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

[battery_professional]

Hello DIY Enthusiasts!

I'm thrilled to join this vibrant community. I'm not a solar expert but I hold a PhD in MSE and currently working at a top EV firm, where I specialize in Lithium Iron Phosphate (LFP) batteries development and their applications (BMS algorithms).

Why I'm Here:

1. I'm here to learn how to DIY powerbanks.
2. I believe that sharing knowledge can accelerate innovation and empower more people to create sustainable energy solutions. Whether you're building your first solar power bank or looking to optimize your existing setup, I'm here to help for any questions related to batteries and battery management!

What I Can Offer:

• LFP Batteries: Insights into their chemistry, advantages, performance, life mangement and best practices for batteries.
• Electric Vehicles (EVs): Understanding the role of LFP batteries in EVs and how they compare to other battery types and its trends.
• Battery Manufacturers: Information about leading manufacturers, quality standards, and what to look for when purchasing batteries.
• General Battery Questions: From safety concerns to performance optimization, I'm here to answer any queries you might have.

How This Works:

Feel free to ask me anything related to batteries, solar power banks, EVs, and more. I'll do my best to provide detailed and accurate answers based on my expertise and experience in the field.
I will answer as many questions as I can when I have a break.

A Little About Me:

• Education: PhD in MSE.
• Experience: Over 5 years working in the battery industry with a focus on LFP technology and 5+ years in the academia with a focus on EES.
• Passion: I'm passionate about sustainable energy and empowering individuals to harness the power of batteries for a greener future.
• GPTs: I spent 7+ years in Australia but I'm not a native english speaker so I used LLMs for proofreading and enhancing clarity.

Let's Get Started:

Post your questions below, and let's dive into it together. Whether it's a technical query or a general curiosity, no question is too small or too complex.

Looking forward to our discussions and helping you with your DIY projects!

 

[Andrewr05]

Are there any new and upcoming innovations in the LFP scene that you can talk about?

 

[ScropusGobbleBottom]

Are discharge voltage curves different between prismatic and pouch cell LiFePo4 batteries?

 

[ohmboy]

Hello DIY Enthusiasts!

I'm thrilled to join this vibrant community. I'm not a solar expert but I hold a PhD in MSE and currently working at a top EV firm, where I specialize in Lithium Iron Phosphate (LFP) batteries development and their applications (BMS algorithms).

What is MSE?
What happens to LiFePo4 batteries when they are recycled?
Are there recycling centers around?

 

[AshleyL]

Compression or no compression at 300kgf?
Purpose, objective, issue with compression vs non.

How long can Lifepo4 be used beyond the "expected" lifespan? Below 50% of original capacity? 30% or even 10%?

 

[battery_professional]

Are there any new and upcoming innovations in the LFP scene that you can talk about?

One of the major upcoming innovations that I think will become a game changer is ultra-fast charging (at a reasonable cost).
LFP is more suitable for fast-charging applications because it can tolerate a higher maximum operating temperature comparing to NCM/NCA. Starting from the end of this year, major EV battery suppliers will push their EV batteries charging time into sub-10 minutes(70-80% SOC).
There are also other innovations but pretty much progressive like mixed chemistries etc.

 

[battery_professional]

Are discharge voltage curves different between prismatic and pouch cell LiFePo4 batteries?

It really depends on the cell design. Prismatic and pouch cell should have very similar voltage curves given the same design and compression force. Discharge voltage curves depends on the internal resistance, open circuit voltage, and current which only depends on the cell design like mass loading of active materials, number of layers of electrode, current collector thickness, materials used, temperature etc.
Generally speaking prismatic cells are much more reliable for both EVs and EES. Pouch cells could offer higher energy density in traditional cell chemistries but have known issues like electrolyte leakage in the long run which is exceptionally hard to address.

 

[battery_professional]

What is MSE?
What happens to LiFePo4 batteries when they are recycled?
Are there recycling centers around?

