Cells physically swelled, popped bus bars - are they fried??

NMNeil

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Mar 14, 2020
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387
I've been charging my 200ah cells, one at a time because of my small power supply. Aiming for 3.4 volts with the plan of top balancing them all together to 3.6 volts later. One of the cells got to about 3.36 volts at 5 amps and it began to swell. Not slightly; it was blowing up like a balloon as I watched. I now have an unusable 15 cell 48 volt battery bank and am questioning the health of the other cells.
No excess heat, no overcharging just cheap junk Chinese, supposedly new cells.
Anyone have a spare 200 ah cell for sale?
 

HRTKD

Boondocker
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Apr 24, 2020
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Somewhere South of Denver
I've been charging my 200ah cells, one at a time because of my small power supply. Aiming for 3.4 volts with the plan of top balancing them all together to 3.6 volts later. One of the cells got to about 3.36 volts at 5 amps and it began to swell. Not slightly; it was blowing up like a balloon as I watched. I now have an unusable 15 cell 48 volt battery bank and am questioning the health of the other cells.
No excess heat, no overcharging just cheap junk Chinese, supposedly new cells.
Anyone have a spare 200 ah cell for sale?

Makes you wonder if the vent on the cell would have let loose if the cell and been in a compression frame.
 

NMNeil

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Makes me wonder why the vent didn't rupture before the cell became the size and shape of a football.
 

NMNeil

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Compression is a suggestion to extend the useful life; it's not a requirement.
It shouldn't be a case of which gives way to pressure first, the safety vent, or the aluminum case.
 

mrzed001

Voice of reason
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Compression is a suggestion to extend the useful life; it's not a requirement.
It shouldn't be a case of which gives way to pressure first, the safety vent, or the aluminum case.

If you compress then cells can not bloat as much ... so they went.
 

NMNeil

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Looking at all the cheap, and expensive batteries that Will has dismembered on YouTube, I can't remember one that had the cells compressed.
And how would you compress cylindrical cells like Battle Born uses?
Don't misunderstand, I intend to compress my bank of cells. Not sure how though :)
 

mrzed001

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Looking at all the cheap, and expensive batteries that Will has dismembered on YouTube, I can't remember one that had the cells compressed.
And how would you compress cylindrical cells like Battle Born uses?
Don't misunderstand, I intend to compress my bank of cells. Not sure how though :)

The manufacturer already put the cells in a tight place. You do not need to press them hard. This is (almost) enough.
Cylindrical can not be pressed ... even this statement is not exactly true. Tesla batteries have a (fire extinguishing) hard foam around the cells.
Also the alu case of the cell is stronger (little cell)
 

HighTechLab

Small Business Owner
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Sep 23, 2019
Messages
432
I will get rid of them for you.....and pay the shipping....where are you located. I am in Michigan..

Thanks
As a business owner that ships lithium batteries, this is a TERRIBLE idea! LiFePO4 cells are class 9 hazardous goods. You need a HazMat license to legally ship them, and on top of that, if you ship cells like this that are damaged (ticking time bombs) and they go critical and burn up in shipping, you literally could go get into some very serious trouble for shipping compromised hazardous goods. Read:
  • The maximum civil penalty is $75,000 for knowingly violating federal hazardous material transportation law.
  • The maximum civil penalty for knowingly violating laws and regulations that result in death, serious illness, severe injury to any person, or substantial destruction of property is increased from $110,000 to $175,000.
Compression is a suggestion to extend the useful life; it's not a requirement.
It shouldn't be a case of which gives way to pressure first, the safety vent, or the aluminum case.
I disagree with you completely. I've discussed this with engineers from many battery manufacturing companies, some manufactures do not require it while others do. It varies widely. E.g. Fortune cells with the separators between them absolutely don't need compression. CATL 302ah, Lishen 202ah and CALB 230ah are all cells that I've worked with that absolutely must be compressed, whereas the Lishen 170 ah (Read: nearly identical size of the 202ah) has a thicker aluminum case as the 202ah and does not require compression.

Engineers in general regularly face the challenge of fitting “more” into “less”. Compromises must be made. To create more space, a thinner, less structurally integral material is used. The thin aluminum case cannot withstand the internal forces exerted when the cells are charged, but the new design never expected the cells to be used on their own. We all know these LiFePO4 cells on the market today are originally intended for use in EVs...pack manufacturers are already designing the packs with the compression in mind, because the demands of a solidly held pack in an electric vehicle where vibration is guaranteed are much more intense than a stationary solar power system. By using a single compression fixture on an entire pack as compared to many thick plastic cases, significant space and weight is saved, leading to higher capacities in the same space. You will see the trend across the board with many EV manufacturers demanding more energy in less space/weight.

Last though, I want to use the example of BigBattery and Fortress Power. In BigBattery's OWL-MAX-2 using CATL 228ah cells, they are built with a fixture to put the cells in compression. Fortress Power also compresses their 100ah cells in their Evault 5.2kwh pack. Both of these packs are very nice quality builds, but BigBattery being more budget friendly compared to the fortress pack.

If the point of compression was only to give a few thousand more life cycles, why would any pack manufacturer go through the trouble if it's the difference between a customer coming back to buy more batteries in 4000 cycles instead of 5000 cycles? Wouldn't they want to plan obsolescence to keep their future business moving??? Seems really silly to go through all the trouble if it's just a suggestion that only benefits in longer life.
 

NMNeil

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It's like my other hobby, beekeeping, and if you ask 5 beekeepers the same question you'll get 6 different answers :LOL:
As I said, I intend to redo my battery bank and compress the cells so this can't happen in the future.
My focus now is buying 4 replacement cells so I can complete the battery bank and have 3 cells as spares in case one does vent on me.

Benjamin Franklin hit the nail on the head years before AliExpress and AliBaba even existed.

“The Bitterness of Poor Quality Remains Long After the Sweetness of Low Price is Forgotten”
 

Bob B

Photon Sorcerer
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Sep 21, 2019
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If the point of compression was only to give a few thousand more life cycles, why would any pack manufacturer go through the trouble if it's the difference between a customer coming back to buy more batteries in 4000 cycles instead of 5000 cycles? Wouldn't they want to plan obsolescence to keep their future business moving??? Seems really silly to go through all the trouble if it's just a suggestion that only benefits in longer life.

A lot of good information .... except in that last paragraph I can think of other reasons the manufacturer would want to add cycle life to the cells .... the most significant one being that they can then advertise the increased cycle life .... and sell more batteries. Eve has now jumped to 6000 cycles spec'd if you control the temperature and the compression.
If the cells get too hot, any benefit from compression is quickly lost .... we should probably be trying harder to keep them in a conditioned space when used mobile.
 
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