Eve LF280K 6000cycle rated for solar at .5C 32cell build

michael d

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There will be no imbalance is just a voltage delta when the cells are at the full charge level. The voltage delta when the cells are around 100% SOC will not indicate an unbalance.
There will be less than 10mV delta as long as the battery is not fully charged so the last few seconds before the charging is stopped.
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At typical 0.2C charge rate a cell will get from 3.4V to 3.55V is just a few seconds meaning the SOC of the cell at 3.4V will be almost exactly the same as at 3.55V even if there is a 150mV delta between the two measurement points.
Say it takes a cell 36 seconds to get two 3.4V to 3.55V while it is charged at 0.2C (that will be 20A for a 100Ah cell).
The SOC will increase by 0.2% in those 36 seconds (it is just an example it may take way less than 36 seconds but this is a round number as there are 3600 seconds in one hour).
Unless your cell balancing can dissipate 0.2C so 20A in this example with 100Ah battery you will not be able to correct that 0.2% SOC delta in a single charge cycle.
0.2C in this example means 200mAh as the delta between the cell at 3.4V and at 3.55V so it will require one full hour of 200mA of cell balancing to reduce the cell SOC by that 200mAh
Since cell balancing only has 36 seconds in this example it will require 100 charge cycles to reduce the energy in that cell by this amount.
If the delta is large enough between cells (more than 10mV) then cell balancing will start way before cells get to 3.4V and there will be a lot of time even multiple hours to correct the larger imbalance.
The last small imbalance that 0.2% or so will require more time as it is only visible in the last few seconds of the charge cycle and it is not very relevant since it is so small.
To correct those last 0.2% imbalance can be done in two ways.
One will be to have a huge cell balance current 20A in this example but in real life may need to be 60A for a 300Ah battery or more and it just not an economical option to have such large cell balancing currents.
The other option is to reduce the charge current to what the cell balancing can do say 200mA but then instead of 36 seconds of charging to get to full it will take one full hour and so there will be higher battery degradation as batteries like to spend as little time as possible charging.
Cells are not equal no matter the quality of the cells. They will have both different capacity and different internal impedance.
If they only had different capacity but exactly the same internal impedance then after the cells will be perfectly top balanced they will remain that way and all cells will get to 3.55V at the exact same time.
Of course cells will also have different internal impedance meaning each time you charge and discharge them they will get slight imbalance and that small imbalance is what is corrected by cell balancing.
The small 100 to 200mA cell balancing current is sufficient to keep a battery in balance (withing 0.2% or so) forever even for large battery capacity in the 1000 to 2000Ah
Say you have a cell with 0.5mOhm internal DC resistance and one with 0.6mOhm
Then during charge or discharge at 20A the 0.5mOhm cell will have a voltage drop of 0.01V * 20A = 0.2W so 0.2W will be wasted as heat instead of charging the cell.
The other cell that is 0.6mOhm will have an internal voltage drop of 0.012V * 20A = 0.24W so more of the charge energy will be wasted thus over say one hour of charge at this current the 0.5mOhm cell will have 0.04Wh more energy than the 0.6mOhm cell and that is how imbalance happens and it will happen both on charge and on discharge.
 

michael d

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the above is in reference to the Electrodacus SBMS0 balancing the LiFePO4 pack courtesy of the electrical engineer....hope it helps you to understand better the LiFePO4 chemistry.... cheers all😎👍

I am not an electrical engineer but would believe their experience and expertise over arm chair folks...🤔

I am a DIY type person with a farm agricultural background with many years in construction design and application.. I was an honors chemistry major in college among other things and analytical chemistry and organic chemistry many years ago.... we were taught to be very precise in our measurements to get accurate results...

the LiFePO4 and BMS world is a steep learning curve but worth your efforts.😎
 
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upnorthandpersonal

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Unless your cell balancing can dissipate 0.2C so 20A in this example with 100Ah battery you will not be able to correct that 0.2% SOC delta in a single charge cycle.

That's because the SBMS0 doesn't balance unless there is a charge current. If you compare that to a 2A active balancing JK BMS, you can get that imbalance gone in a matter of hours.

By the way:
I only use a 24-volt setup but 12 volt or other voltage could be done similarly with the Electrodacus SBMS0...

