What 280's do I buy from Amy?
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Lt.Dan
Solar Wizard
The old version might be 10AH low, is it worth the difference in cost to you?
10ah low would not make a difference. Has anybody bought bulk Eve cells from Amy? Is it a crap shoot? I'll spend the money for grade A, but is it worth it. I'm 66, building an off grid cabin for fun. 6000 cycles takes me to 80. Is it worth buying grade A?
BatteryNut
New Member
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They’re rated and binned.
You should see how processors are binned and sorted (like die disable). It’ll freak you out if cell grading triggers you.
You should see how processors are binned and sorted (like die disable). It’ll freak you out if cell grading triggers you.
Short_Shot
Solar Addict
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The extra testing for matched cells is worth it in my book if you are doing anything in parallel.
If all of them will be in series for a 48 volt pack then the worst case is you get a bit less capacity by being limited by the first cell to reach a fully discharged state and trigger the BMS. This makes matching less important but still valuable.
If all of them will be in series for a 48 volt pack then the worst case is you get a bit less capacity by being limited by the first cell to reach a fully discharged state and trigger the BMS. This makes matching less important but still valuable.
Amy buys direct from the factory. The factory will produce batteries, then they match them so that all of the internal characteristics are a perfect match. So when you buy 16, 280ah batteries, each one acts exactly the same throughout the entire voltage discharge curve. That means you get the full rated 280 (usually 285-290) out of the pack. It also means the batteries should last a really long time without swelling, or without failing, or without going out of balance.
Bulk cells are the rejected cells from the manufacture. Maybe they were too heavy, or they were too large, or too light or they tested under capacity or they had too much internal resistance. These are still great cells, but they don't fully meet the grade A data sheets and are sold as bulk grade B.
If you buy bulk, buy an extra cell or two for when one fails.
I would (and did) buy grade A matched cells because an extra couple hundred to ensure I have great cells, factory data test reports, and cells that will last a while without issue.
RCinFLA
Solar Wizard
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My decision would be based on how I plan to use the used cells. If you normally will be drawing less then 60 amps from them they will probably be okay.
Biggest issue with used cells is over-potential performance degrades over aging of cell. This is greater terminal voltage slump for given amount of load current. This is not just cell internal resistance times current. Ion diffusion rate is reduced in older cells so overpotential drive must increase to meet demanded current. Overpotential has a time delay decay so need to wait a couple of minutes at load current before it stabilizes. It also varies over temperature, being a lot worse at cold temps.
Likely to have more mismatching between used cells. Same AH capacity and cell impedance is not only criteria for matched cells. Terminal voltage slump due to overpotential with load current is important for matching and seldom checked. More overpotential variance between cells drives faster cell imbalance progression, particularly if subjected to high discharge or charging rates. Older cells are also likely to have more variance in self leakage rate. Both mean older cells are usually tougher to keep in balance.
Biggest issue with used cells is over-potential performance degrades over aging of cell. This is greater terminal voltage slump for given amount of load current. This is not just cell internal resistance times current. Ion diffusion rate is reduced in older cells so overpotential drive must increase to meet demanded current. Overpotential has a time delay decay so need to wait a couple of minutes at load current before it stabilizes. It also varies over temperature, being a lot worse at cold temps.
Likely to have more mismatching between used cells. Same AH capacity and cell impedance is not only criteria for matched cells. Terminal voltage slump due to overpotential with load current is important for matching and seldom checked. More overpotential variance between cells drives faster cell imbalance progression, particularly if subjected to high discharge or charging rates. Older cells are also likely to have more variance in self leakage rate. Both mean older cells are usually tougher to keep in balance.
Thank you for all the great info. The cells I buy will be in series 48v. The maximum load I calculated is 30 amps. The cabin is small. 20x24. Biggest draw will be Split AC 15amps and small 8amp microwave running at the same time. Heat and fridge are propane for now.
I'm still confused.
BatteryNut tells me the "new" cells are rated and binned. Good cells vs poor cells, but all cells still new. Makes sense. Quality control.
Shortshot tells me bulk is probably ok if I connect the cells in series'. Makes sense. The weakest cell will determine pack quality
Bobdelso warns me that I need to buy more cells if I go Bulk because some will fail due to being bulk. Makes sense, but cost wise I might as well go Grade A
RcinFLA Tells me that I am probably ok if I'm under 60amp draw with bulk. Makes sense. Then tells me about used cells. Great info.
Finally DLtooley tells me he bought bulk cells from Amy due to cost savings, and has not had any problems.
