Dead shorting an 18650 Battery to test cell level fuses
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- เผยแพร่เมื่อ 6 ม.ค. 2021
- As requested - dead shorting a 18650 battery bank with cell level fusing.
What did you think was going to happen!
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When we started to make these battery blocks, we added these fuses on each cell, mainly to isolate a cell if it shorted. The role of these fuses is not to protect the unit against an external short circuit, but exclusively to disconnect the defective cell. For protection against an external short circuit, a main fuse is required for all the blocks in series. We had chosen to use fuse wires of 5 to 6 amps, If these fuses do not burn when the unit is in short, it is because the cell is unable to supply sufficient energy.This can be seen in the test of the last block which is insufficiently loaded. Sory for my bad english.
My exact thought. Not enough amps (fuses work on amps not volts). And I would add a fuse to the positive terminal/s. Would be nice to know what the amp rating of the fuses are (amps + time), would probably find it will accept 2-3 batteries in series on short circuit, which seems to be what is happening.
exactly
Double fuse adds resistance in the shorting loop, that lowers the max short circuit current, might be just enough so the fuse doesn't blow.
You can determine the max current output as following: Current = tension / resistance
So you'll get different result if the cell is charged or discharged !
Once you have your cell's voltage, you just divide it by all the resistance in serie (for the short) :
1rst fuse res + internal res of the cell + second fuse res + 2 x Bussbar res
And you have your maximum current output.
It's clear that 2 fuses add resistance and lower the current, and that it is to be taken into account for the choice of the fuse.
For this use I would personnaly choose a fuse just above the draw per cell in normal use. If not, this is impossible to detect a short in this case !
But then it might become too resistive and lower the efficiency of the pack..
(Sorry for my bad english)
The fuses that don’t blow are obviously connected to high-ir cells, that’s why they don’t blow, the cells can’t push enough current. That’s why we need fuses that blow at 2A maximum
But only if the draw per cell is less than 2A, otherwise the fuses should be rated just above the draw per cell.
@@18robsmith you really don’t want to draw more that 1A from old recycled cells anyway!
@@ThanosSustainable In part you are right, but, what are those fuses actually rated for - they look to be too big for even 2A....
(I aim for 0.75A from old cells, but on new cells I go for 50% of the manufacturer's discharge rating as a maximum)
I am wondering if the DOUBLE fuse also increased the resistance.
@@bubbaberk2670 That depends on what you mean by "double fuse" - if you mean a fuse on each end of the cell then it may well cause an increased resistance to blowing under a given load. If you mean putting two fuses in parallel on one end of the cell it goes under the heading of "bad practice". Generally, in this sort of low current (per cell) situation it is better to have one fuse one only one end of the cell - the big debate is which end you put the fuse - it really depends which line is considered the zero-volts line (often dictated by the attached equipment).
Fusing both sides doesn’t make sense, just extra work. Kirchhoff’s law means current in = current out, so one side is OK unless you think the body of the cells will short to each other. But in these holders they won’t.
Also the fuse wire should be in tension somehow, so when they break they disconnect quickly. In the Slo-mo you can see some of the fuses broke but continued to arc across.
I just wanted to add similar comment.
1000IQ, love reading these comments
I would like to see some current measurement to see how much actual current it takes for 1 fuse wire to blow connected to a single cell. Also an IR rating of the batteries in which the fuse wire does not blow.
he did these years ago...
Glad to see that you are back to making videos!
I use miniature glass protected 2A fuse. I tested it with degradated cell less than 100mAh of residual capacity, high internal resistance and tested at low voltage (3V), it blow immediately. Best use glass protected fuse that are of constant lenght and perform always very good.
makes sence.
Kinda why Ive been using the glass fuses from the start. I wonder if those that didnt pop have a dirty wire where the solder is so it didnt "connect" the best. Interesting for sure. I love these type of videos!👍👍
The pack is all wired in parallel so it has the same voltage across all batteries, so some batteries - with lower internal resistance and higher actual capacity - will produce more current, and will blow the fuse more readily. Odds are some cells will just be so bad that they can't blow their own fuse. Lower capacity means less charge per every unit of voltage charged or discharged, so less current.
can you tell me the electromagnetic law where your "glass" fuse works and a wire without the encapsulation does not ?
