EVE-280 cells should these be clamped tight or spaced for expansion?

[ArthurEld]

You are ambitious.

Now this is what I was talking about with the uneven sides to the eve cells. You can see the marks on my end plate where they are touching. A thin line across the top and 4 thin patches vertically down the sides. I would say it's the same on all cells. Hmmmmm.
View attachment 27330

It's a shame @ghostwriter66 has already spoken to the engineers, I would have been interested what their take on this is in relation to compression.

Is that painted wood? It looks good.

 

[Colonel.lp]

You are ambitious.

Is that painted wood? It looks good.

How do you mean ambitious?

Thanks, Sprayed 10mm aluminium plate. The surface had a slight texture.

 

[Colonel.lp]

Make a mold in some sand, put a plastic saran wrap, then pour in a little clear epoxy for a perfect fit spacer.

Crystal Clear Bar Table Top Epoxy Resin Coating for Wood Tabletop - 1 Gallon Kit: Amazon.com: Industrial & Scientific

Crystal Clear Bar Table Top Epoxy Resin Coating for Wood Tabletop - 1 Gallon Kit: Amazon.com: Industrial & Scientific

www.amazon.com

I think two boards with this small innertube would allow measuring PSI.. I'm guessing 0%-100% charge size difference wouldn't make much of a difference in pressure since it's such a small relative distance.

Amazon.com

edit: this one looks better for this use.

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Epoxy did cross my mind too, but I need to draw the line somewhere. ? While the pack is up on the bench, I might try some 1mm neoprene sheet I've got lying around just to see how it holds up over time. The way things are going, these cells will be replaced, maybe the lishens are flatter.

 

[ArthurEld]

How do you mean ambitious?

Thanks, Sprayed 10mm aluminium plate. The surface had a slight texture.

lol, that ambitious line was for the guy with the resin and inner tube.
I decided not to reply to his post but forgot to remove the sentence.

Your plate looks good. I thought about painting wood black.

 

[SuperShort]

The way things are going, these cells will be replaced,

Are these new EVE? Are you having issues with them? I'm about to order some, but Basen just said they are GradeA-5 not A-1??
I'm waiting to see what that means exactly. Lishens would be around $100 cheaper, but I thought EVEs were better.

 

[Colonel.lp]

Are these new EVE? Are you having issues with them? I'm about to order some, but Basen just said they are GradeA-5 not A-1??
I'm waiting to see what that means exactly. Lishens would be around $100 cheaper, but I thought EVEs were better.

These are new eve from xuba, but my problems have not been experienced by others, at least not in this forum. I've not heard of the grading scale being used, I would be interested to know what the grades stand for. Why do you think the eves are better? I've not looked into the lishens yet.

 

[Colonel.lp]

lol, that ambitious line was for the guy with the resin and inner tube.
I decided not to reply to his post but forgot to remove the sentence.

Your plate looks good. I thought about painting wood black.

I thought the same, great idea but beyond my patience at the moment, although have thought about using pourable epoxies for other projects, it looks fun.

I think the black end plates and spacers with the red springs will look good, shame it's going to be hidden in a locker on my campervan.

 

[SuperShort]

Basen said the Lishen are normally 272ah, but a 'good matched' set will deliver 280ah. The EVE are 280ah normally. I'm guessing better quality/standards, but who knows. Specs even put the Lishen's 3mm or so taller. I'll post what they say about the grades.

 

[Luthj]

I think we need to adjust our expectations some. CALB and some others under state their capacity. And as they improve the MFG, the capacity can rise some with time as well.

In the case of EVE, I think they are keeping the best cells for their premium channel sales. We should expect the 280AH to be the absolute maximum, and really most applications aren't going to be using the bottom 5-10% for longevity reasons. Given how cheap these cells are compared to other low volume channels, I can't say we aren't getting a decent deal/value.

 

[DThames]

This was enough for me when built it last month. I just tightened the thread rod until it felt snug.

Ampster, can you provide more photos? Maybe a wider shot and include the top? I am looking for ideas. (Thanks)

 

[SuperShort]

Also, with Aluminum, I would be worried about having conductive material raised up above terminals. I'm thinking using Poplar instead may help spread load a little over a slightly uneven surface since it will give a little on the high spots and it's not conductive for a little extra safety.
I'm clumsy and will probably drop a wrench or busbar across the aluminum and terminal.