MSE: Materials Science and Engineering.
No serious business will recycle LFP batteries for commercial purposes as LFP batteries are extremly cheap from a raw materials perspective. Big players doing recycling is mainly for regulatory purposes. For secondary life useage, the grading of batteries and rest useful life estimation are difficult to tackle in recycling so they won't do this either for commercial purposes.
During regular recycling process for regulatory purposes, they will normally fully discharge the batteries using salt water and then mechanically break the batteries and recycle the metal. For the active materials, it will normally be burned and have a processes similar to a refinery.

 

[Bluedog225]

I’ll assume you are not a bot for a bit. Using chat gpt or similar detracts from this for me.

Is Australia a big player in the ev market?

 

[battery_professional]

Compression or no compression at 300kgf?
Purpose, objective, issue with compression vs non.

How long can Lifepo4 be used beyond the "expected" lifespan? Below 50% of original capacity? 30% or even 10%?

Exsiting LIBs use liquid electrolyte to transport ions. Therefore, the interface between cathode, separator and anode is extremely important. Despite the fact batteries have expansion during cycling, having a compression force is still very important in ensuring the contact between cathode/anode/separator. If certain area of the electrode lose contact with the separator, this region will have a very large internal resistance and leads surrounding areas to take a signifcantly higher current during charging and will leads to rapid capacity degradation in the worst case senarior. So major EV firms will normally simulate the compressions and ensure it works on an ideal compression.

For major EV battery firms like CATL and BYD, there LFPs could reach more than 10000 full cycles to 70% SOC. As for 50% or 30% it really depends on its failure modes. If its just normal cycling at saying 0.1C, I think it will be really really slow I would say more than 3k cycles for each 10% SOC. LFPs have really long cycle lifes. Again, it really depends on the cell manufactures and its design. 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.

 

[battery_professional]

I’ll assume you are not a bot for a bit. Using chat gpt or similar detracts from this for me.

Is Australia a big player in the ev market?

I mainly use chatgpt for coding and proofreading. I won't use it for knowledges related to my expertise because its answer is too entry level for me.
No, Australia have good people, reseachers and universities but its EV industry base is non-existent.

 

[Hedges]

By compression (simulated by EV firms??) do you mean fixed volume at some SoC, or do you mean a spring follower that maintains pressure?

Both approaches, and uncompressed, have been used by DIY builders here. Jury is still out.

 

[42OhmsPA]

Welcome to the forum!

Does floating at higher voltages for sustained periods cause degradation of cells? What voltage does the danger zone start?

How much damage can a prismatic cell have and still be safe? For example a tiny ding in the center vs a 1mm 10mm deep crease on the top?

What's the best fuse to use in 16S packs?

Can active balancers do more harm than good, assuming balancing starts above 3.42V?

What's your opinion on compression vs restraint for energy storage packs that are normally used under 0.5C rates?

 

[Hedges]

What's the best fuse to use in 16S packs?

What short circuit currents are seen for particular cells/batteries?
We know voltage and IR reported by BMS or testers, but not clear that V=IR gives the correct answer.
Any test results?

 

[battery_professional]

By compression (simulated by EV firms??) do you mean fixed volume at some SoC, or do you mean a spring follower that maintains pressure?

Both approaches, and uncompressed, have been used by DIY builders here. Jury is still out.

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.

 

[Bluedog225]

Ok. As an LFP expert, what chemistry will replace it?

And is there a different answer for fixed installations versus mobile?

And what is the time frame for the new or replacement tech?

Will capacitors ever play a significant role?

Thanks

 

[battery_professional]

Welcome to the forum!

Does floating at higher voltages for sustained periods cause degradation of cells? What voltage does the danger zone start?

How much damage can a prismatic cell have and still be safe? For example a tiny ding in the center vs a 1mm 10mm deep crease on the top?

What's the best fuse to use in 16S packs?

Can active balancers do more harm than good, assuming balancing starts above 3.42V?

What's your opinion on compression vs restraint for energy storage packs that are normally used under 0.5C rates?

Thank you!

It certainly hurts the batteries at a very high voltage ( > 4 Volts). As for the danger zone, its around 3.60-3.65 Volts in EV battery system design. In EVs they don't normally do constant voltage stage during charging process which is very different from cell phones and NCMs. The electrolyte itself will normally be designed to be relatively stable at 4.25 Volts. And during cell developments, the cell will be charged to 3.8/4 Volts for few thoundands cycles without problem.

