Adam, I believe this is exactly how Tesla do it with tens of thousands of cells in their packs - the probability of a dud cell goes up considerably with quantity! As more cells from a pack drop out of the circuit, then the rest of the cells in the pack carry more current. If the current increases and all of them fuse, identifying the original dud cells would get a bit more tedious, as they'll all be fused!
I watched this video several times, and i cant understand one thing. If one the cells shorts out then fuse blows, but why LED stops glow after short circuit cell is disconnected by a fuse? Is that means, that whole pack is no longer delivering energy? Am I missing something from video?
Gintautas Raštikis I don't get it either. I would think that for the duration of the short, the LED would be out as it receives no current, but once the fuse goes, the circuit is restored. Adam, please enlighten us?
If you look how its soldered, its connected to the battery holder leg, not the nickle strip connecting it to the rest of the pack. So when the fuse blows, the circuit is broken.
Yeah, the LED is attached to the lug of that empty slot that he shorts so when the fuse blows it isolates the LED. I was confused at first as well. I would have prefered to see an LED attached to the bus bar as well to show the REST of the cells still working in addition to the LED showing the cell losing connection.
Good test result there. I just tested out my fuse wire (I use 30AWG) and it melted just like yours does. Seems the 5A wire is ~31AWG, so the wire I chose is just a bit higher rating, ~6A, should be about right for the paired cells I'll be using.
I found this handy reference giving estimates of fusing current for wire gauges. www.powerstream.com/wire-fusing-currents.htm It says 30AWG copper is 10.2A, so that's about OK.
Another reference that says 10.2A for 30AWG copper. www.litz-wire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire_R2.011609.pdf
10A is a common melting rating, this table lists 6A as the "current rating" www.gxk.org.uk/info/wire.htm and this one about 8.5A: electricguru.in/page_view.php?id=29
Thanks for those tables. They clearly show the distinction between fusing current and fuse rating. I learn something there, and 30AWG is good for the fuses.
Please excuse my ignorance ... Having watched this video, why has the led gone out ? The other 3 cells are still connected ? Only the shorted fuss blew out. Shouldn't the led still be lit by the 3 remaining cells ? I understand the principal but can't understand if they're common negative/common positive fed and only 1 fuse blew why led went out.I Again sorry for my ignorance can you please explain
Impressive Adam... thank you so much for dilligence and fullfilment of follow thru. A year of real world reaults. Just dont see that with youtubers... Im living of he grid in an private RV park if you will in Colorado. Since Ive been living here wich has only been less than a couple weeks, and no power other than neighbor charging my phone and using fashlight at night.. Ive been cramming solar info... Now while im starting with cheap 100w system from harbor freght and going to use their inexpensive sealed agm... Li Ion 18650 is the direction I want to go for myself.
Adam, could you repeat the test but with a resistor instead to simulate a cell that has a 'soft short'. I think this is a much more likely scenario than a full short. A bad cell draining just a few amps will get very hot over time but may not draw enough to blow the fuse.
Great, look forward to seeing what happens. So much talk about fuses but not much testing so what you are doing is great and sharing the knowledge makes it safer for everyone.
The led was attached between the two battery lugs which I shorted. The power to the LED was also cut when the fuse blew between the nickel strip and the battery lug at the positive end of the led circuit. It was intentional, but not explained sorry :-/ I wanted to ensure you could see when the fuse blew - but actually it wasn't needed and has caused some confusion. I'll do better next time.
Thanks for the explanation. I was scratching my head at this, too, given that the positive and negative rails were all linked together and the fuses were intended to supply uninterrupted power in case of a fault.
@@AdamWelchUK you did great LOL...just next time put a similar LED light on the bus bar to show the contrast of how one light goes out and the other light stays on but reacts to the power dip/surge elsewhere in the system etc etc etc...that way it will mimic your actual load on your shed system...thanks for the great ideas and vids
Good to see that test. I'd love to know what the peak current was. Any chance you could do that again with a (high current) ammeter in series with the fuse?
