Beginners Guide to Processing 18650 Cells | Cell Database


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CRUD's Powerwall Project
#1
So i'll start off with my projects documentation here.

Short background:

I am planning an off-grid powerwall for the garden house. 

Goal is to have enough power to run LED lights, Laptop and maybe the espresso machine (if i get one with watts below 1000 ;-) ).

I'd prefere to go for a 7s 64p system at the time being.

With at least 115 AmpHours i hope to get a 2,5 to 3 kWh pack.

Right now i finished the first two packs and extracted half of the third pack.



Needs resorting and maybe some retesting, but i am happy with the little progress so far.

After each round of getting the cells from the Laptop batteries, i do a charge test, internal resistance and voltage check using these two battery chargers:



I already tested some fusewires by setting up a little test environment to get the length and stuff right.

 

I use a 50W 1R Wirewound Resistor to validate the correct amperage flow and prevent shortening out warning of the meter or power supply. 

So, on we go, i hope i'll get this finished by the end of june to get the chance to catch some rays with the solar panels :-)

Initally, i wanted to build a solderless pack to maintain broken cells easily.

So i came up with this design:



But by now, i realized that it might be no good compromise between maintainability and cost ... maybe.



Have to redesign for 4 rows (as shown in the first real picture of the finished pack), because initially i thought of a smaller
setup using only 32p.

Decided to go for a soldered version after all, like everyone else did successfully.

I'd like to keep the busbar design, though. 

I want to change the design so the the top of the cell is exposed through an opening in the top plate so the fuse can go from the top of cell
to the busbar.


Any thoughts and critique highly appreciated :-)
Ragulin83, Korishan, hbpowerwall And 1 others like this post
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#2
Neat Design. I like it. Cannot wait to see more
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#3
you are still free to redo my idea in a proper cad^^
jdeadman likes this post
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#4
So finished my third pack and new cells for the last 4 packs are on their way :-)

Today i had some time to think about the basic procedures concerning going solderless.

I found an very interesting thread over at endless-sphere : https://endless-sphere.com/forums/viewto...14&t=85912

I really fancy nuxland's idea concerning the coppersheet layout.

As i still struggle with the idea of a solderless design, i thought i could probably go for a hybrid solution and use pressed copper on the bottom (removable)
and do the best practice copper-busbars with fuses on the top.

On the bottom i am thinking of removing the little edges of the batteryholders permanently to make the cells slip through at the bottom (As shown in https://www.youtube.com/watch?v=uyFm1PfmdSE).

I'll check and do a redesign of that, might be worth a try.
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#5
Found a new source for cells this week:

Used ebike batteries. Lots of defect packs around for sale.

I'll receive 4 of them today (hopefully). The packs contain 60 18650 Cells each. All of them have broken electronics, so
i am looking forward to a good harvest :-)
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#6
They are a good source when they are not too old, older sometime have crappy lipo who inflated. 18650 based are usually like your's, just faulty bms and good cells. Smile
Current setup: 21x 215wc poly, 7.5kWh 7s 18650, PIP 2424msxe.
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#7
Disassembled my first used ebike battery today. Got myself a pair of electrician safety gloves first.

Caution with such a pack.

So much fun. So less glue (absolutely easy to remove)! Fingers don't hurt. Got 60 cells from this pack :-)

Sure, have to test them first. No guarantee they are still ok. But it took only 1 hour for 60 cells :-)
Korishan likes this post
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#8
So tested cells from the ebike pack. About 25% is dead on the first pack :-(. Expected that, somehow.
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#9
What do you call dead ? 0v ? <1000mAh ? shorted/leaking ?
Current setup: 21x 215wc poly, 7.5kWh 7s 18650, PIP 2424msxe.
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#10
(05-15-2017, 06:51 AM)coolfx Wrote: What do you call dead ? 0v ? <1000mAh ? shorted/leaking  ?

Cells look good, no leakage, but they are not recognized by the charger. So i suppose they are shorted or 0v. 
But now that you say it, i should check with the multimeter. Just to make sure.
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