Cell compression: zip ties and lexan?

[Batvette]

First thread. Recently ordered 8 lishen 272 ah cells for 2 4 cell banks in my van.
Trying to keep it simple. Is there any reason why i cant accomplish cell compression using 2 or 3 175# zip ties? The ones that are like 3/8" wide. Theyre insanely strong.

HellermannTyton T150XL0X2 Heavy Duty Cable Tie | Waytek

HellermannTyton T150XL0X2 Heavy Duty Cable Tie Nylon, 175lb, 43", 25 Per Bag is in stock and ready to ship. Order today!

www.waytekwire.com

I was thinking of using clear lexan polycarbonite, (not acrylic plexi) 1/8" between cells and 1/4" on the ends.
I could oversize the lexan spacers and ends by 3/8" on each side and drill/cut a slot so the zip tie can hold it all together, the plates would keep the zip ties from moving.

 

[cargovanconversion]

First thread. Recently ordered 8 lishen 272 ah cells for 2 4 cell banks in my van.
Trying to keep it simple. Is there any reason why i cant accomplish cell compression using 2 or 3 175# zip ties? The ones that are like 3/8" wide. Theyre insanely strong.

HellermannTyton T150XL0X2 Heavy Duty Cable Tie | Waytek

HellermannTyton T150XL0X2 Heavy Duty Cable Tie Nylon, 175lb, 43", 25 Per Bag is in stock and ready to ship. Order today!

www.waytekwire.com

I was thinking of using clear lexan polycarbonite, (not acrylic plexi) 1/8" between cells and 1/4" on the ends.
I could oversize the lexan spacers and ends by 3/8" on each side and drill/cut a slot so the zip tie can hold it all together, the plates would keep the zip ties from moving.

Cant give you a qualified answer, but that should work fine.
I have the same batteries and setup but used the threaded rods and plywood ends. You can see it here:

 

[HRTKD]

You don't need anything between the cells. Check the deflection of the 1/4" material. It may not be stiff enough. I haven't worked with that material enough to say one way or the other, just raising the point.

The problem with the zip ties is that you don't know how much compression they are or are not creating. Maybe it's enough, maybe it isn't. It's likely better than nothing.

 

[Batvette]

Cant give you a qualified answer, but that should work fine.
I have the same batteries and setup but used the threaded rods and plywood ends. You can see it here:

Looks like it works. Im thinking zip ties and lexan because they dont add much bulk.
Q: looked at a few of your videos, wish I had such a spacious vehicle to work with. Mine is a 3rd gen honda odyssey, I guess the trade off is that it drives like a car. Anyway, flexible panels. 3 years later how are they holding up? You keep it garaged? Flexible panels would have been so much easier but didnt see any that had stellar reviews. Ended up buying 2 hqst 100 watt panels, just finishing an aluminum mounting frame. They were the only ones that would fit between the odysseys roof rails. Looking for stealth too. Plus I might adapt the frame to be able to tilt up on either side, with a second frame and two pairs of hinges. Maybe powered with linear actuators. Anyway painting the frame to match the roof rails. Shouldnt be too obvious.

 

[Batvette]

You don't need anything between the cells. Check the deflection of the 1/4" material. It may not be stiff enough. I haven't worked with that material enough to say one way or the other, just raising the point.

The problem with the zip ties is that you don't know how much compression they are or are not creating. Maybe it's enough, maybe it isn't. It's likely better than nothing.

You might be right about the thickness. Maybe .5" more appropriate. As for compression whats our goal here... To be held neutrally at a half state of charge?

 

[cargovanconversion]

Looks like it works. Im thinking zip ties and lexan because they dont add much bulk.
Q: looked at a few of your videos, wish I had such a spacious vehicle to work with. Mine is a 3rd gen honda odyssey, I guess the trade off is that it drives like a car. Anyway, flexible panels. 3 years later how are they holding up? You keep it garaged? Flexible panels would have been so much easier but didnt see any that had stellar reviews. Ended up buying 2 hqst 100 watt panels, just finishing an aluminum mounting frame. They were the only ones that would fit between the odysseys roof rails. Looking for stealth too. Plus I might adapt the frame to be able to tilt up on either side, with a second frame and two pairs of hinges. Maybe powered with linear actuators. Anyway painting the frame to match the roof rails. Shouldnt be too obvious.

