Severe capacity degradation of 280Ah cells -- warning!

Amy Zheng

Docan Technology(Shenzhen) Co.,Ltd
I'm sorry for your situation, but I feel compelled to observe that you chose to return to a marketplace you knew supported fraud, and roll the dice on an untested vendor. If we all just refused to do this, Chinese vendors would learn that a reputation for honesty supports higher prices.

One of the major benefits of this forum for me is the shared experiences. Ditto for Will's videos. Amy Zheng at Docan is an example of a Chinese rep who has learned through years of experience that honesty and product support build brand credibility which has real value in the US market. She follows the forum and communicates through it; she recently posted this acknowledgment of what she's learned through interacting with us.

Old proverb: "A smart man learns from his mistakes. A wise man learns from the mistakes of others."

Right now, like it or not, all the LiFePo4 products come from China. Disreputable Chinese companies (and entire marketplaces) figure they have us by the 'nads. Happily, a few seem to have figured out that having a trusted brand is good for business. Let's look for those, call them out publicly here, and support them.
Thank you very much! I will keep learning from this forum. We also can offer pickup or UPS fast delivery service from US warehouse
 

Just John

Photon Sorcerer
I ordered 16 280Ah Varicore cells for $2020 via AliExpress from the LiitokalaVariCoreFlagship Store. It took two months for the cells to be delivered from China to Arizona.

All 16 cells were capacity tested with an EBC-A40L tester upon receipt, and all cells tested to 85% of 280Ah advertised capacity. An average of 238Ah capacity was measured for all 16 cells.

Below is the capacity test result for cell 6 (238.1Ah measured capacity). The capacity test results for cells 5-12 are attached. The blue curve is voltage in volts, the red curve is amperage in amps, and the horizontal axis is time in hours. The capacity test results are in Ah and the energy units are Wh. The test charged the cell fully using 3.65V, followed by a 30 minute wait, followed by a discharge at 40A until 2.5V reached, then charged at the end in order not to leave the cell in a discharged state. The max charging and discharging rate for the EBC-A40L tester is 40 amps, corresponding to 0.143C for these cells.


View attachment 66454

The manufacturer specifications for these cells shows capacity degradation vs. cycle below. The horizontal axis is cycle number and the vertical axis is percent of 280Ah capacity. We see that 85% measured capacity corresponds to 2750 cycle loss. The lifetime cycles was advertised to be 4000 cycles for these cells.

View attachment 66446

Lifetime Ah is defined as the total Ah over all 4000 cycles. Percent Lifetime Ah loss of these cells = the area under the above curve out to 2750 cycles divided by the area under the curve out to 4000 cycles. Doing that calculus, Lifetime Ah loss = 73.4%. I disputed the transaction and requested a 73.4% refund based upon Lifetime Ah loss.

I paid for 8 of the cells with a credit card and 8 of the cells with Paypal. All were bought on the same day in May 2021. AliExpress dispute resolution was horrible. They resisted the 73.4% refund, sided with the seller fraud, and closed the dispute associated with each package of 4 cells. In response, I contacted my credit card company and Paypal. The credit card company, Chase, was excellent. My credit card now shows a full refund. Paypal dispute resolution has so far been horrible. Paypal completely ignored all the definitive evidence that I provided. That evidence took over two weeks to measure. You never get to talk with the person making the dispute resolution decision. The initial response from Paypal was to side with the fraud committed by the seller and close the dispute. I called Paypal twice after they sided with the seller fraud. The first person refused to reopen the dispute. The second person correctly reopened the dispute. You never get to talk to the Paypal dispute "judge" to make sure they understand the evidence. The first anonymous Paypal "judge" response did not address the evidence. It's as if they didn't at all understand the evidence and just skipped it. Anonymous backroom blackbox "judges" in the Paypal dispute resolution have so far been horrible.

This is not the first time that I have experienced fraud from a seller on AliExpress. I ordered 500g of what was supposed to be Nicotinomide Riboside. It failed a basic melting point test and taste test. The seller sent a sugar. I submitted a picture of the melting point test and got my money refunded. However, the seller was allowed to continue to sell the same fraudulent product on AliExpress, so I submitted a review with pictures of the melting point test. The seller delisted the product to erase the review and relisted the exact same product on AliExpress. AliExpress allows proven fraudulent sellers to continue to use their platform. This is one reason why there are so many fraudulent sellers on AliExpress.
Just as an FYI, in the USA there are consumer protection laws that limit your liability when using a credit card. You can get the government involved if the credit card company doesn't listen.
PayPal protection is not based in law. You depend on the good faith of PayPal to fulfill their promise of protection.
Use a credit card with PayPal and get an extra option for dispute.
DO NOT think that Alibaba or Aliexpress will "do the right thing".
DO NOT think that PayPal will "do the right thing". They get their profit from the seller after all. Maybe they will......
 

