Help with 128 batteries each one is 280ah, and want to configure for 48v system.

Ohms_Cousin · Nov 21, 2020

Steve_S said:
In a nutshell, YES. If two identical packs are in parallel then that load would be split between the two and they would discharge fairly evenly.

Right. I understand that part then.

So if a total battery pack is setup as 1 x 16s 280Ah cells + another 1 x 16s 280 Ah cells (to be clear, so 2 x 16s of 280Ah cells -16s2p?) then a total of a 200 amp draw on that total combined battery would be 100 amps across each of the 16s sets in the total battery ? (wording it awkwardly but want to make sure its crystal clear what I am trying to get at)

So 100 amps of load is drawn from each 16s string to make up the total combined draw on the battery of 200amps overall ?

What I dont get is, (or want to be sure about) from that one 16s string of 280Ah cells that is contributing 100 amps to the total 200 amp load, how much is each 3.2v cell contributing to the 100 amps being drawn from the 16s string?

I think its really really important to understand this concept well - so I would like to make sure I am getting this 100% correctly. Its a steep curve to get on top of while trying to ingest all this information and understand battery packs well when you are a beginner. Thanks for any insights, its all good.

Steve_S · Nov 21, 2020

You have a fairly good handle on it.... The "individual cell" question is another matter, KISS says divide 100A by 16 cells which comes back as 6.25A per cell but that isn't 100% either...

Ohms_Cousin · Nov 21, 2020

Steve_S said:
You have a fairly good handle on it.... The "individual cell" question is another matter, KISS says divide 100A by 16 cells which comes back as 6.25A per cell but that isn't 100% either...

thanks Steve S for the info.

cinergi · Nov 21, 2020

No. If the battery is supplying 100 amps, each cell is supplying 100 amps.

Honuz · Nov 22, 2020

ericgrand said:
I'm sorry, I think there is a misunderstanding here...In Serie, all cells are pushing the same Amp amount. Voltage maybe different. But definitely, if battery is outputting 140A, then all cells are outputting 140A. But as there internal resistance may vary, the total voltage is the sum of all individual voltage.

You are right, but they do not with an active bms which is able to pass some amps to an other cell (1-2 A). And that's the advantage of an active balancer which will be able to suck a little more amp from one cell then the other when the voltage delta is out of the configuration profile (let's say 30mV, 50mV).
For this 128cells I would do 8 bank of 16 cells each bank, 8 bms then parallel all that... And I would constraint those cells in 8 boxes. A shunt per pack for capacity display and a circuit breaker to isolate pack(s) if needed.
And some warning stickers...do not short circuit one pack....cause that's a lot of energy in one place...

JoeHam · Nov 22, 2020

cinergi said:
No. If the battery is supplying 100 amps, each cell is supplying 100 amps.

I think the difference is “supplying” 100 amps vs supplying approximately 1/16 of 100 amps while the sum of the amps supplied by the other 15 cells still passes through.

Trying to parse supplying as an active action vs. passing through as a passive action.

cinergi · Nov 22, 2020

JoeHam said:
I think the difference is “supplying” 100 amps vs supplying approximately 1/16 of 100 amps while the sum of the amps supplied by the other 15 cells still passes through.

Trying to parse supplying as an active action vs. passing through as a passive action.

In series, amps don't add/subtract each other - only volts. So each cell is supplying 100. A cell won't act as a passive conductor and pass 100 amps but "provide" less. The electrons must flow from one side to the other. IR will impede the ability to pull higher currents and differences in IR will cause differences in temperature and all kinds of other effects, but it only becomes really important in parallel setups.

ericgrand · Nov 22, 2020

Honuz said:
You are right, but they do not with an active bms which is able to pass some amps to an other cell (1-2 A). And that's the advantage of an active balancer which will be able to suck a little more amp from one cell then the other when the voltage delta is out of the configuration profile (let's say 30mV, 50mV).
For this 128cells I would do 8 bank of 16 cells each bank, 8 bms then parallel all that... And I would constraint those cells in 8 boxes. A shunt per pack for capacity display and a circuit breaker to isolate pack(s) if needed.
And some warning stickers...do not short circuit one pack....cause that's a lot of energy in one place...

I agree, an active BMS would transfer from one cell to an other but:
-average would still be 100 A (if 100A are drawn from the whole pack)
-in no case the 100A would be divided by the number of cells.

This is in my opinion the minimum basics one should know before "toying" with such huge cell capacity!

In serie:
-power is divided because voltage is divided between each cell, ampere are (without active BMS) the same across all cells

In parallel:
-power is divided because amps are divided between each cells, voltage is the same across each cell...

