DIY 24-volt 560Ah LiFePO4 battery (272x2=544Ah) with Electrodacus SBMS0 and Electrodacus DSSR20

michael d

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this soc chart has no verifiable origin as to its accuracy; so if it was me i would not believe it is accurate for safe charging and discharging. the blue zone in that excel spreadsheet is where one would want to operate their LiFePO4 battery banks. between the knees as some have referred to the blue zone.
 

michael d

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black and decker 20v leaf blower worked to remove the snow from the 6 south facing panels this morning. yea ha! easier than the push broom and it is DC power off-grid to recharge the batteries! the six-panel array is about 9 feet tall or so at a 45-degree angle to get the winter sun. the top is herd to get with a push broom. but each day is getting longer now!
the sun is out and the battery bank at full charge again with 1300 watts out of the 1.5K south-facing 250-watt 60 cells used polycrystalline panel PV array. pushing 47.299 amps or more into the battery and inverter loads. so the trickle charger works great. need more loads to hook up but other things to do at the moment.
 

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BarkingSpider

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Did you try the wifi module for the ElectroDacus? I connected mine up a few weeks back and now can access all the data from the SBMS with a Raspberry Pi and report it with Grafana.

BTW, I spoke with Dacian (the engineer at Electrodacus) and asked if he would ever do a 16s (48v) version. He said there are no plans as he feels you can do everything you want with 24v, regardless of the size of your project. I was going 48v at one time, but now may revert back to 24v for my offgrid cabin project.
 

michael d

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Did you try the wifi module for the ElectroDacus? I connected mine up a few weeks back and now can access all the data from the SBMS with a Raspberry Pi and report it with Grafana.

BTW, I spoke with Dacian (the engineer at Electrodacus) and asked if he would ever do a 16s (48v) version. He said there are no plans as he feels you can do everything you want with 24v, regardless of the size of your project. I was going 48v at one time, but now may revert back to 24v for my offgrid cabin project.
yes, I really want to use the wifi part of SBMS0; but have not got that part checked out yet. 24-volt is safer. you can get 6000 and 8000 watt 24-volt inverters and you can get 24-volt lights to run directly off the battery bank. I ordered some 300 led rope lights to use directly off the battery bank. currently, I have some 48-volts led 16 led square lights running directly off the battery bank through the 10 amp dc breaker. 3 of those wired in parallel 5 more to go. I also bought some photocells to automate some of the dc lighting. I will have to get more details on the wifi setup. all cool. keep up the good work.😎 got me a coyote hunter to try to thin out the coyote issue. darn varmints anyways! Ted Nugent will be proud!
my goal is to make it all off-grid DIY. get away from paying the grid owners.
I have never used a Rasberry Pi setup.
thanks for the info.
I tend to agree with Dacian and bought 40 250 watt panels to prove his system.
as the "bused as" from New Zealand you tuber says I am "keen" on it.
 

michael d

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This guy didn't few test with the drss20 vs an mppt controls.
yes, YouTuber "bused as"from New Zealand is a great craftsman. check out his acrylic set up for the Electrodacus etc components. I have had various conversations with him. his videos are good and he has a great sense of humor with reality.his setup is for the bus he is remodeling. many nifty things he does.
 

CaptGregR

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you will want to get double the bus bars to top balance in parallel. I bought some 6 gauge lugs with 1/4 inch holes to make cable interconnects so I can balance more cells. my Lishen cells came with 4 busbars per 4 cells. also if you get the 6mm diameter x 20mm long set screws/ aka grub screws with flange nuts that is the way to go.
my 1st 32 Lishen 272Ah cells came with 16mm long grub screws and flange nuts. the 16mm is not long enough for some connections so you want 20 mm long ones. the second set of 32 Lishen 272Ah cells came with bolts and washers.--- they did not fit good or tighten well -- I replaced all of those bolts with 20mm x 6mm grub screws. you will find that the grub screws sticking up are better for mounting the busbar interconnects together with fewer problems of accidental arc-ing between cells. do not over tighten the set screws!!!!!! snug them down carefully -- they are only 6mm which is 1/4 inch approximately and you will hate yourself if you strip one out. I plan to use lock-tite on the threads also.
 

