Beginners Guide to Processing 18650 Cells | Cell Database


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Why do we need laptop cells when we can make these?
#1
Tongue 
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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#2
Now you have done it... out with the stupid lithium 18650's... gona replace all of mine with these great sand batteries (capacitors?) Big Grin

Add this to the FAQ "how to build your own 18650 cells" Wink
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10KW 3phase hybrid inverter. 25Kwh 18650 storage (for now)
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#3
And..... no need Batrium BMS !
Hydroélectric 800W PELTON Générator - 6 x 270W solar Panel
Oct 2017 : 850 cells collected : Test in progress
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#4
I do wonder what kind of amps it could put out, and what the capacity would be. I'm sure it'd be close to 100mAh. Probably less.

And no worries of fires Wink Altho, I don't think these are rechargeable. Unless you make it so the salt/water solution is replaced (aka, a flow battery)
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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#5
It may be cheaper to replace the salt than mounting solar panels!
Korishan likes this post
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#6
No, they aren't rechargeable, no matter what you do Smile

By the way, the Youtube comments section of this particular video is the perfect demonstration of why we send our children to school. There are people there who think this is a fake! Big Grin
We built several variants of such cells in school.

It's a voltaic cell with an aluminium anode, a copper cathode and salt water as the electrolyte. Paper is used as a separator and sand is used to bind the electrolyte and stop the copper cathode from moving around. It would work without sand as well. Actually this is close to a simple version of a LiPo cell in terms of turning a fluid electrolyte into a semi solid one Smile

You can't recharge such a cell, it produces electricity through the chemical reaction between aluminium and copper. The copper corrodes/oxidises the aluminium with the help of the electrolyte. This isn't reversible by forcing a current through the cell. Replacing the salt water won't be sufficient as the anode is going to disappear.
Other metals and other electrolytes work as well and produce different characteristics. Zinc is usually a more popular choice for the anode than aluminium. That's why we have several different common chemistries today and will continue to develop even more in the future.

The maximum current is extremely low as you would think. The internal resistance is huge, we are in the low mA regions here and even that will cause a significant voltage drop.
The capacity is, well, difficult to estimate and impossible to calculate (in advance) Big Grin It depends on how much material from the anode can be oxidised and that depends on how big it is but also on how stable the electrolyte is and how well the reaction runs.

Wikipedia got you covered with more details if needed, but I rather recommend this article about a special version of the voltaic cell: https://en.wikipedia.org/wiki/Lemon_battery
It contains simply biblical phrases like "By multiplying the average current of a lemon..." and also teaches you that you need 6 million lemons to start your car, that cans of sauerkraut are a dual purpose product and that you can improve the electrical characteristics of your potatoes by boiling them! Big Grin
ruby2, Korishan, cmg_george like this post
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