How is using Li-Ion a sustainable option, we don’t really know what to do with the Lithium (yet) as far as I know? Please enlighten me if there’s a way to upcycle or realistically recycle Lithium?
the first of the two integrates used will balance 16 cells, while the other will balance 10 cells, and you know how these circuits can be connected to each other, please can you help
While charging to 4.2V is fine, and usually the "max" for most batteries like the 18650, you're not doing yourself any favors. The perfomance difference between 4.1 and 4.2V is negligible in smaller sized battery packs, and it has been proven that charging to just 0.1V under the specification's max can increase the amount of charging cycles considerably. That means longer times in between needing to replace the battery pack. Personally, wherever possible I'd rather add another series and undercharge the battery pack a little bit than pushing the charge voltage to the maximum. This, of course, I would do in applications where I would see a significant overall voltage output by charging to just 0.1V less per cell (example: a 12S battery pack where charging to 4.2V yields 50.4V and charging to 4.1V yields 49.2V). Hope this helps you or someone!
Hello, do you know how the cells are balancing? Is it active or positive balancing ? And do you have the thought about the logic of balancing, is it a constant or top balancing (just at the top of the charging curve of lfp) ?
This should be a HUGE lesson in QC. I am sure LG saved some money in not having proper QC. It might have even been a LOT of money they saved... Not proper staffing, not buying some validation equipment, etc... But not having that proper not only led to fires, which to be fair as you mentioned, that happens. The fact is, you will never be able to get rid of all problems in any tech. The REAL issue is that their QC and auditing didn't allow them to narrow down which batches had the issues. As a result, instead of just replacing the batteries from one line or one machine or whatever, LG had to replace ALL the batteries. So it was somewhere under $2B dollars... Yeah, great that you might have saved a couple hundred million dollars or whatever... Until it costs you $2B to fix... That said, as a Bolt owner, I haven't told anyone I'd never buy another Bolt. Love this car. Got over 100k miles on it before my battery was replaced. No significant degradation. Except for the slower fast charging, which is fine for my use, this is a great car... Problems can happen to any car. Recalls happen. GM took care of it. I'm still happy... And hopefully LG has learned an important and expensive lesson. ;-) Also, there haven't been a lot more fires as they have been replacing packs, so it really was a very very small percentage of the packs that had an issue...
It's important to know that just because you don't violate the rules on a lithium cell doesn't mean TR (thermal runaway) won't happen. Dendrite growth and impurities in construction can cause TR even in the best cells. It's widely known in the industry that between 1 in 4M and 1 in 10M cells, even from top tier manufacturers, will develop an internal short. If you continue to use the cell, this can cause TR. We also have to realize in any device there is the problem of mechanical mangling due to some sort of abuse. The bottom line is you always have to assume at some point TR will happen, so design for safety.
Kevenc, I absolutely agree with your comments. I think I can believe the one in 4E6 failure rate from the best manufacturers for an 18650 cell. But my engineering intuition tells me that the failure rate for a larger cell will be higher. Two factors at play here. 1. Failure rate per square area of separator due to contamination and/or defects, 2. Damage due to final cell assembly. I suspect 1 above is is the greater part, but I have no data on this. Be that as it may a BESS INSTALLATION may be 50 MW total. If each cell is 100 WH, 500,000 cells are needed. So our chances of infant mortality are 4E-7 x 5E5 or about 2E-1. 1 in 5! Now not all failures will lead to thermal runaway, hopefully the BMS will notify the operator to take corrective action before things go south. Unfortunately this seems not to have happened in Surprise AZ, etc etc. Even if no one is injured in such events, we, the electric utility rate payers will ultimately pick up the tab.
