18650's have a PTC and CID so why fuse?

[telefunken]

So I am in the planning stages of my own build and of course safety is my foremost concern. I've been looking at several options for temperature monitoring and cooling, but that's beside the point.

Anyway, onto the Nth topic about the controversial fuse wire. The whole fuse wire ordeal seems to have started with the Tesla packs, Tesla has fuse wires and thus it must be a good idea right? Let me first make it clear that I am not an opponent of the extra added layer of security, I say extra layer because the fuse wire goes on top what is (should be) already present there.

So let's first reflect on what security measures are already there built into the cell. A properly manufactured 18650 has a fake top, in that fake top you will find a PTC (Positive Temperature Coefficient) and a CID (Current Interrupt Device).
1. The resistance of a PTC will rise according to the temperature of the cell, this means the amount of current which can flow through the cell will become a function of the temperature effectively limiting and eventually cutting the cell off when it starts to overheat.
2. The CID is a mechanical device, effectively it's just a pressure release valve. When pressure builds up inside the battery the CID will pop out and thus mechanically cut the battery off.

Note that it doesn't matter if your cells are protected or unprotected, protected just means there's an extra chip at the bottom of the cell which adds another layer of protection, but using protected cells in a powerwall setup has other disadvantages.

So at some point along the line Tesla decided to add external fuse wires to cells in their packs. I am struggling to understand why they did this. The whitepaper of the Tesla Roadster BMS mentions that they are using cells with a PTC and CID, it doesn't mention anything about fuse wires besides saying they have some active and passive measures (can't post link because rules do not allow me to-do that just yet).

Keep in mind that the Tesla Roadster was their first prototype platform, when they built that they didn't have their own batteries. When the Model S came around they were producing their own batteries. It could be they decided to ditch the PTC, I could think of several reasons for doing this. The battery pack is actively cooled, maybe they found the PTC doesn't do much because of the cooling. Maybe they found the PTC affects the battery performance too much in extreme weather conditions.

The reason for this is unknown to me and I would appreciate the comments from somebody who has more insight on the matter.

So onto the fuse wires used by some people in their own builds. Is this extra added security measure necesary? The best guess until now is that we do not know. So the Tesla engineers must have thought about this right? They did the math, designed a robot which uses a properly defined wire and welds that wire onto the cells according to a properly defined procedure. The Tesla engineers can say with some amount of certainty that their fuses conform to narrowly and specifically defined properties.

So this has been said a few times before and I will repeat it again, the wires used by most people here are just rule of thumb wires with no thought put into them. When push comes to shove nobody can exactly say when and if the wire is going to fail. When I look at some of the pictures on this site, I see people have gone to great lengths to put the wires in but then made it all obsolete with a botched soldering job. The wires are covered in tin which runs up the wire. So the wire might have had some property but that property is now gone because it's covered in tin. On top of that when I look at some of the builds I see cells which have a rated continues output current of 20A. That cell gets soldered onto a teeny tiny little wire as a measure of protection, the only thing you're doing there is building an expensive light bulb.

So let us come together and figure this one out once and for all. Let's start collecting information how these DIY systems behave so we can start defining best practices.

Any comment from people who have more insight in the matter (other then the standard, I did it this way and it works or the I did it this way because my gut tells me to) would be greaty appreciated.

---

Link to Tesla Roadster BMS whitepaper:

http://sa.indiaenvironmentportal.org.in/files/TeslaRoadsterBatterySystem.pdf

 

[Jeremy Choy]

The biggest reasons:
- I do this in my home/garage not in a manufacturing plant. so fusing large battery packs can prevent any accidental mistakes. I don't want a venting battery going off in the house.
- some don't use industry standard/best practices at times which increases risk.
- When you're tired, you make mistakes, and when you make mistakes, you can ruin a whole pack or in my case because I fused it, save a whole pack

 

[daromer]

Not every cell have the PTC. And the fact that fusing does not take that much longer time in the whole.

Regarding the fuse wire itself. The whole pack can put in punch so you can easily have 100s of amps going into a cell from the other cell if there is a short. Not just that single cell
I have no scientific input to your statement more than the PTC part. Other than that i use a fuse wire i have tested and know will do the job in case. If this will save me i dont know but on the other hand i still had to solder something to the cell

I though i had links to the part about PTC/CID in cells but apparently not on this computer....