@@josep.3364 I didnt say that bare wire does not work as it obviously does as shown in the video. What I ment by me specifically using glass fuses is, I know I didnt want to discharge much more than 1a per cell since there all used laptop batteries. I went with the standard rule of 1.5 to 2 times over for current rating. So I chose a little axial glass fuse that would pop at 2amps. You could find that in bare or encapsulated wire but was very hard to work with. So I chose the glass fuses.
@@josep.3364
what has a "electromagnet law" to do with the kind of fuse?
@@AveRage_Joe How many Amp can u pull out from ur 2Amp fuse ? I mean ur whole pack
It's called internal resistance the battery 🔋 has so much internal resistance that is can not produce enough amps to blow the fuse
Absolutely. These cells are junk, that's all that is going on here.
@@antontaylor4530 They are not junk. they are lap top battery's which obiviously are not meant to deliver alot of amps. They do their job for their purpose.
@@prckata Completely wrong, they're junk.
I don't think you understand Lithium chemistries at all. No-one has made laptop cells below 2000mah for YEARS, and *no* lithium ion chemistry is unable to push 1.5C sustained - most can push 1.8-3C for long periods of time without any trouble *at all*.
In fact, most cells will push 10c or more when shorted no problem, although it will damage them if you regularly pull high C (hence the fuses).
Even if they're half their original capacity, say, 1000mah, they should still be able to push 5C when shorted - 1000mah@5C is 5A. And if they're at half original capacity, then they're junk.
The fact that these cells cannot blow a 2A fuse means they are clearly way, WAY beyond being junk.
@@antontaylor4530 Completely wrong, they are not junk. Second, you can't really judge how much i understand Lithium chemistries just because i said that , + Im going to said again, they are not junk, also as i could only tell you that Im working at unmanned aerial electric vehicle sector, jet engine and subsystems development and testing sector, Installation of test equipment; Battery testing, monitoring, upkeep and storage. Trust me, I know more than you can imagine about all types of lithium batteries.
So, i could agree with you that no-one has made laptop battery cell below 2Ah in years, but i dont know what you wanna say with that. It’s perfectly normal for a fucked up 18650 to lose 50 or even 70 percent of its original capacity and it is perfectly normal that it cannot deliver more than 1 or 2 amps in such a fucked up state, so i dont really know what you are saying with that " I dont understand Lithium chemistries at all" really.
I agree with a good part of your text, that almost every lithium battery should be able to deliver at least 1.5c + etc, but that still doesn't mean that these batteries are junk. They just aren’t designed, even when they’re new to be able to deliver more than 1.5 amp constantly, unless you want to fuck them up fast.
So, they're not junk, they're designed to work the way they're meant to be, the fact if you expect them to deliver 10 amps, when they have already gone through a good part of their exploitation good for you. After all, they are not even intended to be used as a power wall, but as laptop batteries.
p.s. I'm not saying that there is no JUNK batteries, even when they are new, they could be badly done, but most of them are completely ok, and they do what they are intended for.
@@prckata Wrong. Doesn't matter that they're not designed to deliver more than 1.5c constantly, they will still deliver far more than rated when shorted unless they're JUNK. Doesn't matter if doing so for long periods will fuck them up, that's not relevant to the discussion of whether or not they should be able to blow fuses.
The fact that you don't understand that proves you are either lying about your job, or you're incompetent. And if you don't understand why I'm mentioning that no batteries are made of a capacity below 2000mah just before I start talking about their C rating, then you clearly don't understand the relationship between capacity and C rating.
Meaning that again, you are either lying about what you do for a living, or you're incompetent. How could an engineer not understand the basics? There is no chemistry ever manufactured - for laptops or otherwise - that cannot deliver 2A easily when shorted, unless they're total JUNK.