JoeHam · Nov 22, 2020

cinergi said:
In series, amps don't add/subtract each other - only volts. So each cell is supplying 100. A cell won't act as a passive conductor and pass 100 amps but "provide" less. The electrons must flow from one side to the other. IR will impede the ability to pull higher currents and differences in IR will cause differences in temperature and all kinds of other effects, but it only becomes really important in parallel setups.

Yes I fully understand the difference between series and parallel.

Trying to define the meaning of “supply” is what I was trying to differentiate but it’s not important in the big picture.

JoeHam · Nov 22, 2020

Allow me to clarify what I am trying to point out.

We use our batteries to “supply” us with power. As an example let’s use a 48v battery, 16 cells at 3v each.

At 100 amps that “supplies” 4800 watts.

Each individual cell supplies 300 watts.

So each cell is responsible for 1/16 th of the power supplied.

cinergi · Nov 22, 2020

JoeHam said:
Allow me to clarify what I am trying to point out.

We use our batteries to “supply” us with power. As an example let’s use a 48v battery, 16 cells at 3v each.

At 100 amps that “supplies” 4800 watts.

Each individual cell supplies 300 watts.

So each cell is responsible for 1/16 th of the power supplied.

Great way to think about it, and it works for both series and parallel discussions.

Honuz · Nov 22, 2020

ericgrand said:
I agree, an active BMS would transfer from one cell to an other but:
-average would still be 100 A (if 100A are drawn from the whole pack)
-in no case the 100A would be divided by the number of cells.

This is in my opinion the minimum basics one should know before "toying" with such huge cell capacity!

In serie:
-power is divided because voltage is divided between each cell, ampere are (without active BMS) the same across all cells

In parallel:
-power is divided because amps are divided between each cells, voltage is the same across each cell...

My post was just a précision, those 2A balancing are nothing in regard of a "high" discharge like 100A anyway.
I agree on what you said, those are not AA cells, there is lot energy in those, we got to be careful.

kromc5 · Nov 24, 2020

Steve_S said:
REF: Li-Ion BMS - White Paper - Dissipative vs. nondissipative balancing (a.k.a.: Passive vs. Active balancing)

QNBBM's from DeliGreen (they own the QNBBM brand)

Battery Blancers/Equalizers - Changsha Deligreen Power Co., Ltd. - page 1.

HelTec Smart BMS'

Products list direct from CN

Main products LoRa Dev-Board, LoRa Gateway and 601 more Products from Chengdu Heltec Automation Technology Co., Ltd. on Alibaba.com

cncdheltec.en.alibaba.com

You may want this as well:
https://diysolarforum.com/resources/general-lifepo4-lfp-voltage-to-soc-charts-tables-12-24-48v.109/

For Quick Math Help (the darn formulas)

Amp-Hours (Ah) to Kilowatt-Hours (kWh) Conversion Calculator

Convert amp-hours to kilowatt-hours using this electrical conversion calculator. Learn the formulas to convert Ah to kWh with examples.

www.inchcalculator.com

Hope it helps, Good Luck
Steve

Went through all the information and yt videos and decided to place the order for 9 Chargery bms systems, wanted to have an extra on hand. After reading over them all Batrium still seems super nice but the chargery is much less overall and seems very easy to work with.

Honuz · Nov 24, 2020

kromc5 said:
My inverter is the growatt 12kw, with two growatt 120 amp charge controllers. When talking with signature he stated that we would need to just be aware of our total load IE is the heater running / stove or laundry plus appliances and James is in a much larger home. Since I have a new meter I have been wanting to get the time to check all appliances, our heating system, stove etc, the mini split is roughly 20 amps. But with only 12kw I suspect I could easily hit that the max if I was not careful. With 8 16s and the max amps from them I calculated that the max load would long hit the inverter before the batteries were maxed. My sub panels is a 200 amp as well.

Most of the time, energy independence come with an other way of consuming this energy.
Lean how to use less, 100kwh of batteries is a lot....

cinergi · Nov 24, 2020

Honuz said:
Most of the time, energy independence come with an other way of consuming this energy.
Lean how to use less, 100kwh of batteries is a lot....

This is why I'm building my RV with propane stove/cooktop and water heater, a good residential fridge, a good dishwasher, and a heat pump clothes dryer (I would have gone propane, but none are available in compact sizes), and 240v mini-split. It does mean I'm burning fuel, but going "all electric" (e.g. induction cooktop or electric oven) just isn't a good option (yet) with these kinds of setups.

kromc5 · Nov 24, 2020

Honuz said:
Most of the time, energy independence come with an other way of consuming this energy.
Lean how to use less, 100kwh of batteries is a lot....