 

[Korishan]

There are several examples on here (and youtube) that show that a fused cell is a good thing and saved not on the packs, but potentially the building.

Several fuses have been blown because of some human error (as Jeremy noted) due to many factors.

The fact of the matter is, we are not robots programmed by a computer to have .0001" and .0001V precision and placement. Fuses are our best friends. The fuses may not burn at exactly 7Amps as expected. However, 10amps is a lot more preferable than to have the cell over heat to where the busbar is starting to glow red hot.

I'll take that few amps discrepancy any day over the alternative. Regardless of how it may look.

Best practice for DIY'ers, fuse your cells.

 

[Wattsup]

So this has been said a few times before and I will repeat it again, the wires used by most people here are just rule of thumb wires with no thought put into them. When push comes to shove nobody can exactly say when and if the wire is going to fail.

---

---

I don't agree with that.

There has been some extensive testing done on fuses.

If you haven't already I suggest
Watching Average Joe's youtube series on fuse testing which produced some good consistent results, particularly with the glass axial fuses. This is what I'll be using

 

[telefunken]

So first of, I've been able to confirm that the Tesla cells do not have PTC's in them. Why this is I haven't been able to determine (guessing because of the performance in extreme weather conditions) but this would explain why the fuse wire is there in the Tesla packs. Also guessing they have extra protection in the BMS like a MOV or a TVS.

Some cells don't have a PTC argument, well if you're unsure what the state, brand and/or type of the cell is you shouldn't be using it in a powerwall build anyway. You can do it and fuse it thinking you've done all you can but the external fuse won't protect against an internal short (Note 7 anyone?) and it most certainly won't protect against an arc.

Use the fuse for a piece of mind while working on it argument, it's nonsense. The PTC's are well enough equipped to catch a basic short without damaging the batteries.

Use the fuse for redundancy argument is something I can understand (like I said before) but if you're going todo it then why not use properly engineered fuses? Just look at the specs of a properly engineered fuse and you'll see they will list that it can go upto something like 250VAC but the DC voltage will only go upto something like 32VDC. This is because designing a DC fuse is much much much harder then designing an AC fuse. DC current tends to arc which is near impossible to counter. Most DC fuses just have two spring coils in them which pull apart the two pieces so they can't arc. Arc suppression is a major component of any DC fuse. So you have this thin piece of wire, which is ideal to start an arc as it burns out, you get a short, an arc starts, everything burns out and you're left wondering what happened. So how did that save the building?

Even if you do not get a continuous arc you are more then likely to get a flash arc (being high current and all) which is dangerous when near a cell. It can damage the cell causing an internal short and you take it from there.

Another aspect is fatigue. The cells will cycle through many use cases throughout their lifetime. Idle -> wire is cool, high load discharge -> wire gets a bit hot, idle -> cool again, high current charge -> hot again... etc. This causes stress which in turn will cause the wire to break over time. 2 thin pieces of wire very close to each other is yet another potential to start an arc.

So why not use Littlefuse super fast acting pico fuses or something. Through hole fuses cost next to nothing when you buy them in bulk and they are exactly defined and are almost similar to the wires everybody is using. But like I said before some of these cells (when properly cooled) can go upto 20 to 30 amps of continuous discharge current. At that point soldering a thin piece of wire onto a cell is like creating a buffered light bulb. Good for heating up, not good for efficiency.

Too be honest I think you're better of with a properly designed BMS which is equipped to handle short circuits and properly designed casings which won't allow for shorting individual cells or complete packs.

@Watssup: I have watched Average Joe's series and to be honest, not impressed. He does static testing in a predefined environment, this only demonstrates a so called "slow blow" situation, it doesn't say anything about a high current shock. The only thing his What if it's cold outside? What if the wire is oxidized because of moisture in the air? What if.... I could've predicted his findings just by looking at the specs from the wire manufacturer.

/EDIT:

So here's a video demonstrating DC arcing:

And here's some videos showing DC arcing in a PV panel:

Here's a vid showing arcing in an AC fuse running DC current (both flash and continuous arcing):

 

[Korishan]

So why not use Littlefuse super fast acting pico fuses or something.

There are several using glass fuses

Too be honest I think you're better of with a properly designed BMS which is equipped to handle short circuits

How about you do us the honor and either build one, or post your listings of what you feel is a "properly designed BMS".


And how about instead of knocking what results people have found, encourage and help refine the results instead of insulting and bashing.

