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

michael d

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Thanks for the reply! I have 250 watt 60 cell panels as well. View attachment 41990
Not sure I would get 21 amps out of my paralleled panels with those specs.

I have had cheaper branch connectors burn out on me but I would prefer those over lets say a bus bar in a joiner box. Would you recommend a specific vendor or just make sure its a Temco branch connector?

The 2P8S is genius, I must have missed that in the manual. Would it be endless as far as paralleling matched cells? For an example a 4P8S or more?

My runs from the solar panels won't be over 25 feet. I think I am gonna go with 10 awg temco wire, could probably get away with smaller wire.

Looking forward to seeing your heating setup in the future! I am wondering other applications for this waste energy as well. It is an awesome setup, thanks Dacian!
looks like the identical label on the PV panels I bought used. the 61 amps I was getting was through 3 DSSR20's. Each DSSR20 was connected to a pair of the 250-watt polycrystalline panels with about 60 feet of 10 AWG PV wire. it depends on the sun and angle of course. mine is a fixed ground mount array. need to trim the tree away now as the sun moves to the north. shorter wire runs should be better -- a bit. I liked the Temco parallel branch connectors as they were very easy to use - just plug 2 panels together at the array and now twice as many amps going to the DSSR20. I bought the Temco branch connectors on eBay.
😎
 

Crebbst

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looks like the identical label on the PV panels I bought used. the 61 amps I was getting was through 3 DSSR20's. Each DSSR20 was connected to a pair of the 250-watt polycrystalline panels with about 60 feet of 10 AWG PV wire. it depends on the sun and angle of course. mine is a fixed ground mount array. need to trim the tree away now as the sun moves to the north. shorter wire runs should be better -- a bit. I liked the Temco parallel branch connectors as they were very easy to use - just plug 2 panels together at the array and now twice as many amps going to the DSSR20. I bought the Temco branch connectors on eBay.
😎
Thanks. I got mine too on ebay used (like you I am sure) for a great price. They look good and I tested them and the voltage was in spec at full sun. Glad to hear they are working out for you! Did you get the diversion with all your DSSR20's?
 

michael d

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Thanks. I got mine too on ebay used (like you I am sure) for a great price. They look good and I tested them and the voltage was in spec at full sun. Glad to hear they are working out for you! Did you get the diversion with all your DSSR20's?
I bought 4 DSSR20's with diversion and 16 without diversion. I may get more with diversion in the future -- time will tell. 😎
income tax time right now.
the taxman going to get it if I don't get after it.😒
 

michael d

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the new Electrodacus DSSR20 has its own user manual. the new DSSR20 v04d that comes in two flavors with and without diversion is the only one currently available.
on new model you only need the Batt connected to EXT IO4- for battery charging while the EXT IO4+ will connect to Battery+ through a resistor.

which is: https:electrodacus.com/DSSR20/DSSR20.pdf

DSSR20D-1.jpg
 

michael d

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1616588570061.png
I thought this would be worth adding as a jpg photo: for the Lishen 272Ah cells if you want to follow the code and you should --- they say to put the battery in a non-conductive container/support members; so the compression jig for increased cell lifespan should be non-conductive (wood, plastic, fiberglass, etc).
I made one with wood ends and threaded steel rods that are also covered with a plastic tubing. i double nutted the ends with a flat washer and a lock washer also. it is all on a slick shelf board. i also add a thin piece of cutting mat between each cell. just a thought for you.
 
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KMac55

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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.

10:51 AM (2 minutes ago)

how to keep you batteries above freezing:
I use a 250-watt heat lamp bulb to heat my 8-foot x 8-foot x 8-foot (512 cubic feet) insulated solar power shed. today February 15th, 2021; it is 25 degrees below zero Fahrenheit. I do not have any thermostat control at this time. it is 57 degrees inside right now so this is the ultimate test for cold temperature. I think insulating your battery space would be the 1st thing to do and then use an incandescent light bulb is likely the most inexpensive option. for 64 cells I would need 64 heating mats at 4 dollars each = 256 dollars plus thermostatic controllers. the light bulb in the well pit in the winter to keep things from freezing is still the most economical method (that is how we kept the well from freezing when I was growing up). the heat lamp bulb is running on the solar electricity generated from the PV panels. which charges a 16 cell Lishen 272Ah per cell battery 2P8S configuration at 24 volts. presently 4 260 watt panels facing south connected to 2 Electrodacus DSSR20's via the Electrodacus SBMS0. I have the 24-volt inverter running 24/7 for the light bulb etc as I build assemble inside the solar power shed. I also use some dc directly connected to the battery lights some but only the heat lamp bulb and 3 dc direct connected light bulbs used overnight to keep it at a balmy 57 degrees Fahrenheit even though it is 25 degrees below zero outside. just a thought on economics. cheers from South Dakota USA
I was in South Dakota ice fishing the day you wrote this. It was -30 the night we spent on the lake in an ice castle (like a camper with holes in the floor to fish through). Coldest I've ever been in. If that light bulb kept them warm enough during that cold streak, it passes my test!
 