I have already reduced it by about 400kwh + monthly but due to our home job there are extenuating circumstances that are out of the ability to control.

yabert · Nov 24, 2020

kromc5 said:
Went through all the information and yt videos and decided to place the order for 9 Chargery bms systems, wanted to have an extra on hand. After reading over them all Batrium still seems super nice but the chargery is much less overall and seems very easy to work with.

Why 8 times 280Ah 48V batteries instead of just one 2240Ah 48V battery?
For me it seem a lot easier to connect 8 cells in parallel to create one big 2240Ah cell and connect those in 16S battery.
After you need a cheap, but super nice, Zeva 16S bms and a large 500A contactor. That it, no?

kromc5 · Nov 24, 2020

yabert said:
Why 8 times 280Ah 48V batteries instead of just one 2240Ah 48V battery?
For me it seem a lot easier to connect 8 cells in parallel to create one big 2240Ah cell and connect those in 16S battery.
After you need a cheap, but super nice, Zeva 16S bms and a large 500A contactor. That it, no?

I had looked at that but many responded that 16s by 8 would be easier to manage and monitor.

yabert · Nov 24, 2020

To me it easier to manage only one battery instead of 8 or, preferably, manage only 16 cells and one BMS instead of 128 cells and 8 BMS.
Well, I can only see one advantage to have 8 BMS and it's about the balancing current capability who will be 8 times higher.
But despite if the BMS balancing current isn't large enough, still you can manually balance the 16 cells (2240Ah) manually once a month, a year or a decade (depend of the quality of the cells).
Or ask at the BMS supplier how you can add external balancing capacity to their BMS... yes, it's a bit of work/trouble.

BiduleOhm · Nov 25, 2020

Personally I'd do 2P16S4P (i.e. 4 packs in parallel, each pack being 16 in series of 2 cells in parallel). It should be the best compromise between a lot of packs/BMS and one giant pack with only one BMS

Honuz · Nov 25, 2020

kromc5 said:
I have already reduced it by about 400kwh + monthly but due to our home job there are extenuating circumstances that are out of the ability to control.

Wow...1800kwh a month...? That's what I use in a year...?
But 400wh a month, a 20% decrease is already quite nice..!

Honuz · Nov 25, 2020

yabert said:
Why 8 times 280Ah 48V batteries instead of just one 2240Ah 48V battery?
For me it seem a lot easier to connect 8 cells in parallel to create one big 2240Ah cell and connect those in 16S battery.
After you need a cheap, but super nice, Zeva 16S bms and a large 500A contactor. That it, no?

And now you got a fail on one cell..you got no spare...what do you do...you dismantle all pack..? In the 8p16s you just disconnect one pack (the one With the faulty cell) and you got time to fix the problem, you can disconnect a pack to top balance it if needed...it's flexible.
You could even sell one (16s pack)...or buy a new one and add it... I feel it's far easier to manage.

yabert · Nov 25, 2020

Honuz said:
And now you got a fail on one cell..you got no spare...what do you do...you dismantle all pack..?

Simple. You identify the faulty 2240Ah cell, after you identify and remove the single 280Ah faulty cells and continue to operate your 48v 1960Ah battery for the time you shout your cell supplier to had sold you crappy cell

After you add a new 280Ah cell and you will be able to operate your 48v 2240Ah battery.
In my case, I have more confident in cells than in electronic BMS. So, to me, less fairly reliable BMS and more ultra reliable busbar is the way to go.

The downside of a single battery is you have to stop your system to play with. If this is really problematic, build two 1120Ah batterie could be a good option.

curiouscarbon · Nov 25, 2020

Splitting the entire thing into two packs sounds pretty smart to me, that way as long as only one cell fails at a time it would be possible to stay online, if needed.

BiduleOhm · Nov 25, 2020

yabert said:
Simple. You identify the faulty 2240Ah cell, after you identify and remove the single 280Ah faulty cells and continue to operate your 48v 1960Ah battery for the time you shout your cell supplier to had sold you crappy cell
After you add a new 280Ah cell and you will be able to operate your 48v 2240Ah battery.

So you need to cut all charge/discharge twice, it's rather inconvenient. If you have multiple packs you can repair the faulty one while continuing to use the remaining ones

yabert said:
In my case, I have more confident in cells than in electronic BMS. So, to me, less fairly reliable BMS and more ultra reliable busbar is the way to go.

Then you would want the redundancy of multiple packs. With one big pack if your only BMS fails then the whole system is down. Having no SPoF plays a big role in having a high availability.

Help with 128 batteries each one is 280ah, and want to configure for 48v system.

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