New garage time!

[fatjay]

Took the drone up to get a picture of the array as it stands. Once I figure out how to go around the chimney, I'll be putting another 21 panels into the array for 3 sets of 15 to 3 inverters.

 

[fatjay]

To get the most out of the lifepo4 cells, they need to be clamped at ~700-1600lb of force. At the same time, they need to be allowed up to 3% expansion. The cells are 570m end to end, so 3% is 17mm or 1.7cm. That's not a small amount.

I ordered some aluminum compression plates. I'll drill some holes and run all-thread between the two ends with a bolt on one end. On the other end, I'm going to get a fender washer and bolt, and put a valve spring under the fender washer. A valve spring is 250lb to compress and has a range of travel of about an inch.

So that's my plan for the moment. When I built this I wasn't taking into account the plates, or springs. So it's going to be a bit tight.

Fingers crossed.

 

[ning]

Given that the batteries may have varying temperatures, do they themselves expand at all?
Also temperature cycles may allow for fastener movement, though that may be mitigated by the all-thread also expanding and contracting.
Still, I'd consider using locktite, or some sort of lock nut (nylock or double-nut).

 

[Kyle_in_Tex]

You might research belleville washers to get your force with less space.
McMaster-Carr

You need about up to 3/4" of movement. With these, you can put some on each end to save space maybe?
you stack them in opposing pairs to get your force/distance needed like this,
()()()()

 

[fatjay]

Given that the batteries may have varying temperatures, do they themselves expand at all?
Also temperature cycles may allow for fastener movement, though that may be mitigated by the all-thread also expanding and contracting.
Still, I'd consider using locktite, or some sort of lock nut (nylock or double-nut).

The batteries don't really change temperature with use, only expand/contract as an effect of the gasses forming and getting re-absorbed.

You might research belleville washers to get your force with less space.
McMaster-Carr

You need about up to 3/4" of movement. With these, you can put some on each end to save space maybe?
you stack them in opposing pairs to get your force/distance needed like this,
()()()()

I can't see if it says where the specific tension is provided. And even once flattened, it still needs to provide a degree of expansion. How much force does it take the washer to be flattened?

 

[fatjay]

Well, its a start. At 18 inchpounds the springs are exhibiting 175lb of force. 6 springs will be 700lb. At full compression it's 250lb of force, or 1500lb total.

I just needed to get this far so I could mark my outer holes.

The springs are from the valve train of a 1997 corvette.

 

[Kyle_in_Tex]

The batteries don't really change temperature with use, only expand/contract as an effect of the gasses forming and getting re-absorbed.

I can't see if it says where the specific tension is provided. And even once flattened, it still needs to provide a degree of expansion. How much force does it take the washer to be flattened?

A stack of these is what is used in a cnc mill's spindle to provide strength to the pull collet which grips the tool's pull stud.

It will take some engineering to get the right number, diameter, thickness of each washer. They are spring steel and will work for a long long time.

Belleville Spring Washer Equation and Calculator

A Belleville spring or washer is formed into a conical or cone shaped geometry. The slight or aggressive conical shape gives the washer a spring characteristic and action. Belleville washers are typically used as springs where the spring action is used to apply a pre-load or flexible quality to...

www.engineersedge.com

 

[airbiscuit]

This is a big project. How much of all this did you know in advance, and how much are you learning as you go along?

 

[fatjay]

This is a big project. How much of all this did you know in advance, and how much are you learning as you go along?

I'm just learning as I go and hoping it doesn't all fall down

 

[fatjay]

Now with the springs the mounts are to wide. To turn the orientation, 17" deep to 27" deep, I needed more brackets, which means more floor. So I pumped that out tonight.