Number of Series Cells? -- NOT Series Strings or Series Voltage

[eMark]

.
At first glance, and second, and third and ... thought the following photo was 10S12P ... really can't tell from photo that it's actually 20S6P. If you look really, really close at the top right cell in the middle top group of 12 you can barely make out the negative end (with some imagination :wink: ); whereas the bottom left cell in that same group of 12 looks to be the positive end (red insulator ring).

That's the only imaginary clue that would support that it actually is a 20S6P pack ... other than Ron's word which is trustworthy.

My point of all this beginning with my first (locked) thread is that the contact of series cell bus bars with parallel cell bus bars helps to keep all the cells balanced (to a point) depending on cell quality, usage and condition of the pack as it ages with more and more c/d cycles.

Molicel 21700 P42A cells, 0.10mm copper sheet, plus 0.15 nickel squares only to facilitate welding. 20S / 6P
https://endless-sphere.com/forums/viewtopic.php?f=14&t=108006

How many series cells in this "20S / 6P" triangular pack ... anyone else think there are 120 series cells ?

Can someone post a photo or diagram of a battery pack that believes fewer series cells than parallel cells is an advantage ?

 

[john61ct]

How many series cells in this "20S / 6P" triangular pack ... anyone else think there are 120 series cells ?

There is no such thing as "series cells", and also no such thing as "parallel cells". Therefore ghat is a nonsensical question as phrased.

There is also no need to decipher what the xPyS layout of a pack is from looking at a photo. Just ask, ideally in the thread where you see that pack.

the contact of series cell bus bars with parallel cell bus bars helps to keep all the cells balanced

That is not true. It does not even make sense.

A pack getting unbalanced is not important, so long as LVC and HVC are at the cell/group level voltage.

But if for some reason you want to balance at a given SoC/voltage point you must do so using gear designed to do so, it cannot just happen through normal usage cycling.

Also there is no "advantage" to having the S count (voltage) be greater or less than the P factor (Ah capacity).

You need a certain voltage for a given motor/controller/ desired top speed

and the Ah capacity determines range and peak current.

 

[john61ct]

Related threads

https://endless-sphere.com/forums/viewtopic.php?p=1671784#p1671784

https://endless-sphere.com/forums/viewtopic.php?p=1671961#p1671961

 

[john61ct]

As for the "proportionality" between the S count (voltage) and P count (Ah capacity)

The former is not arbitrary, but dictated by what voltage your rig needs for its use case (speed, weight, terrain, motor & controller etc)

Ideally there would just be one string, and no paralleling needed, if you wanted and could carry say 40Ah, you just buy your S-count of 40Ah cells plus maybe a spare or two.

If you only wanted 17Ah then you buy that many (your S-count) in the appropriate size.

Problem is using the tiny cylindricals, not that much choice, and that is why we have parallel connections (NOT "parallel cells")

to get to our desired Ah capacity.

 

[999zip999]

Emark read read read .
https://www.amazon.com/DIY-Lithium-Batteries-Build-Battery/dp/0989906701/ref=asc_df_0989906701/?tag=hyprod-20&linkCode=df0&hvadid=312014160183&hvpos=&hvnetw=g&hvrand=4876981831918297621&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031538&hvtargid=pla-323272206900&psc=1#
read read read by the book then read it and read it again. that's where you need to start

 

[eMark]

Emark read read read .
https://www.amazon.com/DIY-Lithium-Batteries-Build-Battery/dp/0989906701/ref=asc_df_0989906701/?tag=hyprod-20&linkCode=df0&hvadid=312014160183&hvpos=&hvnetw=g&hvrand=4876981831918297621&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031538&hvtargid=pla-323272206900&psc=1#
read read read by the book then read it and read it again. that's where you need to start

As posted before i purchased it several years ago and read it and read it as it's likely thee book that every beginning DIYer should have in their Li-ion library to read again and again until it all makes sense (eventually sinks in).

It's not uncommon for a beginner to come across a concept in Micah Toll's book that may seem confusing. An ES newbie member gave the impression that Micah's wiring instruction for a BMS was wrong. Maybe he needs to reread it (digest it) again and again until it's no longer confusing or just move on and return later to digest it until it makes sense.