michael d

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I was in South Dakota ice fishing the day you wrote this. It was -30 the night we spent on the lake in an ice castle (like a camper with holes in the floor to fish through). Coldest I've ever been in. If that light bulb kept them warm enough during that cold streak, it passes my test!
yes, it would almost immediately freeze your fingers even with gloves on. I went out several times per day to give the livestock water and hay. but not for more than 15 minutes at a time before going in to thaw me out a bit. I figured the insulation was the main thing to keep everything from freezing. glad spring is here now.
 

michael d

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this information is courtesy of Dacian:
The Lithium batteries do not like to be charged all the time so no absorption or flat charging as it will be detrimental but absorption and float are required on Lead Acid.
There are two mods you can use the DSSR20 charging one is that charging will start as soon as all cells drop below 3.35V (set the SOC to 99% in DMPPT menu) and the other is charge based on SOC so if say you set the SOC limit to 90% then charging will only start when battery drops below 87% and stops charging when battery gets back to 90%
So in first case where is based on voltage if you connect a large load then charging will start within seconds supplying the Load but if you get more from PV panels than your load uses at some point the battery will be again fully charged and charging will stop for a few seconds or minutes.
There is not a huge difference with LiFePO4 but if you want to protect a bit more the battery setting something like a 90% SOC limit will slightly prolong the battery life as battery will not stay at full charge all day.

LiFePO4 can do half a million cycles at just 3 or even 5% DOD so it is about the same as super capacitors in this levels and those charging ON/OFF with 3% hysteresis will have no impact on battery life and is way better than using float charge like with Lead Acid.

1617439707630.png
 

michael d

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Dacian notes below:
the takeaway here is to have the charge source controlled by the SBMS0. the LiFePO4 is monitored at the cell level by the SBMS0 and when any cell goes above 3.55volts for a preset time the SBMS0 will turn off the charging. this functions well if you use the DSSR20's as the charge source for your expensive LIFePO4 battery. it can also work with MPPT type solar charge controllers (SCC) if you choose those.


You can not just use a charger without having SBMS0 controlling it and it is normal that one cell will be the first to be fully charged no matter how equal the cells are.

Not sure what other errors you had when you discharged the pack to 50% as that will not be normal so it is not related. The OVLK flag will be reset in about a few minutes at most of having a load on the battery less than 1% DOD

You will just damage the battery if you use a charger that SBMS0 has no control over. There is no such thing as setting the charger to 3.65V as charge can not measure each cell you likely set at 14.6V and then one of the cells most likely exceeded 4V and that will just damage your pack. LiFePO4 are not increasing the voltage linearly with SOC when they are full they will increase the voltage almost instant as they can no longer accept electrons.

1617702280022.png
 
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Joe Mu

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Dec 27, 2020
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i've almost got everything i need to put mine together. almost. now shopping for a batt fuse/holder. still undecided on the inverter. my piggy bank is about empty. i've got the SBMS0 wired up and monitoring my 8 lishen 272's. i have four 355w 72 cell panels waiting to be hooked up.
amazing how many small parts (hardware) that is required, not to mention the tools needed. sheeesh.
i'm in so calif. no lack of sunshine here.
 

djkarau

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Great information here. Currently waiting for 16 x 280 ah EVE cells (these are the new ones that reportedly get closer to 295ah), I will have 2p8s. SBMS0 w/WIFI in the mail and am hoping the new DSSR50 will be available before the batteries get here, but if not then I will get 4 x DSSR20's for my 8 x 330 w 60 cell panels. This is all going into my 5th wheel which we are retiring into from our 80 acre home now! I already removed the inefficient RV Air Conditioner and am installing a 12,000BTU Mini Split Air Conditioner. 3000 watt Victron Multiplus on order as is a 24-12v 70A DC to DC for all my DC loads.
 