We are a community of thinkers, tinkerers, DIYers, and hobbyists. Most have not go to a 4+ University in and are learning as we go. That's what makes a community effort so valuable. We learn from each other.
Yes, AverageJoe could of just looked at the datasheet of the wiring. However, how does that help someone who doesn't know how to read a datasheet. Or, how do we know that the datasheet is that accurate in a real-world situation. The datasheet is based off of clean room, white lab, non-external infuences results. AJ's results are real-world application with random variables included.
Stop tearing down the work of others and help us all learn more. If there is something that you see wrong, explain with results and actual numbers and evidence of your views. Otherwise, it's just noise and has no merit. I can hoop all day long that UV light doesn't really do any damaging effects to us. But that doesn't make it right. I'd have to provide proof/evidence to show my views to be credible.

 

[telefunken]

So why not use Littlefuse super fast acting pico fuses or something.

There are several using glass fuses

Too be honest I think you're better of with a properly designed BMS which is equipped to handle short circuits

How about you do us the honor and either build one, or post your listings of what you feel is a "properly designed BMS".


And how about instead of knocking what results people have found, encourage and help refine the results instead of insulting and bashing.

Well that's not really nice, for the record I've insulted nor bashed anyone. Unfortunately the world is full of people who can't take criticism, too bad. The only thing I'm trying todo is ask questions and understand the choices people have made. This: "well if you know better, then do it yourself" attitude doesn't help anyone to bbe honest and it most certainly doesn't help the discussion nor the community (DIY hobbyists, thinker and tinkerers, in your words).

Also for the record, I've already helped by ponting at a problem most people here hadn't thought about before, DC arcing. By adding and complementing each other we could build something better but it seems some people don't like it when other people point out things they haven't thought about.... Too bad.

Yes, AverageJoe could of just looked at the datasheet of the wiring. However, how does that help someone who doesn't know how to read a datasheet.

Well in my opinion he's creating a false sense of security but you can interpret anyway you like.

The datasheet is based off of clean room, white lab, non-external infuences results.

Uuum no, those are specs found to be safe within the rules and regulations, they build upon years and years of knowledge and data.

For the rest, I've just joined this community and at my 3th post I'm already greeted by arrogance. If you can't play nice and/or come up with facts to back up your claims then I would rather have you stay away from me.

 

[Korishan]

Perhaps you haven't gone through the threads and noticed the in depth talk about fusing. It is one of the primary topics of discussion and has been given a LOT of talk AND thought.

We are aware of Arcing in DC. It has been discussed before. However, DC arcing occurs at a higher voltage, not at the 4V and less that we are fusing for. If you've looked at the designed, the fuses that are just wires are for just that. Less than 4.2V, as it's per cell.
Also, the major area where arcing could occur, there are larger disconnecting devices. Several use DC breakers, other use DC fuses. As noted, arcing is known and is protection is built for it.

As I noted in my first reply; there have been several instances where the cell level, wire fuses, have been used, proven a safety factor as it protected not only the cell, but the pack, and in one instance, the whole BMS setup, and in another the other packs. And one of them was recorded on youtube.

It's not that I have the arrogant attitude, it's that I'm replying with what has been shown to be proven several times over. After all, isn't that the whole deal with the Scientific Method. Have a repeatable method that is proven true or false to the known parts. In this instance, the known parts are that the wire fuses work as the method has been repeated several times and has protected several pieces of hardware multiple times.

You state that you've just joined the community and in your 3rd post you're greeted with arrogance.
Well, in your first post in this thread: "the wires used by most people here are just rule of thumb wires with no thought put into them". This is a bashing. Plenty of thought has been put into them, and lots of work and study and repeatable methods.
"I see people have gone to great lengths to put the wires in but then made it all obsolete with a botched soldering job". Another bashing. There are several electrical engineers on the site that have pitched in with recommendations and design ideas. If the whole thing was 'botched' from a soldering job, for one, I think one of them would have said so, second, those who have done bad soldering jobs has been informed about it and they fixed the soldering as they were learning how to solder in the first place.
"Any comment from people who have more insight in the matter". We tried to give you some insight on the matter, and you threw it to the wind and took offense immediately.

