Beginners Guide to Processing 18650 Cells | Cell Database


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Watson Expedition
#11
I agree if you start working with diodes you need to matrix it full out. Otherwise no use. There are already diodes in the panels as such. Its just a matter of the matrix part.



If you just have minor shading it might not be an issue or just make sure that you design the series paralell in such way that you try to collect all shaded panels to same serie.
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#12
I had some time to sit down and open all the boxes and get the packs analyzed.  Outside of some minor damage (that I don't care about since I'm busting the packs apart), all 200 packs (each with 20 cells) are in good shape!  Only 8 packs are sitting below 3.5v per cell.  One pack is at 30.2v, I think this was maybe a discharge cutoff test of the BMS that didn't get recharged?

I've attached histogram of voltage measurements of all 200 packs.

Also have a video for this update: https://youtu.be/kA-M2_e7aKA





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#13
Pretty good haul! Smile
You could just strip all the cells of their wrappers and have a true tesla sytle pack; all silver Wink
It's good that the BMS actually cutoff the pack.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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#14
Yes!  Once I realized why the oddness was occurring, it actually comforted me to see that pack voltage.  The oddness was actually due to my FINGERS!  In the video you can see it, my fingers slipped in and touched the probes, which caused just enough of a voltage sag to partially trigger the BMS protection (there's apparently a very short ramp, and my fingers touching the leads put me somewhere in the ramp, the light bulb was low enough resistance to push me all the way off).

Also, bare metal cells make me super nervous!  I hope you're joking there!  Tongue
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#15
hahah, not entirely joking. Just put some protective rings on the pos end and if that end is in a plastic holder, then it's even more protected from shorting out. But, I am also respectful about the possibility of shorts occurring.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#16
Yeah I see your reasoning.  I'm still a scaredy puss.  If wraps were more expensive, perhaps, but it's kinda like cell level fuses - cheap insurance.

Bare metal batteries do look cool tho
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