Anyone considered using poly strapping for compression?

[Gould]

I’m finally getting around to building my batteries and was down the path of threaded rod but stepping back from the wooden creation, it’s going to be very difficult for me to find a waterproof enclosure that will fit the batteries with compression and be small enough to install in the front of my RV.

We’re not talking about a ton of compression here, got me thinking about the poly strapping you see on every warehouse box. There is a tensioning tool that can be used but it’s big and bulking. They do have a clip that can be used with manual tensioning. At the end of the day this may be no different than using fibre enforce packing tape but thought I’d throw it out there.

 

[Northernchateau]

I have seen specs call out for compression to be anywhere from 7 to 13 psi ( pounds per square inch)
So lets assume the battery your using is 7" x 8" or 56 square inches.
10 psi x 56 in2 = 560 pounds
Not sure how easy it will be to get strapping to adjust top that kind of load.
I also do not think it will like making a 90 deg turn at each corner.

 

[Supervstech]

I’m finally getting around to building my batteries and was down the path of threaded rod but stepping back from the wooden creation, it’s going to be very difficult for me to find a waterproof enclosure that will fit the batteries with compression and be small enough to install in the front of my RV.

We’re not talking about a ton of compression here, got me thinking about the poly strapping you see on every warehouse box. There is a tensioning tool that can be used but it’s big and bulking. They do have a clip that can be used with manual tensioning. At the end of the day this may be no different than using fibre enforce packing tape but thought I’d throw it out there.

The 24V BYD batteries all use the poly banding, but they band into a formed aluminum heatsinc that has formed corners for the banding.

 

[rickst29]

Your main issue will be that straps, after you have tightened them, will be fixed in size. When the batteries are at lower SOC and being used with only low current, the straps will be completely loose (with no compression at all). Then, when the batteries are highly charged and handling high current, they will run into the fixed straps all at once - with very high and non-linear compression behavior.

I don't like this scheme.

 

[Gould]

All great points, thanks. I’ll keep plugging away looking for alternatives. Part of me is thinking how important is the extra 1000 cycles for my use case; why not just go with multiple layers of fibre tape and be done with it.

 

[Bob B]

When I first put my pack together, I used ratchet straps to get some compression on them. Not only is there the problem @rickst29 mentioned above, but I also found the strapping would stretch over time. I also experimented with some stuff similar to that video and couldn't get it nearly as tight as I wanted.... and would probably also have the stretch over time problem.
Have you seen the compression using springs thread?

 

[Gould]

I have but it’s too complex for my liking, also doesn’t help with my bigger problem which is space. I’d originally thought I had more than enough space in my storage bay to house them. With them now in my hands there’s no way - I’m forced to use the space at the front of the trailer behind the propane tanks for those who are familiar.

I’ll have to do some experimenting, starting with an enclosure that’s close to the maximum size of the install location, working back from there. Maybe there’s a middle of the road compromise, using wooden plates and strapping vs the threaded rod.

 

[Bob B]

To save on the space, you could use extension / tension springs .... you could still use the strapping if you want, just connect it to an extension spring on each corner.

 

[Gould]

Ah, I follow. I was assuming the springs were attached to the rods out the back of the wooden plate.

 

[Gould]

I’ll read through the thread again, any cliff notes on the recommended springs

 

[Bob B]

It can be done either way .... just need the opposite spring action.

 

[Bob B]

I don't know if anyone on that thread has listed an extension spring part number .... If you post the question over there, maybe someone will show up who has done it that way ..... or maybe you can break that ground for us.

 

[Gould]

Lol, trust me, you don’t want me breaking that ground!

 

[time2roll]

For better or worse I plan to use some large zip ties. I see nothing wrong with the strap if it will really hold tight over time.

 

[NMNeil]

I suggested using A/C ducting zip ties in another thread.

GARDNER BENDER 36 in. Plenum Cable Tie (25-Pack) 49-536P - The Home Depot

Gardner Bender's Plenum Cable Ties are most commonly used in plumbing; electrical (low and high voltage), heating or air conditioning (HVAC) applications where ductwork or plenum cable (CAT5) is being

www.homedepot.com

And for an extra touch of adjustable tightening a few of these wedges would do the trick.

Sioux Chief Wedge-It Soft PVC Toilet Shim-460-20 - The Home Depot

Wedge-It is a multi-purpose stability wedge. Available in Stiff polypropylene or soft PVC. This product has dozens of uses.

www.homedepot.com

Still waiting for my batteries so I would have changed my mind on how I'll do it a few dozen times between now and then

 

[time2roll]

Those ties say 180 pound strength. Wrap it twice and you have up to 720 pounds available compared to 560 pounds needed as described in post #2. With any luck the nylon material may have some spring effect.

 

[Gould]

I’m going to give a hose clamp a try with plywood bookends cut slightly larger that the cells and rounded edges to coax the strap.

I have a somewhat related question - my cells came slightly bloated. Should I compress then top balance or would it be better to top balance, draw them down through a capacity test to flatten them, then compress?

 

[Gould]

Just found a company in Canada that sells nylon zip ties up to 60” in length and 250lb tensile strength. Hmm, might give that a run.

 

[Just John]

I don't know how well it will work, but for final assembly I'm going to try plywood ends (to save the cell corners) and stainless steel 3/4 inch straps.
I'll try it and see how well it works.

Amazon.com

ISO LG161 Type 201 Stainless Steel Lite Gauge Band, 3/4" Wide x .020" Thick x 100' Foot roll: Amazon.com: Industrial & Scientific

ISO LG161 Type 201 Stainless Steel Lite Gauge Band, 3/4" Wide x .020" Thick x 100' Foot roll: Amazon.com: Industrial & Scientific

smile.amazon.com

I have the tool, haven't bought the buckles and strap yet.

 

[Supervstech]

I don't know how well it will work, but for final assembly I'm going to try plywood ends (to save the cell corners) and stainless steel 3/4 inch straps.
I'll try it and see how well it works.

Amazon.com

ISO LG161 Type 201 Stainless Steel Lite Gauge Band, 3/4" Wide x .020" Thick x 100' Foot roll: Amazon.com: Industrial & Scientific

ISO LG161 Type 201 Stainless Steel Lite Gauge Band, 3/4" Wide x .020" Thick x 100' Foot roll: Amazon.com: Industrial & Scientific

smile.amazon.com

I have the tool, haven't bought the buckles and strap yet.

If you do, put spacers in the center of the plywood to keep even pressure on the cell surface.