Note that you can't use 48V systems with the Electrodacus, and that his charge controller is PWM, not MPPT so your solar panel strings have to be close to the battery voltage. If that works for you, great, but the cost of copper wire to run this is getting very high with larger systems.
 

michael d

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I do not have an imbalance in my batteries actually... the information I provided was to help others to understand the theElectrodacus SBMS0 cell balancing abilities. they are working well in my 4 battery builds (the Electrodacus SBMS0 and Electrodacus DSSR20s).
yes, I use the Electrodacus DSSR20 with 2 of the 60-cell 250-watt panels which is exactly what the Electrodacus DSSR20s are designed for. I purposely did that. they are not PWM controllers, they are digital solid-state relays...
the Electrodacus DSSR20 is not a PWM charge controller>>> it is a solid-state relay that is controlled by the Electrodacus SBMS0 to give all the amps it can when solar PV charging is allowed by the Electrodacus SBMS0....
I parallel two of the 60-cell 250-watt solar PV panels at the array with Temco brand branch connectors. (easy)
one can use an MPPT if you choose that route as the solar charge controller for use with the Electrodacus SBMS0 for up to a 24-volt system...
but other than the numerous wire runs, I definitely do like the modular ability to add 2 panels at a time and the Electrodacus DSSR20 has the diversion capability to use the excess solar electricity generated for heating...with the large array small array set-up...
i purchased about half of the Electrodacus with diversion built-in and half without the diversion option.

yes, that is why I say it is better to try to make the wire runs shorter if possible...the copper wire will add to the overall price
I bought about 2000 feet of red PV wire and 2000 feet of black PV wire for about 30cents per foot including delivery and tax before the inflation on all materials kicked in. I would have to search out the exact price later...
one is a 1088 amp 24-volt battery and two are 544 amp 24-volt batteries and the 4th 24-volt battery is an 1160 amp battery... I use 2P8S and 4P8S 24-volt configurations.
the advantage is a low C-rate and higher capacity...
need to air-condition the off-grid solar power shed....but it is superinsulated, so not much to heat, the difficulty is keeping it cooled to the 78 degrees Fahrenheit for component lifespans... in the summertime!
people talk about 48-volt a lot but there is only a small difference in the cost of slightly larger AWG wires to the inverter as it will require more amps to get the same watts.... I use 4/0 copper cables to the inverters with hydraulically crimped tinned copper lugs....and 400AMP class T fuses....between the inverter and the LiFePO4 batteries...
more later,
time to feed the hair sheep bottle lambs again at the off-grid farm...😎
ps... I like the EVE LF280K cells with the welded-on screw holes, I think will end up being a better option than the welded-on studs...
 
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upnorthandpersonal

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they are not PWM controllers, they are digital solid-state relays

It's PWM-like. It's like a shunt type charge controller: short panels to battery and divert to a shorted circuit when battery full, i.e. panels either shorted to battery or shorted to themselves. In the relay type, the PV is open circuit rather than shorted to itself. PWM just takes that one step further and uses solid-state electronics and hundreds/thousands of times a second allowing for true battery voltage regulation, unlike the shunt and relay type.

people talk about 48-volt a lot but there is only a small difference in the cost of slightly larger AWG wires to the inverter as it will require more amps to get the same watts

If you want to pull 5kW on the the inverter, that translates to 208A on 24V, and only 104A on 48V. That's the difference between #2 and 4/0.

I was actually talking about the cable size from solar panels to charge controller. If you don't have to match your battery voltage, you can go much higher and send a lot more power over standard 6mm² solar cable - especially with larger arrays or panels that operate at higher voltages (which are very common and readily available).

the information I provided was to help others to understand the theElectrodacus SBMS0 cell balancing abilities.

Of course. I was just pointing out that the SBMS is no panacea and probably not the best choice unless you really know what you're getting into.
 
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RCinFLA

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That's because the SBMS0 doesn't balance unless there is a charge current. If you compare that to a 2A active balancing JK BMS, you can get that imbalance gone in a matter of hours.
I have heard that about Daly BMS's also.

