michael d
off-grid solar pilgrim
as i have said i am not continuously maintaining lfp cell voltage above 3.43v.....
not sure where you get that from
Eve LF280K 6000cycle rated for solar at .5C 32cell build
- Thread starter michael d
- Start date
not sure where you get that from
michael d
off-grid solar pilgrim
can you provide the reference documents so I can read more....
someone wrote this and published it or is it just made up>>>> a theory without published documentation....
I want to read the published documentation....>>>> references....
I am not an electrical engineer or an electrician by trade >>> but I want to read the documentation....
Here is a doc from 2012 describing the issue of keeping a cell at high voltage for prolonged periods of time. Note that some of the terminology/etc. reflects the time this document was written:
Note that in that paper, the recommended charge voltages were "4.0V for Winston cells, 3.9 for CALB cells, 3.7 to 3.9 for many other brands of LiFePO4 cells)". We've come down from those as well in the mean time.
I know there are some more recent papers on this topic, but I can't find them right now. I'll see if I can find them later today.
Note that in that paper, the recommended charge voltages were "4.0V for Winston cells, 3.9 for CALB cells, 3.7 to 3.9 for many other brands of LiFePO4 cells)". We've come down from those as well in the mean time.
I know there are some more recent papers on this topic, but I can't find them right now. I'll see if I can find them later today.
Marinepower
Solar Enthusiast
- Joined
- Apr 24, 2020
- Messages
- 224
Not sure what the OPs meanth by this - but the Electrodacus bms is designed to be both a BMS and SCC.
It requires the solar panel input voltage to be marginally higher than the battery voltage. The BMS controls solid state relays which turn on/off solar input ( it can also divert unused solar input to other loads, like water heating).
By default it charges to when any one cell reaches 3.55v. and then stops.
So unless the default settings have been altered, i don't think the Electrodacus is holding the battery at high state of charge for a prolonged period of time.
michael d
off-grid solar pilgrim
exactly,,, the electrodacus SBMS0 has preset controls to protect the battery (LiFePO4) and I use specific Electrodacus DSSR20 as the solar charge controller...
this morning the LifePo4 had a delta of 6mV with a battery pack voltage at a safe level... I took another picture of the Electrodacus SBMS0 this morning and will upload it a bit later...of the 4P8S 32-cell 24-volt DIY battery build.....
at 93 percent soc the battery says 26.613 volts and shows a 6mV delta between the sets of 4 parallel cells
today February 3rd, 2024 >>this is the Electrodacus SBMS0 #3 build with 4P8S 24-volt configuration
cloudy outside today...
the cellular does not always get a good picture....I use WhatsApp to email it to myself, download it and add it here....
I may get a cell phone tripod to improve the photos...
WhatsApp is how I communicate with my Spanish-speaking friends in Bolivia for free...
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michael d
off-grid solar pilgrim
here is the Electrodacus SBMS0 #1 at 73 percent soc this morning February 3rd , 2024
I label them to differentiate which one is doing what but rarely babysit them,,,, other things to get done
they just chugged along and worked fine for me .... in my off-grid solar PV setup....
the Electrodacus DSSR50 will be utilized with some used 290-watt PV 72-cell panels soon
soon as in the speed of molasses flowing in January in the north country ...
lambing season is in full force it seems here ....
Electrodacus SBMS0 #2 is at 99 percent SOC and I may use some of its reserve to charge up some of the new 280 version 3 cells tonight...
26.987 volts divided by 8 equals 3.373 volts average per group of 2 cells in parallel as that Electrodacus SBMS0 is protecting a 2p8s build of lishen 272ah LiFePO4 cells running for about 3 years I think...
I label them to differentiate which one is doing what but rarely babysit them,,,, other things to get done
they just chugged along and worked fine for me .... in my off-grid solar PV setup....
the Electrodacus DSSR50 will be utilized with some used 290-watt PV 72-cell panels soon
soon as in the speed of molasses flowing in January in the north country ...
lambing season is in full force it seems here ....
Electrodacus SBMS0 #2 is at 99 percent SOC and I may use some of its reserve to charge up some of the new 280 version 3 cells tonight...
26.987 volts divided by 8 equals 3.373 volts average per group of 2 cells in parallel as that Electrodacus SBMS0 is protecting a 2p8s build of lishen 272ah LiFePO4 cells running for about 3 years I think...
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michael d
off-grid solar pilgrim
3.373 average cell charge on sbms0 #2 means the average full charge is between 98% and 99 percent so the Electrodacus SBMS0 is doing what it is designed to do and is not constantly overcharging as a previous commenter eluded to....
I still do not understand what he was trying to imply....
when you look at his chart and the numbers below
I still do not understand what he was trying to imply....
when you look at his chart and the numbers below
michael d
off-grid solar pilgrim
the article the upnorthandpersonal directed me to was interesting and helpful....
thanks,
thanks,
michael d
off-grid solar pilgrim
I ordered a NEEY 15-amp active balancer....
I think that may be helpful with the larger battery builds...
still top balancing a new batch of cells.
I think that may be helpful with the larger battery builds...
still top balancing a new batch of cells.
Top balanced the cell (guess you only need to do it once with 15A balancer), then find the cell with the lowest capacity in the pack and use that lowest capacity as guide for deep-cycling.
Beware though, if you really use 15A balancing, pay attention to the wire heat. Slight warming is normal. You might want to configure the balancer to use slightly low current.
My Neey 10A cabling get a bit warm when balancing at 10A.....before the balancer kicked the bucket with less than 2 month of usage........
michael d
off-grid solar pilgrim
thanks for the reply.... I will not use it continuously ,,,, but hopefully, it will help the balancing of the large ESS (LiFePO4 280Ah version 3 cells).