What i see as DIFFICULT is ES members (newbies and especially stalwarts) not taking the time to digest the content of my posts to better understand the concept being put forward ... unable to think outside their box of conditioned "phrasing". Thus writing-off certain terminology (series cells and parallel cells) as not being valid once interconnected in a DIY pack.

Anyway, anyhow, anycase, anyrate, nevertheless ... if everyone's brain thought exactly the same how boring life would be ... thus the expression "thinking outside the established box of conformity"... even though it's never an easy task. Like accusing me of trolling and calling me obnoxous.

What i see as DIFFICULT is ES members (newbies and especially stalwarts) not taking the time to digest the content of my posts to better understand the concept being put forward ... unable to think outside their box of conditioned "phrasing". Thus writing-off certain terminology (series cells and parallel cells) as not being valid once interconnected in a DIY pack.

Was interested to see how many ES minds are closed to the possibility (in my mind actuality) that those 120 cylindrical cells (20S / 6P) connected in series and parallel are functioning as both series cells and parallel cells at the same time. I'm getting the impression that you guys can't wrap your brain around that concept ... "thinking outside the box" (really inside the box as to what's going on).

I previously mentioned that i believe Micah Toll is not only a genius, but a great guy we'd all love to have as a neighbor. Agree that he doesn't refer to "series cells" or "parallel cells" in a DIY pack, but rather "cells in series" and "cells in parallel". However, that is NOT to say that all 120 cells in this 20S / 6P pack are functioning as both series cells and parallel cells at the same time. It's my understanding that this interconnected arrangement helps to keep the pack balanced via the 120 cells connected in parallel.

The concept that these 120 cells are functioning as 120 cells in parallel and 120 cells in series seems valid. So does the concept that these 120 cells are both series cells and parallel cells functioning together at the same time. At first glance this DIY pack appears to be a 10S / 12P, but it is actually a 20S / 6P .

Getting the impression that Ron wants to change the subject to spot-welding cylindrical cells, but that's not the purpose of these recent threads i've posted. Perhaps Ron believes the concept of series cells and parallel cells functioning together at the same time will only confuse newbies as well as stalwarts conditioned to the "proper pharasing".

Au contraire as i don't see it as a difficult concept to grasp that all 120 cells are functioning as both series cells and parallel cells at the same time.The point being that doing so is the most EFFICIENT way of wiring an 18650 pack whether rectangular shape or triangular shape.

What i see as DIFFICULT is ES members (newbies and stalwarts) not taking the time to digest the content of my posts to better understand the concept being put forward ... unable to think outside their box of conditioned "phrasing". Thus writing-off certain terminology (series cells and parallel cells) as not being valid once interconnected in a DIY pack.

 

[pickworthi]

To help someone who is struggling with what you mean - that's me of course - it would be really helpful if you could post the wiring diagram showing how your concept works.

 

[ZeroEm]

eMark your getting blow back because of sentences like this one.

by eMark » Aug 25 2021 8:07am
The concept that these 120 cells are functioning as 120 cells in parallel and 120 cells in series seems valid.

While this is true:
Concept is - something conceived in the mind : thought, notion.

This is not:
Valid is well-grounded or justifiable : being at once relevant and meaningful.

While the concept that all 120 cells are functioning in both rolls of having parallel and series connections is true.

120 cells in parallel

To be paralleled the positive much connect with the positive of the other cells and the negative with the negative.

They are not functioning as 120 cells in parallel, they are in groups of 6 to act like 20 single batteries not in parallel with each other. Each cell paralleled will add it's ah to the group. If you think all 120 cells are in parallel then do a draw down test to see if you get 120 x ah of one cell. Fletcher has it right "One test is better than all the opinions"

120 cells in series

Series must be positive to negative.

They are not functioning as 120 cells in series. They are functioning as groups in series not at the cells. You can test this functionality, each cell will add its voltage to the total. Check the total voltage and divide by the cell voltage and this is the number of series connections you have.

The concept is not wrong. The application would be bad.
1. Teach how to build a battery. tell them all cells will be connected in series with parallel connections to each cell. The use of 20s6p is a waste of time they are all S and P's, 120s 120p. Set all 120 cells and parallel them with two sheets of copper. One for positive and the other for negative. Now start your 120 series connections. What is going to happed?