Please educate yourself. You clearly don't understand lithium battery technology and trying to pretend that you do. There are plenty of educational resources on the net.
As for me expecting then to deliver 10A, you clearly don't understand what I was saying. I never said anything about demanding 10A from a cell, although I regularly work with cells designed to deliver constant 20A (LG HG2's) for various projects. I don't push them that far. I simply stated that in a short, no lithium battery of any chemistry would have any trouble pushing crazy amperage. Whether or not doing so for extended periods will damage the cells is neither relevant to the discussion, not evidence that these cells aren't junk.
"They're designed to be used in laptops" - how much do you know about the chemistry of a laptop cell? I just tested a few cells I pulled from laptops. All of them (even the junk ones that were below 600mah) managed over 10A when I used them to spin up a cordless drill for a fraction of a second. They would ALL blow a 2A cell EASILY. Even the real junk that I kept for curiosity's sake.
You clearly don't understand. Please stop pretending that you do.
I am eager to hear more thoughts about your safety concept. Like the fuses, but you have very little isolation in the setup for unwanted touching with metal objects and stuff.
That cell is incapable of producing enough current to blow that fuse.
Yeah, that's the problem. A high IR causes the cell current to drain slowly, even if the cell is shorted, so the fuse wire will only get warm but not burn.
Yap obviously
What Amp fuse wire did you use? And what cells did you use? What is cell max discharge current? May be those sells that fuse still ok are weakest.
@@OlivierLopezCh That's exactly what I was thinking. ie, internal resistance.
Yess some cells are too high internal resistance. First you can test single cell bye short circuit using those fuse wires
no it`s not boring thankyou
Try editing it lolz
Cell level fusing is to protect the remainder of the pack in the event an individual cell goes to a short condition. So a 1S40P pack (as per your demonstration) with one shorted cell could dump a minimum of 20 amps if the pack is in a very low SOC. Conversely the same pack in a high SOC could dump nearly 200 amps (assuming 5 amps per cell). I believe your current fusing scheme is correct and should be continued.
You are correct in your comment about do we really need two fuses per cell. 2 fuses per cell (one on +ve and the other on -ve terminal) just means the weaker fuse will blow first as is a series circuit. A single fuse will work just as well.
If you wish to protect the pack as a whole, then a circuit breaker or fuse at the pack level is required. The sizing of that protection will have to be less than the maximum current capability of the pack. Using the numbers above, and say you wish to limit cell protection to 5 amps, then a 1S40P pack may have a 160 amp circuit breaker which limits each cell to 4 amps. This would protect the pack (assuming the cell level fusing is at 5 amps).
I'm currently working on a battery design for 1S144P pack for an EV conversion of a Suzuki Jimny. 28 of these should give me some serious capacity and range.
To me, this shows exactly what fuses are supposed to do. The purpose of a fuse is to protect the pack from a *single cell* that goes bad/shorts. Its not about every fuse blowing if the pack shorts out. In the case where 1 cell was left on 4.2v pack AND the case where the pack was 3.2v - there is not enough amps in the short circuit to melt the fuse wire. So the question - will an individual cell catch fire if its externally shorted... (not necessarily).... which is a different that if 1 cell shorts (within itself) within a 40p pack where there's 39others to flow / burn the fuse wire.
Interesting wonder what amp of fuse wire was used I like to use the Bussman BFW-1 1amp wire which actually takes more than one amp to blow but worked in my tests. I only tested with single cells so makes me want to try a whole pack now.
thanks a lot for repeating this test cause now I could see the relevant part in the timelapse video.
Seems a new way to test the internal resistance of the cell!lol
But as I can understand ... the idea to use that kind of fuses is to isolate a shorted cell from the rest of the pack, in order to avoid a collapse of the entire pack and avoid the faulty cell to heat and even catch fire.
In order to protect the entire pack from a short circuit, should be enough to fuse the positive terminal of the pack with the correct current you need for your system to work in normal operation.
Fusing both sides does seem rather unnecessary. It would be like having a fuse on both the live and neutral of a plug (in the UK) or having a breaker on both the live and the neutral lines back at the consumer unit/breaker panel (individual circuit breakers not the RCD/GFCI).
