Anyone buying these 305ah envision cells?

[hardtop]

That's because you had them clamped since they were new. But clamping them without compliant material risks damaging them long term as they age.

What material do you think is compliant?

 

[soakupthesun]

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.

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]

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).

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?

 

[upnorthandpersonal]

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.

 

[Kornbread]

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]

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?

I'd settle for what the automotive folks have to design to. At least it could provide a baseline.

 

[soakupthesun]

I'd settle for what the automotive folks have to design to. At least it could provide a baseline.

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]

Are the Envision 305s a wet cell like Eve, or one where the Electrolyte will not be heard sloshing around if they are tipped?