Beginners Guide to Processing 18650 Cells | Cell Database


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help to build first pack
#1
I want to build a 12 or 16 cell LifePO4 battery.  I am thinking of using 32630 cells.  I don't know where to get the cell connect straps.  Is the same strap used for welding and for soldering?  If I will give close attention to the cells, do I need cell balancing electronics?  Can I balance them separately - manually once every few months?  How much does cell balancing electronics cost for this?  Thanks.
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#2
Thats alot of questions. I will give short answers as start.

1. No the straps/busbars are not the same in general. Spot welded are commonly nickel strips while when soldering "we" often use copper.
2. Yes you might need balancing! BUT you NEED monitoring. Because if they go out of balance you need to have a system that can disconnect the packs from charge/discharge. In general balance is added in same system...
3. You should balance them whenever you need. On some systems you can run 1 year in others 1 day....
4. BMS system cost from 20USD to 2500USD!... A normal decent system around 500USD that does it all. Though you need to add upp breaker, fuses, shunts.. And even more if you want it bulletproof and dont have to watch it. Then lets say 800-1000USD. In total for a full blown system this is nothing.

Yes you can do it cheaper and many does. But its generally good to start with the better ways since we dont know your intiial knowledge Smile
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#3
(09-08-2017, 06:05 AM)daromer Wrote: 1. No the straps/busbars are not the same in general. Spot welded are commonly nickel strips while when soldering "we" often use copper.

Thank you.  Where do I buy the straps?
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#4
Nickel strips? You can get on ebay but some are fake strips and may not be good to go. I have not done tests so not sure which ones are real and hopefully someone else can recommend some that are genuine!

Ant to the one recommending make sure you have tested them!
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#5
If it is not nickel then usually nickel plated steel. And some sellers even sell pure steel as it seems. You can find out the difference with a Dremel or a similar tool by grinding, sanding or cutting the strips. If there are sparks then it is nickel plated steel or pure steel. You could also scratch the surface (to get through the nickel if it is nickel plated) and put it into saltwater. If you can see rust after a day or so then it is steel.

But there are honest sellers as well, it won't be too hard to get nickel strips. Many state the nickel content of the strips, pure nickel strips contain at least 99.9% nickel.
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#6
You could also just use a magnet. If it sticks, it's steel or nickel plated. The nickel strips in the laptop packs are nickel plated as well. I found that out when I was trying to make nickel sulfate. The iron ruined the mixure
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#7
You can't use a magnet, nickel is ferromagnetic as well Smile
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#8
It may be, but it's no where near as strong as iron.

In the chart below you see that iron is 200,000 vs 6000 of nickel on the Susceptibility index. So the magnet will stick much harder to the nickel plated iron than to solid nickel stripping  Wink

Also, scratching the strip will show if it's iron or nickel; esp if you get it wet and let it sit out over night. Rust will always show up on iron in a few hours.


Taken from: http://metals.comparenature.com/en/magne...son-22-7-6
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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#9
(09-08-2017, 08:17 PM)DarkRaven Wrote: If it is not nickel then usually nickel plated steel. And some sellers even sell pure steel as it seems. You can find out the difference with a Dremel or a similar tool by grinding, sanding or cutting the strips. If there are sparks then it is nickel plated steel or pure steel. You could also scratch the surface (to get through the nickel if it is nickel plated) and put it into saltwater. If you can see rust after a day or so then it is steel.

But there are honest sellers as well, it won't be too hard to get nickel strips. Many state the nickel content of the strips, pure nickel strips contain at least 99.9% nickel.

If my max current will be 5.5amps... what size strips will I need, nickel or copper?
Thanks
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#10
Nickel for 5.5A is no big issue as long as its spread among several cells. 7*0.15mm should be good for 7A it says.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
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