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Regarding Pack design and naming convention
#1
t-What-does-S-and-P-stand-for-What-is-Xs-Yp-or-XsYp-with-X-and-Y-being-numeric-digits

In the thread referenced above, certain naming conventions are laid out that (with all due respect) make not a lot of sense. I read through that thread, hoping to find some standardization of the naming but found it to be self contradictory, and only made things worse.

A resource i read elsewhere said that they always represent the X-Series value first because they are always connected in parallel first anyway (a la Tesla) which again makes no sense to me since i know of projects that went the other way entirely. 

Now, I don't know if there is a higher order authority that decides these things, but i would propose that, given the potential complexity of battery pack configurations, that naming be done in a logical way. For instance, I know there is a group of people who are building 7 cell series boards, connected in parallel to whatever capacity they are looking for.

I would call this a 7S(whatever)P pack(or string or array).

Meanwhile Tesla in at least one of their vehicles apparently does ~20 cells in parallel, connected in series to another ~20 cells in parallel and so on (lets say 10 times just for a number), inside a string of a 5 string pack for the vehicle.

I would call this 20P10S(5(?)) (unsure whether the strings are connected in parallel or in series or totally independent of each other)


To me this makes sense in that it is the most clearly descriptive way to describe the way it is designed.

Does this make sense to anyone else? or am I that guy?

Quote:• Order makes a difference. A 4S3P is not the same as a 3P4S.
.   - A 4S3P is 3 cells in parallel, and then connected in series to make 4S.
.   - A 3P4S is 4 cells connected in series, then 3 of these connected in parallel at the ends of the series strings.

[Image: ptcbej1.jpg]

specifically, this seems dead opposite of what it should be.
4S3P is 4 cells in series, each of those 4 cell series packs connected in parallel.. 

and 3P4S is 3 cells in parallel connected in series with 3 others to make 4 series clusters

right?
#2
Hi ccerberus,

It makes sense, that's right. But if you write always the s first, as normal, you see at first what voltage the whole pack has, so for me this is better.

And I don't know why you should connect x cells in series and y packs of those in parallel, because this way you need y BMS's and if you connect y cells in parallel and x of those packs in serial you just need one BMS with y times the current.
#3
If we were talking about baskets of pine cones, we'd say we have 3 baskets of 20 cones. So, that's be 3b20c. This is exactly the same way for the cell/pack designation. If we have 14 packs of 80 cells, we have 14s80p.
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#4
(01-06-2019, 12:46 AM)LEDSchlucker Wrote: Hi ccerberus,

It makes sense, that's right. But if you write always the s first, as normal, you see at first what voltage the whole pack has, so for me this is better.

And I don't know why you should connect x cells in series and y packs of those in parallel, because this way you need y BMS's and if you connect y cells in parallel and x of those packs in serial you just need one BMS with y times the current.

Wherever the S is, it would tell you the voltage ballpark, whether it was beginning, middle or end..

I agree that X cells in series and y packs in parallel is problematic for all the reasons you state, but the solution they had was to have a break out header on each board with a terminal for each cell for balancing, then connect all those breakout headers with a ribbon cable. its a cool idea but then that is actually paralleling each 2nd cell, and each 3rd cell and each 4th cell etc. 
And being a ribbon cable it can't handle any actual current, but it is used for balancing..
#5
There is a technical sheet on how this should be said but we have not gotten our hands on it and it cost money. Until this electrical techsheet arrives in my hand the above is the correct naming Smile
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#6
(01-06-2019, 08:29 AM)daromer Wrote: There is a technical sheet on how this should be said but we have not gotten our hands on it and it cost money. 

Link to it ? - the paid for version please.
#7
I dont remember the number of the document out of my head but see if I can look it up.
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#8
We have discussed this at length when putting this together, especially with regards to complexity for people new to the business. The problem is that the notation of XsYp does dictate what the final result is, but not necessarily the way to get there.

4s3p can be 4s+4s+4s / 4s x3 or 3p+3p+3p+3p / 3p x4 and both ways give you 4s3p if you have connections in between the cells. The 3p x4 is just easier to build and makes more sense. And under no circumstances it will give you 3p4s. The latter is rarely used anyway and you shouldn't make batteries like this unless you have a specific reason because there is no way to access specific cells unlike you can do in 4s3p configurations. You could argue that the difference between both notations is very small and you'd be right, but we can't rely on no one building 3p4s batteries so this has to be accounted for in some way. This adds more complexity to the subject but it can't just be ignored. The fact that you bring this up confirms this.
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#9
"officially" posting this attempt at a battery stringing convention, and its obvious ambiguity does appear to be at odds with the recently introduced "dont blame us" terms that we've all had to agree with before forum content access is granted.

Having to agree with "dont blame us" terms is a wise move - but it really doesn't make sense to be posting ambiguous data regarding a fairly critical component of a system.

I have access to standards and conventions across most of the developed World, if anyone can point me to any officially recognised and approved naming or stringing nomenclature I'll produce a simplified version for possible use here - if, as it appears to be the case with the introduction of the "dont blame us" signup, there are concerns about the content of this forum, it would be a wise move to stop trying to invent "standards", or at least ensure the total clarity of them before they are posted.
#10
I'm not aware of any officially published standard on the subject. I'd be interested to have a look if daromer can find it again.

Apart from that, we don't invent a standard here. This is out in the wilds for years and even decades. People will have seen it or heard about it and will try to use it. We're trying to provide guidance on how to use the notations properly to make sure that everyone is talking about the same thing.


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