You could put a higher rated fuse wire on one side of the battery then that should insure only one side of fuses blow but meaning you can still build the packs the same way.
I think that the one battery fues not cut is from the battery.
I think the battery is gives lower ambs that could not cut the fues
And whene you use the 3 volt the power not big
Looks over-fused. Very interesting!
I have a test i would like you to do! Create a pack like you have here of 4.2 volts and use cc cv step converter to run a known resistance and use your Bluetooth cell meter to measure and record each cell at intervals and also the heat of the cells to illustrate the different esr and quality of different cells as some are built for higher and lower ability in their discharge characteristics especially over time as some cells can get a lot hotter than others! 👍🏻
I would think that resistance overall plays a role, not just the internal resistance of a cell but, also that of the fuse wire, the amount of solder which is after all just a lead and tin mixture which is also not perfect and the length of the fuse. Pete, did you not spot weld some of your battery pack fuses? Would that not be a game changer in the way the fuses would re-act??
check the battery internal resistance before parallel
Really interesting video, I first go into your videos because I am interested in the application of these "fuses" in making batteries for electric bikes specifically. Some of the big manufacturers for example do use "fuses" per cell, same concept as yours (not counting tesla of course). So these experiments are super interesting, I really really want to understand what the reason is here for them not popping. Exciting!
Thanks Pete for the additional testing at the expense of your time from the day job (or even your free time)! Are you able to check the size and type of wire that was used to fuse the donated disaster pack? It could be a less conductive wire that has a higher resistance (steel vs aluminium or copper). This might also explain why the fuses didn't blow and the terminals got too hot to hold. Regardless of outcome, thanks for the extra investigation you're putting in to the "decommissioned" pack!
Got them blue PLATO cutters!
Interesting tests. Thanks! Regarding the low voltage short test... I think when SOC is so low like that, short-circuit amps are much lower and cell is much less likely to get hot enough to cause any problems and/or enter thermal runaway. Just my guess though.
This is not a boring video really enjoy your video
Thanks for tuning in ...
Very informative. Thanks
Glad it was helpful!
the fuse wire also blows depending on ambient temp and is greatly affected by any air going over the fuse wire it self
Is the wire you use actual fuse wire like the one used in UK rewireable fuses or is it just a random unrated thin wire?
Boring - NO. Educating - YES. :-) Really like your live testing. I think the low volt test shows that the cels can't produce enough power to blow the fuses....
Excellent, test and I really appreciate. It is a very good example that uses the welder to use fuses wire (without a curve especific). Once again the better protection for short circuit and overcurrent protection is a DC breaker or even a main fuse.
Ps. individual fuse is useless as you presented in lower voltage cells. Why? Because lower voltage mean low current to sent out... so the fuse did not burn because the cell could not achieve the "wire fuse" current rupture...
Thanks for you video! I appreciate!
Best regards.
Rodrigo
That was worthwhile Pete - I think we can take away that the fuse gauge is too thick for the lowest voltage.
Higher IR cells can't produce enough current to blow a fuse at low states of charge.
For the same gauge, longer fusewire tends to blow first.
(I double up the wire on the negative side to encourage +ve fuses to go first, because they're easier to check and replace.)
A fuse test with a standard reference looks useful to identify sub par cells, before assembling them.
Looks like most of the cells in those battery packs are still usable, so I wouldn't throw them away.
1:27 my packs have fuses on both sides and have a pack fuse to protect the cell fuses from shorts across the main terminals.
What kind of fuse do you use for the pack ?
Mine too. Im using 10A fuse for each pack.
in what way will those fuses prevent a cell internal reaction?
Ever considered that the thing that those fuses do is to help you sleep at night, like a placebo ?
@@josep.3364 cell internal reaction is internal short due dendrite growth, in this case the cell will also create a short across the entire pack. also stops you inserting cells backwards in my case.
absolutely not, cell internal reaction can trigger the CID, and then continue.
go luck on your sleep pills, you are going to need it!
