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My Open Source Solar BMS and Digital MPPT
#31
(12-11-2018, 05:20 PM)electrodacus Wrote:
(12-11-2018, 11:03 AM)Charly144 Wrote: Electrodacus. Maybe i am blind but i don’t find a detailed description of tthe bms0 somewhere... can you pls give me a hint!

Thx
Karl

SBMS0 is under development so there is no much more than the description on Kickstarter about it. Just working on the PCB right now. It will be fairly similar to SBMS40 just minus the power electronics and WiFi. The SBMS0 is designed as a low cost and only contains the BMS + the advanced energy monitor so no charger like the SBMS40 or SBMS120.
When that is design and ready it will be added to the current SBMS40/SBMS120 manual.
You say without wifi, is it then without any communication or does it just support just ethernet?

Can you somehow support 14s?
What is the balancing current?
Any chance to put several sbms in parallel for parallel 14s strings...?

Thx
Karl
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#32
There you go, and on one of of the fanciest channel Smile Sweeet!
https://www.youtube.com/watch?v=3OAwr8FulGE
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#33
(12-12-2018, 10:21 AM)Charly144 Wrote: You say without wifi, is it then without any communication or does it just support just ethernet?
Can you somehow support 14s?
What is the balancing current?
Any chance to put several sbms in parallel for parallel 14s strings...?

Thx
Karl


SBMS0 has UART that can be used to receive the same data you get over WiFi but you can also add WiFi and the SBMS0 software will support that either ESP8266 or ESP32 with the default AT firmware will be supported. There will be access to 3.3V, GND, TX, RX and ESP reset on the 16pin extension and programming connector on the SBMS0. Maybe if there is enough demand I will build a simple WiFi extension.
Yes two SBMS0 can be used for a 14s or even 16s setup but is not something I recommend as it is not an elegant solution to have two separate SBMS0.
But with 7s or 8s 24V setup and the up to 500A current shunt you can have loads as large as 12kW and that I consider to be fairly high not sure what will be the reason to go with 14s.
Max cell balancing current is 200mA but with that and the way SBMS is doing cell balancing batteries as high as 20 to 100kWh can be kept in balance. Same type of balancing with similar cell balancing current is present on all commercially available EV's.
Any number of parallel cells will be no different from a single higher capacity cell so first you parallel as many cells as you need to get to desired capacity then you have those groups in series.
Normally I recommend LiFePO4 (also what I use) because they are the most cost effective in therms of cost amortization and those can be had as very large capacity cells 100Ah to 1000Ah are not a problem.

Not sure what you want to do and what sort of battery capacity you are thinking about. Knowing that I may have more exact suggestions.
Korishan likes this post
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#34
Well no 14s that is unfortunate.
Everything I own runs on 48V. Just the cabling alone makes that voltage very attractive. Compared to 12V and or 24V.
I started out with 12V and then looked at cables the size of a quarter in diameter and said ah no.
Now I have cables the size of a dime and actually can manipulate them instead of them manipulating me.
I am sure there are a lot of people out there running 48V systems.

3300 Watts @ 220V =   15A
3300Watts  @ 12V   =  275A
3300 Watts @ 48V  = 68.75A
Never let the numbers get in the way of a good time.
Just my thoughts. 

Wolf
Solexx X and bogptrsn like this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
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#35
(12-13-2018, 07:50 PM)Wolf Wrote: Well no 14s that is unfortunate.
Everything I own runs on 48V. Just the cabling alone makes that voltage very attractive. Compared to 12V and or 24V.
I started out with 12V and then looked at cables the size of a quarter in diameter and said ah no.
Now I have cables the size of a dime and actually can manipulate them instead of them manipulating me.
I am sure there are a lot of people out there running 48V systems.

As mentioned two SBMS0 can be used for 14s is just not as elegant as having a single SBMS
My system is 24V and I have a 10kW PV array as my house is also 100% heated with PV solar and total cost for the PV array cables was a bit less than 1000USD and there are 5.26mm2 (10AWG) wires for groups of two parallel panels.
I'm sure there are quite a few with 48V systems but there are much more with 12V and 24V systems.
An inverter only needs 1m to max 2m of cables and since I only have a 2400W inverter PIP2424 I only have two short 16mm2 (~ 6AWG) silicone isolated wires very flexible.
If I needed more like some of my users have parallel 3kW inverter then each inverter will have a similar short 16mm2 to 25mm2 cable and from there is all higher voltage AC
With a 24V system I can stay in the ultra low voltage requirements typical limited to 50V DC open circuit as a single 60 cell panel is already above 40V DC open circuit and with a 48V battery you will get fairly close to 100V DC open circuit no longer in the ultra low voltage range.
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#36
14S would be so cool! So many systems running 48-56V
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#37
(12-11-2018, 05:02 AM)electrodacus Wrote: Most of you have used cells in the 2000mAh range but when new those cells where around 2400 to 2600mAh that means they are very close to the end of usable life so if new they where good for 500cycles and if now in average they are just good for another 100 cycles ....
I saw you writing this, which is a thing i have just recently made my minf up.

Do you think that increasing of IR is mor closely tied to the "lifetime status" than any absolute Capacity.