The size of the vehicle is all relative A 4WD, high clearance passenger car would do better in off-road boondocking, than a standard large cargo van. Your Odyssee perfectly fits into a garage, my Transit doesn't. That said, has always been parked outside under the Florida sun. Would buy these panels again and have no complaints about their performance. After I've installed the batteries, I will do a new review about the entire 12V solar system, including the panels. Have to say a few important things:
- If you do NOT absolutely want stealth, buy regular panels (much cheaper, longer warranty, better track record).
- If you decide to buy flexible panels: buy HIGH quality, ETFE, backcontact cells.
- These panels fit exactly between the rain gutters, optimizing your install (on a Transit).
- Good flexible panels are expensive ($200, $300 and up). Do NOT buy the cheap stuff.
You made the right decision.
Wish you well with your plans and I hope it works out with the battery setup.
Van Williams

 

[HRTKD]

Everything you ever wanted to know about cell compression:

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

I working on my 4s 280ah battery plans. I thinking of my battery box. should these cells have a air space between them or be bonded tight together with a hose clamp or something similar.

diysolarforum.com

 

[zorlig]

You can but you won't get enough compression to do much more than keep the pack together.

 

[JRG]

I think your zip tie idea would work just fine. Just be sure to protect the edges of the cells where the zip ties make contact so that you don't crush the cell.

Most of the opinions you'll get are based on "feeling" and not testing. So take all comments, including mine, with a grain of salt. Do your research and decide what's best for your application.

 

[Batvette]

Everything you ever wanted to know about cell compression:

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

I working on my 4s 280ah battery plans. I thinking of my battery box. should these cells have a air space between them or be bonded tight together with a hose clamp or something similar.

diysolarforum.com

I think you meant more than I ever wanted to know.

Page 27:

"12 or 15 inch pounds at full charge should stop the bulge
Now we can lay this to rest "
The other day i went thru that lengthy spring compression thread. Whew.
I think a lot of people overthink things here. Easy to do, a lot of qualified opinions, this is a new technology and expensive if you screw it up.

When I was in the navy I was a fire control tech on f-4 phantoms. The radome, which had to be opened to service virtually anything in the radar is secured with 4 fasteners you tightened with a 1/4" drive speed handle to 165 imch pounds. Really. Stays on at mach 2+, or turns at up to 9g, with that little torque. Its a complicated geared mechanism fastener you could ruin at 200 inch pounds. Technically were supposed to use a torque wrench but that meant checking one out of the tool room, it doesnt fit in your tool box... one more thing to carry and keep track of on the flight deck at night. If youre good you really dont need it because that beautifil fastener is so linear... (Like $800 ea?)
So twice a year or so our shop chief took us to the hangar, with a torque wrench, and we used the speed handle by feel on at least 3 tries, and if you got it within 5% of spec on all 3 the chief signed all your MAFs as checked for torque.
I think 2 guys out of a dozen couldnt do it. It became a thing of pride, some of us would hit 163, 166, consistently.
If I could put my hands on a wrench on one threaded rod on a well designed fixture, i think i could nail it with zip ties.

Oh yeah spacers insulators. You dont NEED them, but it doesnt hurt either? Since the case under the plastic is negative, seems prudent.

 

[HRTKD]

I think you meant more than I ever wanted to know.

Page 27:

"12 or 15 inch pounds at full charge should stop the bulge
Now we can lay this to rest "
The other day i went thru that lengthy spring compression thread. Whew.
I think a lot of people overthink things here. Easy to do, a lot of qualified opinions, this is a new technology and expensive if you screw it up.

There is definitely a lot of overthinking in that thread that bled over to the spring thread. Get some compression on there and call it a day.

 

[Supervstech]

FYI the BYD bus 24V 5KWh LFP packs are bound with 1/2” shipping strapping... run through massive aluminum heat sinks...

