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DIY battery longevity

Subdood

Subdood

Photon Wrangler
Joined
Mar 27, 2022
Messages
555
Location
NE Kentucky
Hey all I was checking out 18650's website and saw that they're now selling LF 280K cells for $105. That's insanely cheap compared to just a year ago. They claim these cells are good thru 6K cycles. I have considered maybe doing a DIY battery build, but was wondering how folks who have already built batteries with prismatic cells how their cells have performed over time. Like, particularly people who've had them over 6 months, a year, and so on. Have well have your cells maintained their aH/power ratings? Please include the number of cycles if you can.

Thanks.
 
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One cycle is defined as fully charged to fully depleted to fully charged again.
100% to 0% to 100%.

My 1st pack was commissioned 10/29/21.
2nd pack commissioned 1/15/22.
Typically discharge to 55-60% over night.

Pack 1 has accumulated 411 cycles.
Pack 2 has accumulated 353 cycles.

No detectable capacity degradation, however, I'm not testing to the 4th decimal place. Careful analysis of Solar Assistant graphs and scribbles on the back of an envelope.

Hope this helps your understanding.
 
Subdood said:
They claim these cells are good thru 6K cycles.
Click to expand...
Assuming your seller is actually selling genuine EVE cells, they're not lying.
That 6K figure is conservative with a 0.5C charge/discharge rate @ 140 Amps.
Real world use are very unlikely to approach it.

There has never been a better time to DIY a LFP battery if you need one.

I have my own DIY CALB L160F100 battery for more than five months now integrated into my solar setup and completed 90 cycles to date.
 
TomC4306 said:
One cycle is defined as fully charged to fully depleted to fully charged again.
100% to 0% to 100%.

My 1st pack was commissioned 10/29/21.
2nd pack commissioned 1/15/22.
Typically discharge to 55-60% over night.

Pack 1 has accumulated 411 cycles.
Pack 2 has accumulated 353 cycles.

No detectable capacity degradation, however, I'm not testing to the 4th decimal place. Careful analysis of Solar Assistant graphs and scribbles on the back of an envelope.

Hope this helps your understanding.
Click to expand...
I thought a cycle was down to 20%, not zero. Discharging to zero will shorten the life of a cell, correct?
 
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I DIY a battery for my MotorHome (we full time). It is 544ah 12v with eight Lishen 272ah cells.

I do usable test - (full down to the inverters cutoff). After I installed the battery, I believe I got 525ah of useable power. 18 months later (usually cycling between 100 and 70% (and very seldom below 40%), I got 521ah. The cycle count is lower - but I am using them daily. Occasionally I am at RV parks so they sit in float for a few days to a month.

Good Luck
 
timselectric said:
Zero is fine. As long as you understand that Zero is 2.5v per cell. (Not dead)
I don't cycle below 3v (unless testing) because I want that reserve for emergency.
Click to expand...
So where would 3V be percentage wise, about 10%? From what I've seen when it hits the downslope of that "knee", it's a fast drop to zero.
 
Say I built a 280Ah 48V battery bank, what sized BMS would be sufficient, 200A? I highly doubt I'd have a situation where I'd need that much current at one time.
 
Subdood said:
Hey all I was checking out 18650's website and saw that they're now selling LF 280K cells for $105. That's insanely cheap compared to just a year ago.
Click to expand...

I just purchased 96 cells, LF280K V3 EVE "Grade A" matched, from Amy at Luyan for $78 each, shipping for 96 cells was $1338. Cost per cell with shipping was $91.94

I can wait, I know these won't even ship until late this month. I have PV mounts and panels to install plus choose an inverter and install it so 60 days might not be enough time to be ready for cells.

18650 tends to salt an order with one cell that happens to test lower than others from my experience. The cells aren't in stock either, it will be very late Feb or early March before you will see them and 96 cells from 18650 shipped to my door comes to $111.58 per cell. That is $1885 more for the 96 cells.
 
Subdood said:
Say I built a 280Ah 48V battery bank, what sized BMS would be sufficient, 200A? I highly doubt I'd have a situation where I'd need that much current at one time.
Click to expand...
I purchased the older JK 200A without CAN or inverter communication. The deal is in this thread. You get the first one for the low price and any extra will be about $5 more.
 
My Batrium says 203 daily sessions (system turned on mid March 2023, don't know why it says 203 daily sessions) and it says SOC% cycles is a grand total of 10.

At this rate, it will take 121,800 days to reach 6,000 cycles. :ROFLMAO:

I think calendar aging will get the cells first.

The bright side is if I outlive my cells, I will be almost 400 years old.
 
Zwy said:
My Batrium says 203 daily sessions (system turned on mid March 2023, don't know why it says 203 daily sessions) and it says SOC% cycles is a grand total of 10.

At this rate, it will take 121,800 days to reach 6,000 cycles. :ROFLMAO:

I think calendar aging will get the cells first.

The bright side is if I outlive my cells, I will be almost 400 years old.
Click to expand...
Or you inherit them to your Family members.. 🤣
 
PeSCaLo said:
Or you inherit them to your Family members.. 🤣
Click to expand...
I expect my descendants will say something to the effect that Grandpa or Great Grandpa was a nut. :ROFLMAO:

I can say this about my paternal Great Grandpa. Truly a nut but also a Legend.
 
Zwy said:
My Batrium says 203 daily sessions (system turned on mid March 2023, don't know why it says 203 daily sessions) and it says SOC% cycles is a grand total of 10.
Click to expand...

I figured out the daily sessions, the current date was incorrect. I suppose some data was lost in the process. But still with 203 days and only 10 complete cycles, I'm not too concerned with cycle life but rather calendar aging.
 
Accelerated cycle life test is not that great indicator for battery lifetime as most of the battery systems discussed over here are going to die of old age (self life) or random quality control related failures rather than cycle count. This is especially true for battery packs that sit on near 100% charge level on warm/hot climate.
Battery on cycle test spends very little time at over 80% charge levels.
 
Zwy said:
I just purchased 96 cells, LF280K V3 EVE "Grade A" matched, from Amy at Luyan for $78 each, shipping for 96 cells was $1338. Cost per cell with shipping was $91.94

I can wait, I know these won't even ship until late this month. I have PV mounts and panels to install plus choose an inverter and install it so 60 days might not be enough time to be ready for cells.

18650 tends to salt an order with one cell that happens to test lower than others from my experience. The cells aren't in stock either, it will be very late Feb or early March before you will see them and 96 cells from 18650 shipped to my door comes to $111.58 per cell. That is $1885 more for the 96 cells.
Click to expand...
I have purchased a lot of cells from 18650. They have never shipped me one that did not meet capacity. I fully test each cell for IR and capacity.
 
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