If there is no balance dump unless there is charge current, after a BMS has overvoltage shutdown (no longer any charging), how does it get out of overvoltage situation? I guess you just wait, possibly up to a couple of days, for surface charge to bleed off enough. That does not sound like a good design.
 

upnorthandpersonal

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I have some strong opinions on Daly, SBMS and a few others which I won't fully express. Sure, they have some uses, but there are much better products out there that make life much easier. All the things Dacian did with his BMS/charge controller makes perfect sense if you know where he comes from and know his opinions (which are, let's say, also very strong), but it's not something I would recommend to people looking at a BMS/charge controller today in 2022.
 

michael d

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yes, the Electrodacus is designed to balance the LIFePO4 cells while it is charging...
the Electrodacus SBMS0 has optoisolators that act as a switch and turn the Electrodacus DSSR20s on when there is a small I believe 300 mv change in the battery voltage, I believe that is called hysteresis. the Electrodacus DSSR20 (digital solid-state relay) is not PWM and does not do the PWM method as you describe at all. on the contrary >>> it turns the DSSR20 on and gives all that it can give, there is no pulsing as the PWM charge controllers do...

there is no need to balance with an active balancer in the dark... solar PV panels balance it first thing every morning...

even in cloudy weather I still get a small amount of charging.... maybe only 15-30 watts vs 500 watts...out of every 2 panels connected in parallel...

so the bigger the array the more the charging and faster the charging....add 2 panels at time,,,, not too hard.... I add 6 solar PV panels at a time as each array structure support 6 panels (in my setup). edit: i will say the panels weigh about 40 or 41 pounds each so they are a bit challenging to mount at a 45-degree south-facing angle by myself.....(perseverance gets it done though)!😒

the Electrodacus DSSR20 with diversion option solar charge controller will also divert the excess solar PV electricity. I think it is all open source so maybe the schematic is available.... online
the SBMS0 has a fair amount of the schematic online...for sure...

SBMS0 stands for solar battery management system with the 0 designating the new and only version of the SBMS0 currently being produced...

I have the newest version of the Electrodacus SBMS0 version 3 .... using them on the 24-volt battery builds with the LiFePO4 cells....
I have 4 of the Electrodacus SBMS0 operating and they balance 96 cells in the large LiFePO4 batteries with no problems...

the reply I pasted above from my excel spreadsheet was a response to someone who only had a charger but no solar panels as he was just getting started...
it was the Electrodacus response as he is the electrical engineer....from Canada....

I was considering putting 2 batteries (((24-volt in series with another 24-volt )))in series to get 48-volt but not sure about that at the moment. I have some 4inchx12inch by 1/4 inch thick copper bus bar tinned for that idea...... still analyzing that idea...

I have never used a Daly brand BMS....so no information on that brand...

every time you add 2 more panels connected in parallel, a higher number of amps is charging the batteries...

there is a YouTuber "Everlander" I believe who has a video of the Electrodacus SBMS0 and the Electrodacus DSSR20 with the diversion option heating water for his adventures...it also charges his LiFePO4 battery bank...


If any of my verbiage is incorrect please show me the way... I have been using and studying these for the past 2 &1/2 plus years...
it won't be the 1st time I learn as I go...
presently working on an automated inverter shutdown as another safety mechanism....based on the cell level monitoring of the SBMS0

to me, the idea is to heat with all-electric off-grid solar generated PV power and this is a much better option than very expensive heat pumps...to buy and install... others will surely go other routes of plug and play for ease...
thanks for all replies...😎🤔
 
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michael d

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I have heard that about Daly BMS's also.

If there is no balance dump unless there is charge current, after a BMS has overvoltage shutdown (no longer any charging), how does it get out of overvoltage situation? I guess you just wait, possibly up to a couple of days, for surface charge to bleed off enough. That does not sound like a good design.
I have never had an overcharging problem yet with the Electrodacus DSSR20s and the Electrodacus SBMS0, and my inverters are running 24/7 so that there is always a load on the large LiFePO4 batteries. the Electrodacus SBMS0 turns off charging from the Electrodacus DSSR20s via tiny 26awg sense wires when any cell reaches 3.55 volts for a preset time...

I also have some DC LED direct-wired lights on two of the batteries ((that I use a small fuse and a circuit breaker as a switch on those....))
All is off-grid...in a stationary build in my super-insulated solar power shed...

i have a AC breaker panel running some loads also via the split-phase inverters...

in the USA we use 120/240 AC wiring so I have split phase inverters....

this is strictly an off-grid solar DIY build with no connection to the electric grid at any time....
 
