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

michael d

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I tried with the ac inverter (bypassing the bms) maybe I try this method
did you top balance the EVE LF280K cells with a bench power supply before assembling the 16S battery? i do not use a daly BMS at this time...but also suspect a faulty BMS.... cell 15 is definitely the one you need to monitor as your screenshot displays the terribly low voltage....
 

Justeric

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Anyone who has tried Venus OS on raspberry Pi 4 rev 1.4? Am having trouble accessing the local console
 

michael d

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What charger do I use
do you have a bench power supply?? I am getting the impression that you think the supplier of the cells balanced them...???? suppliers of these commodity cells do not balance the cells.... they normally are shipped at 3.29 volts but this is not balanced for a correct top balance.....

I am still not sure what is the problem with your cell 15 ...>>> is it a bad cell or did the Daly BMS not shut off the discharging ?? for if (I assume) you have an inverter changing the DC from the assembled battery to AC for use to power other things....
I hate the word assume because one can be so far off on what the actual situation is...
please forgive me for using the word. (assume)

the cells need to be top balanced to 3.55 before assembling the battery pack, and most people top balance all the individual cells to 3.65 volts per cell before assembling them into the series-connected battery...(highly recommended)

the top balancing should be done by you with a bench charger....
you may already have one.... I hope all works out for your cell.... especially cell number 15 seems to be the problems cell...
did the Daly BMS malfunction?
I do not use a Daly BMS....

let me know how cell 15 is reacting to the charge when you pull it out of the assembled battery to charge it by itself.
i am interested in how it progresses.
🤔🤔😎
 

michael d

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Wouldn't be surprised if this was caused by inadequate balance current on the Daly. Pretty much all of the Chinese BMS options have pathetically small balance currents (usually 50mA, 0.05A). This would be adequate for a small battery bank (<100Ah), but most off-grid systems are considerably bigger than that.

Adding insult to injury with LFP is that it's only possible to balance cells when they near 100% SOC--because otherwise, their voltage is ~3.4vpc regardless of the SOC from 20-80% (or is it 15-95%?) That coupled with a paltry 0.05A balance current--means that said BMS units' balance capability is basically useless.

And if you're doing huge DOD (depth of discharge) cycles on a daily basis, that only increases the problem by several magnitudes.



Regardless, seems the Daly didn't disconnect @ 2.5v on the low cell...it'd only get down to 0.2v if the cell was completely destroyed due to overcharging (resulting from inadequate balance current), or overdischarged.

"Sid" wrote the above to me when I noted your problem with cell 15...

I do not use the Daly BMS...


another commented bad about Daly BMS below:

Adding insult to injury with LFP is that it's only possible to balance cells when they near 100% SOC--because otherwise, their voltage is ~3.4vpc regardless of the SOC from 20-80% (or is it 15-95%?) That coupled with a paltry 0.05A balance current--means that said BMS units' balance capability is basically useless.

I lost over thousand dollars of LFP with Daly BMS because LFP has a flat charge curve and low balance current . The LFP drop to near zero volt and can not be recharge .

a third commenter said the below:

Two cents worth of comment on this. The piddly balance current works if you have decently matched cells and raise the cell voltages high enough to move them far enough up the curve. If you have crappy and/or mismatched cells a completely different strategy is needed, hence high current balancers and active balancers. If things are bad enough ditching top balancing completely and using bottom balancing can be a solution but that has its own bugbears.

Prebuilt elcheapo batteries often have crappy and mismatched cells. Part of their solution is to use a standard low current BMS but specify a low charge current to give the BMS a chance of keeping the cells comparatively in line. It's a dead give away that when you see a 200AH lifepo4 battery with a charge rate of 30A it's going to be crap.

i hope you have some success reviving or trying to revive cell number 15,,,, but according to the replies I received when I presented your issue with cell number 15.... they all seem to blame the inadequate cell balancing of a cheap Daly BMS...

Again I personally have zero experience with the Daly BMS.... but hope you can find the cure or you may need to replace the BMS and cell number 15....at the minimum....

best wishes for you😎
 
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michael d

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I will try it it
It should also disconnect on cell over voltage. If the BMS is set up correctly, and actually does what it is told, all that should happen is the battery capacity falls over time as the cells get progressively further out of balance and the BMS top / tails the amp hour rating. No cell should ever be observed below 2.5V or over 3.65V. To see cells at 0.2v says something has gone badly wrong.

