Lipo Manufacturing?

[sikeston34m]

I've been wondering something.

Does a Lipo cell have any charge when it is first formed? When the slurry and all the other materials are first rolled up and formed into a Lipo cell?

I've been wondering because after recently purchasing a 3S pack only to find one of it's cells completely dead. I put this single cell on slow charge, brought it up to full charge, and it performs great.

Anyone know?

[redshift]

Did some sniffing and found your answer

"Once the cell assembly is complete the cell must be put through at least one precisely controlled charge / discharge cycle to activate the working materials, transforming them into their useable form. Instead of the normal constant current - constant voltage charging curve, the charging process begins with a low voltage which builds up gradually. This is called the Formation Process."

Full text here: http://www.mpoweruk.com/battery_manufacturing.htm

Also the Wiki page: http://en.wikipedia.org/wiki/Lithium_polymer

[sikeston34m]

VERY good read! Thank you Redshift.

Solid Electrolyte Interface/Interphase (SEI)
The SEI layer is essential for the stability of Lithium secondary cells using carbon anodes


The electrolyte reacts vigorously with the carbon anode during the initial formation charge and a thin passivating SEI layer builds up moderating the charge rate and restricting current




The deposition of the SEI layer is an essential part of the formation process when the cells take their first charge.

BUT the SEI layer increases the cell internal impedance and reduces the possible charge rates as well as the high and low temperature performance.

Excessive heat can cause the protective SEI barrier layer to beak down allowing the anode reaction to restart releasing more heat leading to thermal runaway.

The thickness of the SEI layer is not homogeneous and increases with age, increasing the cell internal impedance, reducing its capacity and hence its cycle life.

[redshift]

You're welky sikes.

Looks like your one dead cell must have slipped past the initial charging 'activation' process. One would have to assume there would be some charge present if it hadn't.