Thanks Paul. My vici multimeter only go up to 20 amps and I'm not sure it would be quick enough to capture the maximum current. I think I might be able to perform this test using a resister and an oscilloscope better, but I'm not sure my little JYEtech is going to be good enough. I have a 'proper' scope on my shopping list but I'm having to save my pennies.
Adam Welch easier solution, connect meter in line with the same length of "fuse" and a power supply. Gradually increase current and watch meter for max
You diagram at 0:49 implies each cell individually connects to a common bus bar via fuse wire. Whereas just prior to that at 0:45, each cell connects to another cell in a series string, not a bus bar? Is there a bus bar under the white tape, which is commoning all of the +ves and -ves in each parallel pack? If true, why didn't you just solder fuse wire directly to that? Also, if true, you've connected two bus bars together with 4 parallel strips of fuse wire, again not the same as the diagram. I realise this is very old and you've changed your setup completely, but because people are still looking at the video, could you explain this a little further please? (You prior videos don't make this super clear either) Thanks.
So Adam, in conclusion solar charge controller can charge lithium ion pack and balance itself reasonably. Recently I was fumbled by BMS in a pack of battery while charging it with charge controller. It drain all my battery to less than 12v and the charge controller did not turn on or sometimes produce a blinking screen. Your video is very helpful cos now i cam see that i have to remove the BMS and connect it directly
+Dunkelheit667 No they are unprotected cells. The led was connected to the other cells via the fuse. I connected it that way in case the fuse blowing wasn't obvious on video, but I don't think that was a problem!
Got it now, the LED was connected in series with the fuse and went out because there was no connection to the other cells as soon as the fuse blew. Thank you for the explanation! :o)
From all the videos I've watched they use 1/8w resistor legs/leads, so they cut the wire lead off the 1/8w resistor, keep the leads for a fuse and toss the resistor. Packs of 1000+ are around $15-20 Canadian for me so fairly cheap to do this. You can buy fuse wire but I've had limited success finding it, whereas 1/8w resistors are pretty easy to find.
I love the video series! Just a theoretical question from a perspective of a newbie: What would happen if 3 cells die at the same time? Delivers the one healthy cell enough current to burn the 5amp fuse wire? If I remember correctly you said that those cells can deliver current up to 2A each Definitely looking videos about short circuits now! Thanks a lot.
It’s very unlikely the internal structure of the cells would break down so rapidly in three cells concurrently. In reality, the breakdown of the internals would be gradual, meaning the current going into the cell would slowly increase. If everything is working as it should, you should notice a weak pack well before a fuse blows, giving you the chance to locate a bad cell.
Hi Adam I really like your videos which are well researched, clearly explained and nicely presented! I have a narrowboat with the usual 12v lead acid leisure batteries, total 345 Ah, and four 50 watt 12v solar panels which are set up in 2x24 volt strings to charge the batteries via an MPPT controller, and also of course by the boat engine alternator. One day when they are cheaper, of course I'd like to have all lithium batteries, but in the meantime, I wondered whether it might be possible to have a two-stage system, in which the first stage is a 24 volt lithium battery pack of the sort you have described but rather larger, charged directly by the MPPT controller. The second stage would comprise the existing lead acid batteries still charged by the alternator in the usual way, and also charged from the lithium bank via a second controller which would step down the voltage from 24 to 12 - this could be a cheap PWM controller of course. There would be a number of advantages in doing this: as you have pointed out, the 24v arrangement of the lithium batteries is better for the batteries, but of course a lot of people have got everything set up on 12v systems. In addition, with the alternator still connected only to the lead acid batteries, the system could accept solar charge even when the alternator was running - at the moment that won't happen because the MPPT charge controller sees the alternator voltage of say 14.4 volts at its output and thinks the batteries are already fully charged. As we are most likely to be running the engine in the daytime of course, this means that a lot of solar input can be wasted, which could now be stored as additional battery capacity. The lithium bank wouldn't need to be huge as long as it could store say, one day's solar output, but could give the whole system a significant boost - what do you think? Thanks very much if you have read all this - I can see it's got a bit long! Regards Nigel
Just noticed a slight error in the above - of course if you used a cheap PWM controller in the second stage, it couldn't handle the stepdown from a possible 28 volts, so would need to be supplied via a DC-DC stepdown converter. But these are now very cheap as well.