I have a dc-dc boost charger I want to try using also...
my thought is the dc -dc will be more efficient for some of the charging...
and the NEEY will help to balance them...
the NEEY 15 Amp active balancer is not here yet..
Thank you....
michael d
off-grid solar pilgrim
A small update to all on this 32-cell build:
it has been running for over 2 years now;
the Electrodacus SBMS0 can monitor up to 750 amps of charging....
that is the limit of the hardware inside of it (the electrodacus SBMS0) as I now understand it...
so the 32-cell build ((4P8S using the 280Ah Eve LF280k cells)) is actually ok as I never charge with 750 amps or anywhere near that amount with my strictly off-grid solar builds...
the Electrodacus SBMS0 can control up to 20,000 watts array then another SBMS0 should be utilized if the array is larger than that....
more later, windy, cloudy, and cold today February 27th, 2024 ; it is 25 degrees F now but colder than that with the fierce winds>>
that must have been the high temperature for the day as it turned into a mini blizzard and the temp dropped to 13 degrees Fahrenheit with a lot of wind...
it has been running for over 2 years now;
the Electrodacus SBMS0 can monitor up to 750 amps of charging....
that is the limit of the hardware inside of it (the electrodacus SBMS0) as I now understand it...
so the 32-cell build ((4P8S using the 280Ah Eve LF280k cells)) is actually ok as I never charge with 750 amps or anywhere near that amount with my strictly off-grid solar builds...
the Electrodacus SBMS0 can control up to 20,000 watts array then another SBMS0 should be utilized if the array is larger than that....
more later, windy, cloudy, and cold today
February 27th, 2024 ; it is 25 degrees F now but colder than that with the fierce winds>>that must have been the high temperature for the day as it turned into a mini blizzard and the temp dropped to 13 degrees Fahrenheit with a lot of wind...
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michael d
off-grid solar pilgrim
I put the numbers in microsoft word then in an Microsoft excel file....
I have lately observed the 2p8S and 4P8s builds and they areat right at about 27 volts when the Electrodacus turns off the charging...at 99 percent SOC
so never overcharged for long periods of time if ever...
I have lately observed the 2p8S and 4P8s builds and they areat right at about 27 volts when the Electrodacus turns off the charging...at 99 percent SOC
so never overcharged for long periods of time if ever...
| LFP Rested Open Circuit Voltage | ||||||||||
| % SoC OCV (open circuit voltage) | ||||||||||
0% | 2.5201 | |||||||||
1% | 2.8476 | |||||||||
2% | 2.9619 | 28% | 3.2803 | 54% | 3.3045 | 80% | 3.3398 | |||
3% | 3.0389 | 29% | 3.2835 | 55% | 3.3058 | 81% | 3.3405 | |||
4% | 3.0943 | 30% | 3.2853 | 56% | 3.3073 | 82% | 3.341 | |||
5% | 3.139 | 31% | 3.2866 | 57% | 3.3079 | 83% | 3.3413 | |||
6% | 3.1713 | 32% | 3.2885 | 58% | 3.309 | 84% | 3.342 | |||
7% | 3.193 | 33% | 3.2894 | 59% | 3.3103 | 85% | 3.3426 | |||
8% | 3.2011 | 34% | 3.2903 | 60% | 3.3114 | 86% | 3.3435 | |||
9% | 3.2033 | 35% | 3.2909 | 61% | 3.313 | 87% | 3.3439 | |||
10% | 3.2064 | 36% | 3.2925 | 62% | 3.3155 | 88% | 3.3443 | |||
11% | 3.2104 | 37% | 3.2934 | 63% | 3.3176 | 89% | 3.3437 | |||
12% | 3.212 | 38% | 3.2944 | 64% | 3.3211 | 90% | 3.3444 | |||
13% | 3.2165 | 39% | 3.295 | 65% | 3.3224 | 91% | 3.3444 | |||
14% | 3.2218 | 40% | 3.2951 | 66% | 3.3235 | 92% | 3.3461 | |||
15% | 3.2275 | 41% | 3.2951 | 67% | 3.3255 | 93% | 3.3458 | |||
16% | 3.2333 | 42% | 3.2954 | 68% | 3.3268 | 94% | 3.3481 | |||
17% | 3.2383 | 43% | 3.2968 | 69% | 3.327 | 95% | 3.349 | |||
18% | 3.2438 | 44% | 3.2978 | 70% | 3.33 | 96% | 3.3516 | |||
19% | 3.2496 | 45% | 3.298 | 71% | 3.3311 | 97% | 3.3546 | |||
20% | 3.2544 | 46% | 3.2989 | 72% | 3.3318 | 98% | 3.3643 | |||
21% | 3.2578 | 47% | 3.2994 | 73% | 3.3339 | 99% | 3.3804 | |||
22% | 3.2678 | 48% | 3.2998 | 74% | 3.3349 | 99.50% | 3.397 | |||
23% | 3.2661 | 49% | 3.3004 | 75% | 3.3354 | 100% | 3.43 | |||
24% | 3.27 | 50% | 3.301 | 76% | 3.336 | |||||
25% | 3.2725 | 51% | 3.3013 | 77% | 3.3366 | |||||
26% | 3.2764 | 52% | 3.3021 | 78% | 3.3376 | |||||
27% | 3.2784 | 53% | 3.3029 | 79% | 3.3384 |
michael d
off-grid solar pilgrim
27 divided by 8 = 3.375 volts per cell so someplace near the 99 percent mark....
sometimes they are a few millivolts above 27 volts....
so the LiFePO4 cells are never charged and maintained at 3.43 volts or above....
sometimes they are a few millivolts above 27 volts....
so the LiFePO4 cells are never charged and maintained at 3.43 volts or above....