How about this for a possibility. Some momentary event happened that shorted out the pack many hours before the fire started, but due to one or two cells with high IR, the pack didn't then read 0V and was presumed by the batreon to still be healthy. In reality though the pack was changed from a 200Ah pack down to a 4Ah pack. The pack continues to get charged at the normal rate, but as it's now only two cells with high IR they're just heating up all day long. At 4pm the heat gets too much and the cells catch fire.
Good point, but I believe voltage of that pack would sky rocket in such case resulting in the BMS shutting it down. Unless the BMS tries to balance it and that way keeps the charge current following through the high IR cells.
Overvoltage would then happen on cell level - and it is also still limited by the fuse wire for charging...
I appreciate this comment is a bit late from when the video was released. But I have a bit of OCD, and stopped the video and counted the black dots. There were 20 on one side and 17.
But I saw another cell that had both fuses intact.
Counting from left, it was number 4 and on the red side it was third row and on the black side it was 2nd row.
Also i believe the battery was heating up despite having been shorted and left to sit because its internal resistance had been increased either from the short, or maybe even just heat damage from soldering. But increased internal resistance would definately be cause for a battery to stand out amongst a series or parralelled set.
at lower voltages the cell level fuses seem to be allot less effective, also the type of wire used for fuse might be an issue eg: steel vs alloy, the length of fuse might cause issues too, it also seems fusing both sides can be a hit or miss, did the cell level fuse for the nickel strip from BH behave the same way?
the smaller pack also had higher resistance then the un used pack
as i have said to many people many times dont go overboard on the fuse thickness i think if these had been high current drain cells the fuses would of blown easy but as they are low current flow cells they dont have the power to melt the fuses that have been used
I would love to know more about the IR numbers, for example what constitutes a high resistance with that IR reader? What is a good resistance number?
yeah was looking for the ir from the buss bar ie the total battery ir
How would the glass axial fuses I see some build there pack with work out?
The more I watch your channel lately, the less I want to play the mixed chemistry second hand cells game.
I need to build up some hefty 48 volt packs for inverter that currently has AGM fitted.
New A grade LiFePo4 will be my choice.
Thanks for the education.
Hello friend. This is Sophy from TOPA Technology Limited. We are a battery manufacturer. If you need some batteries. Pls contact me at WhatsApp/Skype 008615324942070
Do a video fusing 10 cells together with a few known heaters. Use low current fuses (2A maximum) and charge it up to max to see what will happen with the heaters
Hey mate, what meter are you using to measure IR?
How many years your diy power wall in operation?
Internal Resistance does play a role in battery packs, I think that it's just as important to match cells capacity wise just as it's important to match them by their internal Resistances.
I have been contemplating the idea of using a diode on each cell so that energy only can flow out of the cell to the buss bar, but that would mean that each cell would have to be charged separately at 4.2V which adds complexity but it isolates each cell so that they don't get charged by the stronger cells in the pack! Of course a diode adds a voltage drop to each cell so I might have to add another row of cells to get the same voltage... It definitely needs looking at from all angles and possibilities, I think that the optimum goal is to obtain the best safety and reliability... Using Automotive blade fuses instead of the wire method would give better consistency due to the constant fuse length but at the same time it adds more complexity...
I have a bunch of single cell protection PCBs that I got from eBay, they are not expensive and small enough to be shrink wrapped to the cell, they offer over and under voltage protection as well as short circuit which is great but the cells would need to be charged individually... I also had the idea of using those drop in type battery holder's mounted on a pcb which should then allow me to install the battery protection PCBs directly to the drop in battery holder so that I have swap out batteries without having to worry about de soldering cells, that sort of setup allows quick and easy testing and replacement if necessary! It's a little more work involved to set up but once done, it should make life easier for maintenance... There's another channel, I think it's called jhenga or something like that, he's done something similar, he sells them but being in the US, he doesn't ship to Australia simply because the shipping and import charges cost more than that kit itself! Kinda sucks because it looks pretty good! I don't remember if each cell is protected individually which is what I would like to accomplish but it certainly looks the business! Otherwise, the only other option would be to purchase protected cells which I use in my torch, I have tried to short circuit them but it's impossible! They are branded as keeppower with 3500mah rating from an eBay seller in Sydney, they cost me $30 for two and I'm happy with them for the few years that I have been using them for.