I'm wondering about the fuse test that you've done, it seems that the test isn't testing what you've actually got connected. In your test, you don't have a nickel strip across the whole section of the positive side before it gets to the fuse, you just have a straight fuse connection, if you did, wouldn't it short out across the whole nickel strip and thus cause serious current draw? Could you test with a nickel strip on the positive behind the clips and another one in the same place you have it to see if that would short?
Hi David. Each group of cells is commoned at the negative end - therefore each group is also commoned at the positive end. The difference is that at the positive end there is a fuse between each individual cell and the nickel strip commoning the previous groups negative. I'm not sure I'm explaining this very well... I'll draw a couple of pictures... Test Setup... goo.gl/photos/JNSmQSA7Q1QfNWxg6 Real Setup... goo.gl/photos/GhYnX6pboTeFxii66 The test is intended to point out that if a single cell in a group dramatically failed and went short circuit the fuse would blow. Now in reality it wont fail that quickly and will likely draw less current than demonstrated here. But if it fails in a more controlled manner the fuse isn't likely to blow - but the cell isn't likely to get too hot either and ultimately we'd see a pack struggling to keep the same voltage as the rest under load. Hope that helps - Unless I've misunderstood the question?
Ah, no that's answered it, thanks, that helps a lot. I thought there was nickel on each positive and negative side of your real rig (ie. non test rig) so I was confused, but that makes sense. I'm planning on doing the same setup as you've done with the 7s 24v. I really like how modular it is and how the charging characteristics of gel are conducive to li-ion charging in a 24v li-ion configuration.
Adam Welch that got complicated in a hurry didn't it! I'm looking in to building these packs. and I'm wondering the dimensions of the nickel. and the current capacity. before I buy anything.
30AWG copper = 10.2A fusing current www.litz-wire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire_R2.011609.pdf Is that too high I wonder ?
Deviation is the difference in capacity within the group of cells. So it's the difference between the lowest and highest cell within one group or pack.
That idea of the LED is great. Congratulations on your videos.
But shouldn't the led turn back on after one of the fuses blows?
Nice to see a test of the fuse system. I didn't realize how simple it would be to create a fuse system for 18650 banks...
I'm not sure how expandable this is - if you want to make a bank with 100 cells in parallel I think there are probably better ways :-)
Adam, I believe this is exactly how Tesla do it with tens of thousands of cells in their packs - the probability of a dud cell goes up considerably with quantity!
As more cells from a pack drop out of the circuit, then the rest of the cells in the pack carry more current.
If the current increases and all of them fuse, identifying the original dud cells would get a bit more tedious, as they'll all be fused!
Nice video Adam, clear concise and relevant. Keep up the good work.
Thanks Simon.
I watched this video several times, and i cant understand one thing. If one the cells shorts out then fuse blows, but why LED stops glow after short circuit cell is disconnected by a fuse? Is that means, that whole pack is no longer delivering energy? Am I missing something from video?
Gintautas Raštikis I don't get it either. I would think that for the duration of the short, the LED would be out as it receives no current, but once the fuse goes, the circuit is restored. Adam, please enlighten us?
Gintautas Raštikis A comment a bit further down from Adam says that the LED was connected in series with the fuse that blew.
If you look how its soldered, its connected to the battery holder leg, not the nickle strip connecting it to the rest of the pack. So when the fuse blows, the circuit is broken.
Maybe the LED was somehow damaged by the short and so even though power is restored after the short, the LED didnt light back up??
Yeah, the LED is attached to the lug of that empty slot that he shorts so when the fuse blows it isolates the LED. I was confused at first as well.
