What tightening torque for my mb31 cells 🤔

[marty35]

Hello, I searched everywhere on the forum but I did not find at what tightening torque I should screw the threaded rods on my installation. 4 M10 threaded rods in zinc-plated mild steel, 8 cells of mb31. I am French so if you could give me the value in Newton meters I would be grateful
I asked chatGPT and he answered me 3.5Nm but it is really very little
Thank you for reading me, looking forward to chatting with you.

 

[SomethingAppropriate]

It has handles! How thoughtful.

 

[marty35]

It has handles! How thoughtful.

Unfortunately, they will not be used given the little compression to be exerted on the cells, I thought it was much more and that the whole thing would hold up on its own.

 

[SomethingAppropriate]

Unfortunately, they will not be used given the little compression to be exerted on the cells, I thought it was much more and that the whole thing would hold up on its own.

Oh , I thought it would to.

I'm sorry, I don't know the call calculation for any of it. Just thought I would say hi

 

[JäseH]

The data sheet says 6 N⋅m.

 

[marty35]

The data sheet says 6 N⋅m.

 

[marty35]

the technical sheet does not give the tightening torque of the rods and in any case the example shown there is made of 6 threaded rods.

 

[SeaGal]

Torque of rods will depend on thread of rods, elasticity of material (thickness of rod) and number of rods to achieve the 300Kgf pressure specified - quite a few threads about this on here. It's not a lot of pressure needed.

 

[kommando]

You are going to have to calculate it from first principles, ie the contact area, force pre mm2, compression from the specs, number of rod, physical property specs for the rods such as tensile strength etc.

J

Thread 'How to achieve up to spec battery compression?'

Jul 4, 2024

Let me come back to the confusing matter of compressing prismatic LiFePo4 cells.
Let's focus on the thread subject and not diverge into whether you should or shouldn't compress.

Manufacturer recommendation is to compress with the force of 300kgf +/- 20kgf
That means 2941 N over the surface area of the cell, correct? (1kgf=9.807N)
The cell I have in mind is 204mm by 174mm that's equals to 0.035m2
So the pressure is 2941N/0.035 ~84kPa
or 12.2 psi which is in accordance with discussions on similar threads

12 psi doesn't seem like much but that is 12 pounds on every square inch, over entire...

• jazzy
• Replies: 52
• Forum: DIY LiFePO4 Battery Banks

 

[jjww]

bolt torque is calculated by the distance torque is measured (1 meter) divided by the radius of the bolt
(the lever arm of the force in your case 5 mm) , so 1000/5 = 200 times multiplication of the force.
then multiply by number of bolts.

 

[JäseH]

the technical sheet does not give the tightening torque of the rods and in any case the example shown there is made of 6 threaded rods.

By threaded rods I thought he meant the terminals. I completely missed the photo.