And what do you think of a figure "CapLeft%", menas capacity left in Percent, as being tie to the same lifetime status ?

Thanks in advance.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#38
(12-15-2018, 11:54 AM)Cherry67 Wrote:
(12-11-2018, 05:02 AM)electrodacus Wrote: Most of you have used cells in the 2000mAh range but when new those cells where around 2400 to 2600mAh that means they are very close to the end of usable life so if new they where good for 500cycles and if now in average they are just good for another 100 cycles ....
I saw you writing this, which is a thing i have just recently made my minf up.

Do you think that increasing of IR is mor closely tied to the "lifetime status" than any absolute Capacity.

And what do you think of a figure "CapLeft%", menas capacity left in Percent, as being tie to the same lifetime status ?

Thanks in advance.


Both cycling and calendar aging will contribute to capacity fade/loss.
So say a 2600mAh that lost 15% of original capacity will now be 2600mAh x (1-0.15) = 2210mA
This capacity loss can be mostly from cycling if you did a lot of cycling in a very short period of time, or calendar aging alone if cell was in storage only and not used, or a combination of both as that will typical be the case. 
With this high energy density cells LiCoO2, NMC internal DC resistance increase is fairly significant and sort of proportional with capacity loss so at 10% capacity loss you may already see a 50 to 60% increase in internal resistance that will in turn accelerate the degradation even more as there will be higher internal loss and that will end up in higher internal temperature and by the time you are at 20 to 30% capacity loss the internal resistance may be 2x to 3x the original.

LiFePO4 has no internal resistance increase so that is another positive future of that chemistry.

The highest effect on calendar aging is cell temperature as increasing the cell temperature by 10 degree Celsius will double the rate of aging degradation.
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#39
That means really only using the top notch ones. And don’t charge to make them warm?
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#40
(12-15-2018, 10:53 PM)electrodacus Wrote:
(12-15-2018, 11:54 AM)Cherry67 Wrote:
(12-11-2018, 05:02 AM)electrodacus Wrote: Most of you have used cells in the 2000mAh range but when new those cells where around 2400 to 2600mAh that means they are very close to the end of usable life so if new they where good for 500cycles and if now in average they are just good for another 100 cycles ....
I saw you writing this, which is a thing i have just recently made my mind up.

Do you think that increasing of IR is more closely tied to the "lifetime status" than any absolute Capacity?

And what do you think of a figure "CapLeft%", means capacity left in percent, as being tied to the same lifetime status ?

Thanks in advance.


Both cycling and calendar aging will contribute to capacity fade/loss.
So say a 2600mAh that lost 15% of original capacity will now be 2600mAh x (1-0.15) = 2210mA
This capacity loss can be mostly from cycling if you did a lot of cycling in a very short period of time, or calendar aging alone if cell was in storage only and not used, or a combination of both as that will typical be the case. 
With this high energy density cells LiCoO2, NMC internal DC resistance increase is fairly significant and sort of proportional with capacity loss so at 10% capacity loss you may already see a 50 to 60% increase in internal resistance that will in turn accelerate the degradation even more as there will be higher internal loss and that will end up in higher internal temperature and by the time you are at 20 to 30% capacity loss the internal resistance may be 2x to 3x the original.

LiFePO4 has no internal resistance increase so that is another positive future of that chemistry.

The highest effect on calendar aging is cell temperature as increasing the cell temperature by 10 degree Celsius will double the rate of aging degradation.
First, the typos in my request where gruesome, and i corrected my own citation.

Thanks for your answer. it is nearly along what i have expected.

As explanation, since a few weeks i try to bring myself more light ito the usefulness of (proper) IR Measurement in the decision process of the harvesting strategies these guyos on the board here do make.
You find my little efforts here:
https://secondlifestorage.com/t-Kelvin-m...nce?page=3
And the next page. (Previus pages deal with DIY IR Measurement)

In essence i have tried to correlate IR and its increase to Capacity loss issues (and any/all other defect issues, whatever would show up), and by luck i saw somebody propose to use the capacity loss instead of the absolute capacity.
So i went through my little stock of good and bad cells, and putting them in a Sheet CapLeft% over IR it looked like this:



It does not really look like a strong absolute correlation. But the deviations might come from the fact, that capacity measurents are not that stable, and here are all sorts of chemistries, cells and capacities mixed.
So it might either be a quite good correlation which is disturbed by other parameters, or the IR and capacity loss are  not tightly correlated, for instance when capacity loss CAN happen without increasing IR.
Whatever this is, as a side note most of the damage issues like heaters and SD are quite tightly correlated to increased IR to about ove doubling IR.

Now, for what is all that worth:
Even when you criticize the use of this chemistry for the powerwalls, its what the people do atm. From one of the mods i saw a usual succes rate of 30 % they have, that means they charge and discharge 3 times more the amount of cells compared to what they get to use in the end. Plus they store them to identify cells with increase self discharge issue.
And many of the big players lament about the time consuming process.

My Idea from the beginning was, if IR (increase ) would have ANY significance in determining the Spent or remaining lifetime, it could be used, in the right way, to ientify bad cells more quickly instead of processing them through the capacity test. IR would be quick, for sure.

So, after this long story, the simple question is- am i on the wrong track, or do you confirm something of this ?
Thanks so much.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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