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

michael d

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Enjoying the thread of your build. I’m getting ready to install a SBMS0 and need to order the DSSR20 for my skoolie. And I just bought a ferrule kit.
Where did you get the circuit breakers?
I ordered the circuit breakers on Aliexpress.com from a vendor named Zhejang Tongzheng Electric Co., LTD, (they were very inexpensive there).
just search for dc circuit breaker (fast shipping arrived in 18 days from the date I ordered them).

I like the Baomain ferrules with yellow plastic ferrules I bought those on Amazon.com for the 10 AWG PV wire.

Baomain AWG 10/6.0mm² Wire Copper Crimp Connector Insulated Ferrule Pin Cord End Terminal Yellow 100pcs

sorry about the bold letters I copied it off the Amazon website. 😎
 
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michael d

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The SBMS0 can only protect your battery if it has remote ON/OFF control over all charge sources and separately over all Loads.

Yes SBMS0 has some self-consumption and should not be left connected for weeks or months if there is no charge source available like a solar panel as that 0.8W or so SBMS uses with WiFi ON adds up to 0.8W x 24h = 19.2Wh per day 576Wh per month

So important is that you do not use any device that can not be controlled ON/OFF by the SBMS0 as else SBMS0 can not protect the battery from over-charge or over-discharge and second is that if you store the battery for the long term the battery should be left fully charged or very close to that and SBMS0 should be disconnected if is stored for months with absolutely no charge source.

The info above via Dacian 3/1/2021 on the electrodacus google groups forum
I think this is important information. You need to be able to control the load (discharge via an inverter or other things such as the DC direct-wired light I am also using) and the charging sources (either DSSR20 as I am using or the MPPT chargers if you use those to charge your LiFePO4 battery).

Cheers all
😎
I am currently running my inverter 24/7 and the DC direct-wired lights. this is all a small load for system testing and set up for long-term use. I definitely need to get the inverter controlled in my setup. 😎
 

michael d

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March 4th 2021: 41.5 amps charging the LiFePO4 battery (about 1000 watts) sunny but hazy/partly cloudy outside and about 59 degrees Fahrenheit 12:30 p.m.
the LiFePO4 battery is a 24-volt 2P8S configuration using 272Ah Lishen cells. so a potential capacity of 13,926.4 watt-hours.
6 250-watt 60 cell used polycrystalline PV panels south-facing stationary ground mount with 45-degree tilt angle. every 2 panels are wired in parallel at the array using a Temco branch connector (easy plug and play). then the 10 AWG PV wire goes into the DSSR20's about 55 to 60 feet away. each DSSR20 is the solar charge controller for 2 250 watt panels. so 3 DSSR20's for the 1500 watt 6-panel array.
trying different background colors to see if the cell phone pictures will improve for your viewing. 😎
 

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michael d

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for the LifePO4 you want to keep it between the knees on the flat part of the curves. use 70 percent from 30 to 90 SOC for a long life span when using the LiFePO4. see and study the charts above. for my build at 24-volt using the Electrodacus components I would like to run it from 27.00 volts to 26.80Volts for the battery. I never even try to get it down to 26.8 as so far I have been keeping the SOC (state of Charge) to 59 percent or higher.
SteveS has this in the DIY solar forum under resources. a good guide to help one comprehend the LIFePO4 chemistry a bit more.
 

michael d

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actually, it should say run from 27 volts to 25.8 volts to keep it between the knees on the flat part of the curve. i was too late to edit the above post. my eyesight is not so good or my typing skills.. sorry for any confusion.😎
this morning after uses the battery and inverter on about 350-watt load all night the battery is at 70 percent SOC (state of charge) and 26.45 volts.
looks to be a sunny day but still below freezing, no wind, frost last night but possibly 60 degrees later today the snow is almost all melted.
some people use all kinds of abbreviations without defining what they stand for. need to make an abbreviations list(to do, to do)
 
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michael d

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as I read and understand more the SBMS0 balances up to 7 of the 8 cells at a time as needed with 100mA. it does this with tiny mosfets of very low power consumption. the word police made me study more -- a good thing and this is considered passive balancing.
the SBMS0 monitors each cell and balances each cell and turns off the DSSR20's when the battery is full or any cell reaches a voltage of 3.55 volts( preset in the SBMS0).
the DSSR20 is the solar charge controller for each pair of 60 cell 250 -watt used polycrystalline panels and is capable of controlling up to 24 amps.

the SBMS0 also will work with the more expensive MPPT if one so chooses.

the SBMS0 requires no extra heat sink as no real amount of power actually goes through the SBMS0.

