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EVE LF280 Charge/Cutoff Voltages

Colonel.lp

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Jun 8, 2020
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I'm waiting to build my bank for a camper, and since a lot of us on here have built batteries from the Eve 280ah cells. I'm interested to know what voltages you have picked for your end charge point and low cutoff point and what usable percentage you believe that is giving you?
Please give your per cell voltages so it's easy to compare.

Personally I'm not interested in making these cells last 10+ years, 5 years will do me. I want good usable capacity over the winter months when my solar is useless. I'm thinking 10% to 90 or 95%
 
I'm waiting to build my bank for a camper, and since a lot of us on here have built batteries from the Eve 280ah cells. I'm interested to know what voltages you have picked for your end charge point and low cutoff point and what usable percentage you believe that is giving you?
Please give your per cell voltages so it's easy to compare.

Personally I'm not interested in making these cells last 10+ years, 5 years will do me. I want good usable capacity over the winter months when my solar is useless. I'm thinking 10% to 90 or 95%

With the disclaimer that I dont own these cells so this is pretty speculative and based on the datasheet, I think:

I think 85-95% usable capacity, daily cycling, and a goal of 5+ years, should be doable, particularly if you (1) can mostly avoid cell temps above 85 to 90ish, fahrenheit (2) can mostly charge and discharge below 0.5C, (3) can mostly avoid charging below 40*F and totally avoid charging below freezing, and (4) can mostly avoid dipping below 10% or 15% even if you do so sometimes.

I suspect a bandwidth in the ballpark of 2.9-3.1 to 3.5-3.6 would give you the cycle life you want, and maximize usable capacity. Its hard to tell specifics based on the discharge curve which is pretty coarse, and no charge curve is shown:
Screenshot_2020-10-12 德赛能源科技有限公 标准文件 - LF280 (3 2V 280Ah) Product Specification(Version E)-201...png
One thing to bear in mind is that the standard discharge curve in datasheets is at 25*C, at lower temperatures, the curve may be more gradual and at a slightly lower voltage:
 
EVE recommends compressing the cells (to keep the cells from expanding) for extended cycles from 2000 cycles to 3500 cycles. Of course another reason to compress the cells is to keep the cell terminals from being stressed.

If the cells are mounted in a fixture so they can't expand, then one can expect to get 3500 cycles and have 80% capacity left if charged and discharged at 1C rates. A cycle is measured each time the battery is fully charged to 3.65 volts and discharged to 2.5 volts.

Assuming ideal temp conditions, of 25±2 centigrade, and not storing the cells with a high SOC, the cells would last for 9.5 years if run through a full 1C cycle every day.

Even if the cells are not compressed they would last for 5.5 years.

If implementing the above at 45 degrees centigrade then there is a drastic change and the number of cycles expected is 1800 cycles with the cells compressed.

This is all noted in the EVE spec sheet. EVE does note standard charge and discharge rates to be .5C.

So the way I read the spec sheet the cells will last a very long time under ideal conditions.
 
The cells will be at between 10 & 20°C mostly
Charge rate will be 0.3C max every 3 days over winter, in summer the solar will be topping the back up at less than 0.1C
Have some 10mm aluminium plate coming and threaded bar to clamp the cells.

So looking at your comments 3.1 to 3.5 looks good. Guess I will monitor current to see what's going on at the top end.
 
EVE recommends compressing the cells (to keep the cells from expanding) for extended cycles from 2000 cycles to 3500 cycles. Of course another reason to compress the cells is to keep the cell terminals from being stressed.
.
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Hi, can you provide a reference to this info? I couldn't find it in the EVE datasheet that I have. It seems your data is more comprehensive.
Thanks.
 
Hi, can you provide a reference to this info? I couldn't find it in the EVE datasheet that I have. It seems your data is more comprehensive.
Thanks.
I have attached the latest spec sheet I know of. It's under the heading 5.1 Electrical performance. Note the tests were conducted at 1C charge and discharge rates. I also contacted the company directly because I was confused about the part that notes a 300kgf fixture and they replied and basically said the reason is to keep the cells from expanding. There are pouches inside of prismatic cells and it's been said they can delaminate if allowed to expand and contract. Makes sense to me.

Having said that there is a lot of discussion on the forums concerning this and different ways people have compressed their cells. I am planning on using .5 inch plywood and threaded rods. I will tighten the nuts so they are snug and maybe use a bit of blue Loctite. From what I have read it's best to do this with the cells at around 50% SOC. However if I don't notice any expansion after top balancing I am going to proceed to mount them. I will be top balancing with a 10 amp power supply so I don't anticipate any expansion.
 

Attachments

  • EVE LF280N-72174  Specification.pdf
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This info can also be found in the datasheet in the resources section of this forum which is. I believe it is a revision from 2018 Early 2019, and at this point our best guess (evidenced, but unconfirmed) is that these cells are all from 2018ish. Older versions may not have referenced fixture but Revision E (2019 certainly does). What version of the datasheet do you have?
 