 

[Colonel.lp]

Also, with Aluminum, I would be worried about having conductive material raised up above terminals. I'm thinking using Poplar instead may help spread load a little over a slightly uneven surface since it will give a little on the high spots and it's not conductive for a little extra safety.
I'm clumsy and will probably drop a wrench or busbar across the aluminum and terminal.

I've sprayed my aluminium, however the plates shouldn't be connected to either terminal.

 

[DThames]

Which one of those did you get? Did you have any problems buying from them direct? How much did they cost?

I was looking for an online seller. There is a vendor on Ebay that is selling the Danly springs (toolandequipsales) and I was considering sending them a message to see if they could get the ones I was looking for.

I am looking at these.

 

[DThames]

I am a LONG ways from being a mechanical engineer, but maybe one will check in.

Here is my theory.
Assuming we are in agreement that the desired pressure is 12 PSI,
The first step would be to determine the square inches for the side of the battery. For my 7" x 8" battery that would be 56 Sq inches.
Second, Multiply that by 12 to get the desired total pressure. For mine that is 56 x 12 = 672 lbs force.
Third, divide 672 by the number of threaded rods to get the pressure / rod. 672 / 4 = 168 lbs per rod.
Fourth ... convert that to KG. So we need a spring with 76.2 KG at a reasonable compression rate.

So .... for my batteries it looks like the 93-2030 on page 15 might be a good fit. (They show how much to compress it for 3 different pressure on the right side of the chart. Every spring in that group has the same capability but with different lengths.

I am not an ME either but I have been talking to one that I work with and trust. You are correct. You take 4 of the springs as seen below and you get about 10.2 PSI on the Eve 280ha (with 53.6in^2 surface) if you compress them to max deflection. 137x4

Maximum Deflection Load (Lb.)	137.00
Maximum Deflection (Decimal Inch)	0.3000

 

[Bob B]

I am looking at these.

Might be a little cheaper here if you consider free shipping .... and have a few spares. https://www.ebay.com/itm/DANLY-9-1204-26-RED-DIE-SPRING-3-4-X-1-7PCS-AB2491-7/281898130096?

 

[Bob B]

Here's a list of ones that will give 160 Lbs at max compression .... 4 of those will be almost 11.5

https://www.mscdirect.com/browse/tn/?searchterm=160+max+deflection&hdrsrh=true

 

[Gone]

I've decided to use HDPE; my Basen cells arrive via FedEx Monday, so will start with the grub screws, etc. Looking forward to implementing everything I've learned in these forums over the last two months while waiting on the seemingly forever shipping...

 

[Dzl]

Am I correct in thinking that the proper specs for springs would differ depending on how many cells 'inline' are being compressed and home many 'rows' of cells are being compressed by one fixture?

For instance, would optimum spring parameters differ with, say:
Four cells 'inline'
or
Sixteen cells 'inline'
or
Sixteen cells in two rows of 8

My thinking is there is each cell inline expands and contracts by roughly (whatever EVE says in the datasheet, 0.5MM? ) So 16 inline what be 4x the expansion/contraction as 4 inline, and thus would have a higher and lower max and min pressure for a given spring specification.

With multiple 'rows' I'm less clear on the effect. Do the calculations need to be doubled to achieve the same pressure?

 

[Bob B]

With multiple rows, the total Sq inches of the side to be compressed would have to be calculated and the spring pressure determined from there ... but if the number of rows are doubled, and the number of rods is also doubled ... the spring pressure would remain the same.

With more cells in a row, I don't think the pressure would vary since every cell in the row should have the same pressure.

 

[Luthj]

Am I correct in thinking that the proper specs for springs would differ depending on how many cells 'inline' are being compressed and home many 'rows' of cells are being compressed by one fixture?

It depends on your desired compression tolerance range from 0-100% SOC. The greater the total spring compression distance, the less sensitive it is to changes in pack length due to SOC. Its fairly easy to calculate.

Pack length change / Total spring compression distance = % change in clamping force.

So for a 16 cell stack that's something like 8mm max? So then a spring with 16mm of compression would result in a 50% tolerance. So if you set the spring at 50% SOC, then you would get +25% force at 100% and -25% force at 0%.

If this range is too great, simply choose a spring which requires more total travel to reach the desired clamping force. lets say 32mm. so 8/32=25% or plus/minus 12.5%

Of course I am just using ballpark numbers, and the cells may not expand that much at all. Remember the springs solid height needs to be avoided to prevent the clamping force going very non linear.