Kens's diy powerwall build

I did a Craigslist posting asking for used batteries. I almost bit off more than I can chew :p I had to take down the posting cuz I got so many in the first 2 loads.
 
Ken140tdi said:
On a side note how do you guys get hold of so many used laptop packs to tear down and get all your cells.
I've been asking around a few computer shops and some friends that do lap top repairs but not had much luck
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Hi Ken,

in Germany it is really difficult to get some used laptop batteries. So many people are chasing after them.
But here is one reliable source from Netherlands for new cells:

https://eu.nkon.nl/rechargeable/18650-size.html?buttontop=26&protected=9

Best regards

BigBen
 
Funny you should mention Nkon. I just bit the bulet and ordered 504x 2850mah lg cells from them today.
That should be around 5.1 kWh. Will see how I get on with them.
I spent ages working out which capacity cell was the best value for money.
 
Ken140tdi said:
Funny you should mention Nkon. I just bit the bulet and ordered 504x 2850mah lg cells from them today.
That should be around 5.1 kWh. Will see how I get on with them.
I spent ages working out which capacity cell was the best value for money.
Click to expand...

Oh, that's the reason why they are "out of stock" :)
Ok, let us know the expirience you have made.
 
Korishan said:
I did a Craigslist posting asking for used batteries. I almost bit off more than I can chew :p I had to take down the posting cuz I got so many in the first 2 loads.
Click to expand...

Damn.. thats crazy.. I tried this on our local Gumtree - so far onlyviews, not one reply or msg :(

Called up the local recycling centre, they were not interested or possibly someone else has already taken them.. even when I offered money per pack or per kilo etc..

Tried a few battery placesthat I know take old lithium cells/packs, same deal - not interested. One place I have bought a AGM Deep Cycle for doing dual battery in my4wdbefore who was keen to sell me more of those, asked them for cells, all gone! Told him if he got anymore to call me and gave him my details.

Sighs... Might have to start visiting some junk yards or thinking of other places.
 
Very fast delivery. As the cells arrived this morning by sod

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Pretty sure they are genuine as they each weigh 45 grams.
 
Nice box you got there :)

sod - Some Odd Delivery ?? :p
 
Finnished putting all the cells into their plastic holders to make up the packs tonight. Next job will be to make up the main wires that carry the current from each cell. I've also bought a hot glue gun so I can get them firmly stuck to each pack.
 
Korishan said:
I did a Craigslist posting asking for used batteries. I almost bit off more than I can chew :p I had to take down the posting cuz I got so many in the first 2 loads.
Click to expand...

what did you say in your craigslist ad? Any offer of money for them or just an ad to see if anyone would give them to you?
 
Here's what I put:
Recycle Your Old Lithium Laptop/Cordless Battery Packs | $1.50/lb

Have old Laptop or Power Tool battery packs you don't need anymore? Paid all that money for them and just going to "throw" them out? How about getting some money from those old batteries to help with the purchase of new ones. Will pay $1.50/lb for any type of Lithium Ion, Lithium Polymer, Lithium Phosphate batteries.
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That seemed to have worked. Though, doing a repost, I'm gonna drop to $1.25/lb.
 
I finnished making my first pack last night. It's not quite as neat as I wanted but the next one should be much better as I found a better way of twisting the copper wire that's used to interconnect all the cells.

image_tqrcim.jpg

image_fheixn.jpg
 
Looks good! It's definitely a learning experience. My most recent packs look better than my first packs, but the first pack is equally as functional. Keep posting the progress!
 
This is probably a bit of a daft question but how do I find out what charging current to use on my home buts battery. The byd batteries take 50 amps for each 2.5 kWh battery so as I have two of them it's curently set to 100 amps max my 18650 packs will total 5.1 kWh and will have a total of 504 cells with 36 in each pack and 14 packs in series
 
You should not charge your home made packs with more current than you did test them with is my recomendation. if you tested at 1A you should keep max current below that. In this case 36A.

When it comes to mixing batteries its not as easy as just say "I got 3 packs and 1 is laptop cells so 1/3rd charge goes to each"
Because that wont happen in real life since they are different. You need to either go deep and test/read up on them and calculate or you need to test this.

Personally i recomend to test this since its 2nd hand cells. Ie hook all upp and start charging slowly. Meassure how much goes into each of the strings and make sure you stop on the lowest value.

if any of the strings get to much you "could" sort that by just using longer wires/cables to it or thinner ones to raise the resistance and therefore raise the voltage drop.
 
Hi Ken,

as far as I knew, you bought new LG INR 18650MG1 cells.
According the spec the nominal charging rate is 0.5C => 2850*0.5 = 1.4A
That's the amount you charge every cell. In one pack you have 36psc * 1.4A = 50.4A.
The advise of daromer to load with 36A is also OK. The lifetime of your cells will only increase.
But the max. charging current for your LGs is 1C i.e 2.8A for each cell - according to the spec.
So if you would have sometimes stronger charge look for it not to exceed 2.8A * 36 = 100.8A.

BigBen
 
Thanks guys thatsreally helpful.
Yes Ben I did but brand new cells and the ones you mentioned. The byd batteries have a charge curent rating of 50 amps each and as I have two of them curently the charger is set to a max of 100 amps as the makers recommend.
So when I add in my home made packs if I increaced the charge curent max to 150 amps I should be well with in the safe margins for my 18650 cells.
Just to be clear and check I u derstand this properly. I have 14 packs to build so am I right in thinking that the charge curent would be 14times the curent for the first pack.
Or will it be just the amount for one pack
 
Though you cannot just say that 150 will be fine since you mix. You dont know which pack will take what charge :) They have different resistance so they might split the charge/discharge weird and give 2/3rd to the home built pack... (Example)

In your case with new cells this would most likely not be a problem but its still wise to crosscheck it if you can.
 
Ok so I will need to check how many amps are going to the 1850 packs. I presume this can be done with a simple multimeter.??
 
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