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michael d

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I think 6mm is the same as the standard 10Awg solar PV wire and is the standard size for the MC4 connectors I use on all my solar panel connections. I better double-check that....
yes, they are the same standard wire size....
in the USA I am so used to using AWG vs the metric mm versions...
10AWG solar PV wire is the same as 6mm....

I think in the year 2020 or 2019 I bought the 2000 feet of 10AWG solar PV wire along with some other wire and the copper wire was more economical then than now....
in 2019 I bought 500 feet for 32 cents a foot, later in the year 2020, I bought a larger quantity 2000 feet for 25cents per foot, so each 2 panels I use about 30 dollars of 10AWG Solar PV wire as my array is about 60 feet away from the inverters and SBMS0 & DSSR20s etc.

shorter runs will require less wire and decrease the solar PV wire cost...that is for sure....
 

upnorthandpersonal

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the Electrodacus DSSR20 (digital solid-state relay) is not PWM and does not do the PWM method as you describe at all. on the contrary >>> it turns the DSSR20 on and gives all that it can give, there is no pulsing as the PWM charge controllers do...

Yes, that's what I clarified in my reply: it's PWM-like in its mode of operation without the advantage of actual PWM where you can have a mismatch between panel and battery voltage.

there is no need to balance with an active balancer in the dark... solar PV panels balance it first thing every morning...

In your case, because you might have an optimal set-up as is required with a SBMS. How high is your C rate charging/discharging the batteries? How low do you take them?

even in cloudy weather I still get a small amount of charging.... maybe only 15-30 watts vs 500 watts...out of every 2 panels connected in parallel...

That is normal and has nothing to do with it being driven with a DSSR20.

so the bigger the array the more the charging and faster the charging....add 2 panels at time,,,, not too hard.... I add 6 solar PV panels at a time as each array structure support 6 panels (in my setup).

Again, this is a normal thing to do. I've done that too when building the array. Every string needs to have a fuse and you join them in a combiner box before going to the charge controller. It doesn't need anything in addition. But because you can go higher voltage, you just join them at the combiner box at the panel installation and go with two wires to the charge controller for all strings combined.

it was the Electrodacus response as he is the electrical engineer....from Canada....

And my responses are as an Electrical engineer, from Finland.

It feels like you think I'm maybe attacking you - I'm not. I'm putting out here that the SBMS and DSSR20 combination is not a good option for everyone unless you know exactly what you're getting into. With current solar panel prices (where large panels are cheaper per Watt than small panels, but run at well over 24V) and the availability of MPPT charge controllers and BMS at low prices, this is a easier and more convenient way to built a system.

presently working on an automated inverter shutdown as another safety mechanism....based on the cell level monitoring of the SBMS0

This is something that comes, and should come, as standard with a BMS. As soon as a cell goes over or under a set voltage, the BMS should disconnect the battery. Ideally, you want to disconnect only charging when the cell goes over a set voltage but allow discharging, and the other way around, allow charging when the cell reaches low voltage disconnect but keep discharging disabled.

to me, the idea is to heat with all-electric off-grid solar generated PV power and this is a much better option than very expensive heat pumps...

I dump my excessive solar (in spring/autumn) in a 3000L water tank for heating (hydronic underfloor heating). In summer I use a smaller tank. The big tank is used for cooling in summer (hydronic underfloor cooling) with an air to water heat pump I made myself (for testing). This will soon be replaced with a proper air to water heat pump (look up monobloc heat pump), taking care of both heating and cooling the large tank with excessive solar since it's more efficient than just resistive. With a CoP of 4, you can get 4kWh of heat with 1kWh of electric.
 

michael d

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Have you ever heard of a battery with cells out of balance?
that is why they use the BMS is to balance the cells....
the BMS is an essential part of maintaining the liFePO4 battery bank....and is included in all the prebuilt server rack batteries as well as tesla car batteries and essentially all Lithium batteries...being assembled today....
have you?

the Electrodacus SBMS0 turns off the Electrodacus DSSR20s to prevent overcharging... but all cells have slightly different characteristics with-in the battery builds....even if in mv differences while being charged or discharged...

they talk a lot about cells that do this.... so balancing is utilized.... (runner cells that charge or discharge faster than the rest)
the SBMS0 has balancing and biddle ohm indicated it is passive and not active even if it appears to be.... it wastes a small amount of electricity (up to 150mA I believe) via the resistors to balance the cells while it is charging.... that is the purpose of the BMS (battery management system)

again I am not an electrical engineer and glean a lot of new knowledge via reading and studying what people are doing.
all the small pieces and parts and their interactions are still a bit beyond me....
I am studying capacitors and inductors and resistors and mosfets and transformers every day, but still will never claim to know diddly compared to an electric engineer.

to track some of this I have been adding tidbits to an excel spreadsheet..... for years

I am always in awe at how things have changed.
I have some solar panels that cost 1000 dollars each and some grid-tie micro-inverters from about 12 years ago...
but when I can buy 250-watt panels delivered for 50 dollars each this past 3 years in the USA.... then the economics tell me it is great to get off the grid...

