them in some DIY electronics project.

 

Hate to throw if i can salvage cells, i can use them in something. 

2 hours ago, TempestCatto said:

Unless you really want to dive in and learn and do a fun diy project, I'd sooner recycle the current bank and get yourself a newer much more powerful one. Just my two Canadian cents.

Not DIY but they can be usefull, 

 

2 hours ago, manikyath said:

false.

 

the direction doesnt matter anything, because there is no ground reference. the circuit is the exact same seeing the + as your ground or the - as your ground (when the battery + is ground, the - would be seen as a "negative voltage source"), and no matter where in the chain you cut you will introduce essentially the same amount of resistance doing the cut. a circuit requires a complete loop, and no matter where in that loop you cut, the result is the same.

 

also - at work (i'm a battery repair technician by the way..) we sort of have a habit that if a battery pack has a wire between different cells in series (we see anywhere between 7S all the way up to 20S regularly), we cut that wire first so that the potential total voltage is already halved while we do the rest.

 

on that note.. if anyone's gonna pop in and talk about an electrocution hazard, 4.2 volts isnt enough to properly pierce the human skin, let alone drive propper current trough the human body. i'm well aware that cell pack can probably do upwards of 10A, but that will never happen by a human fingering battery terminals. we handle up to 10S bare hand at work, because it's just safer to feel what you're doing. (and to be honest.. we handle 20S bare hand too, we just take precautions not to grab the pack *across* the end terminals with 74 volts on it, because that does give a nice tingle.)

Does this mean i go first + to cut then - 

 

The battery have 2.7v so i think it will nothing happen  Also do i cut the 3 connection where are 3 battery connected at - side. 

 

On this type of powerbank, 3 battery are separetad from these 2. (i think that on this board it have 2 plus and 1 minus)

 

Plus is on side where is charging port, that plus is for 2 battery that are connected and top 3 battery are separetad. I think it is  

 

Anyway thanks for info  Love ya

[manikyath]

2 minutes ago, Paingamesyt said:

Does this mean i go first + to cut then - 

it doesnt matter, as long as you mke sure to cut one, then cut the other. it was more meant as a "dont cut both simultaniously" thing initially.

2 minutes ago, Paingamesyt said:

The battery have 2.7v

that's not a good sign.. that's WAY low for it to be settled down at.  you're probably dealing with some very deteriorated cells here, so they may not even be worth salvaging for other projects.

4 minutes ago, Paingamesyt said:

 Also do i cut the 3 connection where are 3 battery connected at - side. 

just cut the ties between the cells and the circuit board one at a time, make sure not to short out the wires to the sides of the cells (if you're using sharp snips, they'll poke right trough the plastic protecting the cells), and make sure nothing wil touch what it shouldnt after you're done snipping them off.