The price difference between Grade A and bulk is about $600. Trust me, I've pissed away 600 bucks many times in my life, but try to avoid if possible. Im trying to find the best value for my money. What I need to find out is when the word "bulk" describes cells does it mean they could be "used" Maybe the Mandarin word for used is bulk.
I'm still confused.
BatteryNut tells me the "new" cells are rated and binned. Good cells vs poor cells, but all cells still new. Makes sense. Quality control.
Shortshot tells me bulk is probably ok if I connect the cells in series'. Makes sense. The weakest cell will determine pack quality
Bobdelso warns me that I need to buy more cells if I go Bulk because some will fail due to being bulk. Makes sense, but cost wise I might as well go Grade A
RcinFLA Tells me that I am probably ok if I'm under 60amp draw with bulk. Makes sense. Then tells me about used cells. Great info.
Finally DLtooley tells me he bought bulk cells from Amy due to cost savings, and has not had any problems.
The price difference between Grade A and bulk is about $600. Trust me, I've pissed away 600 bucks many times in my life, but try to avoid if possible. Im trying to find the best value for my money. What I need to find out is when the word "bulk" describes cells does it mean they could be "used" Maybe the Mandarin word for used is bulk.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Amy's Bulk cells are those which do not meet the overall performance specs for Grade-A during the Matching & Batching process, but are new production batch, not Old Stock nor from Battery Brokers (grey market).
I have both types in my packs.
Matched will perform through the operating voltage very closely, all cells vary a little during operation. They will generally be able to handle full capacity as designated, so a 280AH Pack built with Matched Cells have 280AH Capacity within it's "Working Voltage Range" of 2.900-3.450Vpc and most often can be "pushed" to 290AH from 2.500-3.650Vpc Max Voltage Limits.
Bulk cell Packs are "dominated" by Runner Cells. These are either weaker or stronger, usually a different internal resistance. They can either take charge faster than the other cells, therefore running to Hi Volt Cutoff @ 3.650Vpc OR then could discharge faster than the others, reaching Lo Volt Cutoff @ 2.500Vpc leaving the other cells in a higher state of charge. See Special Note. This can mean that the Full Working Voltage Range is reduced to the Lowest Denominator and as the efficiency over time decreases for any single cell, it will bring down the rest. While you may build a pack with 280AH Cells, a Runner or two could very easily limit it to 270 or even 260AH...
Special Note: Active or Passive Balancers CANNOT Fix this ! An Active Balancer can minimize "take the edge off" but only in a limited way, that is not their purpose or design. Passive Balancing is of little use on Large Cells above 100AH and only actually makes a difference when used with perfect Matched, Batched & Binned cells which are identical.
Please download the Lyuan Tech LifePo guide & Voltage chart from my Signature, they'll help you a lot and explain several things.
Hope it helps, Good Luck.
Steve
I have both types in my packs.
Matched will perform through the operating voltage very closely, all cells vary a little during operation. They will generally be able to handle full capacity as designated, so a 280AH Pack built with Matched Cells have 280AH Capacity within it's "Working Voltage Range" of 2.900-3.450Vpc and most often can be "pushed" to 290AH from 2.500-3.650Vpc Max Voltage Limits.
Bulk cell Packs are "dominated" by Runner Cells. These are either weaker or stronger, usually a different internal resistance. They can either take charge faster than the other cells, therefore running to Hi Volt Cutoff @ 3.650Vpc OR then could discharge faster than the others, reaching Lo Volt Cutoff @ 2.500Vpc leaving the other cells in a higher state of charge. See Special Note. This can mean that the Full Working Voltage Range is reduced to the Lowest Denominator and as the efficiency over time decreases for any single cell, it will bring down the rest. While you may build a pack with 280AH Cells, a Runner or two could very easily limit it to 270 or even 260AH...
Special Note: Active or Passive Balancers CANNOT Fix this ! An Active Balancer can minimize "take the edge off" but only in a limited way, that is not their purpose or design. Passive Balancing is of little use on Large Cells above 100AH and only actually makes a difference when used with perfect Matched, Batched & Binned cells which are identical.
Please download the Lyuan Tech LifePo guide & Voltage chart from my Signature, they'll help you a lot and explain several things.
Hope it helps, Good Luck.
Steve
BatteryNut
New Member
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- Aug 13, 2021
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Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Amy Wan,
Luyuan Tech on Alibaba,
szluyuan.en.alibaba.com
For a Proper Quote, you must open a Chat or Messenger session and give her the shipping addrtess. The Quote Guesstimator is way out of whack.
