Parallel series battery architecture

[zacksc]

A Ligo battery is, as I understand it, a 36 volt battery made from 10 cells in series. That is, a 10 x 1. If you put four of them in parallel, then you can make essentially a 10 x 4 battery. That 10 x 4 battery which consist of 4 individual chains working together in parallel.

On the other hand, I am thinking that if you were to buy a 10 x 4 battery, that would be compromised of units of four batteries in parallel connected in a single series chain. Does that sound correct? I’d be interested in discussion of the differences in pros and cons of those two different types of architecture. I’m thinking that it makes a difference for balancing, for example.

 

[e-beach]

..........On the other hand, I am thinking that if you were to buy a 10 x 4 battery, that would be compromised of units of four batteries in parallel connected in a single series chain. Does that sound correct? .........

Not necessarily. If you want to purchase a 12v battery (fully charged to 14.4v) then you purchase a 12v battery. If you want to purchase a 36v battery (42v fully charged) then you purchase a 36v battery.

Nobody really purchases a battery based on something like 10 x this or 4 x that. They purchase a battery on voltage and amperage (watt hours).

So, IMO, the answer to your question is "no" your statement does not sound correct.

 

[DogDipstick]

..........On the other hand, I am thinking that if you were to buy a 10 x 4 battery, that would be compromised of units of four batteries in parallel connected in a single series chain. Does that sound correct? .........

So, IMO, the answer to your question is "no" your statement does not sound correct.

You, my friend, zacksc, have stumbled upon a phenomenon not many battery builders address.

Yes, between those two scenario that you presented, the circuits ARE different, and WILL show a different (Intrinsic, or "internal") resistance between the two scenario. Different resistance = differnt output.

Resistance. Presented in "real" numbers, and very easily mapped on a circuit diagram... using V=IR.. and you might be surprised how different the two scenarios are. This is the kind of stuff that only electrical engineers ( trained in circuitry design, and laws of electricity) see, honestly. If you didnt know any better you would assume they are the same, or identical, but they are absolutely not.

Look at this: A (pair of ) diagrammed circuit(s). Drawn up by a friend.

"Both provide a power supply of 15 volts at 5 amps. Both use (25) 3 Volt batteries. Both use (25) 0.1 Ohm links. By calculation there is a hugh line loss difference between the two types."

The pictures show the obvious, laid out clearly like this ( difference in circuit), and show the difference you refer to when batteries are wired in this way.. or that way... and the resulting loss over a line.

Significant difference, based on the numbers in the scenario above.

27.5 watts lost, or 2.5w loss... over a tenfold difference.

Just the way they are wired. same cells, same number of cells, same current, same voltage provided.... Significant difference in loss based on circuit choice.

 

[hallkbrdz]

I guess I don't understand what you are trying to show here. Why would it make any difference which way you arrange them (other than for monitoring with a BMS)? Series resistance sums, parallel resistance divides.

 

[BDamari]

Just the way they are wired. same cells, same number of cells, same current, same voltage provided.... Significant difference in loss based on circuit choice.

So in a language I can understand, the only difference between these two is the amount of nickel (or any conductor) on the series connections, resulting in different sums of resistance?

 

[hallkbrdz]

So in a language I can understand, the only difference between these two is the amount of nickel (or any conductor) on the series connections, resulting in different sums of resistance?

That, and the number of BMS leads and units you need. That is why normally they are wired parallel series, not series parallel.

 

[john61ct]

There is standard terminology for discussing these layout issues.

A Ligo battery is, as I understand it, a 36 volt battery made from 10 cells in series. That is, a 10 x 1

aka 1P10S

The "1P" for parallel can be left off, so 10S means 10 in series to get 36V nominal.


> If you put four of them in parallel, then you can make essentially a 10 x 4 battery.

aka 10S4P

Usually the parallel is first, 4P then 10S, grouped at the "lowest level" so that each acts as a single cell for charging / BMS monitoring purposes.


> That 10 x 4 battery which consist of 4 individual chains working together in parallel.

Groups for parallel, strings for series, chains are not a thing.