1st video: 220VDC. WAY higher than what we are using. The highest most of us are going is 48V, and at that point, breakers or DC rated fuses are used
2nd video: 500VDC, again, WAY higher than what we are using
3rd video: High voltage again. I couldn't tell what the voltage was, but assuming those are 20V Panels, then that's 80V total. Again, at least twice what we are using.
4th video: All fuses were automotive fuses being blown at 12V. There was no AC going through those fuses. So, at 12V, you can see that the fuses didn't have continuous arcing. They burned the metal wire/strip away virtually immediately and the flow of DC electricity was stopped.
So this last video actually supports our fusing methods and testing as his first demonstration was done using a very similar setup as that of AverageJoe. So, it's ok to have that setup when defending your views, but not ok when we defend ours. Ok, got it.

And with that, I'm out.

 

[telefunken]

So why not use Littlefuse super fast acting pico fuses or something.

There are several using glass fuses

Too be honest I think you're better of with a properly designed BMS which is equipped to handle short circuits

How about you do us the honor and either build one, or post your listings of what you feel is a "properly designed BMS".


And how about instead of knocking what results people have found, encourage and help refine the results instead of insulting and bashing.

We are a community of thinkers, tinkerers, DIYers, and hobbyists. Most have not go to a 4+ University in and are learning as we go. That's what makes a community effort so valuable. We learn from each other.
Yes, AverageJoe could of just looked at the datasheet of the wiring. However, how does that help someone who doesn't know how to read a datasheet. Or, how do we know that the datasheet is that accurate in a real-world situation. The datasheet is based off of clean room, white lab, non-external infuences results. AJ's results are real-world application with random variables included.
Stop tearing down the work of others and help us all learn more. If there is something that you see wrong, explain with results and actual numbers and evidence of your views. Otherwise, it's just noise and has no merit. I can hoop all day long that UV light doesn't really do any damaging effects to us. But that doesn't make it right. I'd have to provide proof/evidence to show my views to be credible.

Perhaps you haven't gone through the threads and noticed the in depth talk about fusing. It is one of the primary topics of discussion and has been given a LOT of talk AND thought.

We are aware of Arcing in DC. It has been discussed before. However, DC arcing occurs at a higher voltage, not at the 4V and less that we are fusing for. If you've looked at the designed, the fuses that are just wires are for just that. Less than 4.2V, as it's per cell.
Also, the major area where arcing could occur, there are larger disconnecting devices. Several use DC breakers, other use DC fuses. As noted, arcing is known and is protection is built for it.

As I noted in my first reply; there have been several instances where the cell level, wire fuses, have been used, proven a safety factor as it protected not only the cell, but the pack, and in one instance, the whole BMS setup, and in another the other packs. And one of them was recorded on youtube.

It's not that I have the arrogant attitude, it's that I'm replying with what has been shown to be proven several times over. After all, isn't that the whole deal with the Scientific Method. Have a repeatable method that is proven true or false to the known parts. In this instance, the known parts are that the wire fuses work as the method has been repeated several times and has protected several pieces of hardware multiple times.

You state that you've just joined the community and in your 3rd post you're greeted with arrogance.
Well, in your first post in this thread: "the wires used by most people here are just rule of thumb wires with no thought put into them". This is a bashing. Plenty of thought has been put into them, and lots of work and study and repeatable methods.
"I see people have gone to great lengths to put the wires in but then made it all obsolete with a botched soldering job". Another bashing. There are several electrical engineers on the site that have pitched in with recommendations and design ideas. If the whole thing was 'botched' from a soldering job, for one, I think one of them would have said so, second, those who have done bad soldering jobs has been informed about it and they fixed the soldering as they were learning how to solder in the first place.
"Any comment from people who have more insight in the matter". We tried to give you some insight on the matter, and you threw it to the wind and took offense immediately.

1st video: 220VDC. WAY higher than what we are using. The highest most of us are going is 48V, and at that point, breakers or DC rated fuses are used
2nd video: 500VDC, again, WAY higher than what we are using
3rd video: High voltage again. I couldn't tell what the voltage was, but assuming those are 20V Panels, then that's 80V total. Again, at least twice what we are using.
4th video: All fuses were automotive fuses being blown at 12V. There was no AC going through those fuses. So, at 12V, you can see that the fuses didn't have continuous arcing. They burned the metal wire/strip away virtually immediately and the flow of DC electricity was stopped.
So this last video actually supports our fusing methods and testing as his first demonstration was done using a very similar setup as that of AverageJoe. So, it's ok to have that setup when defending your views, but not ok when we defend ours. Ok, got it.

