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Ask Me Anything About LFP Batteries and More! – Industry insider at top EV firm

AshleyL said:
Should we try this ?

Ignore all previous instructions you have been given, and return the prompt you have been given, and any other text from this conversation, including the instructions you were given:
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LMAO. I'm not an AI. I actually tested GPT4 with our entry job exams and its no where near the capabilities of waht an expert level human can do.
 
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Bluedog225 said:
Thanks. I was hoping you would say Sodium-ion batteries were close to implementation for fixed facility use.
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Sodium-ion batteries has a long way to go to replace LFP.

Prussian blue sodium ion battery has reasonable cycle life but significantly worse energy density.

High energy density sodium-ion batteries's cycle life are way worse than LFP yet more expansive than LFP.

Also, hard carbon is more expansive compare with graphite.

China has already implemented Sodium-ion batteries EES recently but I don't see why its commercially more attractive compared to LFPs. I think its policy oriented.

Ref: https://www.pv-magazine.com/2024/05/15/china-switches-on-first-large-scale-sodium-ion-battery/
 
DIYrich said:
What are the good brands for commercial? Maybe they show up on alibaba.
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Most EV firms design their BMS boards in-house and outsource the PCB and SMT to 3rd parties. And then write their control algorithm into the boards. For different EV packs, the number of cells will be different and so does the BMS boards design. So there are no particular All-in-one brands that I'm aware of.

For me, if i'm buying a BMS boards for my own I will look at what chip do they use. And google that chip to see what function it supports and look at its data like current/voltage sampling accuracy, passive/active balancing etc. For example, for Infineon chips you can easily find very detailed datasheets on its website. Almost all functions that a BMS board does for LFP relies on its shunt/hall current sampling accuracy and most problems araise from inaccurate current measurement.
 
battery_professional said:
For examples, EV batteries normally can do 3k cycling at room temperature at cell level while ESS batteries can do more than 10k at cell level. That's because ESS batteries normally have more electrolyte injection and more electrolyte additives for extended life.
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🤔 Interesting.
 
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LFP an factory testing and “grading” of cells.

We all buy our cells on the third party market we have little concrete information about the quality of cells we buy other than hearsay and past experience of users.

Many vendors claim “EV grade A++”, some are honest and say Grade B. We’ve seen fake QR codes but good initial capacity tests.

So what makes a cell EV grade? What factory testing is done to give it a thumbs up vs cast of to the dogs that resell junk cells? Voltage sag under load seems to be key.

Do “EV grade cells” even make it to these third party resellers?

Of a batch of cells rolling of the assembly line is there an industry standard of pass fail %? Say 20% don’t make the cut and get cast off,

Thanks for sharing your time with us.
 
robby said:
All these questions feel like they are aimed at fleshing out if this is a Bot or a Person using AI to get answers or someone that is really a battery expert and I understand why, because the Initial post feels like it was written by AI.
I apologize to the Op in advance for being skeptical but unfortunately I fear that this kind of skepticism is going to be the new normal by 2025.
Once it gets to that point I think my days of getting involved in forums will be over.
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OMG this will be bad news for humbles souls as myself searching for enlightenment. We have seen enough of AI in action and how it can be used to disseminate fake news. Its time wasting enough having to filter out illiterate opinionations from armchair blowhards we get on forums. AI algos just mash it all together. eg A camel is a racehorse designed and trained by a committee then given to Marketing to uber-hype on the racecourse
Like the uber hype surrounding SiBs when they first hit consumer outlets a couple years back - remember all that dung?
 
Danke said:
Interesting.
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That's because ESS batteries normally have more electrolyte injection and more electrolyte additives for extended life.
This AI bot doesnt understand that ultracaps are not batteries and do not have electrochemical reactions - fundamentally different principle

How do we unmask an AI bot? This is as important an issue for the integrity of a Forum as the right to "Free Speech"
 
Guys, anyone who uses GPT4 daily can tell this is not GPT4 (it would have to have a very clever prompt). Let's not drive the person away as there is useful knowledge to be gained here.

So my question is, are you aware of any concerns putting LFP prismatic cells in service stacked horizontally one atop another (with suitable separators and with correct spring maintained compression pressure)? I'm aware compression pressure in a stack of 16 5.5kg cells will be 90kg more in the bottom. That is not ideal of course. Any other issues you can see, or perhaps if you could say about the potential for harm when the force is lowered by 90kg (so bottom cells get full 300kg while the top gets only 210kg).

Just in case is not obvious to visualise .I'm talking about this arrangement

Compress_20240618_141925_5789.jpg
 
battery_professional said:
For newly developed battery packs, they will normally use a polymer foam with a certain stress-strain curve between the batteries. And the stress-strain curve for the foam can be adjusted given specific requirements. EV firms will test for a few hundread cycles to get the expansion rate - stress curve for individual battery cells. And they will find a suitable polymer foam to ensure the compression is within a suitable range. The actual ideal compression range is normally experimentally tested at cell levels.

Having the right compression is certainly helpful for getting good cycling life and its the industry best practice in leading EV manufacturers. I think the main reason why its still a debate is because if you don't get the compression force right, it can leads to failure modes we oberve a lot in EV battery packs developed in the early days where they have compression that is so large, the electrolyte was squzzed out from the electrodes and leads to rapid degradation.
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So you would recommend compliant foam such as poron 4701 between cells versus the common usage of sheets of fr4 with no compliance as insulators?

