What is the easiest way to compress prismatic Cells?

[Wet1]

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

Too funny, I'm an engineer for a major film coater and most of the names on that list (including Roger) are customers of ours!

Even though I could likely get the foam for free, I would feel more comfortable using springs as I'd think they are likely to have a more consistent load over time and at temp extremes. Something like this would probably work well over the life of the batteries:

https://www.oreillyauto.com/detail/c/melling/melling-valve-spring/mel0/vs360?q=Melling+VS-360&pos=0

Just my 2 cents...

 

[MiPaul]

Too funny, I'm an engineer for a major film coater and most of the names on that list (including Roger) are customers of ours!

Even though I could likely get the foam for free, I would feel more comfortable using springs as I'd think they are likely to have a more consistent load over time and at temp extremes. Something like this would probably work well over the life of the batteries:

https://www.oreillyauto.com/detail/c/melling/melling-valve-spring/mel0/vs360?q=Melling+VS-360&pos=0

Just my 2 cents...

I haven't seen that much data on valve springs. I was looking at oval wire die springs, for the same reasons as you.

 

[S Davis]

double post

 

[S Davis]

I haven't seen that much data on valve springs. I was looking at oval wire die springs, for the same reasons as you.

These are what I used, they were about $6.00 when I bought them, the price has gone up.

Die springs

 

[Wet1]

I haven't seen that much data on valve springs. I was looking at oval wire die springs, for the same reasons as you.

They are essential the same thing. The data is listed in the link I provided and should be a good fit (IMO) for this use. Obviously preload them. Buying these from a parts store is cheap and typically have them on hand or can get them for you next day. They're typically about $3-$5 each.

Pro tip, clean and paint them to keep them from rusting...

 

[curiouscarbon]

Who knows how high the pressure might be?

Only way to know is to include a sensor.

There are load cells that can go on the threaded rod, that can measure the force, which with surface area can be converted to PSI.

Springs and foam are two compliance materials that seem quite popular.

I plan on using solid metal end plates, threaded rod, and some poron foam that is not battery specific. For at least the first pack, also load cells to directly measure the forces.

Lots of great examples of how to properly calculate the spring option, which is also great.

The extra space added by the springs is extremely undesirable for this build, which motivates the sensor and foam only approach.

 

[Ozark Tinkering]

The last couple of videos I've seen indicate (to me anyway) that compressing the cells isn't necessary? Check out Will's last video on that, also Signature Solar has a video indicatng that none of their EG4 packs have compressed cells, in fact they are spaced apart far enough to see daylight from the other side...

 

[Wet1]

The last couple of videos I've seen indicate (to me anyway) that compressing the cells isn't necessary? Check out Will's last video on that, also Signature Solar has a video indicatng that none of their EG4 packs have compressed cells, in fact they are spaced apart far enough to see daylight from the other side...

The data from Eve seems to suggest under compression the Ah drop off quicker at the early part of the cell's life, but significantly extends useable Ah for the remainder. I don't have the graph handy, but it was enough to make me realize it's wise to use compression if you're looking to get maximum life out of the batteries. Clearly the manufacturer knows more than we do on this topic, so who am I to argue?

Regarding the videos, with the money Will is making off YT and getting free batteries in the mail weekly/monthly, I'm sure he doesn't care about maximum cell life. The guys selling them likewise have space and financial constraints, not to mention do you really think the consumers buying these pre-fab batteries will notice the difference or care 5-10 years from now? Chances are either the sellers will no longer be around, or the technology will have moved on to something better anyway.

 

[RV10flyer]

132 kwh bank. All 16s batteries surrounded by 3/8" thick ceramic cloth. Oak end plates cut 8" X 13 3/4". Install one or two 1" ratchet straps around each battery. Tighten light-med tension. 3-5 minutes of cutting/assembly...done. Easy to loosen to replace cell. Cut off excess strap.

 

[curiouscarbon]

Regarding the videos, with the money Will is making off YT and getting free batteries in the mail weekly/monthly, I'm sure he doesn't care about maximum cell life. The guys selling them likewise have space and financial constraints, not to mention do you really think the consumers buying these pre-fab batteries will notice the difference or care 5-10 years from now? Chances are either the sellers will no longer be around, or the technology will have moved on to something better anyway.

i'm weird consumer, me want 20 year operation lifetime battery.

regulating LFP temps to between 15-30C

restraining cyclic casing flexture of large format cells

these two simple avenues seem to offer me something approaching what i want :D


lead acid requires maintenance so frequently. i was lazy and allowed a small bank to boil over due to neglect. cleaning up was annoying. want 20 years of no watering and it still works, because the 2-5 year design life of most commercial devices leaves me unsatisfied

maybe it'll be replaced sooner than expected

but i wish to assume not ? and design from there

cheers

 

[curiouscarbon]

The data from Eve seems to suggest under compression the Ah seems to drop off quicker at the early part of the cell's life, but significantly extends useable Ah for the remainder.

yea! that pattern confused me at first.
slightly accelerated early aging
notably decelerated late aging

I don't have the graph handy, but it was enough to make me realize it's wise to use compression if you're looking to get maximum life out of the batteries.

?
nobody "has to" compress their cells.

but it is clear to me that there is a measurable and significant impact on projected operational runtime.

so i continue to consider it a worthy endeavor for builders interested in long operation time?

 

[Zwy]

The data from Eve seems to suggest under compression the Ah drop off quicker at the early part of the cell's life, but significantly extends useable Ah for the remainder. I don't have the graph handy, but it was enough to make me realize it's wise to use compression if you're looking to get maximum life out of the batteries. Clearly the manufacturer knows more than we do on this topic, so who am I to argue?

Regarding the videos, with the money Will is making off YT and getting free batteries in the mail weekly/monthly, I'm sure he doesn't care about maximum cell life. The guys selling them likewise have space and financial constraints, not to mention do you really think the consumers buying these pre-fab batteries will notice the difference or care 5-10 years from now? Chances are either the sellers will no longer be around, or the technology will have moved on to something better anyway.

I agree, the charts showed lower lifespan without compression. Calendar aging may play into longevity here more than compression/non compression, especially if cells are not cycled fully. As for the CATL and EVE videos, those banks are being built for EV's which will kill the cells long before calendar aging as the EV's could run 1C rates. Many also have bank cooling to keep temps down.

Considering the C rates of discharge and charging in a solar system, compression and calendar aging would have a larger effect than C rate charge/discharge.

 

[CB-OTB]

what constitutes a “cycle”? If a battery is partially depleted to 60%, recharged back to 80%, is that a cycle? What about down to 75% and recharged back to 80%”

 

[Rossman]

A cycle is typically defined as fully depleting and then fully charging

 

[NwCali]

Hello,

I am thinking about would be the easiest way to compress 16S (~300ah) cells?

Seems like everyone is using thread rods and springs. Is that easiest to apply compression to keep the battery cells from moving?

Any other simple solution instead of having to build a compression structure with threaded rods + springs?

Thanks

Run them over with your car, well, its easy, not very effective though.

 

[CB-OTB]

A cycle is typically defined as fully depleting and then fully charging

How many of us actually do that? In my use case, I might do this 300 times over a 10 year period. ”might” being the key word. In my case, I am more interested in keeping them from shifting and putting pressure on the terminals than I Am cycling these batteries out of life.

 

[Wet1]

what constitutes a “cycle”? If a battery is partially depleted to 60%, recharged back to 80%, is that a cycle? What about down to 75% and recharged back to 80%”

I believe they spell out all the conditions in the spec sheet.