250-watt solar PV panels for 50 bucks delivered equals 20 cents per watt for the solar pv panels. they cost more now with the inflation in the USA.

cheers all, from South Dakota😎 USA
 
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michael d

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I think my 60-cell 250-watt panels run at about 29 volts and I purchased them in pallet pricing...and easily charge the LiFePO4 batteries...
the inverter I am using is not compatible exactly so that is why I have been working on the automated switch as a second way to prevent over-discharge... still learning about it and acquiring the parts...

I have a higher voltage system also with MPPT outback flexmax 80 and 327-watt panels, but I am looking to be totally off-grid with battery backup and want to utilize more of the Solar PV power....
on the off-grid build...

yes, there are other brands of BMS out there for other higher voltage use, but at present, I am concentrating on the Electrodacus SBMS0...which is working great for the 24-volt system...

edit: to use the higher voltage systems requires more fusing on the strings and then a higher degree of safety when working with 150 volts or more from the solar PV panels. so be careful in all systems and study a lot as it is your safety and others that is the most important part....

edit: I am not an electrical engineer. and assembling the 4P8S battery with 32 280Ah EVE LF280K cells is a bit hair raising.... I wear gloves and safety glasses and all is being done in an off-grid solar power shed so it is not in my living quarters....

edit: I have a super inquisitive autistic young one (11 years old) who I keep away from these things....and now glad that I did the extra nine yards of safety to do so! Hopefully all people do the same or more with their electrical projects..... A 4P8S 24-volt nominal battery built with 280Ah cells is 1120 Ah....

which BMS is best??? i have no way to compare them.... nor the time....
I am just posting things to try to help others on a similar journey....
in the last 2 years in the USA I was able to source PV solar panels inexpensively 40 at a time in 2 pallets quantities, so keep making the system large for the shop and off-grid farm...about 50 dollars per 250-watt 60-cell panel or so including delivery (approximate)... more expensive now...

I also have been into passive solar structures and have 3 buildings in 2 different states with a lot of south-facing glass in superinsulated buildings that I want to add Solar PV to....
Insulation and conservation always makes the most sense to me...
the USA gives a 26 percent tax credit for solar so that makes all solar off-grid a bit easier on the budget also...
time to go enjoy the sun!😎

I like the EVE LF280K cells in the 4p8s build....purchased for $4300 dollars including tax and delivery to South Dakota USA via the slow boat ride from china in 2021. more expensive today...😢😢
 
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upnorthandpersonal

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I like the EVE LF280K cells in the 4p8s build....purchased for $4300 dollars including tax and delivery to South Dakota USA via the slow boat ride from china in 2021. more expensive today...😢😢

I just bought another 32 of those: $4102 including shipping and taxes from China.

I have a higher voltage system also with MPPT outback flexmax 80 and 327-watt panels, but I am looking to be totally off-grid with battery backup and want to utilize more of the Solar PV power....

I'm also off-grid here in the north, and I use all the solar PV I can generate except in summer where I have too much. Next step will be an EV that supports bidirectional charging so it can act as a battery extension to the house as well.
 

michael d

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the Electrodacus SBMS0 balances the 4P8S lishen battery to a 6mv delta...
it would be 272 x4 = 1088 Ah battery at 24-volts
if you use the 3.2 volt nominal per cell to do the calculations.

it has 2 250-watt PV panels connected to it using only one Electrodacus DSSR20 at the moment...
the attached photo was this morning with the sky totally clouded over.

it is connected to a 15000 watt LF 24-volt inverter.... which is wired to the AC a 100 Amp breaker panel >>> all off-grid....

I will put this over in my thread for Electrodacus as I think I created this thread more for the EVE LF280K 6000 cycle-rated cells...
 

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