I have lately been looking at those sand bag lithium polymer batteries that are available on eBay, they are the cheapest for their capacity, they come pre packaged in blue shrink wrap and have a power switch and two barrel jack type connectors already fitted, those sand bags kinda worry me but they are usually found in those portable car jumper packs and can deliver a lot of current! But using those would mean that the enclosure design to house them would need to be able to keep each pack separated from each other just in case one failed and caught on fire.... But if you have enough of them and you aren't drawing excessive amounts of current from each one, then I guess that they should give no problems...
It's just an idea but everything has to be carefully considered...
With these packs that you say were pushed fairly hard. Do you know if they used a fuse rated wire? Some types of wire increase in resistance each time it is heated. Not wanting to be an armchair engineer, I wonder if new and uncycled fuse wire would be different. I remember your early vids with the fuses. They were informative. Cheers Pete!
Could it be that battery need little more time on short circuit before it blow?
What is the AWG size do you have on the pack?
As far as I understood, cell level fusing has never been for protection against shorts. You need a fuse after the pack for that.
Cell level fusing is to stop the other cells unloading into a failing cell with loads of current. So one cell fails, self discharges and heats up, and the other cells would put their current into that cell and just raise the heating with a lot of current. And the cell level fusing would then prevent this from happening.
This is at least what I gathered was the reason for cell level fusing. :-)
Sir . For making battery pack can we use different brand batteries of same capacity ?
An easy test...
Run the dead short with an ammeter to measure the current flow.
Use the min/max feature to capture the highest current flowed, and measure the voltage of the battery during the current flow.
The fuses blow with current flow and not necessarily the voltage, the IR will affect the reading and change with temperature.
That would be an expensive ammeter
Great video...😁
What is the manufacturers specification for internal resistance and at what frequency was the measurement made, could be the cells around 80mOhm are duff
Ciao molto interessante complimenti per il test di resistenza fusibile 🤝🔋🔔
A high resistance joint would act as a current limiter.
And use up energy by warming? Makes no sense...
My fuses seem half the thickness have you got any thinner fuse wire?
I'd be curious to find out what current is coming out of the 'X' cell under short cct conditions.
My take away from the low voltage pack test is that, you can make your wiring and connectors hot by having a large pack of low voltage cells short circuited, but the fuses won't blow, let's hope everything else can take it until there is no energy left. If it was a cell in the middle of a pack that went short cct, the rest of the pack would keep dumping into it, with what consequence?
I tested the 1/8 watt resistor leads and they blow at about 8 amps so I decided to use 1 amp 10mm X 2mm miniature glass fuses. These blow in about 1 second at 2 amps.
In what way will any type of fuse prevent any cell internal reaction ?
i'm curious about the far right straight wave after the fuses were blown on the right most cells was that a reflection ripple?
nope top right-most fuse let rip and the discharge flew past the lower-most cell food for thought
Of what type of wire did you make your fuses? I have been thinking of making fuses out of automotive fusible link wire rated at 5 to 6 amps for 32650 cells rated at 6 amp continuous discharge.
it depends on your load & battery.
Just another thought, maybe, just maybe, when testing cell level fuses, it would be a good idea to test the fuses closer to the nominal cell voltage or closer to minimum voltage or "empty" to make the fusing more reliable. Adding to that, spot welding it to the cell, thereby decreasing the contact resistance to the cell, and, if possible a spot weld to the bus bar, being copper I don't know if a spot weld would work I know that spot welding copper is another beast entirely, I think you need carbon electrodes for that, (I stand to be corrected there though) could you maybe explore something like that for us Pete?
Do have have a link for fuse wire?
What fuse wire do you use?
