Could use a plate or support for the ends to give some moderate pressure.Duct tape would provide zero pressure on that face.
Could use a plate or support for the ends to give some moderate pressure.Duct tape would provide zero pressure on that face.
I didn't say it was the same product.This is absolutely not the same product as Rogers Corp EVExtend Poron foam. Review the specs, they are not the same thing at all.
You could, but spec is 300kg or 661 lbs. I'm not sure duct tape is that strong.Could use a plate or support for the ends to give some moderate pressure.
I haven't looked at plate design yet, but that has a gut feel of sufficient. Assuming a 1/2"-13 thread, it has a minor diameter of 0.404". Using the tensile yield strength of common A36 steel, that rod would yield at around 4,600 lbs. (0.128 sq in of solid area * 36,000 psi).5/16" plate steel and 1/2" threaded rod? Those I have in the garage.
You must think these cells are like hydraulic pressure. They aren't.I haven't looked at plate design yet, but that has a gut feel of sufficient. Assuming a 1/2"-13 thread, it has a minor diameter of 0.404". Using the tensile yield strength of common A36 steel, that rod would yield at around 4,600 lbs. (0.128 sq in of solid area * 36,000 psi).
Using 4 rods, each should only see 165 lbs at ~12psi. The problem with threaded rod is there is no compliance, no stretch, at these low loads. The expanding cells would be pushing against the solid wall of the end plates. Who knows how high the pressure might be?
The SDS of the McMaster materials says it's Rogers Corp Poron. The 4701-40 is rated (soft), and the 15 pcf from the description has a spring rate that's in the 11 psi range at 25% compression.This is absolutely not the same product as Rogers Corp EVExtend Poron foam. Review the specs, they are not the same thing at all.
Well the manufacture of pretty much every large prismatic cell call out a fixture pressure during cycling, so yes I do believe they require a force applied to the wide side to control expansion. They've even went to lengths of testing cells to show the lifetime benefits of compression at a specific pressure. I suspect they know something.You must think these cells are like hydraulic pressure. They aren't.
First problem with springs on the end is the ability of the cells to actually move inside the fixture. You might not think it's important. however for an application such as my truck camper, the springs would be worthless. Have you seen any EV manufacturer use springs for a compression fixture? I haven't. There is a reason why.
BTW, my end plates have foam on them.............
Rogers manufactures many types of Poron foam. Just was making it clear that the linked foam is *not* the Rogers Corp Poron foam designed for battery applications - specifically called EVExtend - and has entirely different properties & thicknesses than many of the poron foam products that people have been linking from mcmaster/grainger.The SDS of the McMaster materials says it's Rogers Corp Poron. The 4701-40 is rated (soft), and the 15 pcf from the description has a spring rate that's in the 11 psi range at 25% compression.
My cells have not moved at all, they are clamped at 640lbs. But they are mounted on vibration dampers. They do expand length wise I can see the spring length change from 10% to 90% soc, so I would be concerned about too much pressure building in a ridged fixture. My cells are in a work rig that is driven on very rough roads.You must think these cells are like hydraulic pressure. They aren't.
First problem with springs on the end is the ability of the cells to actually move inside the fixture. You might not think it's important. however for an application such as my truck camper, the springs would be worthless. Have you seen any EV manufacturer use springs for a compression fixture? I haven't. There is a reason why.
BTW, my end plates have foam on them.............
Every manufacturer of off-the-shelf batteries uses a rigid enclosure though, and the higher end ones include foam on one side to, presumably, take up some of that pressure from expansion under full charge.My cells have not moved at all, they are clamped at 640lbs. But they are mounted on vibration dampers. They do expand length wise I can see the spring length change from 10% to 90% soc, so I would be concerned about too much pressure building in a ridged fixture. My cells are in a work rig that is driven on very rough roads.
No, I get they're not exactly the same, the 4701-40 at 15pcf is the closest material to the EVExend that is available to consumers. Too many unknowns for me, that's why I decided to design using springs.Rogers manufactures many types of Poron foam. Just was making it clear that the linked foam is *not* the Rogers Corp Poron foam designed for battery applications - specifically called EVExtend - and has entirely different properties & thicknesses than many of the poron foam products that people have been linking from mcmaster/grainger.
Edit: I actually spoke with people at Rogers and the only way to get the Poron foam EVExtend product (which is their foam specifically designed for this purpose) you need to go through one of their preferred converters.
Here's a link to the LEGIT Rogers foam product that is engineered for this purpose: https://rogerscorp.com/elastomeric-material-solutions/poron-industrial-polyurethanes/poron-evextend
From what I've been reading, no pressure is preferable to over pressure. Are these name brand batteries and are they using prismatic cells?Every manufacturer of off-the-shelf batteries uses a rigid enclosure though, and the higher end ones include foam on one side to, presumably, take up some of that pressure from expansion under full charge.
Excellent news. I was thinking of using isolation dampers too.My cells have not moved at all, they are clamped at 640lbs. But they are mounted on vibration dampers. They do expand length wise I can see the spring length change from 10% to 90% soc, so I would be concerned about too much pressure building in a ridged fixture. My cells are in a work rig that is driven on very rough roads.
Absolutely, everyones favourite unit (gyll lifepower4) is built like this, and if you watch LithiumSolars YT he tears down a bunch of different batteries and shows what all the manufacturers are doing.Are these name brand batteries and are they using prismatic cells?
.5mm per cell.What's still unknown is the amount of expected growth
You are right, that is the problem. No one knows what happens if you do not allow the ~0.5mm of expansion to happen or how much pressure is built up within the cell. Does the short side expand instead? top and bottom? What pressure do they actually see? You are right to not absolutely confine them.I haven't looked at plate design yet, but that has a gut feel of sufficient. Assuming a 1/2"-13 thread, it has a minor diameter of 0.404". Using the tensile yield strength of common A36 steel, that rod would yield at around 4,600 lbs. (0.128 sq in of solid area * 36,000 psi).
Using 4 rods, each should only see 165 lbs at ~12psi. The problem with threaded rod is there is no compliance, no stretch, at these low loads. The expanding cells would be pushing against the solid wall of the end plates. Who knows how high the pressure might be?
Thanks, is that 0.5mm documented someplace or is that your experience? And is that under a known load, or free to roam?.5mm per cell.
There was a spec sheet posted somewhere for the EVE cells that had a width at 30% state of charge and another width listed at 100% state of charge. Unfortunately I no longer remember where I saw that particular document, it might have been in one of LithiumSolar's videos on the subject.Thanks, is that 0.5mm documented someplace or is that your experience? And is that under a known load, or free to roam?
As others have said, it is documented. In my own personal experience, it's been just under .5mm measured in a compression fixture. I used .5mm in all my design decisions though.Thanks, is that 0.5mm documented someplace or is that your experience? And is that under a known load, or free to roam?