I would have prefered to see an LED attached to the bus bar as well to show the REST of the cells still working in addition to the LED showing the cell losing connection.
Good test result there. I just tested out my fuse wire (I use 30AWG) and it melted just like yours does. Seems the 5A wire is ~31AWG, so the wire I chose is just a bit higher rating, ~6A, should be about right for the paired cells I'll be using.
+R Brown Thanks. Useful to know.
I found this handy reference giving estimates of fusing current for wire gauges.
www.powerstream.com/wire-fusing-currents.htm
It says 30AWG copper is 10.2A, so that's about OK.
Another reference that says 10.2A for 30AWG copper.
www.litz-wire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire_R2.011609.pdf
10A is a common melting rating, this table lists 6A as the "current rating"
www.gxk.org.uk/info/wire.htm
and this one about 8.5A:
electricguru.in/page_view.php?id=29
Thanks for those tables.
They clearly show the distinction between fusing current and fuse rating.
I learn something there, and 30AWG is good for the fuses.
Please excuse my ignorance ...
Having watched this video, why has the led gone out ?
The other 3 cells are still connected ?
Only the shorted fuss blew out.
Shouldn't the led still be lit by the 3 remaining cells ?
I understand the principal but can't understand if they're common negative/common positive fed and only 1 fuse blew why led went out.I
Again sorry for my ignorance can you please explain
Good insights into battery backup solar, thanks.
Good to see an actual test on this theory that seems to be the norm, and rather than you just saying "it will probably do!" like most say! :)
Steve
Impressive Adam... thank you so much for dilligence and fullfilment of follow thru. A year of real world reaults. Just dont see that with youtubers... Im living of he grid in an private RV park if you will in Colorado. Since Ive been living here wich has only been less than a couple weeks, and no power other than neighbor charging my phone and using fashlight at night.. Ive been cramming solar info... Now while im starting with cheap 100w system from harbor freght and going to use their inexpensive sealed agm... Li Ion 18650 is the direction I want to go for myself.
Thanks. Good luck with your system and the off grid lifestyle!
Great video
Thanks mate.
Nice video, proves that the "proof is in the pudding".
+Javier Palla Lorden :-) Thanks.
Adam, could you repeat the test but with a resistor instead to simulate a cell that has a 'soft short'. I think this is a much more likely scenario than a full short. A bad cell draining just a few amps will get very hot over time but may not draw enough to blow the fuse.
I will try this out and post if it show dramatically different results. Cheers.
Great, look forward to seeing what happens. So much talk about fuses but not much testing so what you are doing is great and sharing the knowledge makes it safer for everyone.
But why the LED stay off. Should not be again after the fuse run off??
Hi Adam
Why did the LED go out?, the other 3 cell's are good so the LED should have stayed on.
The led was attached between the two battery lugs which I shorted. The power to the LED was also cut when the fuse blew between the nickel strip and the battery lug at the positive end of the led circuit. It was intentional, but not explained sorry :-/ I wanted to ensure you could see when the fuse blew - but actually it wasn't needed and has caused some confusion.
I'll do better next time.
A Mathamagition !
Thanks for the explanation. I was scratching my head at this, too, given that the positive and negative rails were all linked together and the fuses were intended to supply uninterrupted power in case of a fault.
@@AdamWelchUK you did great LOL...just next time put a similar LED light on the bus bar to show the contrast of how one light goes out and the other light stays on but reacts to the power dip/surge elsewhere in the system etc etc etc...that way it will mimic your actual load on your shed system...thanks for the great ideas and vids
Great video, At max load for your entire cell bank how much current do you think you will be drawing from each cell? Thanks.
+Jeremy Hall I won't be pulling very much at all. I can't imagine pulling more than 3 or 4 amps normally. Probably less. Thanks for the kind words.
Anytime, you make great videos.
thank u so much for all your time, u have help me out so much on solar
Excellent demo
Good to see that test. I'd love to know what the peak current was. Any chance you could do that again with a (high current) ammeter in series with the fuse?
