Belleville Disc Washer Springs - Learn About

High Loads in Small Spaces

When your compression spring application requires a high load in small spaces, Lee Spring's Belleville Disc Washers can be the solution. Their conical configuration enables them to support high loads with relatively small deflections and solid heights compared to helical springs. Belleville Washers are often used to solve vibration, thermal expansion, relaxation and bolt creep problems.

With competitive price and timely delivery, HEGONG SPRING sincerely hope to be your supplier and partner.

Lee Spring Standard Series Belleville Disc Washers are manufactured from 300 Series Stainless Steel. Additionally, Lee Spring Standard Series Belleville Disc Washers are passivated in accordance with specification ASTM A967 (supercedes QQ-P35) to remove contaminants and further improve resistance to corrosion. 300 Series Stainless Steel is slightly magnetic and is recommended for applications with temperatures up to 500°F (260 °C).

The Lee Spring DIN Belleville Disc Washer Series offers metric disc spring washers to meet global demand for sizes specified by DIN .  Lee Spring also expand on size options past DIN ’s standard size tables, made to DIN manufacturing and quality specifications to provide component flexibility for product designers. DIN Belleville Disc Washers are made with 51CrV4 spring steel (AISI ) and finished with a phosphate and oil surface for general protection from corrosion. 

If you want to learn more, please visit our website High Temperature Disc Springs.

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DIN Belleville Disc Washer Series designs are classified into three groups based on the material thickness:

Group 1 – This range applies to disc spring washers with material thickness less than 1.25mm.  Lee Spring DIN Belleville Disc Washer Series include 88 sizes in Group 1, over a selection of outside diameters from 6mm (0.236”) to 40mm (1.575”) with inside diameters from 3.2mm (0.126”) to 20.4mm (0.803”).

Group 2 – This range applies to disc spring washers with material thickness from 1.25mm through 6mm.  Lee Spring DIN Belleville Disc Washer Series include 161 sizes in Group 2, over a selection of outside diameters from 20mm (0.787”) to 200mm (7.874”) with inside diameters from 10.2mm (0.402”) to 102mm (4.016”).

For more information, please visit flange washers.

F.Y.I.

I found a source for 120mm x 16mm, M6 braided ground straps rated at 150A. These would work for diagonal bus bars (eliminating the risk of stress on the cell terminals).

Ground Strap, 150mm Long, M6 Holes,
For my application (W Inverter), 150A is plenty. If you need the full C rating of the cells, you could double them up.

Nice find. Is 120mm long enough to connect cells diagonally?

Those would definitely solve the issue of any stress on the terminals, but at the cost of longer bus wires and greater I^2R losses. I see these are rated for 150A max, but does that mean they have roughly the same resistance as 3AWG wire (0.197 mOhms/foot or 0. mOhms over 120mm)?

The plated busbars that shipped with my cells are about 1.5AWG (halfway between 1AWG and 2AWG and probably represent about 0.14 mOhms/foot or just under 0.03 mOhms over their 2.5” conductance path.

260% the I^2R losses of standard rigid busbars isn’t the end of the world, but is at least worth thinking through...

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I’m sure if you speak to any springs manufacturer they will be able to supply a spring with a 15 psi expansion and contraction rate. It can’t be that hard and I’m sure it’s available off the shelf. No need for custom orders

Oh one of those, yeah I’d seen those earlier. I had the sense they were very large but maybe I was wrong - what is the diameter and length?

Also, at 15GBP each, it’s not a very budget-friendly solution (we need 4).

But yeah, if diameter isn’t too large to be cumbersome and length isn’t much longer than we need (~1mm per cell, meaning ~1/2” FPS 8S), could be an attractive option. PSI is not a meaningful spring rate. Springs are rated using force per distance (lb/in or kg/mm) and free length.



Here is a design process I came up with that should work. I am not an ME so if someone wants to double check my work, please do so.

You have to know 3 things going in:

1. The compliance distance the spring has to work over. This is how much a cell is going to expand and contract as you go from 0% to 100% state of charge over the operating temperature range multiplied by how many cells you are compressing in a stack.
2. The minimum and maximum force at each end of the compliance range.
3. Minimum Spring ID (diameter of the threaded rod plus some clearance value)

Here is what we think we know:

1. The optimal compressive force on the cell is 12 PSI with an acceptable range of 8 PSI to 16 PSI. For my design I am going reduce the acceptable pressure range to 10 to 14 PSI.
2. Cell Dimensions (measured from my cells) = 173mm x 200mm = 0.m^2
3. Compliance (how much the cells expand from 0% to 100% SOC) = 1mm per cell x 4 cells = 4mm total
4. The individual spring force is the total force divided by the number of springs (4)