it balances my 2P8S 24-volt battery with no problems at all.
the battery is 16 272Ah Lishen cells connected in a 2P8S configuration. so potential capacity is 272Ah per cell X 3.2 volt X 16 cells = 13926.4 Wh for each of my 24-volt batteries.

they are charged to 27 volts every day by the solar PV panels and I have never discharged them below 58 percent SOC (state of charge).
the Lishen cells I bought as new grade A but most say all commodity cells are not matched at the low price point we are paying. no problem here.
the 272Ah Lishen are reported to output up to 285Ah per cell. i did not test them and have no plan to do so.

the DSSR20's charge the LiFePO4 24-volt battery with all the solar panels will put out. The large LiFePO4 battery is the resistor controlling the input current from the Solar Panels.
the DSSR20 is a digital solid-state relay and is designed to be matched up with 60 or 72 cell PV solar panels in parallel pairs. it is not a PWM or a MPPT controller and does not pulse at high rates as they do. it has no large electrolytic capacitors to break down and is a very small form factor.

the DSSR20 pushes a constant current at the amount the solar PV panels output and is supposed to be on the range of maybe 99 to 100 percent efficient in that process of charging the LIFePO4 battery. ( don't quote that number please).

the ducks are back in the artesian well-fed pond this morning and the Canadian geese are flying south everyday now.
the pic below is at about 9:30 a.m. this morning as the sun is just getting up and around the old summer kitchen, the 6 250 watt south-facing used polycrystalline PV solar panels are putting out about 850 watts at 31 amps to charge the battery back up.
it will do more amps and watts later this morning. but gotta go do other things.
bye, all for now.😎

more later,
cheers all, 😎

went to get the mail and now over 1040 watts at 39 amps in less than 40 minutes as the sun breaks through the morning haze.
 

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michael d

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March 7th,2021 at 2 pm: the 2 250-watt used panels wired in parallel at the array facing west are putting out 303 plus watts at 11.348 amps into the second lifepo4 16 cell 272Ah Lishen build 24-volt (2P8S)and the battery says 26.987 volts. the west-facing array does not have a good angle to the sun but none the less is charging the 13926.4 Watt-hour battery. this uses 1 dssr20 on approximately 30 feet of standard 10 AWG PV wire.
i am not utilizing the second battery so only a few dc direct lights running 24/7 exercising and balancing this battery with the sbms0 balancing while it charges to a safe level and then the sbms0 turns off the dssr20 so the charging stops and the battery is protected as al cells are individually monitored by the sbms0.
cheers all😎
says 64 degrees Fahrenheit outside right now.
 

michael d

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the use of the Electrodacus DSSR20 is also for diversion to heat water and heat the floors of the house with the excess solar electricity generated from the Solar PV panels in the winter. the DSSR20 with diversion is cost-effective this way.

again this is an off-grid DIY build with LiFePO4 batteries stationary I will have about $10,000 invested for a 10,000 watt PV array including 20 DSSR20 charge controllers, and 4 13926.4 watt-hour LiFePO4 batteries, 2 inverters, 40 250-watt 60 cell solar panels, etc.
then uncle sam will give me back $2600 so the net cost is about $7400 dollars. I think the payback period will be about 3 years from the electric and heating savings.😎
it is not for everyone but I think it is a very good way to build a DIY off-grid system at a safe low voltage. 😎

LiFePO4 batteries were the most expensive part of the $10,000 investment($3063.80 and $2903.19 = $5966.99 including delivery to South Dakota from alibaba.com for 64 Lishen 272Ah cells).
$5966.99/64 = $93.23 per cell average including delivery! 13926.4 x4 = 55,697.6 watt hour potential battery storage capacity.
$5966.99 divided by 55.697 kWh = $107.13 per kWh for the LiFePO4 battery storage including delivery.
Although the Lishen 272Ah cells have been reported to do 280 to 285 Ah per cell I choose to use the lower number of 272Ah.

