[SPLIT] Test: Can overcharge/discharge light up 18650 with fuses attached

daromer

daromer

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ozz93666 said:
With these fuses it's 100% guaranteed certain no fire can in anyway start!
Click to expand...

Im afraid that is not true. Just because we have the fuses it does not make it 100% safe. It does not protect against over or under voltage. Neither does it protect for over current unless you go above the fuse rating. For instance charging to 5V@3A wont trigger any of our fuses we have used :=)

The fuses are there for dead short protection and only protects against that.

ozz93666 said:
Measuring each cells capacity to the nearest mA has no effect on improving safety.
Click to expand...

This on the other hand i agree on. I measure it to nearest 100mAh. In general just contact problem can cause more issues than last 2mAh you get out :)

On the other hand i would not leave them out at all. Im using them and will be using them on 2nd hand cells all day long.



Originates from: http://secondlifestorage.com/showthread.php?tid=514&pid=3562#pid3562
 
daromer said:
ozz93666 said:
With these fuses it's 100% guaranteed certain no fire can in anyway start!
Click to expand...

Im afraid that is not true. Just because we have the fuses it does not make it 100% safe. It does not protect against over or under voltage. Neither does it protect for over current unless you go above the fuse rating. For instance charging to 5V@3A wont trigger any of our fuses we have used :=)

The fuses are there for dead short protection and only protects against that.
Click to expand...

I offer a $1000 reward (must have a paypal account) to anyone who can make a video showing that a fused cell , in a powerwall type setting, can cause a fire ...put any voltage across it you like , it's just not possible to get enough energy into it to ignite (if the melting fuse falls onto petrol covered rags this does not count ) .. the fire must come from the cell.
 
:) Il do my best. I have seen where it happened but never got it to happen myself.

Im going to rig it up. Had a plan to do this u just have to do it earlier.

Im going to rig it with 35AWG fuse wire. Same length of wire as i have today on my packs. Ie ~10mm. I think it will run between 7-11A depending on some factors and time.
Im also going to run this with my bench supply along side with a resistor so i can stress it meanwhile never breaking the fuse!
It will dont inserted in a pack. In this case im just getting several cells together and leaving this one in the middle.

Lets see how it goes. I do not guarantee i will succeed but in this case i hope for it :p

On the other hand i will not bet against you since i know they are pretty safe.
 
Unlikely and impossible are two different things.

It's unlikely that a damaged 18650 cell can catch fire from being overcharged, that doesn't mean it's impossible.

If I have to ruin $10,000 worth of cells and waste $30,000 in time winning a $1,000 internet bet I don't see that as a prudent use of resources.
 
Aww, come on, where's your sense of adventure :p
 
Adventure is someone a long way away having a difficult time.

"Hold my beer and watch this" is the credo of my people and most of them wouldn't do it either.

Most.
 
daromer said:
:) Il do my best. I have seen where it happened but never got it to happen myself.

Im going to rig it up. Had a plan to do this u just have to do it earlier.

Im going to rig it with 35AWG fuse wire. Same length of wire as i have today on my packs. Ie ~10mm. I think it will run between 7-11A depending on some factors and time.
Im also going to run this with my bench supply along side
Click to expand...
 
Sounds like some sort of variation of Clarke's first law..

"1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."
 
Note that u can feed the cell with 10v at 5a too... fuse dont blow. 80c at 24h is enough for a cell to start a reaction.

Lets see. If all is well the cid will blow and nothing happens. Il try some today. I quickly tested yesterday. 75c within 30 min with 4amps at 6v....

Its also worth noting that what would happen if 2 or even 4 cells in the middle go wild. Then they will heat each other too in some sense
 
daromer said:
Note that u can feed the cell with 10v at 5a too... fuse dont blow. 80c at 24h is enough for a cell to start a reaction.

Lets see. If all is well the cid will blow and nothing happens. Il try some today. I quickly tested yesterday. 75c within 30 min with 4amps at 6v....

Its also worth noting that what would happen if 2 or even 4 cells in the middle go wild. Then they will heat each other too in some sense
Click to expand...


I did say in my other post 'use whatever voltage you like' ... but in a powerwall situation a cell is in an 80p pack , and canonly experience the voltage of that pack ...4.1 V ... although this pack may be part of a string of 7 packs with a voltage of 27 the cell cannot experience this voltage , would only be subjected to 4.1 .... but no problem if you use 10 V ...I've just discovered some surgical equipment containing our cells , is regularly sterilised at 120*C !!!!!
 
But the charger can malfunction. Yes from other cells it can not go higher. Lets see how it goes... first just blow cid at 75c or so

120c is hot :) but at same time some cells are said to be able to go 200c before thermal. And on other hand if its just short 120 should work
 
Also to remember is that while the medical cells may be being hit with 120C, they are not discharging. There is a difference between internal heat and external heat. The cell can handle external heat a whole lot better than internal heat. The prior maybe start to damage it while it's discharging, but it'll be minimal, and may not even be noticed. The latter, it most likely will damage the cell. Now, if it's subjected to both, then things could get really bad.
 
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