michael d

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Just a small update to this thread.
it is raining out and I am still getting 31 watts into the battery with 2 250-watt PV panels only.
this 24-volt 16 cell 272Ah Lishen build is running 24/7 hooked to a 6000-watt inverter at low loads constantly.
right now it is at 77 percent SOC.

the second 24-volt 16 cell 272Ah Lishen build is at 88 percent SOC (state of charge).
it has 8 250-watt PV panels connected to an 8000-watt inverter also running 24/7.
it is collecting 116 watts in the rain from the 8 solar panels connected to it. need more AC loads right now. slow but sure. I will use the excess to heat water and heat the house this winter.

these are connected to the Electrodacus SBMS0 and Electrodacus DSSR20. two 250-watt PV panels to each DSSR20.
I have an Electrodacus SBMS0 for each 16 cell 24-volt Lishen battery. actually 25.6 volts nominal. cell are at 10mv delta so balancing by the SBMS0 is working great when it is charging. te cell balancing is done while the batteries are being charged by the Electrodacus SBMS0(the BMS for each LiFePO4 battery). the Electrodacus DSSR20 is the solar charge controller.

20210901_165613.jpgCurrently assembling a 3rd Lishen 32 cell battery using 32 Lishen 272Ah batteries.
in process of adding more solar panels, and ordered 40 more panels. so will have 80 250-watt 60 cell panels.
and another 15000-watt 24-volt inverter I have it connected to a 5kw LiFePO4 battery for testing at the moment (coffee maker and a few other things every day); not running 24/7 yet.

seems like the heat has slowed me down some but the rain has cooled it off a bit, but it is sticky outside.
Cheers all!😎

Above are the 28 2/0 cell interconnects I just put heat shrink tubing on yesterday for the 32 cell Lishen battery build.
the cell interconnects were hydraulically crimped using tinned copper lugs with .25 inch holes.
Time-consuming to make, but I like the final product.
it will be 3.2volt X 272Ah X 32 cells = 27,852.8Wh.
I am going to put on gloves and a face shield for the series part of this assembly.
I have 8 groups of 4 cells connected in parallel now for the 32 cell build.
next, they will be connected in series to get the 25.6-volt nominal voltage.
More later,😎
 

1 watt

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Great work and nice documentation, Michael.
How about a batch of pictures showing your ground arrays and how you’re building those?
Will be watching for your venture next into the diversion resistive heating.
Thanks!
Roy
 

michael d

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The ground arrays are difficult for me as each solar PV panel is about 41 pounds or so and I have them in 6-panel array structures at the moment. the upper panels are the most difficult for one person to mount. the array is facing south at a fixed 45-degree tilt angle. this was because I have no plan at the moment to go out and adjust the angles, but could modify them later if I so chose.

I will go take some pictures of the array with a bit more explanation of how they are constructed after the sun comes up. I built 45-degree triangles out of 2x6 treated wood, set them on concrete blocks to level them and get them off the ground, then connected them together with unistrut using lag screws into the 2x6's, then I used strut nuts and square strut washers with lock washers and 3/8 inch bolts to connect the solar PV panels to this array structure.

For winter snow reveal I guarantee you it is best to get them up off the ground a bit! I used a shop broom with a long handle, and a 20-volt cordless leaf blower to remove snow last winter. you will have to scoop snow away as it gets deeper if you are in snow country. winter is on the way. I don't care for the cold but sure enjoy getting outside even if in several layers of clothing. Sorry rambling...

more later on the array structure ( I tend to overbuild all construction projects for long-term durability). unfortunately wood and steel have increased in price about 50 percent from a year ago.

the two 544Ah 16 cell batteries (2P8S) have been running non-stop since last winter, the 32 cell 1088Ah battery (4P8S) has been functioning correctly for about a month or 2 now. I used lishen 272Ah cells for those 3 battery builds. Each 24-volt battery (actually 25,2-volt nominal) is connected to a separate Electrodacus SBMS0.
 

sunday

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Oct 22, 2021
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Hey Michael,

I have a SBMS120+DMPPT450 and am just getting the final stuff together. Lots of crimping and cutting.

As luck would have it, I have some of those concrete blocks and some used pressured treated 2x6 and 2x8 from an old deck, so my solar array may end up looking a bit like yours.