I am after advise. Battery for ebike 14s4p max discharge current per cell is 13A. Controller with max current 45a. What current of fuse wire to use in this battery? I have 10a and 5a. For now is 10a, and bms current reduced to 30a. Think that 10a fuse will not blown, but may get hot. Will blown if go back to full current. Would be ok to solder one more 10a fusewire?
Appreciate this video! Can you share the name or link to the cell holders you're using?
They are just aliexpress/ebay type cell holders s.click.aliexpress.com/e/_AludVH
These test are pushing me further into lifepo4 territory. Have used small glass fuses on the 18650 packs that I already have, although during testing at lower the voltage the fuses don't act 100% or take their time. Multiple causes I would assume: high Ir limiting the current that goes through the fuse, also when the pack is at a lower voltage this would limit potential energy to blow the fuse.
I think the fuses work great as long as your weakest cell is capable of twice the current rating of the fuse at min cell voltage. The Only reason tesls gets away with it is extreme quality control on the battery side. Even then can we ever be sure that Tesla fuses work 100% of the time.
Looking at the "X" battery, the fuse, looks like it started to burn (slight darkening and mishape of the wire is visible) and I think that simply all the other batteries due to lower resistance fried their fuses before this one was able to. So it was just a matter of timing on this one.
It could happen where when you accidently short your battery the connection could potentially weld together but by that time I'd say the fuses would blow
~ 11:20 was/is that battery, bottom right, 1 left. Already blown?
Idea! Did anyone ever made a battery pack of their worst cells? The heaters and the leakers? And try to discover what is needed to make these fail (fire like)?
Really interesting idea. He should try that
when you had fully charged all batteries and those batteries where fuse didn't blow up I think it has high internal resistance, is any chance to test them? I think cos it has high internal resistance it don't have peak power to blow up the fuse...
I think you're spot on
heya and what should be the IR for the 18650 ???
The individual fuse wires are used to isolate a bad cell from the rest of the pack and as you have seen they do not provide whole pack protection. Had that short not been momentary the cells that did not disconnected could have gone ballistic.
Fuse wire length does matter!
That's one of reason why on one side must be used not the same fuse wire, but some more think wire, which has lower resistance, will not blow up and will not cause voltage (think - power) drop on the side where proper fuse is.
Also, those 2 far corner sells have longer wire (longer than usual ~10mm) and that's also not so good. It's possible to solder in a way (on cell and bus bar) in a way to keep it shorter than ~15mm.
HB, good as usual! No, not boring. Uhm, I'm not an electronics guru. But if those fuse wires should blow at 5A and they don't blow I would say that resistance in the circuit raises so circulating current doesn't reach 5A. With 4V tension it means that resistance raises to 0.8 ohm or more.
please post what fuse wire you use
I can't even remember it was so long ago but it was VERY thin
What size fuse wire was you using? Increased fuse wire length will result in increased cell resistance so better use a consistent length to balance out cells. double fuses not required as will only add to the resistance. The higher the resistance the higher the voltage require to burn out. Also more often than not, a “3amp” fuse wire for example will require atleast 5amps for a duration of time to burn out, and if you want instantaneous blow then would need into the 10s of amps if not more so it becomes extremely important to carefully choose the correct fuse wire size based on max discharge current design plus keeping in mind the max discharge current will vary based on cells discharged state.
if you wan to check if all fuses are "blown" just recheck voltage with the multimeter after shorting the cables.
Internal resistance isn't the only thing at play surely. I'd theorise that the cells with intact fuses not only have high internal resistance, but also very low capacity. Low capacity plus high resistance equals very low ability to deliver current/amps, resulting in intact fuses.
Please capacity test some of the cells which consiststantly blow fuses against ones that don't, so we can see if capacity divided by internal resistance gives a reliable indication of a cell's ability to blow fuses/deliver current.
Did you test the cells for internal resistance before building the battery packs? Having a small apparatus for measuring voltage with a resistor can help you figure out the IR of the cells so you can ensure any future packs you build have cells with comparable IRs along with weeding out those with a high resistance. Just need a cell holder, resistor, voltage display, and a switch.