Each blade is made up of multiple cells. They're in parallel, not in series. You add the voltage in series, but the voltage of a single blade is sitting at the normal 3.2 V for LFP cells. Either it's one long prismatic tape (one big cell), each layer is a separate cell, or each layer is multiple cells. If there are more than one cell in each blade, then they're paralleled; you add the amps, not the voltages. If the blade was just one really big cell, then it would be one continuous foil for each electrode, and the nail would complete the circuit, thus causing the entire cell to short. We know that didn't happen because it didn't explode, it didn't get real hot, and most important of all, the voltage didn't drop to zero. If the blade was a cell per layer, then you would still short out every cell if you drove a nail through it. It doesn't matter where the nails are located, it would connect the foils and short every part of the cell. We know that both of the above cases are wrong because there was a fairly quick loss of the battery's voltage, then the voltage drop stopped. Somehow the short was disconnected from the majority of the battery. However, if there are multiple smaller cells per layer, say 10-20 cells per layer, then driving a nail straight down through the battery would only short out 1 cell per layer. If there are 20 layers, it would short out 20 cells.... of the 200 - 400 cells in the battery... or between 5% and 10% of the battery. Definitely safer than shorting out 100% of the battery. Shorting a cell or multiple cells would cause those cells' voltage to plunge, and cells in parallel of unequal voltage will cause the higher voltage cells to charge the lower voltage cells, which is shorted out, so it would almost be like shorting the entire battery. UNLESS you can disconnect the shorted cells. How do you connect hundreds of cells in parallel and disconnect one that's shorted out? Simply, you connect all the anodes to a bus bar, and all of the cathodes to a different bus bar using tiny wires that serves as a fuse in case the current running across it gets too high. So, one cell per layer shorts, all of the other cells attempt to charge it, pushing high current through it, and the fuse breaks. You've now disconnected the 20 cells that the nail was driven through, stopping the entire pack from shorting out. The battery voltage drops when those other cells try to charge the shorted cells, there's a bit of heat generated, then the voltage stops dropping and heat stops being produced. The connections have been severed. Watch the BYD Blade production facility video. At about the 14 second mark, you'll see some rolls. Each roll looks like white paper with little dark squares maybe 6 centimeters in width and 10 centimeters high, and they're spaced about every 5-10 mm apart. Seems like the dark squares are either the cathode/anode material, or the current collector. Line them up and sandwich an electrode separator between them, and voila, you have 10-20 cells per layer. You just need to run a bus foil along side them and connect each cell to the bus. That could be done by either placing a tiny wire between the cell and bus line, or by printing a tiny metal wire between the two. I can't imagine this manufacturing process would be all the complicated or expensive to setup. Voila... blade battery.
Nail Penetration was originated to cover shorts by inner particles. Panasonic consumer cells catched fire bake in the 2000‘s and hence this test was developed. Despite that, the test is pretty controversial regarding this failure mechanism.
The way this guy explained I would haven fallen asleep in the past… changing myself , this is my topic of interest. Dude more enthusiasm to make sleepy once to wake up and listen. Anyway good battery technology.
Hi Akshay, so if the IR is related to the distance it has to travel inside the cell, the 18650 cells which are capable of 8C have an IR of 15mOhm whereas same 18650 cells which are capable of 1C have an IR of 45mOhm. Does it means the roll is smaller in 8C cells compared to 1C cells and it has to travel lesser distance? Hence the IR is less but since the roll is smaller meaning the active material and all will be less so the life cycle is less right? Please let me know the relationship between IR and the life cycle of a same 18650 cell.
The fold and short situation should be detected by bms management SW the first time powered it up and charged, it was not that logical the short developed after so many batteries were on the market for months, may be something more basic that the cell factory using material not following specification? Falsify QA report? skipping maintenance of production machines causing material misalignment and floating debris inside the pouch? When the cost was squeezed to the bottom, it came back hit them on the top.
BYD blade cell will offer minimal contribution to vehicle chassis structural rigidity. Tesla 4680s will be permanently embedded in epoxies. Think AL soda cans, it has no strength unless the thin walls are bonded with adjacent cans for sheer strength. Removable cells must have built-in allowances for manufacturing tolerance/replacement. No cell-to-cell sheer strength as structure compared to 4680. (btw 4680 just a form factor, same for NNNN)
So, this is a manufacturing defect in the LG cells? Poor quality control? Not knowing which cells are defective until the smoke escapes, total recall is the only way to insure the cars, houses, shopping malls, apartment building, don't burn down as a result of the battery defects. After seeing how a folded and stack can have manufacturing issues and the steps required to manufacture these batteries, no wonder Tesla's cylindrical batteries are so much faster, simpler, and cheaper to manufacture while being less prone to defects.
Is this battery format still needed as Tesla moves to LFP? The new Tesla battery using LFP from China does not seem to be using the 4680 batteries, it looks cleaner and far less complex, see Munro Live videos. 43% of EV produced by Tesla in China use LFP batteries, moving to the BYD blade battery can lead to another improvement.