Thanks Paul. My vici multimeter only go up to 20 amps and I'm not sure it would be quick enough to capture the maximum current. I think I might be able to perform this test using a resister and an oscilloscope better, but I'm not sure my little JYEtech is going to be good enough. I have a 'proper' scope on my shopping list but I'm having to save my pennies.
Adam Welch easier solution, connect meter in line with the same length of "fuse" and a power supply. Gradually increase current and watch meter for max
Great project !! Any updates on battery's performance??
Thank you. The batteries are all doing well thanks - but I do need to do another video soon because I want to adapt things a little.
You diagram at 0:49 implies each cell individually connects to a common bus bar via fuse wire. Whereas just prior to that at 0:45, each cell connects to another cell in a series string, not a bus bar? Is there a bus bar under the white tape, which is commoning all of the +ves and -ves in each parallel pack? If true, why didn't you just solder fuse wire directly to that? Also, if true, you've connected two bus bars together with 4 parallel strips of fuse wire, again not the same as the diagram. I realise this is very old and you've changed your setup completely, but because people are still looking at the video, could you explain this a little further please? (You prior videos don't make this super clear either) Thanks.
So Adam, in conclusion solar charge controller can charge lithium ion pack and balance itself reasonably. Recently I was fumbled by BMS in a pack of battery while charging it with charge controller. It drain all my battery to less than 12v and the charge controller did not turn on or sometimes produce a blinking screen. Your video is very helpful cos now i cam see that i have to remove the BMS and connect it directly
Nice Video saw it posted on Facebook by Peter Matthews from Facebook, cool :-)
The LED went out, okay. But why? Are these 'protected' cells which will switch off in case they detect a short?
+Dunkelheit667 No they are unprotected cells. The led was connected to the other cells via the fuse. I connected it that way in case the fuse blowing wasn't obvious on video, but I don't think that was a problem!
Got it now, the LED was connected in series with the fuse and went out because there was no connection to the other cells as soon as the fuse blew. Thank you for the explanation! :o)
When you connected the first cell the LED lit up, so its clearly not in series with the 4th cell fuse
Nice dude, thanks.
Nice learning video, i have a question, what size of wire do you use, 0.15 mm ?
From all the videos I've watched they use 1/8w resistor legs/leads, so they cut the wire lead off the 1/8w resistor, keep the leads for a fuse and toss the resistor. Packs of 1000+ are around $15-20 Canadian for me so fairly cheap to do this. You can buy fuse wire but I've had limited success finding it, whereas 1/8w resistors are pretty easy to find.
Hi Adam please tell what wire you use for your fuse?
Great work
Much appreciated
Thanks
I love the video series! Just a theoretical question from a perspective of a newbie: What would happen if 3 cells die at the same time? Delivers the one healthy cell enough current to burn the 5amp fuse wire? If I remember correctly you said that those cells can deliver current up to 2A each Definitely looking videos about short circuits now! Thanks a lot.
It’s very unlikely the internal structure of the cells would break down so rapidly in three cells concurrently. In reality, the breakdown of the internals would be gradual, meaning the current going into the cell would slowly increase. If everything is working as it should, you should notice a weak pack well before a fuse blows, giving you the chance to locate a bad cell.
Just subscribed :) thx again.
Do you have any further updates ?
great work , liked that
it may be a good idea to try again with a 0 voltage cell see if the same rection happens
I'll look into this. Cheers David.
Adam Welch He's right, real world they might charge the cell just slow enough to not pop your fuse
What amp rated fuse wire is it please ,, guess 5 thanks Shane uk
+shaneweightman Yup - 5 amp fuse wire on these 18650s. Probably more than I need really.
Hi Adam
I really like your videos which are well researched, clearly explained and nicely presented!
I have a narrowboat with the usual 12v lead acid leisure batteries, total 345 Ah, and four 50 watt 12v solar panels which are set up in 2x24 volt strings to charge the batteries via an MPPT controller, and also of course by the boat engine alternator.
