The different length nickel is just due to human error and the different widths is because I ran out of the 8mm nickel strips and I had to use the 5mm ones that came included with my spot welder.
Is it a big problem?
Why is the trapezium shape better?
With the way you have it it’s hella lot of work cutting all those strips, and they come out all uneven. And you have basically a line connecting 5 cells. With the trapezoid you will have way way less cutting, more consistent electrical paths, and current sharing will be even. And more metal, so less resistance.
If you have all these different amounts of nickel on each p group, the resistance for the p-groups will vary. If the resistance varies, they will charge and discharge at different rates. Your pack will always be drifting out of balance, and cells will wear at different rates. This effect might be so small as to not matter, or it might be annoyingly large. A lot depends on how the rest of the construction is done (series connections).
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If it turns out it’s a large drift, is there a way to fix it?
The better way to look at it is, because of possible uneven amounts of nickel (therefore resistance), some groups will have less juice flowing through them, which makes them wear out slower. Others will have more juice flowing through them making them wear out faster. This will show up as voltage drift, which will be constantly corrected by balance charging. This correction does not change the fact that some groups are handling more of the load.
The total energy in your pack will be practically limited to the energy in most worn cell, so your pack may have the appearance of wearing out faster than if everything was balanced.
The difference might be small enough to not make a difference, especially if you don’t ask a lot of the pack.
I hope that helps.
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What if I draw less than the maximum rated current from the battery, like instead of 75a draw 60a?
I’m going to challenge you to figure out the answer to this on your own. The quest will give you much knowledge.
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Can I save and reuse this comment? That’s a great way to put it.
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Wow. I actually bookmarked your comment 
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Ok then. Challenge accepted!
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Remember fish paper between the p-groups!
Nickel strip layout is also a bit weird imo. I would have done like this:
Will do
It was at this point that I confirmed that I had built my first working but unfinished battery pack. Now just some more hot glue to tidy up the mains and the PVC wrap I’m waiting on.
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I have, what do you wanne know?
Does it and the app function work well?
What app do you use with it?
Do you run it as charge only or normally?
Hey trying out a new style BMS. I’ve only used D140 up until now. Super straight forward for wiring. I wasn’t paying attention when ordering this BMS and see that there is no dedicated location to solder Charger negative. I planned on using this as charge only. Do I need to get a different BMS or just charge around it? Or would I wire the C- to the BMS negative?
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Upper diagram is the common 2 wire model you have.
You’ll be connecting the negative battery /gnd directly to connector for your ESC or anti-spark for discharge only
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That looks more convenient for a charge only bms
those red charge only bms are really great. much smaller than D140, protected in case so it is impossible to accidentally short pcb and already has wires soldered. + you can choose between common port and separate port. and they are even cheaper than D140. @Acido has much experience with those red Daly bms so he could point out biggest problems with them, if there are any.
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The only problem is that they almost have no balancing current, only 35mA compared to D140 which has 130mA or so if your making a bigger battery I would go with D140 or some other bms
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How much are they? D140 is on sale right now for $21