First convert PSI to kg force applied to each spring:

• 14 PSI = kg/m^2 * 0.m^2 / 4 = 85.1kg
• 12 PSI = kg/m^2 * 0.m^2 / 4 = 73.0kg
• 10 PSI = kg/m^2 * 0.m^2 / 4 = 60.8kg

Once you know this we calculate the spring rate = (max force - min force) / compliance:

• Spring Rate = (85.1kg - 60.8kg) / 4mm = 6kg/mm

Spring loaded length (length where force = 73kg) = 73kg / 6kg/mm = 12.2mm

Spring free length (length where force = 0kg) = 24.4mm

I am using 5/16" threaded rod so the spring ID should be > 8.5mm

Looking at the Lee Spring on-line catalog, one spring that meets these requirement is LC 049E 09 S

Attachments

• LC 049E 09 S.pdf LC 049E 09 S.pdf

As you guys are finding out. ... spring rates and clamping force for threads (torque vs clamping force) is a non-trivial calculation.

Indeed,

I feel much more confident with what I am doing now, since I have a load cell and can actually measure the clamping forces directly. Belleville Disc Springs are great. First pick one with the correct working load then just stack up multiple discs in series until you get the desired amount of travel distance. The disks I picked have a working load of ~ 187 lb which is almost exactly what is wanted. The only remaining question is how much travel is enough. It is looking like 1 to 2 mm of travel is sufficient, so my plan is to use 10 disc washers in series. Charge the cells to 100% SOC. Then adjust the spring preload to the max compression I ever want to the cells to see: 195 lb per threaded rod, or 780 lb total which is very close to 14 PSI and call it a day. As the cells discharge, the springs will relax and the compression forces will drop to a minimum at 0% SOC of 110 lb per threaded rod, or 440 lb total which is very close to 8 PSI. This range encompasses the sweet spot of the life/compression chart that EVE has published.

Thanks. If you don't mind please post when you receive them. I am considering buying the 100mm ones which should provide enough slack between the cells. I know it's not as good as your design but I already have the short cable to connect the cells together.

Will do.

The braided straps I had previously purchased will work, you just want to double them up to get the ampacity high enough. If you are expecting to power a larger inverter, perhaps triple them.

These guys custom built me straps to the length I specified. I did this before I decided to go with the diagonal straps.

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The cost was very reasonable.

Thanks. My inverter is rated at kw and 24 volts. So I think the 150 amp busbars Icotek will be good enough. I oversized the inverter anyways and probably will never use the full . I am concerned about the possibility of the ends of the busbars buckling when mounted. I read it happened to someone else and I do recall they bought the braided busbars from somewhere else, not Icotek. As usual I don't recall where it was posted.

Mine is the same. A Multiplus 24/-50. I am planning on 150A peak load current, so all of my wiring, bus bars etc. are sized for that.

Check out my latest circuit diagram. I simplified the battery design a bit. I like this Inverter capacitor pre-charge concept better than previous ones.

I am accounting for the fact I will be using the braided straps to connect the battery packs to the BMS and circuit breaker. I also moved the battery voltage monitor to cell side of the BMS so it will show the actual cell voltage. The BMV-712 will show the battery pack output voltage.

Attachments

• VanPower15.pdf VanPower15.pdf

Indeed,

I feel much more confident with what I am doing now, since I have a load cell and can actually measure the clamping forces directly. Belleville Disc Springs are great. First pick one with the correct working load then just stack up multiple discs in series until you get the desired amount of travel distance. The disks I picked have a working load of ~ 187 lb which is almost exactly what is wanted. The only remaining question is how much travel is enough. It is looking like 1 to 2 mm of travel is sufficient, so my plan is to use 10 disc washers in series. Charge the cells to 100% SOC. Then adjust the spring preload to the max compression I ever want to the cells to see: 195 lb per threaded rod, or 780 lb total which is very close to 14 PSI and call it a day. As the cells discharge, the springs will relax and the compression forces will drop to a minimum at 0% SOC of 110 lb per threaded rod, or 440 lb total which is very close to 8 PSI. This range encompasses the sweet spot of the life/compression chart that EVE has published.

HaldorEE -- did this end up working out for you? I have went through the calculations and what you say makes sense. You are assuming hooke's law with the belleville disc springs for when the battery drains ... hopefully that is good enough. I'd like to know what you found, were you able to take any measurements to confirm or deny how well it turned out? Thanks in advance ...

If this works, I like it because it doesn't require nearly as much space consumption as compression springs, and isn't as involved as using expansion springs with turnbuckles (and I believe this would be expensive buying all the hardware for expansion).