Lifepo4 cell compression, for a stationary AND low capacity set up, useful or useless ?

[AntronX]

Are the cells in server rack batteries compressed?

From internal views they look contained in rigid frame but have no compression foam in between the cells. As cells age they will overcompress themselves. I would not buy rack battery because of it.

 

[S Davis]

From internal views they look contained in rigid frame but have no compression foam in between the cells. As cells age they will overcompress themselves. I would not buy rack battery because of it.

Depending on the design you can get longer fasteners and add springs

 

[S Davis]

No. Graphite also irreversibly swells and cracks over time. Compression keeps it in contact with current collector foil.

Good luck limiting your cycle depth to 10 - 20%. It will probably swell anyway.

That they yet know of. Do they regularly test cell's remaining capacity? Will have to compare capacity after 10 years.

Yep, my oldest are 2.5 years, I am going to test a control group that have been compressed that will be going into new boxes. I will do it again in a couple years and see where they are.

 

[Skypower]

Yep, my oldest are 2.5 years, I am going to test a control group that have been compressed that will be going into new boxes. I will do it again in a couple years and see where they are.

Bring them to a low state of charge and cool before switching boxes. Try to put them back with the same neighboring cells because they have already conformed to each other once.

 

[S Davis]

Bring them to a low state of charge and cool before switching boxes. Try to put them back with the same neighboring cells because they have already conformed to each other once.

I have solid sheets between so they should be ok.

 

[Checkthisout]

No. Graphite also irreversibly swells and cracks over time. Compression keeps it in contact with current collector foil.

Good luck limiting your cycle depth to 10 - 20%. It will probably swell anyway.

That they yet know of. Do they regularly test cell's remaining capacity? Will have to compare capacity after 10 years.

Thank you for the lesson.

 

[rhino]

Sure, one guy that goes against mountains of research that proper compression does increase cycle life.

That's not what was stated. The point was that the cells will age before you can take advantage of the extra cycles by compressing. EVE even added additional information to the new MB30 spec sheet for another criteria that could "kill" your cell before the cycle count:

The cell life is limited. Customers should establish an effective tracing system to monitor and record the internal
resistance and capacity of each cell during its life. The measurement method and calculation method of internal
resistance and capacity need to be discussed and agreed between the customer and EVE. When the internal resistance of
the cell in use exceeds 150% of the initial internal resistance, or the capacity is less than 60% of nominal capacity, the
cell should not to be used any more. Violation of this requirement will exempt EVE from its responsibility for product
quality assurance in accordance with the product sales agreement and this specification, as well as all related liabilities
such as loss compensation caused thereby.

 

[ScrotusGobbleBottom]

another criteria that could "kill" your cell before the cycle count:

What criteria? The bold text only talks about state of health relative to original, and internal resistance relative to original. BOTH of which could be related to not compressing?

 

[AntronX]

That's not what was stated. The point was that the cells will age before you can take advantage of the extra cycles by compressing. EVE even added additional information to the new MB30 spec sheet for another criteria that could "kill" your cell before the cycle count:

The cell life is limited. Customers should establish an effective tracing system to monitor and record the internal
resistance and capacity of each cell during its life. The measurement method and calculation method of internal
resistance and capacity need to be discussed and agreed between the customer and EVE. When the internal resistance of
the cell in use exceeds 150% of the initial internal resistance, or the capacity is less than 60% of nominal capacity, the
cell should not to be used any more. Violation of this requirement will exempt EVE from its responsibility for product
quality assurance in accordance with the product sales agreement and this specification, as well as all related liabilities
such as loss compensation caused thereby.

Sounds like EVE is covering their ass in case customer uses their cells for too long and causes a fire (dendrite growth?).

 

[ScrotusGobbleBottom]

Sounds like EVE is covering their ass in case customer uses their cells for too long and causes a fire.

That is how I read it as well.