 

[Batvette]

You can but you won't get enough compression to do much more than keep the pack together.

If you use a pair of pliers and leverage them against the head, opposite the toothed side for final tighten, you would be surprised how much tension you can develop on the big ties. Technically, at least 175 lbs. 3 rows ought to do it.

 

[ArthurEld]

I think you meant more than I ever wanted to know.

Page 27:

"12 or 15 inch pounds at full charge should stop the bulge
Now we can lay this to rest "
The other day i went thru that lengthy spring compression thread. Whew.
I think a lot of people overthink things here. Easy to do, a lot of qualified opinions, this is a new technology and expensive if you screw it up.

When I was in the navy I was a fire control tech on f-4 phantoms. The radome, which had to be opened to service virtually anything in the radar is secured with 4 fasteners you tightened with a 1/4" drive speed handle to 165 imch pounds. Really. Stays on at mach 2+, or turns at up to 9g, with that little torque. Its a complicated geared mechanism fastener you could ruin at 200 inch pounds. Technically were supposed to use a torque wrench but that meant checking one out of the tool room, it doesnt fit in your tool box... one more thing to carry and keep track of on the flight deck at night. If youre good you really dont need it because that beautifil fastener is so linear... (Like $800 ea?)
So twice a year or so our shop chief took us to the hangar, with a torque wrench, and we used the speed handle by feel on at least 3 tries, and if you got it within 5% of spec on all 3 the chief signed all your MAFs as checked for torque.
I think 2 guys out of a dozen couldnt do it. It became a thing of pride, some of us would hit 163, 166, consistently.
If I could put my hands on a wrench on one threaded rod on a well designed fixture, i think i could nail it with zip ties.

Oh yeah spacers insulators. You dont NEED them, but it doesnt hurt either? Since the case under the plastic is negative, seems prudent.

You went through that whole thing and quoted me. ?

 

[Batvette]

I think your zip tie idea would work just fine. Just be sure to protect the edges of the cells where the zip ties make contact so that you don't crush the cell.

Most of the opinions you'll get are based on "feeling" and not testing. So take all comments, including mine, with a grain of salt. Do your research and decide what's best for your application.

My feelings exactly.

Corners... Well if I do what I thought about oversizing the end pieces then slotting them, there wont be any pressure crushing the corners.
I also considered, using 4 zip ties for each row, so that at each corner the head is at a right angle. Would have to be anal about the tightening sequence.

 

[Batvette]

You went through that whole thing and quoted me. ?

Naw I read the first two pages then the last two. Went back one more to see a post someone quoted. Nevertheless your post came to a useful conclusion, enough so I didnt have to read any more.
Long threads are like that. Someone usually owns it near the end, and its pointless to keep posting. So you wont find the right answer buried in the middle.

Vaguely related, I love the inherent wisdom of "cunningham's law".

"The way to get the right answer on the internet, is not to ask a question. Its to post the wrong answer."

 

[Gazoo]

Naw I read the first two pages then the last two. Went back one more to see a post someone quoted. Nevertheless your post came to a useful conclusion, enough so I didnt have to read any more.
Long threads are like that. Someone usually owns it near the end, and its pointless to keep posting. So you wont find the right answer buried in the middle.

Vaguely related, I love the inherent wisdom of "cunningham's law".

"The way to get the right answer on the internet, is not to ask a question. Its to post the wrong answer."

Unfortunately the correct answer is buried in the middle of that thread and credit goes to ghostwriter for supplying us with the information she was able to get from an EVE engineer.

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

Do any of them tell you what state of charge the cells should be in when you apply the 12psi? I tightened mine until my lock washers were flat. That is exactly 12psi All the of the people I trust say that the batteries should be at a low state of charge. Like just before you would recharge them...

diysolarforum.com

In the end I decided not to worry about it and decided to put light compression on my cells with a full SOC. I am using threaded rods and plywood.