I bought 24-volt water pumps and 24-volt water heating elements to use more solar PV-generated electricity. I have 14 DC direct-wired led lights and would like some more as no inverter is needed.
most people can install 2 panels at a time to slowly build their off-grid DIY system.
I also like the 24-volt safety factor a bit more than the 48-volt;
but I also do 48-volt in another system off-grid but not with Electrodacus SBMS0 as it is only compatible for up to 24-volt system.
cheers all, 😎
 

michael d

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if one reads up: the LiFeP04 battery does not like to be charged to 3.65 volts per cell.
the preferred for long-term solar is more like 3.4 volts with 3.55 volts being a safer place to stop charging of the LiFePO4 battery cell.
3.65 is really for 1X top balance and not above that, so don't be misled. do not charge above 3.65 as it will cause long-term damage and shorten the LIFeP04 life span as will discharging below 2.5 volts. no reason to get it that low either.
it prefers to get charged with .2C or so which is great for solar. (don't quote that number --- look on batteryuniversity.com I think is the site).
 

michael d

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To sum up, for long and happy LFP battery life, in order of importance, you should be mindful of the following:
  1. Keep the battery temperature under 45 Centigrade (under 30C if possible) – This is by far the most important!!
  2. Keep charge and discharge currents under 0.5C (0.2C preferred)
  3. Keep battery temperature above 0 Centigrade when discharging if possible – This, and everything below, is nowhere near as important as the first two
  4. Do not cycle below 10% – 15% SOC unless you really need to
  5. Do not float the battery at 100% SOC if possible
  6. Do not charge to 100% SOC if you do not need it
this was a DSL post I think, give him the kudos for the above part.

the important thing is to use a BMS so you don't overcharge. The Electrodacus SBMS0 is the BMS.
the way the DSSR20 works is it gives all the current it can(amps) from the solar PV panels. the DSSR20 is designed to work with 60 and 72 cell PV panels but can also work with 30 and 36 cell panels for 12-volt setups.
I have a 24-volt stationary system.
the 2P8S 13,926.4 Wh battery routinely charges every day if there is enough sun with only 6 panels 1.5kw array. and I have it connected to a load all the time so it gets daily exercise. more at night for light in the barn for the baby critters.
I do not need to use any other external charger. I depend on the sun for charging by using the DSSR20 as the solar charge controllers.
I built an insulated solar power shed for all the batteries and electronics so freezing is not an issue.
I keep my batteries between 30 and 90 percent state of charge. I do not want to get every last possible watt nor do I need to (no reason to overstress the LiFEPO4 batteries.

the Lishen 272Ah cells are almost identical to the Eve brand (280Ah) in weight and appearance.

I was a bit worried/concerned that the cells could be overcharged by using the benchtop chargers initially during attempted top balancing, but the 272Ah cells take a lot of power to get to the higher voltage so I did not overcharge any on my 1st 16 cell 2P8S build or my subsequent builds.😎😎

the Electrodacus SBMS0 has the setting you want to prevent overcharging and they also control the DSSR20's up to 30 of them I think but my current build is utilizing 20 of them for 10,000 Watt PV array.

you can get newer higher watt 60 cell panels or 72 cell panels for more money of course, but economy makes the most sense for my off-grid build on the country acreage -- mounting space is not an issue. every 6 panels are about 10 feet wide and 8 feet deep on the triangle 45-degree fixed angle ground mount array. so it will be 7 of those although I may use some as a roof structure/carport(70 feet x 8 feet ground footprint or 560 square feet). still, real estate for this 10,000-watt array is not an issue. The ruminants could sleep under them when it is time to re-digest the pasture!😎 easier than a lawnmower and/or tractor to maintain the pasture.

an acre = 43560 square feet;
1 acre is approximately 208.71 feet × 208.71 feet

43560sf /560sf/array = 77.785 so one could build 77.78 of these 10,000 watt arrays on an acre. (slightly less as you would need some maintenance access space)

I think one could solar PV power many homes/structures with some effort.

more later,
cheers all!
 

michael d

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Fahrenheit vs Celsius:

(Celsius is the newer definition and is considered to have a more accurately defined 0 degree point than the older Centigrade definition. but quite similar in most respects!)

the previous post was quoted in Centigrade (Celsius) so I had to go look up the Fahrenheit numbers as that is what I am more used to using in the USA.

45 degrees Celsius = 113 degrees Fahrenheit (don't let them get above this temperature)
30 degrees Celsius = 86 degrees Fahrenheit (try to keep them closer to here for the high side)

don't charge them below freezing (32 Fahrenheit or 0 degrees Celsius)
i think you can discharge them below freezing but why would you want to chance it! Just get a small heat source with a properly insulated place to keep your expensive batteries.

I chose to make a very well insulated outside solar power shed for the expensive LiFePO4 batteries and other solar components to protect them from nature's harsh unpredictable elements.
I think is the best way for my off-grid solar PV build in the country.
coyotes were out in full chant last night. need a guard dog for the protection of the hair sheep.😎

the higher temperature range to try to maintain the LiFePO4 batteries as quoted in the previous post.

in the USA we use Fahrenheit, and I still only have memorized the freezing and boiling temperature of water in Celsius in memory.