2. Order a battery built with 120 series connections with 120 parallel connections and see what you get?

If you want to discuss concepts that is great still need a common language and word usage. If this is not done then the discussion is doomed.

I apologize to everyone just could not help myself.

 

[eMark]

While the concept that all 120 cells are functioning in both rolls of having parallel and series connections is true.

Thank YOU :thumb:

The concept is not wrong. The application would be bad.

When the concept is valid there is no reason why its application can't also be valid.

To be paralleled the positive much (must) connect with the positive of the other cells and the negative with the negative.

Concept application of following diagrams provided by spinningmagnets -- 28 cells in parallel and 28 cells in series...

4 cells in parallel with parallel connections ... concept application is valid for all 28 cells in parallel.
The above application concept is valid as you can see for yourself.

7 cells in series with series connections ... concept applicaton is valid for all 28 cells in series.
The above application concept is valid as you can see for yourself.

Whether triangular or rectangular the current at every point in an electrical loop should be as close to equal as possible with a well designed fabricated DIY 18650 battery pack (Kirchhoff's current law).

That's why it would be beneficial for spinningmagnets as lead instrutor to prepare an ES advanced class/course for those considering building a pack using spot-welded parallel and series cell connectons. The purpose being that the current at every point in an electrical loop is equal beginning with new first rate 18650 cells (or 2170 cells or LiFeP04). Or if already availalbe in a series of articles -- provide interested ES members with the link.

Was participant in a 4-color process printing class at GATF (Pitsburgh, PA) many, many moons ago. The instructor wouldn't allow any questions or comments until he thought the class had first grasped a concept he was teaching. This was frustrating to some of the students, but was a valid application concept. spinningmagnets might want to consider a similar valid concept application if the opportunity as lead instructor should come about. Spot-welding correct connections so that the current at every point in an electrical loop is equal :thumb:

 

[999zip999]

Please have someone else build your battery with BMS . Move on and quit insulting and belittling members.
Just hope you have learned something.

 

[eMark]

Please have someone else build your battery with BMS . Move on and quit insulting and belittling members.
Just hope you have learned something.

If you can't envision the concept in your mind don't assume it's application is invalid by posting a demeaning comment.

While the concept that all 120 cells are functioning in both rolls of having parallel and series connections is true.

They are not functioning as 120 cells in parallel, they are in groups of 6 to act like 20 single batteries

Never said or implied that it's a 1S / 120P string ... so why should you assume so ? The KEY phrasing was always stated whether 20S / 6P or 10S /10P or another series / parallel configuraton ... so was not helpful for you to invalidate the concept as not applicable.

It isn't necessary to count the number of spot-welded series and parallel connections. Counting the number of cells with series connectons and the number of cells with parallel connections is valid.

The title of the thread "Number of Series Cells ?" has a question mark. Do all 120 cells in that triangular 20S /6P have series connections? .... ______ YES ... ______ NO

The concept that all 120 cells have parallel connections seems valid enough. But do all 120 cells have series connections in that 20S / 6P pack ?

Isn't that the objective with a well-designed triangular pack to have just as many series connections as parallel connetions? This is possible with a rectangular pack ... so shouldn't it also be the goal with a triangular pack?

Is it possible for this 20S / 6P to have as many cells connected in series as it has cells connected in parallel ?

Is it possible for this 10S / 10P to have as many cells connected in series as it has cells connected in parallel ?

 

[spinningmagnets]

the bus plates on the other side of the pack are a completely different group of shapes.

This weekend, I will flip the picture and draw the shapes on the other side, so the flow of current will be more obvious.

edit: tried to figure it out, and I don't know how he did it.

 

[nicobie]

I apologize to everyone just could not help myself.

 

[eMark]

the bus plates on the other side of the pack are a completely different group of shapes.

This weekend, I will flip the picture and draw the shapes on the other side, so the flow of current will be more obvious.

We know there will be as you say a "different group of shapes" because of its a S / P configuration (20S / 6P). As far as knowing the "flow of current" that was never implied as the intent or purpose of the thread title or discussion. The title of this thread is plural ... "Cells" ...Number of Series Cells? or "cells in series" is the discussion (as well as number of cells in parallel).