So the current example being yours "4 groups of ten-cell strings", mine "ten strings of 4-cell groups"

Usually, the 10S4P is considered bad because each string will get a different proportion of the load, uneven wear causes lower performance and reliability and shorter lifespan overall.

However, with spotwelding packs, the parallel and series connections can overlap, and some advocate **for high C-rate** use cases, better to get the thicker serial conductors directly welded to the terminals.

Of course you would not want to buy and manage four BMS

so rather than only connecting the 4 strings at the outermost 36V pos/neg pairs,

getting each cell of the 10S4P example connected to the other corresponding three cells in the other strings

would be a "hybrid" solution allowing one 10S BMS to monitor the groups of four as if each were a single cell.

Hope that helps.

 

[zacksc]

Thanks a lot! That really helps. Groups and strings. Good nomenclature!

So then 4 Ligos in parallel would be technically at 10s4p?

On the other hand, an ordinary 36 volt battery with 40 cells would essentially always be made as a string of 10 groups, with each group comprised of 4 cells. Do I have that right?
Would that be referred to as a 4p10s, or maybe a 4p x 10s, rather than a 10s x 4p? Does the order convey information? What is the convention of that?

 

[zacksc]

So in a language I can understand, the only difference between these two is the amount of nickel (or any conductor) on the series connections, resulting in different sums of resistance?

That, and the number of BMS leads and units you need. That is why normally they are wired parallel series, not series parallel.

Thanks. So then a 10 battery BMS could be used for either a 4p10s or a 1p10s.

 

[hallkbrdz]

Thanks. So then a 10 battery BMS could be used for either a 4p10s or a 1p10s.

Yes. Parallel cells are effectively treated as one larger capacity cell.

 

[zacksc]

There is standard terminology for discussing these layout issues.

Thanks a lot John! So does order matter in the designation?
Is a 4px10s different from a 10sx4p?

(That is, would a 10sx4p be appropriate for 4 Ligos in parallel ...)

 

[999zip999]

Ok now what are you using it for ? Controller and motor amp demand. Yes the important part . Purpose

 

[john61ct]

So then 4 Ligos in parallel would be technically at 10s4p?

On the other hand, an ordinary 36 volt battery with 40 cells would essentially always be made as a string of 10 groups, with each group comprised of 4 cells. Do I have that right?

Yes.

> Would that be referred to as a 4p10s, or maybe a 4p x 10s, rather than a 10s x 4p? Does the order convey information? What is the convention of that?

Many do not follow the order properly but yes as I said your four Ligo's are 10S4P

Where, say I was using fat interconnect wires with crimped rings to connect big cells with bolt terminals, I would usually do 4P10S.

no x's needed.

 

[john61ct]

a 10 battery BMS could be used for either a 4p10s or a 1p10s.

Yes any number of cells per group doesn't matter because electrically the group is functionally one (1S) cell.

Downside is, impossible to test / monitor any cells individually. without "atomizing" the group.

In other use cases, advice is to select your cell size so its Ah capacity is a large as you need the whole bank to be

so you end up with one string.

Or at most two, if redundancy is required for something mission-critical.

e.g. each string 14S (for 52V nominal), at 180Ah per cell, lots easier to manage than thousands of tiny ones.

 

[john61ct]

Almost hate to do this

but some useful information can be extracted by carefully parsing this thread

https://endless-sphere.com/forums/viewtopic.php?p=1514669#p1514669

so long as you completely ignore the posts contributed by the OP

or at least I could never figure out his meanings and I think everyone else in the end bailed out on trying to as well.

______
Also this one, even though I did not ever get a definitive answer to the central question, my understanding / inference from other threads since, is that it is Yes.

https://endless-sphere.com/forums/viewtopic.php?p=1561188#p1561188

 

[zacksc]

Hey, thanks a lot John. and thanks for not just referring me in the beginning to a weedy thread. I think you have spelled it out really clearly in this thread and I really appreciate that. Thanks for clearing up the terminology for me as well, and not just letting me say "chain" when the correct term is string!