DIY 18650 protection?

Has anyone here added protection to harvested 18650 cells?

I ran across this at DX:
http://www.dealextreme.com/details.dx/sku.26112

I would not have known what I was looking at, if it wasn't for the two threads showing disassembled protected cells.

I've got several unprotected 18650 cells sitting around but I rarely use them. If I could add protection, I'd be more likely to use them.

I suppose I'd use heat shrink over the battery after applying, right?

I am planning on trying this. I will let you know how it goes. It's not big priority though, so may take a few weeks.

The Protection Circuit from All Battery

has pads for B+, B-, P+, P-

They're instructions are:

Connection Port illumination

1. B+: Connec to cell's anode

2. B-: Connect to cell's cathode

3. P+: connect to the cell's output or charger's anode

4. P-: connect to the cell's output or charger's cathode

Click to expand...

but I'm still not clear on how to connect it
for a single 18650 do both P+ and B+ have a wire going to the anode, and same for the other two pads?

and can someone help on choice for wire...i'd like to use a pair from cat-5

Thanks,

ps: interesting I can't find any specific directions for this anywhere on the Internet, guess this is that serious...?

pps: I accept responsibility for my actions

18650 Shrink Tubing= 32mm

FYI
All Battery shrink tubing for 18650 please choose 32mm, not 19mm. (their sizes are not diameter)

Please find the typical wiring diagram for a single li-ion battery.

I apologize for not knowing how to read this diagram. I do have good solder technique. Can anyone help a layman understand how to use these boards? Specifically where each pad needs to go to or whether all four need to be used in a single cell configuration?

Thanks in advance,

Unenlightened


ps: I asked the supplier and they said it depends on how I want to configure it. (then I spent several hours on on the internet...nada)

The solder pad P+ and B+ on the board were wired together. P+ is an optional solder pad for the battery pack which doesn't use the positive battery pin as contact point.

thank you very much, i see the trace under the resist now

can i get away with using a pair from some cat-5? or even just one wire - it's not really carrying the load just isolating the negative if tripped?

In theory, the thicker the wire is better because thin wire increase the resistance of the circuit. I would like to remind you not to use Cat-5 cable because the insolator of the Cat-5 cable is made of PE which can not withstand temperature above 70 degree C. When you solder the wire to the battery, the insolator will melt. Flat metal stripe is excellent for this job.

I've been searching for flat wire, but don't know the right search terms I guess, can anybody point me in the right direction? I can't find any online and don't have a shop locally. (I think I found similar on alibaba, but no use for that much wire)

these are the most expensive free batteries in the whole world i think, given the time i've spent

There are two risks in adding Protection PCBs to LiIon cells

1. Soldering to the cells will risk an explosion or permanent damage to capacity at best. You can only use cells which have solder tabs.

2. A wire from the positive button needs to run down to the Protection PCB - you must be absolutely certain that this wire cannot short out to the case - you will have a fire !

MikeAusC said:

There are two risks in adding Protection PCBs to LiIon cells

Click to expand...

VWFringe said:

pps: I accept responsibility for my actions

Click to expand...

i have a hakko 456-16 60watt soldering iron, suitable for fast soldering on Li-Ion cells

where can i find the wire?

i think it's a given this should not be done by someone who is not fully aware of the methods and dangers involved, but leaving the cells unprotected for e-cigarette use would be worse.

I hope this just isn't done much and isn't a secret, hahaha

You ask: "Where can I find the wire?". But the item at DX that you link to in the first post of this thread has the metal strips already connected, ready for welding (or soldering).

MikeAusC said:

There are two risks in adding Protection PCBs to LiIon cells

1. Soldering to the cells will risk an explosion or permanent damage to capacity at best. You can only use cells which have solder tabs.

Click to expand...

I beg to differ. I wrote a guide just for this.

I don't guarantee you won't set fire to stuff by doing that (as clearly stated in the disclaimer), but as far as I'm concerned, LiIons are quite solderable if you know what you're doing.

That said, for a while now I've only considered buying flashlights that have protection circuits built in the driver, and if I had one without I'd solder the protection circuitry to the driver, not to the cell, because using protected 18650s has size complications, and protected cells are more expensive.

Fallingwater said:

[...]and if I had one without I'd solder the protection circuitry to the driver, not to the cell, because using protected 18650s has size complications, and protected cells are more expensive.

Click to expand...

An excellent idea! Now you have protection for any unprotected cell you use in the light, and can buy cheaper, unprotected cells, from known good manufacturers, but still avoid many of the risks.

so i guess the wire's not available,

i very much appreciate the idea to protect the e-cig instead of the battery - it actually solves the problem of having to fabricate a battery terminal, lol, hahahaha

and accomplishes the main thing they need, since the charger they're getting does cc/cv well (thanks to the reviews on this site!), which is prevent them from vaping it down to an unchargeable state!

There are 3 functions for the protection circuit.
1) Overcharge protection 2) Over discharge protection 3) Short circuit protection.
If the protection built in to the driver, overcharge and short circuit protections are dismantled. In order to minimize the risks, you would put the battery back to the torch immediately after recharge. So, a charging connection should also be built in.

Regarding the flat matel wire, do you think the desoldering braid can help? It is copper, flexible, solderable, and flat but not so thin.

someone on ECF suggested contacting my local Batteries Plus store, as salvaging the flat wire maybe possible from dead cells
i'll report back if that's any luck

as to braid, cool idea,

need to buy kapton tape also, lol, free batteries, lol

EDIT:

There are 3 functions for the protection circuit.

Click to expand...

I did understand that wiring it in wouldn't be the same

Hi VWFringe,

Did you read this thread? http://www.lygte-info.dk/info/battery%20protection%20UK.html
It's worth to have a look.