Thanks for sharing info.
 

michael d

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Solar Array ground structure follow up:
yes, lots of wiring to do. I wanted a DMPPT450 but was not available.
I measured the lumber and for the 6-panel array sections I used:
6 2x6's 8 feet long and 3 2x6's 12 feet long. I bought new at the local Menards store.
2 days ago I assembled another set of 3 right-angle triangles which gives me the 45-degree tilt angle I am seeking.
I actually need about 42 or 43 degrees for my location but 45 degrees is easy to build.
the 12 footer is the long side of the right-angle triangle. I think there is about 4.75 inches excess on each end which works out well on the 12 footers.
I also use torq construction screws 2.75 inches long to assemble the treated wood triangles. they do not cam out and are strong.
I am sure this style will work for a lot of people, you may have to modify the size to fit your panels but this works great for 6 of the 250-watt 60-cell solar PV panels I am presently utilizing.
I made another base yesterday with concrete blocks and leveled it in both directions. then I will set up each triangle.
next, I use the unistrut and lag screw them into the triangles running horizontally thus connecting the 3 triangles together.
then I bolt down the solar PV panels to the unistrut with strut nuts and washers. the prices of unistrut and wood are up at least 50 percent from 1 year ago. pics below.....
the old house is an 1840 to 1880 vintage and needs paint, but I have been working on a gazillion other things. inside the house 1st and the new baby lambs etc fence etc. etc.
cheers all 😎
 

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michael d

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michael d

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the above graph is often seen but poorly understood. so I thought a little info about it would help some DIYers.

LiFePO4 cells do not like to stay at 3.65 volts. 3.65 volts is the maximum charge voltage.

you do not want to regularly charge your cells to 3.65 volts if you want your LiFePO4 cells to enjoy a long life span.

on the contrary, they will prefer to be in the 3.2 to 3.35-volt range. when any cell in my battery builds reaches 3.55 volts, the Electrodacus SBMS0 turns the charging off. so use them in the 20 to 90 percent SOC range as much as you can, not at 3.65 volts!!!!!

3.55 volts is 99 percent of full SOC (state of charge). the battery packs will then settle a bit to an overall charge somewhere closer to 27 volts for my 16 cell and 32 cell builds.

the other misconception or argument I have had on this site is what it takes to charge a 24 volt (25.6-volt nominal battery pack of LifePO4 cells).
3.2 x 8 = 25.6 volts. this is the low end of the voltage range you want to try to keep your battery charged to for 8 cells, 16 cells or 32cells LifePO4 battery builds.

I use the electrodacus SBMSO and Electrodacus DSSR20's to happily charge and regulate the LifePO4 battery builds with used 60 cell 250-watt PV panels in parallel pairs. after about 60 feet of 10awg wire, the 2 panels will put a charge in these batteries at about 30 volts, and readily charges a 25.6 to 27.6 LifePO4 battery.

the Electrodacus SBMS0 is the BMS. the Electrodacus DSSR20 (a solid-state relay) is the perfect charge controller for 2 250watt 60 cell PV panels in parallel. the Electrodacus is not an MPPT or a PWM solar charge controller; it is a solid-state relay and hopefully will have a very long lifespan as the creator designed it for.

I have 2 250-watt 60-cell used PV panels charging a 32 cell LiFePO4 battery. 32 Lishen 272Ah cells 4P8S.
that is 272Ah times 4 = 1088Ah.

4 cells are 1st connected in parallel to give the 1088Ah at 3.2 volts nominal voltage ( again this is the low end of the voltage range).
then each group of 4 cells are connected in series to get 25.6 volts nominal voltage. 3.2 x 8 = 25.6.

1088Ah x 25.6 volts = 27,852.8 Wh potential ( again this is the Wh calculated at the lower end nominal voltage of 3.2 volts per LiFePO4 cell ).

what I am trying to stress/explain a little bit is that what normally occurs is the battery gets fully charged with used 250-watt 60-cell PV panel in pairs of 2. if you want it to occur faster you add more pairs of PV panels. I am in the process of adding more solar panels array by array in 6-panel arrays.

the Electrodacus SBMS0 controls up to 18,000 watts of solar PV panels. I have 30 panels working and have more to add as time and weather permits. the wind and the cold and the livestock and family duties slow me at times but I trudge on.

I have 3 batteries assembled and functioning without problems. all are 24-volt builds 2P8S two of those and one 4P8S using Lishen 272Ah LiFePO4 cells.

I plan to use the excess solar PV power to heat my house etc, this winter. All is done off-grid as there is no net metering in South Dakota; why would anyone want a system that is grid-tied and shut down when the grid goes down. at least that does not fit my particular use.

My 2021 Thanksgiving hope for you all is to understand and that this is helpful for you. I also hope I do not have too many typos. I am not a very good secretary. 😎

Time to go feed the bottle lamb! bye
 
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