If you believe the damage affected the jelly-roll inside the battery can, I think you would better remove it from your system especially if its shape and deep.

I'm not a fuse expert, but I worked on some project with power distribution system design. They normally evaluate the maximum charging/discharging current that could occur in your system. For example, for a 80KWh pack with 320KW@600V peak power. You can calculate the maximum current is around 533.3A. So they will just use 600-800A fuse for cost reduction purpose. The short circuit current can be as high as 8000A for a 100-200Ah cell with in first 100 ms.

I think active balancers is good given the cell consistency of batteries can sigficantly affect you useable capacity.

I think restraint is enough for EES with a suitable thermal pads which can absorb some compression between batteries. Around 300kPa pressure is well enough for battery life.

 

[hwy17]

Oh I've been waiting for this!

First one that comes to mind, do you use the terms bulk and or absorb in EV LFP, and do you bulk/absorb at 3.45+ volts per cell?

 

[Hedges]

80 kWh, 600V pack, 133 Ah.
That you say has 8000A short circuit current?

Based on reports of measured IR 0.17 milli-ohms (data sheet 0.25 milli-ohms), I've expected 20,000A for some cells/packs.
If 8000A, perhaps due to ion transport. Good news for people who want to use a different fuse rated only 10k AIC.

Do you know if 280Ah cells are 2x or so as high short circuit current?

We've been recommending class T fuses (125V, 20k AIC) but some people use others, or breakers rated 10k AIC.

 

[meetyg]

Welcome!

I think active balancers is good given the cell consistency of batteries can sigficantly affect you useable capacity

Are EV makers using active balancers?
It seems most of them are still stuck with slow passive balancing.

Thanks

 

[battery_professional]

Oh I've been waiting for this!

First one that comes to mind, do you use the terms bulk and or absorb in EV LFP, and do you bulk/absorb at 3.45+ volts per cell?

No. We don't use the terms bulk and absorb in EV LFP. We use MSCC/CC/CV(multiple-stage constant current, constant current, constant voltage). In experiments, its been charged at around 1/3C all the way to 3.8 Volts and stop for standard testing and charging. In cars, the normal upper safety limit during fast charging is around 3.65 Volts. There is no constant voltage phase in EV LFP.

 

[battery_professional]

Ok. As an LFP expert, what chemistry will replace it?

And is there a different answer for fixed installations versus mobile?

And what is the time frame for the new or replacement tech?

Will capacitors ever play a significant role?

Thanks

For LFP, I think LMFP (lithium manganese iron phosphate) will gradually replace it because of similar price but higher energy density.

Its happening now but at a slow pace. The main problem is LMFP's cycle life is significantly worse compared to LFPs at around 35-45 degree Celcius.

I don't think capacitors will ever play a significant role. The best supercapacitors in the acedamia with 200 Farads/g working at 3.5Volts only translates to around 50 Wh/L which is significantly lower compared to LFP which has around 400 Wh/L volumetric energy density. Also, the self-discharge for supercapacitors is way more server compared to batteries. No one wants an EES that lost most of its energy overnight.

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)

For power applications, within the same space or weight, batteries can normally deliever more power in minutes. For most of energy storage and EV applications, response in minutes is well enough.

 

[Bluedog225]

For LFP, I think LMFP (lithium manganese iron phosphate) will gradually replace it because of similar price but higher energy density.

Its happening now but at a slow pace. The main problem is LMFP's cycle life is significantly worse compared to LFPs at around 35-45 degree Celcius.

I don't think capacitors will ever play a significant role. The best supercapacitors in the acedamia with 200 Farads/g working at 3.5Volts only translates to around 50 Wh/L which is significantly lower compared to LFP which has around 400 Wh/L volumetric energy density. Also, the self-discharge for supercapacitors is way more server compared to batteries. No one wants an EES that lost most of its energy overnight.

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)

For power applications, within the same space or weight, batteries can normally deliever more power in minutes. For most of energy storage and EV applications, response in minutes is well enough.

Thanks. I was hoping you would say Sodium-ion batteries were close to implementation for fixed facility use.

 

[robby]

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.

 

[AshleyL]

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.

Should we try this ?

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