I look at it this way. These cells have a 2000 cycle life. That means the cells should last a full 2000 cycles if charged and discharged 2000 times at 1C rates. EVE and I believe Lishen claim the standard C rated for their cells is .5C. If a cell is run through a full cycle each day it will last for 5.5 years and still have 80% capacity left. NOTE: Temperature will have an effect on this. It's all in the spec sheets for these cells. Anyone who hasn't read the spec sheet for their cells should read through it a few times.... carefully.

I am more concerned about stress on the terminals due to cells expanding and contracting and will most likely switch from solid to braided busbars. I also realize there will be other considerations for cells used in mobile environments. Mine are stationary.

Having said that I very much admire those who are choosing to use springs to extend cycle life and properly compress their cells. I have a great respect for all of them. In the beginning I thought it was silly. However what they are doing is the best method to compress the cells and that comes from EVE...not me.

 

[Batvette]

Unfortunately the correct answer is buried in the middle of that thread and credit goes to ghostwriter for supplying us with the information she was able to get from an EVE engineer.

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

Do any of them tell you what state of charge the cells should be in when you apply the 12psi? I tightened mine until my lock washers were flat. That is exactly 12psi All the of the people I trust say that the batteries should be at a low state of charge. Like just before you would recharge them...

diysolarforum.com

In the end I decided not to worry about it and decided to put light compression on my cells with a full SOC. I am using threaded rods and plywood.

I look at it this way. These cells have a 2000 cycle life. That means the cells should last a full 2000 cycles if charged and discharged 2000 times at 1C rates. EVE and I believe Lishen claim the standard C rated for their cells is .5C. If a cell is run through a full cycle each day it will last for 5.5 years and still have 80% capacity left. NOTE: Temperature will have an effect on this. It's all in the spec sheets for these cells. Anyone who hasn't read the spec sheet for their cells should read through it a few times.... carefully.

I am more concerned about stress on the terminals due to cells expanding and contracting and will most likely switch from solid to braided busbars. I also realize there will be other considerations for cells used in mobile environments. Mine are stationary.

Having said that I very much admire those who are choosing to use springs to extend cycle life and properly compress their cells. I have a great respect for all of them. In the beginning I thought it was silly. However what they are doing is the best method to compress the cells and that comes from EVE...not me.

It probably is because it exerts a compression which adapts to the size changes of the cells, I would term it adaptive or active or progressive compression.
Ive only ordered the cells and this project is unfolding to be more complicated at every turn, so Id also call it...
More trouble than Im willing to bear.

Looking at prices for braided bus bars I think Im going the diy route. I dont have the workshop i used to but i have a big vise, a 1 ton arbor press and lots of soldering tools.
I havent seen enclosures to my liking yet, not at a good price. Want something that hase handles and can take a beating, maybe 2 toolboxes of the right size.
Ive had a digital power supply for years thats 18v and 5a, is that big enough?

 

[GSXR1000]

First thread. Recently ordered 8 lishen 272 ah cells for 2 4 cell banks in my van.
Trying to keep it simple. Is there any reason why i cant accomplish cell compression using 2 or 3 175# zip ties? The ones that are like 3/8" wide. Theyre insanely strong.

HellermannTyton T150XL0X2 Heavy Duty Cable Tie | Waytek

HellermannTyton T150XL0X2 Heavy Duty Cable Tie Nylon, 175lb, 43", 25 Per Bag is in stock and ready to ship. Order today!

www.waytekwire.com

I was thinking of using clear lexan polycarbonite, (not acrylic plexi) 1/8" between cells and 1/4" on the ends.
I could oversize the lexan spacers and ends by 3/8" on each side and drill/cut a slot so the zip tie can hold it all together, the plates would keep the zip ties from moving.

I am using the batteries in my travel trailer. so I put 3 rows of vhb tape between each cell to prevent rubbing and helps lock it into place

 

[HRTKD]

Ive had a digital power supply for years thats 18v and 5a, is that big enough?

Plenty big, if you're patient. 5 amps is a bit small, 10 amps is better. You're top balancing at 3.65 volts. So that upper limit of 18 volts isn't going to come into play.