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That sounds like a florida man story.. I'm glad you're doing well and that no person got hurt, just parts. Thanks for sharing the story and pictures.

Yeah, i was tired. I meant parallel not series. Thanks for pointing that out.

Top balance those cells and add a small lifepo4 cell in series to the weak one. Keep the balancer on, but set it to 3.4V start

Dyson cells usually still have decent capacity, but their internal resistance has grown too much for the super high power application. The majority of time, the cells are still perfectly good for normal power applications like a power wall. However, mixing and matching cells in a power wall is...

0.0005V and 3.9V for my NMC 18650 cells, which only get charged to 3.95V

It has not updated the capacity on my battery after a year of use. The capacity left rating in % is also all over the place, if you dont do a full discharge and a full charge cycle each and every time. Its not very useable if you have a solar system.

I have a few similar cells from all manufacturers. Most of them however were already like that when i scavenged laptop battery packs. The other cells out of such battery packs often work just fine.

What i've seen, is that the MOSFETs leak a tiny bit of current when it shuts the output off. Resulting in a voltage being measurable. Try to attach a tiny load like a 12v car light bulb or something similar and read the voltage again.

https://aliexpress.com/item/1005004843603267.html Here is one store page, with a lot more details. Just scroll down to the item description and open it up. Even your question where to solder what is explained there.

If you want to use a 3s battery, buy the 3s board. If you end up buying the 4s board and want to use a 3s battery, you need to change some tiny tiny tiny resistors on the pcb which is not a joy. It has the correct protection for 2-5s Li-ion/LFP batteries, just not for 6s LFP batteries.

I have a entirely different idea i'd like to pitch to you. https://www.ebay.co.uk/itm/175836376972 How about a 3s Powerbank board, with a built-in BMS ? But keep in mind to buy the correct version in the first place, as changing out the tiny resistors to change the functionality is very tricky.

Besides your cell sorting choice i disagree with, i think that your pack design is very innovative and i'm interested in seeing it in action. ^^ However as Korishan mentioned, longevity might be a issue, which can be solved with a better material choice.

I'm from Saxony. I still think, that you should put in that extra effort if you want a long-lasting battery. Its definitely worth it. My battery will see up to 120A, spread across 240 cells. So 0.5A per cell is the absolute maximum my battery will see That pack 11 has a higher resistance, is...

Greetings fellow German Kamerad. Having dealt with ~7000 18650 cells, i learned that matching just by capacity in Ah is not the best choice. Not all 18650 Li-ion cells use the same chemistry, so the voltage curve while discharging will be different and some cells will degrade faster than others...

Dont forget the resistance of the kWeld and its spot welding tips itself. It can handle over 2000A, you just shouldn't do it too often. Connect it up and give it a try. I use a 60Ah car battery and get around 1200A from it.

I stepped away from glass fuses and just use a tinned copper wire. Glass fuses were just way too annoying to deal with.

Answer to Q1: Assuming all cells have a equal voltage, which with 18650 li-ion cells is not always the case. 20 cells * 3,6V *2,5Ah = 180Wh 180Wh * 16 packs = 2.88kWh 180Wh * 14 packs = 2.52kWh Answer to Q2: Thats what BMS is supposed to do. The "smart" JBD/Xiaoxiang ones even have the option...

It is possible, but you cant really balance that pack well with common equipment and you must use Wh instead of Ah to decide the which cells to group. How about just a 3s Li-ion pack? 9-12.6V or ideally 10V-12V with lowered charge and discharge voltage limits

Impressive build :) Thats some craftsmanship one can be really proud of.

If you want it cheap: This inverter: https://www.amazon.com/1500W-Continuous-3000W-Inverter-Outlets/dp/B07ST4MQTL Just any random car battery Just any random PWM battery charger Just any Solar panel If you want it a bit more reliable, get a LFP (LiFePo4) battery. And dont forget to size your...