Formula
(45°C × 9/5) + 32 = 113°F
 
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michael d

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Ton of info here!
yes, I am trying to touch on the more important aspects of using the SBMS0 and the DSSR20 to charge the LiFePO4 batteries.
in the past, many off-grid solar people used Lead-acid batteries.
LiFePO4 is totally different.
the LiFePO4 has a flat curve and this is where you want to maintain it. between say 20 to 90 percent SOC (state of charge). this needs to be monitored on each cell and that is what the SBMS0 (the BMS) does.

in order to protect the battery from over-discharge, one will need a compatible inverter or one that the SBMS0 can turn off (this is an important part). possibly a Victron battery protect but I have not investigated this part enough yet to say yes or no for my build.
I have not got this part done yet. right now I just use fewer electrical things if the battery is low due to too many cloudy days. in the future, I will have a larger array so I can get more solar power even on cloudy days.

the overcharging is prevented as I have it set up and the SBMS0 turns off all the DSSR20's when any cell reaches 3.55Volts for a preset time.😎
 

michael d

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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
March 13th 2021:
I now use a 65 watt light bulb but sometimes I have to turn it off more often as the weather changes. I bought some thermostats to control the heat from the light bulb in the solar power shed but not yet completed. so many things to do (does your life get busier when you try to slow down)? still down below freezing every night, but maybe 60 plus degrees later today?
 

Crebbst

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This is an awesome thread. Thanks so much for posting this info. I bought almost the exact setup as you... last year, just now getting around to setting it up. Though I have 8 solar panels and 4 dssr20s with diversion and the DEXT16 but you got twice the Lishen cells, I have 8s. I did not know you could use 1 sbms0 with a 2p8s setup or am I reading wrong. I figured I would have to buy another sbms0 if I wanted more cells. Also I see you are using breakers, did you feel like you needed breakers? Or was it just to isolate solar panels. If you recommend breakers, would you use 20 a to protect dssr20s or a 25 amp. From reading the manual it doesn't sound necessary, just interested in your thoughts. Also in Will's new video he highlights the electrodacus and I am hoping he will tackle the DEXT16! I have seen 1 YouTube video of someone setting it up but didn't seem successful. It seems pretty straight forward but I am wondering what is the most efficient way to heat the water.
 

michael d

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This is an awesome thread. Thanks so much for posting this info. I bought almost the exact setup as you... last year, just now getting around to setting it up. Though I have 8 solar panels and 4 dssr20s with diversion and the DEXT16 but you got twice the Lishen cells, I have 8s. I did not know you could use 1 sbms0 with a 2p8s setup or am I reading wrong. I figured I would have to buy another sbms0 if I wanted more cells. Also I see you are using breakers, did you feel like you needed breakers? Or was it just to isolate solar panels. If you recommend breakers, would you use 20 a to protect dssr20s or a 25 amp. From reading the manual it doesn't sound necessary, just interested in your thoughts. Also in Will's new video he highlights the electrodacus and I am hoping he will tackle the DEXT16! I have seen 1 YouTube video of someone setting it up but didn't seem successful. It seems pretty straight forward but I am wondering what is the most efficient way to heat the water.
I used 32 amp breakers for the 2 panels in parallel. basically, it is an on/off switch but is very very helpful when you are connecting everything together(not required but I recommend it anyway). and yes it also functions to isolate the solar panels in pairs(paralleled at the array). when the sun is strong I get up to 21 amps going to charge the battery through each DSSR20.
I have 2 250-watt 60 cell panels connected in parallel right at the array with Temco branch connectors >>> they can put out 16 to 20 amps. but it depends on the sun's power of course.
some panels put out more but the 60 cell panels work well if you keep the distance to 60 feet or less. if over 60 feet then the 72 cell panels will work better.
try to keep your wire runs from the solar array to the DSSR20's short if you can for slightly better performance.

one SBMS0 will control up to 30 DSSR20's.

you should have matching cells with the 2P8S battery build. I bought 32 cells from the same vendor.
I built 16 cell 24-volt batteries 2P8S and it is monitored and balanced by one SBMS0. the SBMS0 turns off the DSSR20's when the battery is fully charged.

I will have to watch for Will's video --- the one I saw was about 10 months to a year old and really needed some edits and corrections. I texted him several times to make a new video. I will have to watch for a newer one.

For the water heating, I bought 24-volt water heater elements but have not got to that part yet. still need a few things! Spring is coming! 😎
 

Crebbst

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Thanks for the reply! I have 250 watt 60 cell panels as well. 20210322_084342.jpg
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!
 

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