If you're so inclined, can probably even figure out how to automate that with an Arduino. (And I think I have a new project to add to my list...) Wouldn't surprise me if you can buy something that can do that for you.
I would say these were not IR tested back in the day. We know much more as a community than we did. These are also not my batteries. They were from a decommissioned DIYPowerwall after a fire started.
Pete just curious but what rating are these fuse wires being used ? Cuz the internal resistance and voltage can dramaticaly change the amperage.. So 4.2volt @ 42mΩ = 100amp but change the voltage to 3.7v @ 80mΩ = 46.25amp so suddenly fusing becomes a whole nother ball game. Pack level fusing would be just as effective in reality as if a battery has internal heating issue no fuse will blow. Plus remember there are "Characteristics" to fuses.. so a 5amp fuse may have a blow rating of 2 to 5x the rated value.. they may also be slow blow or fast blow.. all important in pack design. But even the best design fails if one goes internal heater.. and i would bet those are all higher internal resistances.
High internal resistance seems to be why the fuses don't blow.
I'm fascinated by the temporary nature of lithium and Life itself
Is it possible to get thermal runaway if you totally short one of them batteries and don't let it off
yes
could it be the fuse length? the longer the fuse the longer it takes to blow if I remember correctly
At 2:50, there’s a thermal camera view with “FLIR” showing uppermost left corner.
Is this a dedicated device, or a plug-in for say, a phone?
Pictures like this convince me I’m wanting one before I do much more with such batteries.
It’s an iPhone plugin
Thinking the fuse design/idea is okay for dealing with singular faults within the battery but when its dead shorted it may still go nova on one cell alone thats unable to blow the last fuse.
The side which is placed on table does not become as hot as upward side due to cold table thats why fuses from lower side does not blow.
Fuse of some cells are not blowing beacuse some cells does not give output amp as compared to others. Some cells does not gives enough high amps to burn fuse
Maybe check new vs old cells, with newer cells with less dendrite growth, and more amperage output, fuses might be more reliable, with more internal resistance as they age, less so, and with more of an internal fault scenario become more of a self-heater and thermal run-away scenario, this is why packs need to be monitored both thermally, and charging characteristics
It would be more sensible to use a thinner resistance wire. And I noticed the 2442mAh battery cell and the 2015mAh were in one package, I don't think that's a good idea either. And definitely different company items in one package. This way you can test better results.
What if you score each fuse wire at the center so as to dictate where the wire should break? By scoring I mean running a pair of wire cutters on the center and just spinning it 360 on the wire so it creates a small groove where current can bottleneck and break the fuse at that groove
Probably work but man would that be tedious and inaccurate
curious, wouldn't adding fuses to both sides *increase* the fuse level? Meaning that it would take more energy to burn them?
I'm a noob, an explanation would be great!
both sides doubles the time it takes to check and serves no real purpose i feel.
I wonder if there are fuses made of some special alloy that can change to liquid state at a determined temperature thereby providing a means of physically disconnecting
how do you think the fuse wire works?
@@ursodermatt8809 ok i can see how my description may not fully explain myself, but i did find out that there have already been attempts at what i was curious about.
www.researchgate.net/publication/337226342_Analysis_of_research_and_area_of_application_of_self-resetting_liquid_metal_fuse
so what are these DIY wires? tinned copper, what gauge? 26awg? 0.13mm2 20A fusing?/cell How many cells 80 in parallel. No kit to measure 1600 A from your shorting leads? But very good ground Buddy, keep up this practical research cos the solar fuse/breaker industry is worse than vultures for creating a massive scam on choosing the right protective fusible links - BTW you most certainly need these, but what do we do on the 280Ah prismatic blocks?????????????
i would try to resolder all fuses and make a load test on this pack.
im sure there will not come much from this pack.
only some cells have enough power,
the rest not even enough to blow fuses.
thats my guess
If we charge them fully 4.20 for whole time the capacity will drops to ~ 1000mah and the internal resistance will go too high.