Self balancing happens in a pgroup between the cells hooked in parallel if their voltage is off at all but there wonât be any current flow between groups hooked in series. Variance would be between groups or cells in series though that you need to worry about not the cells in parallel (except when intitially connecting them)
Any connections in parallel will be (eventually) at the same voltage and so will âself balanceâ
self-balancing is a thing⌠but as @mmaner has said his quality cells donât get out of balance very much at all, this is not for the inexperienced user, maybe manual-balancing where the user actively monitors the pack and balancing it himself is a better term.
Hereâs the test I ran.
Take 3 cells at different level of discharge (I had 2.1v, 2.4v and 2.7v) and solder a copper wire across the positive poles and another copper wire across the negative poles, creating a 1s3p group
I let it sit for 24 hours then removed the copper wires and re-measured. Each cell was at 2.38v.
That tells me cells will self balance, at least once. I think we can assume they will self balance until resistance in the cells becomes higher in dinner than others. That will likely be more than 300 cycles if you follow the charge/discharge advice above.
Cells in parallel or any wires in parallel with cells will be at the same voltage so the self balancing in a p group makes perfect sense you donât want cells to be far off in voltage when hooking in parallel initially because it will create a high discharge from the higher voltage battery and a high charge in the lower votlsge battery the greater the voltage difference the more current flows until both cells have the same voltage. Imagine two buckets connected by tube in the bottom of them if more liquid in one current flows to other until they balance eventually.
Anything in series though isnât self balancing each p group or cell in series can drift from others.
That makes a 1S3P group, not a 3S1P group, and P-groups do balance. Series packs do not.
Unless I misunderstood what you meant 
See this gizmo?
Plug into balance lead⌠Hook up to hobby charger on Li-On setting⌠Wham bam manual balancing
Your right, I type that wrong everytime. I shouldnât talk batteries when hungover or half asleep.
Regarding series self balancing, all I can speak to is my personal experience. My 10s3p has never diverged more than . 05v in over 2 years and weâll over 100 charge cycles.
Iâm not recommending the practice of NOT using a BMS. Iâm simple saying that in my experience it can be done either caveats I addressed above.
I think Shaun has the best analogy
Having no balancing is like driving with no oil pressure gauge/light, no âservice engine soonâ light, and no oil changes.
Sure, the car will drive and probably fine. But the longer you drive it, the more chances youâll have a problem that wonât be caught early enough before catastrophic failure
1S BMS has no balance wires. He must be running 1S.
I have a 1S BMS in one of my Mini Remotes. Can confirm; no balance wires.
Fixed that a whole lot 
Ok its looking like no one wants to make me a 10s4p Molicel P42A battery so I think im gonna go with the NESE system.
I will use:
*BMS 60amp version w/ bluetooth : https://www.lithiumbatterypcb.com/product/13s-48v-li-ion-battery-pcb-board-54-6v-lithium-bms-with-60a-discharge-current-for-electric-motorcycle-and-e-scooter-protection-2-2-3-2-2-2-2-2/
*5x 21700 2S3P modules
Then I need some sort of ring terminals for the bms? The wires from the bms to the batteries? Isnât there a thick wire I need to connect from bms to negative and possitive too? Any links or specific on stuff would be cool if yâall know what I need.
Have you checked with battery builders here? IE: @thisguyhere
Also ring terminals arenât necessary. You could simply solder the wires directly to the bms.
I did about a 3 weeks ago still no reply.
Others are backed up and wont put me in line and just said just reach out to me in about a monthâŚ
Others donât do molicelss
Others wanted to do bms without connecting to cells
So solder to the nese system and the BMs?
Sounds like guys arenât biting off more than they can chew, and you have to respect that. Hope Nese works out for you.
Well we have an entire thread about nese systems but Iâm not familiar whatsoever with it other than âno welding requiredâ. So Iâd suggest having a go at questions over there. I believe @mishrasubhransu (hope Iâm right) could help you out
Yup, thatâs the right guy.
Yes, you need ring terminals to connect the balance wires to the NESE modules. For the main leads you need thick gauge silicon wires which you also connect via big ring terminals. The only required soldering is the main leads to the BMS.
If you are going the NESE route check that the modules will fit your decks width and that your enclosure will fit them.
You are saying 10S4P but 5*2S3P = 10S3P? Is that because you donât have enough space for a NESE 10S4P?
I was pointed to this forum from the previous builder. Anyhow, my very first attempt of soldering, and I think I botched it (see picture below). What went wrong: Solder leaked over to the other pin. I fear that this might cause a shortcut in the future. I watched a tutorial on how to solder this. He pretinned the wire and then pretinned the pin, then melting them both and pushing it down. I had great trouble doing this. Moreover, the heatshrink did not fit onto the solder itself.
Now, I would like some tips and tricks on how to solder this. A gentleman on the old forum told me that this forum would steer me in the right direction on how to redo this properly, as is my wish. Now, I checked another guide on how to solder, and his technique seemed more in-line with how one should solder. (by Robojax: Soldering replacing Xt60 Xt30 Xt90 connector perfectly on Youtube) . Any help is appreciated on how I could redo this properly.
@Hoaz
Yes, definitely redo that, itâs absolutely not safe.
Some pointers:
It looks like youâve got a very cold solder joint. Either your iron is not hot enough, or if it is hot enough it doesnât have enough thermal mass/thermal transfer ability to heat up your joint enough. Just judging by that plug, Iâd guess youâve got a ~20-25W âpencilâ style iron with no adjustment - if so, you will basically never get a good joint on larger wires using that type of iron, theyâre only suitable for small stuff.
Bare minimum in my opinion is a variable-wattage iron like this one with at least 40 to 60 watts, and a fairly beefy tip - not one of those fine pointy conical ones, you want either a chisel or a bevel. Expect to pay at least $30.
Ideally Iâd recommend a variable-temperature (actually measures and controls the temperature, not just the power) soldering station, such as a Weller or Hakko, or a knockoff, or a TS100 - Expect to pay at least $50-80.
You also added way too much solder, probably in an attempt to overcome the lack of sufficient heat.
It also really helps to have the connector plugged into another (thatâs not wired to anything obviously), to keep the metal bits from shifting inside the plastic housing while everything is hot.
