Anyone buying these 305ah envision cells?
- Thread starter G00SE
- Start date
18650 will not replace it?
I have not asked, i dont want to have to take it out I already have it fully built into my XR-04 Enclosure, which I absolutely love BTW, for 250 shipped this thing is really well built, I have a 2nd one coming and will do pictures of it and the 2nd build, it's really nice and for the price unbeatable.
contact them. it seems to be a known issue. happened to me and they replaced it quickly with almost no questions asked
soakupthesun
New Member
So, I'm building my first LiFePO4 pack. 4S2P from new 105AH EVE cells, Overkillsolar BMS. Pretty standard stuff. Then I get to the whole compression topic...
I read the EVE data sheet, and I think we need to be a bit more pedantic about what it says, and more importantly what it doesn't say. The datasheet is only a spec for what comes out of the factory, and how to confirm / measure it (i.e. a QA document). The entire discussion in the datasheet regarding compression is under the section where they are specifying the battery cell dimensions. In other words, since the cells do swell with charging, in order to specify the product dimensions (the thing they are going after) they need to specify how much compression the cells are under. They spec'd 300 kgf for this test, describe the test jig, and under those conditions they show what the cell dimensions should be.
They did NOT specify that the cells should be operated at that compression (nor that they shouldn't be, to be clear). This is only a spec for the conditions to measure the dimensions of the cell.
An email exchange with the 18650 support team said that the cells should be used with compression, and pointed to the datasheet. That, in my pedantic mind, doesn't answer the question.
The only information I have seen about what compression should be applied is the graph that Brucey cited in post #441, but I don't believe that came from EVE.
Has anyone seen an actual "This is how you should mechanically construct a multi-cell battery with these cells." document from EVE?? (Or Envision for that matter, to stay on topic... I was going to use the 305's but they were out of stock.)
I read the EVE data sheet, and I think we need to be a bit more pedantic about what it says, and more importantly what it doesn't say. The datasheet is only a spec for what comes out of the factory, and how to confirm / measure it (i.e. a QA document). The entire discussion in the datasheet regarding compression is under the section where they are specifying the battery cell dimensions. In other words, since the cells do swell with charging, in order to specify the product dimensions (the thing they are going after) they need to specify how much compression the cells are under. They spec'd 300 kgf for this test, describe the test jig, and under those conditions they show what the cell dimensions should be.
They did NOT specify that the cells should be operated at that compression (nor that they shouldn't be, to be clear). This is only a spec for the conditions to measure the dimensions of the cell.
An email exchange with the 18650 support team said that the cells should be used with compression, and pointed to the datasheet. That, in my pedantic mind, doesn't answer the question.
The only information I have seen about what compression should be applied is the graph that Brucey cited in post #441, but I don't believe that came from EVE.
Has anyone seen an actual "This is how you should mechanically construct a multi-cell battery with these cells." document from EVE?? (Or Envision for that matter, to stay on topic... I was going to use the 305's but they were out of stock.)
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houseofancients
Solar Wizard
Wrong topic
Brucey
Solar Wizard
With the A123 graph, we can see that with zero compression lifecycle is 3000. With some pressure applied that shoots up to 6000 and then eventually nearly 20,000 cycles.
The majority of diyers prob won't reach that lower 3000 cycle limit due to having larger battery banks etc and calendar aging, so even if there is no compression applied the lifetime results will be good. But with newer cells like the lf560k rated for 12,000 cycles etc it would seem wise to use a fixture and apply pressure for prismatic cells.
Wouldn't these age out around the same time as a 304ah wasting even more cycles, or do they age differently?
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hardtop
New Member
What material do you think is compliant?
soakupthesun
New Member
I understand and agree that many of us may not live long enough to wear out these batteries. But what surprises me is that the battery cell manufacturers themselves seem to be mute on the basic parameters to actually build a proper, safe, multi-cell battery pack using their cells. Is this information only given to an OEM under NDA, leaving the DIY community on its own to figure it out for ourselves? It definitely appears that some sort of compression is desired (yet, see below), but how much?
The only other base component involved in a multi-cell battery is the BMS. I've looked around the OverkillSolar site, and they don't say anything about compression. No surprise, as it's really not their responsibility. But there is a picture of an 8-cell battery using their own LiFePO4 cells showing threaded rods holding things together. Interestingly their 100AH "Industrial" cells seem to have plastic top and bottom caps that are wider than the cell itself, preventing any compression of the cell material. Is this the exception that proves the rule?
It would be really nice to have (find?) some sort of official statement on multi-cell battery assembly from the cell manufacturers themselves. Lacking that, we're potentially misinterpreting the information that they do provide (my point earlier).
Q-Dog
¯\_(ツ)_/¯
It is not possible the manufacturers are building cells to the automotive customer's parameters? and since we are not the original designed use, they just don't have the info you seek?
LFP Aries pack in Tesla. Zoom in on the chart in this video (it's very readable in Highest Definition) at this time stamp:
Ah, forgot to mention, a little further on in the video (16:00 timestamp) you can see the LFP Tesla pack with prismatic cells in their fixture.
Ah, forgot to mention, a little further on in the video (16:00 timestamp) you can see the LFP Tesla pack with prismatic cells in their fixture.
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Throwing this out there and no, haven't watched the video ... have to get to work. Automotive battery packs will probably be cycled more frequently with higher charge and discharge rates than most solar storage systems therefore, they may actually need the extra cycles? They also live in an environment that is mobile with abrupt motions, even crashes, that may require some type of containment?
soakupthesun
New Member
I'd settle for what the automotive folks have to design to. At least it could provide a baseline.
soakupthesun
New Member
ACK! I just noticed that EVE *does* indicate a compression spec (same 300 kgf) under "Cycle life" in their datasheet. Missed that. So, please excuse the dust.
Is there a similar spec for the 305 AH Envision cells? I wonder how universal this is. I haven't found it in their datasheet.
Sverige
A Brit in Sweden
Are the Envision 305s a wet cell like Eve, or one where the Electrolyte will not be heard sloshing around if they are tipped?
HughF
New Member
Wet cell….. Just taken delivery of 16 and a mason 280L kit, currently £1500 at fogstar, delivered. Thats a bargain.
I have put in around 100 cycles on my 2 packs and they have been very reliable. All cells are still well balanced using just the Seplos passive balancer. It’s summertime here, so I fully charge and discharge all my packs almost daily these days. Good bargain.
HughF
New Member
Mine are still top balancing…. Yawn
I went to 3.5V per cell today, which I rarely do. These cells are almost six years old.
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