If you agree with Micah Toll's phrase "cells in series" and "cells in parallel" than why is it so dificult to grasp the concept of "series cells"(plural) being 120 in number in that 20S / 6P (and furthermore the same 120 cells in parallel). In the thread title it reads ... "NOT Series Strings or Series Voltage" (or Current Flow).

Your "flip picture" of the other side may confirm (validate) that all the cells in this 20S / 6P are functioning as 120 "cells in series" and 120 "cells in parallel". Micah Toll in his book (recommended reading) uses the expresssion "cells in series" and "cells in parallel".

Being that the concept is valid then it is not a stretch to say that all 120 cells in this 20S / 6P triangular pack are functioning at the same time as both 120 series cells(pural) via series connections and 120 parallel cells(pural) via parallel connections ... assuming the "bus plates" on the flip side are AOK (positioned and connected properly).

so the flow of current will be more obvious.

The question posed in these threads was never about a preferred or desired flow of current. Rather whether or not it is possible for all 120 cells to function as both 120 cells in series as well as 120 cells in parallel at the same time. There was never any mention in any of the thread titles about current flow.

Apparently a concept that nioble and others are having a difficult time grasping because they don't take time time to read and digest the content, which may be true with this reply. At least ZeroEm took the time to read and digest that the concept is valid (120 cells in series and 120 cells in parallel).

spinningmagnets also grasps the concept in that he never implied it's not possible in either a rectangular or triangular configuration to have the same number of cells functioning in series at the same time they are also functioning in parallel. Even john61ct finally admitted so, but it was like pulling hen's teeth.

This thread title was not about the flow of current, but rather the number of "cells in series" or number of "series cells"(plural). Maybe, it's easier to grasp the concept if we think of all 120 cells (20S / 6P) as "series/parallel cells(plural)" or "cells in series/parallel" in this 20S / 6P triangular configuraton.

 

[spinningmagnets]

All 120 cells shown are "in series" with some other cell, and every cell shown is "in parallel" with some other cell.

Language evolves over time. I apologize if the current usage of description annoys you. We are doing the best that we can.

Could you indulge us, and describe the battery that you hope to build?

 

[john61ct]

The fundamental idea to grasp is that the adjectives "serial" and "parallel" are **not** attributes of any single cell,

but attributes of the relationship, the **connection between** a set of multiple cells.

Note that the **only** reason these packs shown here connect **all** the cells at the same time both in series and in parallel

is that use of those specially shaped plates.

Also can be done with the conductive strips, but only with the overlaying / crisscross type of pattern.

But (usually?) these methods are only done with **spot welded** packs, using these cylindrical cells with flat terminals.

Trying to do the same with cell **posts** connected via copper wiring or nickel-plated buss bars would be very unwieldy, I've never seen that attempted.

And definitely not possible using those NESE modules that OP has used, and may well plan on continuing to use.

These I understand only use parallel connections on the inside?

but can make either serial or parallel connections between each module on the outside.

Or in the case of NESE modules, the relationship, the **connection between** a set of multiple modules which (as paralleled groups) each "perform as" single cells.

With (more normal outside of spotwelded ebike packs) connections using copper wiring or nickel-plated buss bars attached to posts, **not all** the cells will be connected in both series and parallel.

It is up to the designer of the pack to decide if the parallel grouping of cells for increasing Ah comes first, and

then those groups connected in a single series string each to increase voltage from the opposite end of the group - needed for one BMS to protect / control the whole pack

or to build multiple strings (sub packs) first with single cells, then join those strings in parallel.

The latter would be pretty impractical to try with most BMS, and thus is rarely seen.

I hope this helps.

 

[999zip999]

John are you still torturing yourself on this thread
.You ever thought of self flogging yourself for with a cat-of-nine-tails. This is a torture thtead.

 

[john61ct]

No problem, writing out such detailed explanations helps me clarify the fine distinctions in my own mind,

even if OP never groks it, they may be helpful for others.

 

[ZeroEm]

Diversity reveal's character. Thought John was going over the edge for a while, now I see he has regain his footing and is stead fast.

 

[nicobie]

IMHO he has the patience of a saint, As does spinningmagnets.

I'd of given up a week ago.

 

[john61ct]

Thanks, acknowledgments like that make it all worthwhile, just trying to help out, trying my best to give back, as little as it might be.