Beginners Guide to Processing 18650 Cells | Cell Database


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When talking about storage capacity what is your end cost per kwh?
#1
Hi guys,

Hope you are well. I am a complete newbie.

I want to build my own 18650 powerwall and want to start by knowing what is the end cost per Kwh that you got for your powerwalls (not considering inverters and other hardware)

I am asking this question because I want to have an idea of what is a very good price of aquisition for an untested 18650 cell.


When talking about storage capacity what is your end cost per kwh?


I really appreciate your input,

Ioan
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#2
Welcome!

If not considering inverters and other hardware then what are you considering? Just the 18650s and everything that is needed to assemble them into packs? I'm only putting together a small 2 kWh system and got the cells for next to nothing. Cell holders, solder, fuse wire are cheap, they're just a couple of bucks. Let's say 10 EUR per kWh in this case.

Are you buying your 18650s in form of laptop batteries to reclaim the cells? I consider about 1,50 EUR (or the equivalent in your currency, Google will tell you the exchange rates) per battery a decent price but the price is rising due to popularity. I've also seen around 4 EUR and more but that is insane. Especially for the smaller bulk offers of around 20 or so batteries. I guess everything is buying them now as a first step to play around with 18650s or something like that.
We are getting closer to the point where buying new cells is cheaper considering your time and effort and the failure rate.

For single cells that translates to about 0,30 to 0,50 EUR. If you can get single cells then this is the better option because you don't have to disassemble batteries first which obviously is a good thing.
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#3
Thanks very much for your imput!!!

Let me do the math for myself.

suppose that from the cells I get 50% are beyond 2000 mAh.

It means price per valid usable cell is: 1 Euro.

The Quantity of Energy per cell is 2Ah * 3.7V = 7.4 Wh

Number of pieces per KWh = 1000 Wh / 7.4 Wh = 136 Euros

This does not include the price of your time and work and additional materials and hardware.

Please someone could validate my rationale?

Thanks a million Again...
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#4
Well, yes, sure, this is an assumption you could make. And it could turn out to be accurate, but it could be totally off as well.
Apart from the cells I got for free and will use for my system I also bought some batteries and took them apart. I can report that 74 out of about 400 cells were 1900mAh or higher, so nowhere near 50% at 2Ah.

Looking at recent offers on eBay we are more at 2 to 3 EUR per battery at least. Batteries will have three to nine cells usually. The majority will probably have three, four or six. Let's take 4,5 as an example.

2 EUR per 4,5 cells, 25% have 1900mAh or more and will be used, this will average to 2Ah. That's 1,125 cells or 8,325Wh for 2 EUR
1000 / 8,325 ~ 240 EUR per kWh at least, much worse than your assumption but sadly just as possible.

As you can see this varies wildly. And this isn't even the worst case.

If we compare this to buying new cells:
I have seen Samsung ICR18650-22P with 2200mAh for 1,82 EUR each when you buy 500 pieces. 8,14Wh per cell means just over 4kWh for 910 EUR or 227,5 EUR per kWh. You see that is entirely the same ballpark there. And these are new cells. They will give you more cycles and you don't have to put extra work into breaking them free from the laptop batteries.

Another example, Panasonic NCR18650PF with 2900mAh. 2,44 EUR each when you buy 540 pieces. This is a bit more expensive per kWh than with the Samsung cells but at 2900mAh you will get better density and can build your packs physically smaller if that is what you want. [edit] I was wrong, it is a bit cheaper even (227,4 EUR per kWh) [/edit]

And a final example, although they are not in stock at the moment: Samsung ICR18650-26J with 2600mAh, 1,86 EUR each for 500 pieces. 4,81kWh for 930 EUR, ~194 EUR per kWh.
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#5
I get them for free, soooo...
So cost per KWh is the limit of a function in this case, with cost approaching infinity.

Being serious though, you're right. We are recycling cells. You can't compare the raw cost of new cells vs recycled cells. While you get the best bang for buck with recycled cells, the work you put into it is... off putting for most people.
The best bet to get good used cells is mostly lowering the current draw per cell, meaning more cells per parallel pack and higher capacity due to lower current, causing lower resistance, or, trying to get them immediately after they're thrown in the garbage.
It's better to over engineer something than to cheap out.
As I say: You pay once, you cry once.
                                 You pay multiple times, you are a doofus
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#6
For good packs that have a minimum of 10 watt hours per cell, you will pay $1.25.
By focusing my buying at the better packs, I pay more, but also get higher capacity cells.

10 watt hours/3.7 = 2700 mah.

60 watt hour 6 cell packs or 90+ watt hour 9 cell packs are a good goal to shoot for.

If you are forced to buy used packs, look for these capacities.
Then at best plan on 40% cells above 2000 mAh.
Another 40% will be less than 2000mah
The last 20% will be unusable.

If you only use the ones above 2000 mah in your powerwall, then your cost per pack should be less than $4.50 pack for net 3-4 good cells in a 9 cell pack.
$3.00 per pack for 6 cell packs for 2-3 good cells.

Your cost per kW hour is $125. Just for cells. Not including time involved.

And it's a LOT of work to sort these out.

New cells with 2200 mah capacity can be found for 1.25 per cell.
And they are all good cells so you gain your time back.

5kw Tesla battery modules go for $1400 for 444 cells. ($3.15 per cell for 3.5 amp hour cells)
Cost per kwhr is $280/ kwhr.

https://m.ebay.com/itm/Tesla-Model-S-bat...2333679871
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