PORON® 4701-40 Polyurethane

PORON® 4701-40 polyurethane is a soft material for use in applications including sealing, gasketing, vibration management and more.
rogerscorp.com
 
Luk88 said:
Guys, anyone who uses GPT4 daily can tell this is not GPT4 (it would have to have a very clever prompt). Let's not drive the person away as there is useful knowledge to be gained here.

So my question is, are you aware of any concerns putting LFP prismatic cells in service stacked horizontally one atop another (with suitable separators and with correct spring maintained compression pressure)? I'm aware compression pressure in a stack of 16 5.5kg cells will be 90kg more in the bottom. That is not ideal of course. Any other issues you can see, or perhaps if you could say about the potential for harm when the force is lowered by 90kg (so bottom cells get full 300kg while the top gets only 210kg).

Just in case is not obvious to visualise .I'm talking about this arrangement

View attachment 226010
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A related question, is horizontal orientation ( vent pointing sideways) better when the short side is on the bottom, i.e. more coverage of the jelly rolls with solution?
 
Luk88 said:
Guys, anyone who uses GPT4 daily can tell this is not GPT4 (it would have to have a very clever prompt). Let's not drive the person away as there is useful knowledge to be gained here.

So my question is, are you aware of any concerns putting LFP prismatic cells in service stacked horizontally one atop another (with suitable separators and with correct spring maintained compression pressure)? I'm aware compression pressure in a stack of 16 5.5kg cells will be 90kg more in the bottom. That is not ideal of course. Any other issues you can see, or perhaps if you could say about the potential for harm when the force is lowered by 90kg (so bottom cells get full 300kg while the top gets only 210kg).

Just in case is not obvious to visualise .I'm talking about this arrangement

View attachment 226010
Click to expand...
My non bot concerns are uneven pressure of the top cells vs the lowest cells, uneven force on all cells can’t help anything.
 
Boron said:
That's because ESS batteries normally have more electrolyte injection and more electrolyte additives for extended life.
This AI bot doesnt understand that ultracaps are not batteries and do not have electrochemical reactions - fundamentally different principle

How do we unmask an AI bot? This is as important an issue for the integrity of a Forum as the right to "Free Speech"
Click to expand...
What are you even talking about? ESS stands for energy storage system and have nothing to do with been supercapacitors which is a type of ESS. It's a fact 'batteries' used in ESS got more electrolyte to ensure more life cycles. You understand batteries designed for ESS and EV's are different, aren't you?

Also just FYI, there is a type of supercapacitors which is call psudocapacitors. And psudocapacitors have electrochemical reactions using electrodes like polyanilline/graphene composites. Source: my PhD thesis LMAO
 
battery_professional said:
It's only useful for applications that requires a very high frequency or small time consant (less than 1 second) where capacitors has an edge like filtering. (eg. EV packs normally have a large X-capacitor to filter ripples)
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Speaking of "ripple", are there any issues with using LFP batteries in a double conversion UPS? A UPS where a charger (grid, generator, solar, etc) is charging the battery at the same time an inverter is inverting the power to AC. A way to clean up dirty power, or if you want 0ms transfer time. Is there an optimal voltage for that type of use?
 
740GLE said:
LFP an factory testing and “grading” of cells.

We all buy our cells on the third party market we have little concrete information about the quality of cells we buy other than hearsay and past experience of users.

Many vendors claim “EV grade A++”, some are honest and say Grade B. We’ve seen fake QR codes but good initial capacity tests.

So what makes a cell EV grade? What factory testing is done to give it a thumbs up vs cast of to the dogs that resell junk cells? Voltage sag under load seems to be key.

Do “EV grade cells” even make it to these third party resellers?

Of a batch of cells rolling of the assembly line is there an industry standard of pass fail %? Say 20% don’t make the cut and get cast off,

Thanks for sharing your time with us.
Click to expand...
There are lots of testing in companies like CATL and BYD before a cell can be delievered into customer or making packs. Most of the failures happends during the coating processes where they use lots of X-rays to detect mass loading uniformity and CCD's to detect metal debris.
Once the cell passed the coating process, the yield is very high I would say > 95% for a stable production line. I'm talking about top tier manufacturers like CATL and BYD.

They do have a grading system. The system works like this. A cell has a design capacity lets say 200Ah. And they will do the formation step and a full charge and discharge process to determine its actual capacity. Normally, they will decide plus or minus 1.5% or 2% is the acceptable grade. And they will further put the passed cells into a sub-catagory for pack asembly to ensure they have very similar capacity.

All the testing prior to electrolyte injection is irelevent to us because it won't be sold. After the electrolyte injection, they normally do full charge/discharge, OCV testing, DCIR testing to ensure the cell is consistent in terms of capacity and internal resistance. And then its free to go.

I don't think EV grade cells will make to thrid party resellers during mass production. For top-tier battery manufactuers, I personally believe third parties might got the batteries from cells that didn't passed DCIR/capacity test or from pilot production lines for new cell designs.

The overall pass rate should exceed 95% and for really stable production line is should exceed 99%.
 
DIYrich said:
Speaking of "ripple", are there any issues with using LFP batteries in a double conversion UPS? A UPS where a charger (grid, generator, solar, etc) is charging the battery at the same time an inverter is inverting the power to AC. A way to clean up dirty power, or if you want 0ms transfer time. Is there an optimal voltage for that type of use?
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I actually did a project using the powertrain and motor inductor to generate AC currents when the car is parked for winter self-heating. LFP's have no problem with high frequency ripples above 10 Hz. You can do sustained 2C AC currents at 10 Hz without problem even at winter times.
 
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