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  • LF280-RevisionE-2019.pdf
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Last edited:
I have both versions. The one I attached is Version A Effective Date:2019-12-22. Version B is dated: Effective Date:May 25th, 2018
The reason I attached version A is because that's what everyone is referencing regarding the compression force and I didn't want to confuse solarsimon.

Version B also mentions compression as follows:

"Test should be conducted with new batteries within one month after shipment from our factory
and the cells shall not be cycled more than five times before the test. Unless otherwise defined, test
stated in this specification should be conducted at temperature of 25±2℃, humidity 45~85% and Test
should be performed under standard atmospheric conditions with 86KPa~106KPa pressure."
 
I have both versions. The one I attached is Version A Effective Date:2019-12-22. Version B is dated: Effective Date:May 25th, 2018
The reason I attached version A is because that's what everyone is referencing regarding the compression force and I didn't want to confuse solarsimon.

Version B also mentions compression as follows:

"Test should be conducted with new batteries within one month after shipment from our factory
and the cells shall not be cycled more than five times before the test. Unless otherwise defined, test
stated in this specification should be conducted at temperature of 25±2℃, humidity 45~85% and Test
should be performed under standard atmospheric conditions with 86KPa~106KPa pressure."
That pressure is, in my opinion, only referring to atmospheric pressure. 86KPa~106KPa pressure is 860-1060 mBar. I hate kPa.
So this is really just saying only test them in regular atmospheric conditions, not in a diving bubble or plane or whatever.

Thanks for the attachments. I have version E too - but hadn't interpreted it in the same manner as you
 
That pressure is, in my opinion, only referring to atmospheric pressure. 86KPa~106KPa pressure is 860-1060 mBar. I hate kPa.
So this is really just saying only test them in regular atmospheric conditions, not in a diving bubble or plane or whatever.
Thanks. My bad. I hate the older EVE spec sheet...lol.
 
In case its not clear (I'm sure it isn't since A comes after E here) the order of the revisions we are discussing goes:

2017-10LF280 Revision A
2018-5LF280 Revision B
2018-9LF280 Revision C
2018-11LF280 Revision D
2019-4LF280 Revision E
2019-12LF280N Revision A

Blue is the revision I mentioned, Red is the datasheet Gazoo mentioned, which is the first version of the new datasheet. (I'm not 100% sure whether they reset the revision versions because its a new datasheet or if it is a new cell altogether). In either case, both recommend fixture, I believe.

In regards to the explicit mention of fixture compression, when I first discovered and brought up the point about 'fixture' / light compression back in May, I was referencing the Revision E version of the datasheet. You can read through that original discussion here (at least pages 1 and 2 are worth reading, beyond that I can't remember), It includes screenshots of the relevant sections which are explicitly referring to 'fixture' not atmospheric pressure. [edit:] This post has further context
 
Followup:

300 KGF = 2942 Newtons = 661 lbs

Applied to the broad side of an EVE cell (17.36cm x 20.48cm) = roughly 12 PSI

-----

Attached screenshots are from the LF280 Rev E datasheet
 

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  • Screenshot_20200530_175100.png
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However - your earlier post mentioning 300Kgf seems pretty unambiguous. That's pretty much saying "park a small car on top of the cell"
And that's why I was implying to not make it complicated as others have. I also relayed to you what EVE told me. This discussion while good has been beat to death. There are numerous threads concerning it. Dzl has posted one of the threads discussing it and has cleared up what 300KGF means regarding compression. 12 lbs per square inch. I believe EVE is saying to mount the cells in a fixture that will keep the cells from expanding and that's what they told me, and my .5 inch plywood and threaded rods will be fine....lol.

I will copy and paste my discussion with EVE. I wasn't going to and I know I probably shouldn't. I left out the EVE technicians name. Other than that this is it.

Dear sales:
Could you please explain the following quoted from your 280ah cell specification:

"At 25±2℃,the battery under 300kgf fixture : charging the cell with charge current 1.0C(A) and constant voltage 3.65V,0.05C cut off,rest for 30min,discharge to 2.5V cut off with the current of 1.0C(A),rest for 30min,and then start the next cycle,end with the capacity decrease to 80% of the initial capacity.The number of cycles is defined as the cycle life of the battery."

Why is a fixture required?

Is it to prevent expansion of the cells for longer cycle life?

If the cells are mounted in a fixture so they can not expand will that work?

Please reply and explain. Thank you.


EVE's REPLY:

Hello,

Your understanding is right. During the charge & discharge process of battery, the cell will “breath” like people does- swell & shrink effect.

The function of fixture, we use the clamp, is to prevent the over-swelling effect, which is likely to cause electrolyte leak furthermore.

Thus the fixture will guarantee longer life.

Thank you & Best Regards
 
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