A technical view of the overall system involved would be interesting. Has he configured the BMS with completely incorrect settings? Has he damaged the BMS so that it can no longer do low / high voltage disconnection? Has he wired things up so that the BMS does not have the ability to disconnect the load or charger?

hey Justeric >>>this was another follow-up comment about your cell 15 problems....from a commenter in a different forum....
 

Justeric

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I totally agree with you the Daly bms might have misbehaved by not disconnecting the cell at the set lower limits
 

Justeric

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See attached
 

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michael d

off-grid solar pilgrim
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Above is a photo of the EVE LF280K cells in parallel being top balanced 4 at a time with my Riden 6018W bench charger. it is powered by a 120volt AC from a solar-charged battery via an LF inverter. All solar improvements have been off-grid for about 2 plus years now....
this is the new 4P8S battery build....as always slowly at the off-grid farm.....
presently working on an automated shutdown control for the inverters via an optoisolated relay module..... almost have the parts I need for that....!!!! this is a very important part of protecting the very expensive LiFePO4 battery from over-discharge which will drastically decrease their lifespan or totally kill off a cell....
I am working up a wiring diagram with EasyEDA..... a free schematics program....still learning about it though....
cold and windy outside today....new baby lamb was born last night....(hair sheep)
have a great day all!
I do note that the LifePO4 cells keep getting more expensive each year....bummer....😎
 

michael d

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the chart above is for LiFePO4 cells:
at 3.4 volts they are somewhere close to 99 percent SOC (state of charge) the remaining 1 percent to charge up to 3.65 is nothing and no reason to stress your cells to try to get them there more than an initial top balance,,,

the SBMS0 stops charging when any one cell reaches 3.55-volts for a pre-set amount of time and while the 24-volt battery is being charged it is constantly balancing the cells with approximately 140 to 300mA. exact detail I will search out later for you..

as I understand it when the inverter pulls the battery down at least 3 percent then the SBMS0 will allow the charging to continue once again ( I think this was referred to as hysteresis).
forgive any terminology blunders, but I have been utilizing 4 of the SBMS0 systems on 4 different 24-volt LiFePO4 builds and do about a gazillion other things on my off-grid farm and sometimes the windy weather or snow or livestock or family etal dictates what gets done 1st.

i have 4 LF (low frequency) inverters hooked up and doing different things all the time...

presently working toward the automated inverter shut down circuit compatible with the inverters,,,, slowly acquire the pieces and parts...

more later😎
 
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michael d

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Cell balancing is achieved via a 24 Ω resistor switched across each cell by a FET controlled by the ISL94203; nominal balancing current is therefore 3.6 V / 24 Ω = 150 mA. Cell balancing is only enabled when:
all cell voltages exceed 3.2V, and
cell voltage deviation exceeds 10 mV, and
charging current exceeds 300 mA
These parameters are configurable in the ISL94203; refer the datasheet for details. (TODO: verify if exposed by the SBMS0 config.)
 

michael d

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the above was from github....

the Electrodacus SBMS0 balances at 150mA while charging is being done....
I use the Electrodacus DSSR20 with 2 60-cell solar PV panels connected in parallel as it was specifically designed for.

72-cell PV panels could be used in pairs if your distance is over 60 feet and you need to....at the increasingly higher price of copper wire, one should try to keep the wire runs as reasonably short as you can....

I also have been documenting the small details as I find them in an excel spreadsheet... slow but sure
I do find the learning/understanding of the function of the tiny electrical components to be a challenge at times.🤔🤔

but the basic connections, once you get it hooked up correctly work flawlessly.😎👍

the whole time the SBMS0 is allowing charging from the solar panels to commence through the DSSR20 it is balancing the 24-volt battery via a passive balancing.....

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

I have 4 of the Electrodacus SBMS0 set up to 4 different 24-volt LiFePo4 batteries and have a LF (Low Frequency) inverter connected to each set up continuously drawing some load 24/7.....
two batteries of the 4P8S configuration and two batteries of the 2P8S configuration using either 272Ah Lischen cells or the 280Ah EVE LF280K cells.

I do not mix them within the same battery build.... the Lishen vs EVE cells (different brands and slightly different rated Ah capacities)....

Each individual Electrodacus SBMS0 can control up to 20 of the DSSR20s and 18000 watts of solar PV Panels...

have a great day all...😎
 
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