CaptGregR

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1st off, I like the SBMS0 and the DSSR20 set up on 24-volt. if you want to play with higher voltage, look in another thread.
I purposely bought the 60 cell 250-watt panels to match up with the Electrodacus SBMS0.
I also purposely bought the Electrodacus DSSR20 to use as my solar charge controllers.
the Electrodacus dssr20 is a digital solid-state relay that is controlled by the Electrodacus SBMS0.
I purposely bought 32 280 amp LiFePO4 3.2Volt cells to make a 48-volt bank but chose to go with the 24-volt battery builds instead.
Glad I went with 24-volt on these.
most say they are really only 272Ah cells but the vendor claimed they would do 285Ah.
I bought Lishen 272Ah cells that are supposed to produce 285Ah.
I do not believe I need to get every last Ah out as I plan to run them from 3.2 to 3.55 volts for a long lifetime on an off-grid system.
I am not interested in grid-tie. they have no incentive to pay me.
potatoes potatas! :cool:
Michael, exactly what 250 watt panels did you use?
 

michael d

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for the final build of the battery, you will want to use solid copper bus bars in between the Lishen 272Ah cells.
I bought some solid copper bus bar but i still need to cut into lengths and accurately drill the holes.
the 1st 2 batteries are fully assembled 2P8S for a 24-volt battery and are being cycled with the 6000-watt inverter.

I have to note that my verbiage/terminology got a correction today.

TERMINOLOGY the cause of miscommunication.
Battery: A collection of individual cells, assembled as one complete entity with its own BMS. It is fully independent.
PACK: Same as Battery above BUT to be included as Part of a Battery Bank. Can work independently & collectively.
BANK: An assemblage of "Packs", wired together as a large collective battery system on a Common Shared BUS.

so in reality I will have 4 batteries ... each is 2P8S ... and no battery bank as I am not going to connect the 544Amp batteries together to increase their amperage.
each battery will have its own bms and I will stay with 24-volt for this particular build.

272Ah x3.2volt per cell x16cells = 13,926.4 potential watt hour capacity per battery.....
enough for these batteries!😎
 

michael d

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Michael, exactly what 250 watt panels did you use?
250 watt 60 cells polycrystalline pv panels --- --- i will have to look up those details for you. maybe I can get a picture of the label also.
 

michael d

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Batt would be kWh, solar arrays measured (by me anyways) in kW. <<<<I copied that from another forum member!

perhaps this is another terminology issue for me as well.

kwh is the capacity of a battery.
and solar array size may be better stated in watts or kW depending on how many solar panels are in the array.
I have 40 250-watt 60 cell polycrystalline solar panels, so this build will be 10,000 watts or a 10kW array.
the excess solar will be used for heating in the wintertime.

the storage batteries will be 24-volt LiFePO4 (16 272Ah cells in a 2P8S configuration); so they will have 13,926.4 Wh per battery potential capacity or more. the vendor claims they can do up to 285Ah per cell. I will likely never use it at that level of discharge nor do I want or intend to!!!

16 cells x 272Ah per cell x 3.2 volt per cell = 13926.4 Watt hours

I have 4 of these 16 cell batteries I am constructing and charging. so the total LiFePO4 battery capacity maybe be 55,705.6 watt hours or 55.705 KWh.

I will try to improve my electrical terminology so there is less confusion.
 

michael d

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trying to clarify the off-grid build a bit:
the Electrodacus SBMS0 actively balances the cells when they are charging. the Electrodacus SBMS0 prevents the Electrodacus DSSR20's from overcharging the LiFePO4 batteries. when the LiFePO4 battery is fully charged it turns the DSSR20's off.
the DSSR20's are doing the charging. the SBMS0 controls them as needed with small sense/control wires.
Electrodacus DSSR20 is a digital solid-state relay rated at 20 amps input but will handle up to 24 amps, making them a great match for 2 60 cell or 2 72 cell PV panels connected in parallel.
Electrodacus SBMS0 can control up to 18,000 watts of a solar array, there are reports of up to 30,000 watts.
my build is for a 10,000-watt dual array (big array/small array) with some to be used as a diversion for heating purposes.
that is the planned off-grid use.
😎
two 24-volt 2P8S batteries in operation, each 24-volt battery is assembled with 16 272Ah Lishen cells.
LiFePO4 batteries are all stationary.
slow but sure.
 

Dzl

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I appreciate you documenting your design progress and your learning here. The SBMS--being as unique as it is--benefits from threads like this documenting research and build progress. Keep it up, I'm sure others will find many of the details useful

A note on terminology. You may or may not be aware of this, but the SBMS0 is a "passive Balancing BMS" (as are most BMSes). The terms active and passive in terms of balance are poorly worded in my eyes, or maybe I don't fully grasp the context the terms are meant to reflect. In any case 'passive balancing' means balancing using resistors (aka resistive balancing). A passive balancing bms 'burns off' energy from the high cells in a pack. Active balancing uses capacitors (or sometimes induction) to transfer energy from a higher cell to a lower cell (at about 70-80% efficiency, compared to 0% efficiency for resistive balancing since its just shedding energy as heat).

So while it feels logical to say "the Electrodacus SBMS0 actively balances the cells" this is not correct in the context of the terminology the industry (and the community) has settled on.
 