Luyuan Tech on Alibaba,
Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery
Shenzhen Luyuan Technology Co., Ltd., Experts in Manufacturing and Exporting Lifepo4 battery, LTO battery and 0 more Products.
szluyuan.en.alibaba.com
For a Proper Quote, you must open a Chat or Messenger session and give her the shipping addrtess. The Quote Guesstimator is way out of whack.
houseofancients
Solar Wizard
Commodity cells are not matched. If using an inverter that does not have adjustable parameters, then it's best to get matched cells unless keeping the SOC of the cells between the knees. Otherwise one will be relying on the BMS for LVD and possibly HVD if using an inverter/charger.
LF280N and LF280K have the same cycle life. 3000 cycles.....with perfect compression. Each was tested with different C rates as noted in the spec sheets. I believe most will find that cells rated 2000 cycles will most likely age before capacity degradation to 80%. And it's possible that's the number of cycles one will get with no or slight compression.
LF280N and LF280K have the same cycle life. 3000 cycles.....with perfect compression. Each was tested with different C rates as noted in the spec sheets. I believe most will find that cells rated 2000 cycles will most likely age before capacity degradation to 80%. And it's possible that's the number of cycles one will get with no or slight compression.
Hello Amy. Thanks for responding. It is difficult to find a honest overseas source for these cells. Your reputation from what I've read is stellar. I will be buying from you. I did get my quote from you via chat on your Alibaba site. I only gave you my zip code
I'm just trying to find out what bulk cells are. SteveS clarified many of my concerns. Thanks Steve.
Chime in if you think I'm wrong. I think a manufacturer of these cells first test them for impedance. Quick and easy low cost test. If they don't fall in range, why test any further. Call them bulk. They are not going to spend the time with a capacity test or C discharge rate if the impedance is off.
I'm guessing, that a low impedance cell will charge faster than a high impedance cell. A out of range impedance bad cell in the pack screws up the BMS charging. The Bms will be affected by the paremeters of the bad cell in the pack.
Does any of this really matter? Yes I may lose 10-20ah and a few cycles in bulk cells as compared to Grade A. I can correct some of these potential problems by only charging the pack to 80-90% of capacity. The big question is: Are Grade A cells in a 16s 48v packs worth $600 more than bulk? If you do the math the answer is no.
Last questions for Amy. Are your Bulk cells new? Are your bulk cells tested.? Do you know what the reject rate at the manufacturer is for Grade A vs Bulk
I'm just trying to find out what bulk cells are. SteveS clarified many of my concerns. Thanks Steve.
Chime in if you think I'm wrong. I think a manufacturer of these cells first test them for impedance. Quick and easy low cost test. If they don't fall in range, why test any further. Call them bulk. They are not going to spend the time with a capacity test or C discharge rate if the impedance is off.
I'm guessing, that a low impedance cell will charge faster than a high impedance cell. A out of range impedance bad cell in the pack screws up the BMS charging. The Bms will be affected by the paremeters of the bad cell in the pack.
Does any of this really matter? Yes I may lose 10-20ah and a few cycles in bulk cells as compared to Grade A. I can correct some of these potential problems by only charging the pack to 80-90% of capacity. The big question is: Are Grade A cells in a 16s 48v packs worth $600 more than bulk? If you do the math the answer is no.
Last questions for Amy. Are your Bulk cells new? Are your bulk cells tested.? Do you know what the reject rate at the manufacturer is for Grade A vs Bulk
Made a mistake. I thought Amy had joined this thread. It was SteveS speaking how to get an accurate quote from Amy. I did use the chat feature and got a quote to my zip.
Let's chew on this. Is it possible that all cells purchased by a distributor like Amy, have passed quality control at the manufacturer. They are bulk. The distributor, like Amy has the luxury because of their large investment to sift though hundreds of cells and pick out the gems. They take these gem cells and test and match. For this effort you pay $600 more
Let's chew on this. Is it possible that all cells purchased by a distributor like Amy, have passed quality control at the manufacturer. They are bulk. The distributor, like Amy has the luxury because of their large investment to sift though hundreds of cells and pick out the gems. They take these gem cells and test and match. For this effort you pay $600 more
Back in this thread BatteryNut tried to compare the rejection rate of these cells to computer processors. Sorry my friend, I'm not buying your analogy. Computer processors have millions of transistors. The probability of a manufacturing flaw is high. Lithium iron phosphate batteries are the same concept as lead acid. Only the chemistry has changed. All the R&D dollars have been spent on the chemistry. Squirt some measured lithium and iron phosphate goo for the Anode and Cathode in the battery, put an electrolyte in the middle and you done. What could go wrong? I am baffled why we don't have any USA manufactures. Come on Elon