Just John

Photon Sorcerer
40/280 = 0.143. 1C is 280A for a 280Ah cell.

Will Prowse had a video from Jan 2021 about 280Ah cells from the same seller but different cell manufacturer. I tested Varicore cells. Will tested Eve cells. Will didn't experience the capacity fraud with the Eve cells like I did with the Varicore cells.

I will look at Basen. All LiFePO4 roads point to Shenzhen it seems.
I recommend Amy from Luyan. She buys genuine grade A directly from EVE. She has a very long history here, as well as a very long thread.


 

RCinFLA

Photon Sorcerer
I ordered 16 280Ah Varicore cells for $2020 via AliExpress from the LiitokalaVariCoreFlagship Store. It took two months for the cells to be delivered from China to Arizona.

All 16 cells were capacity tested with an EBC-A40L tester upon receipt, and all cells tested to 85% of 280Ah advertised capacity. An average of 238Ah capacity was measured for all 16 cells.

Below is the capacity test result for cell 6 (238.1Ah measured capacity). The capacity test results for cells 5-12 are attached. The blue curve is voltage in volts, the red curve is amperage in amps, and the horizontal axis is time in hours. The capacity test results are in Ah and the energy units are Wh. The test charged the cell fully using 3.65V, followed by a 30 minute wait, followed by a discharge at 40A until 2.5V reached, then charged at the end in order not to leave the cell in a discharged state. The max charging and discharging rate for the EBC-A40L tester is 40 amps, corresponding to 0.143C for these cells.


View attachment 66454

The manufacturer specifications for these cells shows capacity degradation vs. cycle below. The horizontal axis is cycle number and the vertical axis is percent of 280Ah capacity. We see that 85% measured capacity corresponds to 2750 cycle loss. The lifetime cycles was advertised to be 4000 cycles for these cells.

150 mV initial cell voltage drop from OCV with only 40 amp load (near 25 degsC) says it is a very used cell. Seeing that much drop initially pretty much assures it will not make capacity rating.

A new 280 AH cell should only have about 40-45 mV terminal overpotential voltage slump with 40 amp load current at 25 degsC.


Approx equilbrium slump (after 90 seconds of load) for new cell. Red is >0.5 CA rate with layer starvation effect in play.
1634658751048.png
 
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RobertGreen

Solar Addict
I'm glad you got things worked out as it is sounds pretty clear that those cells were not delivered as they were advertised.

But having been on the winning and losing sides of Paypal and credit card disputes as both a buyer and a seller, I have come to recognize that they're usually not scheming to try to screw you over. Paypal, especially, deals with a ton of bad-faith buyers and sellers trying to play tricks each day, and they're always coming up with new ways to flimflam the process. Paypal corporate knows that they will lose users -and money- longterm when someone has a bad experience using their service, and the 3% that they might keep from a single transaction like this is probably lower than they would have made from a lifetime of business with you. In other words, they probably don't want to screw you.
 

brandnewb

Solar Enthusiast
. but that screw paypal website, and others like it, are the result of spoiled little brats who didn't get the right sized shoes
Ahh the snow flakes you mean. THey go hand in hand with the SJW's. I hope that trend gets out of fashion real soon
 

robby

Solar Addict
Someone linked this recently and I hope it’s not weird to link it here in context of LiFePO4 cell degradation:

It’s kind of long and definitely recommend 1.25x playback speed. some interesting info maybe. under the header of general info.

thanks again for posting your analysis!
It's interesting that you mention upping the playback speed as I was just watching a video the yesterday where a guy who is into social development was railing about the ability of people to speed up the playback of YouTube videos and TV shows.