One day when they are cheaper, of course I'd like to have all lithium batteries, but in the meantime, I wondered whether it might be possible to have a two-stage system, in which the first stage is a 24 volt lithium battery pack of the sort you have described but rather larger, charged directly by the MPPT controller.
The second stage would comprise the existing lead acid batteries still charged by the alternator in the usual way, and also charged from the lithium bank via a second controller which would step down the voltage from 24 to 12 - this could be a cheap PWM controller of course.
There would be a number of advantages in doing this: as you have pointed out, the 24v arrangement of the lithium batteries is better for the batteries, but of course a lot of people have got everything set up on 12v systems. In addition, with the alternator still connected only to the lead acid batteries, the system could accept solar charge even when the alternator was running - at the moment that won't happen because the MPPT charge controller sees the alternator voltage of say 14.4 volts at its output and thinks the batteries are already fully charged.
As we are most likely to be running the engine in the daytime of course, this means that a lot of solar input can be wasted, which could now be stored as additional battery capacity. The lithium bank wouldn't need to be huge as long as it could store say, one day's solar output, but could give the whole system a significant boost - what do you think?
Thanks very much if you have read all this - I can see it's got a bit long!
Regards
Nigel
Just noticed a slight error in the above - of course if you used a cheap PWM controller in the second stage, it couldn't handle the stepdown from a possible 28 volts, so would need to be supplied via a DC-DC stepdown converter. But these are now very cheap as well.
I'm wondering about the fuse test that you've done, it seems that the test isn't testing what you've actually got connected. In your test, you don't have a nickel strip across the whole section of the positive side before it gets to the fuse, you just have a straight fuse connection, if you did, wouldn't it short out across the whole nickel strip and thus cause serious current draw? Could you test with a nickel strip on the positive behind the clips and another one in the same place you have it to see if that would short?
Hi David. Each group of cells is commoned at the negative end - therefore each group is also commoned at the positive end. The difference is that at the positive end there is a fuse between each individual cell and the nickel strip commoning the previous groups negative. I'm not sure I'm explaining this very well... I'll draw a couple of pictures... Test Setup... goo.gl/photos/JNSmQSA7Q1QfNWxg6 Real Setup... goo.gl/photos/GhYnX6pboTeFxii66
The test is intended to point out that if a single cell in a group dramatically failed and went short circuit the fuse would blow. Now in reality it wont fail that quickly and will likely draw less current than demonstrated here. But if it fails in a more controlled manner the fuse isn't likely to blow - but the cell isn't likely to get too hot either and ultimately we'd see a pack struggling to keep the same voltage as the rest under load.
Hope that helps - Unless I've misunderstood the question?
Ah, no that's answered it, thanks, that helps a lot. I thought there was nickel on each positive and negative side of your real rig (ie. non test rig) so I was confused, but that makes sense. I'm planning on doing the same setup as you've done with the 7s 24v. I really like how modular it is and how the charging characteristics of gel are conducive to li-ion charging in a 24v li-ion configuration.
Adam Welch
that got complicated in a hurry didn't it! I'm looking in to building these packs. and I'm wondering the dimensions of the nickel. and the current capacity. before I buy anything.
Thanks, i saw the hole serie :-)
The maths tells you it works. But there's nothing to like a real world test to put your mind at ease. 30AWG it is then!
+NERDVille Exactly. I'll get some sleep tonight ;-)
The real world wins again!
30AWG copper = 10.2A fusing current
www.litz-wire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire_R2.011609.pdf
Is that too high I wonder ?
I've measured about 9 amps per 18650 cell peak drain on my lawn mower - so he might be reaching as much as 30 amps from those three cells.
Very good point - 30AWG should be fine then.
Thanks Paul.
Aha! fuse question from your previous video answered.
Neat website you linked (repackr.com) I can't figure out what "deviation" means, however. Can anyone help explain this to me?
Deviation is the difference in capacity within the group of cells. So it's the difference between the lowest and highest cell within one group or pack.
If you look carefully at video, the led is only connected to the battery cell where the fuse is blown.
nice video
U rock