I have never seen a cell off more than 0.005V from bulkbattery. $150 order minimum is the only “catch”.
Go big or go home I say
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Welp it’s been like 6 hours and nothing different, so that is good. I’ll do the spark test tomorrow and check them then as well.
So just finished up a pack and might have fucked up lol… Usually only build with new cells but this was a budget pack for a test.
Its a 12s2p Samsung 22t (if I remember correctly) with cells from 2 DeWalt packs.
All connected correct but wont charge and balance the cells properly instead the BMS cuts when the first 2 P groups reach 4.2v.
The first 2 P are at 4.1v now and the rest are at 3.8 is this to much for the BMS to sort out? I was naive and assumed that the BMS would balance it out.
Its a DS140 BMS. If I need to sort it manually any one got a tip on how? Was looking around for a old powerbank to tear down without success but if I find one I can connect it in parallel with the BMS one P group at the time right?
You don’t always want the cheapest cells, there’s lots of cell grades and its visible difference like grade b and aa
this is a big difference for that BMS. IIRC it has about 50mA balance current. you can do the math to see how long that will take, the BMS just sees a cell over voltage and gives up.
Try charging the p-groups manually as close as you can get them, like .03v or better. Then see if the BMS can sort out the difference 
If you trust fogstar at 3.36gbp for 40T’s than 4.80usd should easily be trusted for them in the US… Bulk Battery is just actually fair price in the US which is somewhat hard to come by.
Based on the experience of myself and others buying from them, the cells are all what you would expect from any other vendor.
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Im not really fimmiliar with the USA market, but cells there cost quite more than in Europe, I guess the tax wars…
Im the end testing them over time is the best 
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We say cheap when talking about BB, because for say 40T’s, IMR or Liion wholesale are $6.99 and $7.25 base price, respectively. This is before bulk price scaling but that’s still not any lower than $6 a cell, for most people. Those prices are basically highway robbery when compared to BB.
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Sweet thanks then its like I suspected 
At least I learn something 
That is: Don’t be lazy! Spend the time to balance the cells before you build haha.
Have my big RC charger hocked up now thru the balance leads to full charge all the cells one by one
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After almost a full day in salt water, looks like this nickel is a go. I might do the spark test before welding, but I am happy with this result.
Here’s the Ebay link for those who are wondering. Shipped quite quickly, US seller.
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Finished my pack and then noticed 2 groups had bad cells
1 group was at 0.5v
The other was at 2.6v
Think the 2.6v group might be salvageable if I can find the bad cell
What’s bad about layers of nickel?
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Still need some?
I have 20’ for right now so that should be plenty for a few packs
Are you going to be selling some of that 2p stuff that you cut a while back?
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Doing a 4wd kaly. So jam packed in there. Not sure why I did it. Molicells don’t fit like the 20700b batteries.
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What’s the best way to connect the main discharge leads onto a pack? Soldering 10AWG wire to the first and last cells seems super sketchy and prone to vibrating loose from the nickel strips.
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I’ve never had anything vibrate loose. I also silicone my wires post soldering. Best is using a short 12awf, then jump to 10awg maybe? Idk.
This is what I would do, you can always tape it well and insulate with foam to stop it from vibrating
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