He stated that this is the latest step in making humans less socially interactive.
His argument was pretty sound. He was pointing out that as people get use to listening to long videos sped up, they will start to use it for almost every video and this in turn will lead them to be totally bored during real one on one conversations. This will then turn them off from talking to other people and lead them to becoming even less social.
He then pointed out how this will effect education which is already filled with lengthy boring speeches by teachers. He fears the lack of attention span will dumb down the population.
I suspect that sped up playback is just a ploy by YouTube to get people to fit in more viewing content per hour and therefore feeding them more advertisements without thinking of the long term consequences to society.

Nothing personal here about your suggestion, I just thought that it was interesting that you mentioned it just 24 hours after I watched his video.
 
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PhotonFire

New Member
robby that post gave me a smile. Interesting theory for sure but slowing down youtube? What is next, forcing a 3 day delay on emails to make the post office less boring? By speeding up lectures offered on youtube or any other server that speeds at 1.25x or greater, if that creates more learning in less time then is it really dumbing down the population as you claim? Maybe you are a person who enjoys line ups and waiting in traffic, but I am still thankful for technology despite the unintended consequences as AI is decreasing the need for human labor and humans altogether. Some ppl process info at different speeds, especially once they are experts. Being able to change video speed is something I am thankful to use because unwatchable videos can become watchable and INCREASE my attention span and knowledge. Your warning of the human consequences reminds me of the unibomber's manifesto. No joke, it is a worthwhile and entertaining read, in my opinion. If you watch it on youtube you can listen to it at 1.25x like I did and slow it down in the heavier parts. The manifesto is about why we MUST destroy technology and it is written by a very intelligent author who also happens to be a serial killer:
He was also used by the CIA to endure prolonged LSD testing.
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
40/280 = 0.143. 1C is 280A for a 280Ah cell.

Will Prowse had a video from Jan 2021 about 280Ah cells from the same seller but different cell manufacturer. I tested Varicore cells. Will tested Eve cells. Will didn't experience the capacity fraud with the Eve cells like I did with the Varicore cells.
Varicore is not a manufacurer they are a reseller of many different cells from different manufacturers, if you received 280Ah cells, they were probably rebranded EVE LF280 cells, Grade B/C from the sound of it. With most of these budget resellers quality is a bit of a crap shoot. I am of the opinion that almost all of them are non-grade-A at the price point we are buying at, but within 'non-grade-A' there can still be a lot of variance.

I will look at Basen. All LiFePO4 roads point to Shenzhen it seems.
Shenzhen and Dongguan seem to be the two big export hubs for LiFePO4

-------------------------
Lessons learned 1) China makes garbage 2) China inflates all numbers 3) Use your credit card.
All LiFePO4 are coming out of China, the good, the bad, and the ugly. Buy through official channels, pay market rates, and the probability of cells that meet spec is high, buy bargain basement cells from unofficial resellers and you may get a good deal, you may 'get what you paid for' or you may get utter garbage. Not all things coming out of China are created equal and this is especially true of LFP cells.
 

curiouscarbon

Science Penguin
It's interesting that you mention upping the playback speed as I was just watching a video the yesterday where a guy who is into social development was railing about the ability of people to speed up the playback of YouTube videos and TV shows.

He stated that this is the latest step in making humans less socially interactive.
His argument was pretty sound. He was pointing out that as people get use to listening to long videos sped up, they will start to use it for almost every video and this in turn will lead them to be totally bored during real one on one conversations. This will then turn them off from talking to other people and lead them to becoming even less social.
He then pointed out how this will effect education which is already filled with lengthy boring speeches by teachers. He fears the lack of attention span will dumb down the population.
I suspect that sped up playback is just a ploy by YouTube to get people to fit in more viewing content per hour and therefore feeding them more advertisements without thinking of the long term consequences to society.

Nothing personal here about your suggestion, I just thought that it was interesting that you mentioned it just 24 hours after I watched his video.
everyone has a responsibility to cultivate multiple “mental gears” and there is no good reason, in my opinion, to sit patiently for a slow digital recording of a lecture because there are people who are one gear only.

disabling faster playback on videos would be comically authoritarian nanny state overreach, individuals and also parents of young people have a BIG RESPONSIBILITY to be more interesting than the Infinite Feed in order to teach good modal responsiveness (“reading the room”). anyways, i’m just sharing my view. lots of people these days treat humans like their Feed and that’s not right. treat humans like humans, and computers like computers. 2 cents

i appreciate you sharing your view 🖖
 

curiouscarbon

Science Penguin
basically the concept of “ethical mental impedance matching” be patient with humans and don’t feel bad about wanting the computer to be faster
 
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