And with that, I'm out.

So what you are saying is: "How dare I doubt and question the hard work of the kings"? Yeah that's how this works. Still haven't learned howto play nice?

FYI, those video's use higher voltages because at those voltages the effects are most evident. You can make an arc welder from a car battery. Something with laws and nature and stuff like that, I don't know you seem to be the expert you sort it out. I don't have the time for charlatans (in case you didn't notice, that was an insult).

 

[1958 greyhound]

Doesnt sound like safety is your foremost concern.

 

[Hanssing]

So what you are saying is: "How dare I doubt and question the hard work of the kings"? Yeah that's how this works. Still haven't learned howto play nice?

FYI, those video's use higher voltages because at those voltages the effects are most evident. You can make an arc welder from a car battery. Something with laws and nature and stuff like that, I don't know you seem to be the expert you sort it out. I don't have the time for charlatans (in case you didn't notice, that was an insult).

Nope, your a troll - plaese go away.
- to others please don't respond to trolls like this.

 

[daromer]

Guys guys. Lets discuss this in civilized way. Skip all personal stuff. Blaming people for doing wrong with no proof what so ever will not work and will just cause baad mood.
We have all different views on things and we will not always agree on stuff and guess what! We dont have to agree either. This is a community of DIY people and we will have all type of people.

If noone have anyting actuall to add to this thread in terms of fact or experience in tests done in the matter Iwill close the thread!

-------------------

Regarding fusing it random: I still think its viable to have the cells in the powerwall no matter if they have PTC or not and being fused. I do not see any personal loss in adding fuse wire on the cells that do have PTC. For me the fuse is just there for dead hard short.

 

[ozz93666]

So at some point along the line Tesla decided to add external fuse wires to cells in their packs. I am struggling to understand why they did this.

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---

Brilliant post , tele ... I also concluded fuses were not necessary, I don't use them in my packs...why does tesla use them ??? they were being sued ,perhaps bypeoplewho misused /sabotaged the battery in order to get big money from the courts ... also they had to appearto the public to be doing something to make the product safe , and it costs very little money to fuse ...

Another myth I think I've identified is the cooling myth ...look into this before you set up cooling for your cells !! Tesla sells cars to climates which sometimes have air temperature of 50*C ..rapid charge and discharge , so they do need cooling .... but in 99% of cases I think this is unnecessary for our usage .. cells are happy upto60*C which is HOT ...too hot to touch ! do some experiments and you'll find in normal use they don'teven get warm.

I had no idea some top caps had a safety device .. I know some bottom covers do , I think these are rare and not on the cells we or tesla use ... they will add to the resistance of the circuit in normal use ...it wouldbe interesting to know by how much.

Putting fuses on each cell seems to be because there is concern one cell will suddenly go "bad' short the whole pack at high currents ...I don't believe there is evidence this will happen ... what is surely more likely is a cell will go progressively badder , slowly drain all those in parallel with it , but not at such a high current that it will blow the fuse ....this would be more troublesome , not from a safety angle , but for operation... Has anyone even seen this in practice , I have not,

 

[1958 greyhound]

From what I understand is Tesla's batteries don't have the internal protection that a laptop cell does.

I also think tesla has a bigger battery because of how many amps they pull out if it at full throttle, not just to get more miles.

 

[daromer]

Regarding heat. Yes there is no need for cool our cells in most cases. For instance in my case i hardly get over 200mA and thats 10+KW pulled out of the bank.

 

[Geek]

Regarding heat. Yes there is no need for cool our cells in most cases. For instance in my case i hardly get over 200mA and thats 10+KW pulled out of the bank.

So, OP, what daromer is saying is that his packs never get a heavy load, why would you, no point in pulling a heavy load, your battery life will be short. Put simply daromers batteries could discharge at 30kw. Short circuit that setup, that's 60kw or more. That is 20,000amps. Your bus bars would blow like fuses, probably copper plating your hands, yes this can happen. You will be blind burned and in front of a massive lithium cluster grenade.

Fusing at a cell level is the easiest way to avoid this. Its easy to implement while assembling a pack, so why on earth not. Not to mention it is so much easier to safely solder a thin wire to the top of a battery.

As Jeremy pointed out, it can save you a lot of trouble. So, why would you not implement a solution that is simple to set up, that could save everything from your batteries to your life. Fuses have no negative effect on performance (or it would be so small it wouldn't be worth measuring)

Not to mention by using such large quantities, often of used cells, why not take into account that one of these safety features may fail, causing a cell to go high internal resistance, without fuses, it would explode instantly.