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michael d

off-grid solar pilgrim
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I appreciate you documenting your design progress and your learning here. The SBMS--being as unique as it is--benefits from threads like this documenting research and build progress. Keep it up, I'm sure others will find many of the details useful

A note on terminology. You may or may not be aware of this, but the SBMS0 is a "passive Balancing BMS" (as are most BMSes). The terms active and passive in terms of balance are poorly worded in my eyes, or maybe I don't fully grasp the context the terms are meant to reflect. In any case 'passive balancing' means balancing using resistors (aka resistive balancing). A passive balancing bms 'burns off' energy from the high cells in a pack. Active balancing uses capacitors (or sometimes induction) to transfer energy from a higher cell to a lower cell (at about 70-80% efficiency, compared to 0% efficiency for resistive balancing since its just shedding energy as heat).

So while it feels logical to say "the Electrodacus SBMS0 actively balances the cells" this is not correct in the context of the terminology the industry has agreed upon.
what I directly observe is the Electrodacus SBMS0 identifies and directs the charging to the lowest cell and charges the lowest cell in the battery of 8 cells and does not charge the highest cell as much when it is charging. I will have to read up on this terminology more. it balances when charging. I don't think it is just burning off energy from the high cell but I will try to investigate this further.
do you have any direct knowledge of how it balances?
have you studied the open-source Electrodacus SBMS0 on how it balances?
let me know.
it turns the Electrodacus DSSR20's off when any cell reaches too high a limit for too long and waits for the battery to utilize some energy on the load side before it turns the DSSR20's back on to charge the LiFePO4 battery more.
I turn on more loads (either thru the inverter or the direct-wired DC lights) when the battery is charging to use more of the PV energy.
more later!😎
perhaps it does not fit either of the definitions of balancing you define!
i am not an electrical engineer.

Can you clarify with this statement below of what the Electrodacus SBMS0 is doing? does this help or complicate it more?
The default is set to start charging when all cells drop below 3.4V but you can go in to DMPPT settings menu and set the SOC limit to something lower than the default 99% say maybe 95% then charging will not restart until SOC is below 92% and will stop charging at 95% (except for first charge in a day that is made to 100% SOC for calibration).

I have the inverter running and dc lights. so there is a load. if the battery SOC gets lower than I like I just turn off some of the loads.
 
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michael d

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that may help me a bit for my understanding.😎
 
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Dzl

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what I directly observe is the Electrodacus SBMS0 identifies and directs the charging to the lowest cell and charges the lowest cell in the battery of 8 cells
I don't believe it has this capability physically or functionally. However it could appear this way to an observer maybe, by burning off energy from the highest cells while charging, I imagine it could look like more charge is directed at the lower cells, when in reality its just bleeding energy from the high cells.
it balances when charging. I don't think it is just burning off energy from the high cell
I believe this is the normal way that passive balancing works, as the pack charges the BMS is continuously burning off charge from the highest cells to try to keep them in line with the rest of the pack. I don't know what sort of smarts/logic the SBMS does or doesn't have to coordinate this, but the general premise is how passive balancing works (seems very "active" for being called passive doesn't it 😄, I like the terms dissipative and non-dissipative or Active energy transfer, I think they are a bit clearer, but since active and passive are standard terms I stick to them mostly)
I will have to read up on this terminology more.
Some of the links that inform my understanding of balancing can be found here

have you studied the open-source Electrodacus SBMS0 on how it balances?
A modest amount

If you can confidently interpret a PCB schematic (I can't) its available in the last few pages of the manual. Passive balancing will show resistors, active will show capacitors or something capable of transferring energy..

If not, here is a short excerpt from one of Dacian on the topic:
As for the dumping energy in a resistive element (as is the case with SBMS and all non DIY EV cars) vs active energy transfer here is an example.
Cell balancing starts as soon as there is more than 10mV between two cells and this is possible since a single device ISL94203 can see all cell voltages and has build in logic to know what cells need to be balanced. So cell balancing can be done for hours if it is the case and not just a few seconds that is why with just less than 200mA the SBMS can keep in balance very large packs tens of kWh is not a problem.
fuller comment here
perhaps it does not fit either of the definitions of balancing you define!
It may have some differences to other balancing schemes I'm not sure.
But the fundamental difference is Passive = burns off energy from high cells, Active = transfers energy between cells. Fundamentally I believe it has to be one of these two options, and I'm pretty certain its the former (passive)
 
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michael d

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February 4th, 2021 about 12:30 pm slightly after noon >>>>>trickle charging with 6 250 watt panels connected through the Electrodcus DSSR20's. 2 panels to each Elecrodacus DSSR20 in parallel so 3 Electrrodacus DSSR20's being monitored by the Electrodacus SBMS0.
1499 watts going into the Battery at 42.579 amps. woohoo!!!
they actually went over 1500 watts at times.
the dssr20's with the sbms0 work great.
1.5Kw array putting out as much and more than their rating.
these are used 60 cell 250 watt polycrystalline PV panels maybe 8-10 years old.
wow, you can become a sun worshipper in winter.
come on sun!!! 😎
 

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