My suggestion is to assemble a pack, maybe 1S10P, probably big enough to prove the point, not big enough to do serious injury. Put on a welding mask and a fire proof suit, and short it out. If the bus bars don't get hot enough to cause a cell to go runaway, Id be surprised.

Hell if you won't do it, Ill accumulate enough cells that don't have enough capacity, and show you myself.

I have done this dissembling a laptop battery. Luckily I do this outside, and if something goes wrong I will throw it, and pick up it charred remains from down the yard. (I live in the county, no neighbors to upset)

 

[daromer]

I have done several short tests and have so far not once been able to cause a fire. Both on new and 2nd hand cells. NOTE that I dont say it WONT happen... I still think it CAN happen its just not happening every time.


Regarding my bank. It can do 100+kW continous And easily burst 300+kW regarding to specs on my LiFePo4 bank its not 20 000A but atleast 4000A. but yes dead short will most likely be alot more. Personally i have fusing on each cells on the laptop pack and then on all series packs. On my LiFe pack I do not have fusing and thats because they were preassembled like this from factory. But I still have fuses on each string to each other.

--- Above is ramble ----
Neither less if you can then design your system so you dont live on the edge. Also protect it so you cannot go to the edge and you save alot of grief.
There is a reason my car only have 250hk instead of 600+..... I need it to work every day back and forth to work without having to wonder if a rod will break after next accelleration

 

[Geek]

I have done several short tests and have so far not once been able to cause a fire. Both on new and 2nd hand cells. NOTE that I dont say it WONT happen... I still think it CAN happen its just not happening every time.


Regarding my bank. It can do 100+kW continous And easily burst 300+kW regarding to specs on my LiFePo4 bank its not 20 000A but atleast 4000A. but yes dead short will most likely be alot more. Personally i have fusing on each cells on the laptop pack and then on all series packs. On my LiFe pack I do not have fusing and thats because they were preassembled like this from factory. But I still have fuses on each string to each other.

--- Above is ramble ----
Neither less if you can then design your system so you dont live on the edge. Also protect it so you cannot go to the edge and you save alot of grief.
There is a reason my car only have 250hk instead of 600+..... I need it to work every day back and forth to work without having to wonder if a rod will break after next accelleration

Video time. Just as soon as I get these crappy cells charged. Good example too because thier IR does not allow maximum discharge. I have seen laptop batteries burn ho
Es in their own bus bars. I did have one spot weld itself together, overheat. So I threw it downthe yard. Yes it did catch fire and explode. Ok those nickel bus bars may be smaller but so is the pack.

Never underesimat li-ion batteries. Im a saftey freak and will be 1a glass fueses on mine

---

I have done several short tests and have so far not once been able to cause a fire. Both on new and 2nd hand cells. NOTE that I dont say it WONT happen... I still think it CAN happen its just not happening every time.


Regarding my bank. It can do 100+kW continous And easily burst 300+kW regarding to specs on my LiFePo4 bank its not 20 000A but atleast 4000A. but yes dead short will most likely be alot more. Personally i have fusing on each cells on the laptop pack and then on all series packs. On my LiFe pack I do not have fusing and thats because they were preassembled like this from factory. But I still have fuses on each string to each other.

--- Above is ramble ----
Neither less if you can then design your system so you dont live on the edge. Also protect it so you cannot go to the edge and you save alot of grief.
There is a reason my car only have 250hk instead of 600+..... I need it to work every day back and forth to work without having to wonder if a rod will break after next accelleration

My point exactly. Dead short is deadly.

Video time. Just as soon as I get these crappy cells charged. Good example too because thier IR does not allow maximum discharge. I have seen laptop batteries burn ho
Es in their own bus bars. I did have one spot weld itself together, overheat. So I threw it downthe yard. Yes it did catch fire and explode. Ok those nickel bus bars may be smaller but so is the pack.

Never underesimat li-ion batteries. Im a saftey freak and will be 1a glass fueses on mine

 

[daromer]

Yeah if just 1 catch fire... Lets say 1 out of 10 000 cells can catch fire. Thats enough to cause big issues.

I really want to be able to short a cell and get it to catch fire hmm.. I need to do more tests there. Because that will get me the personal experience that it could happen!