Dan-O's DIY 105ah LiFePO4 cell holder springy contraption things!

Stitzebr1

New Member
Joined
Mar 11, 2021
Messages
5
Very nice engineering, has anyone tried use shipping straps?
you know the nylon woven straps you’ll see on some heavy items in cardboard boxes they don’t want to break open. I have access to a strapping machine at work and I’m going to try it out on my 280ah when they arrive and post.
They just seem a little cleaner look with a lot of tension ability.
 

Gazoo

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May 12, 2020
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2,794
Location
Texas
Very nice engineering, has anyone tried use shipping straps?
you know the nylon woven straps you’ll see on some heavy items in cardboard boxes they don’t want to break open. I have access to a strapping machine at work and I’m going to try it out on my 280ah when they arrive and post.
They just seem a little cleaner look with a lot of tension ability.
Just be careful you don't put so much tension the cells get crushed. You could put something on the corners of the cells to prevent that from happening. But really threaded rods and plywood makes for a cheap effective fixture and you have control over the amount of torque applied to the cells whether or not springs are used.
 

Stitzebr1

New Member
Joined
Mar 11, 2021
Messages
5
Just be careful you don't put so much tension the cells get crushed. You could put something on the corners of the cells to prevent that from happening. But really threaded rods and plywood makes for a cheap effective fixture and you have control over the amount of torque applied to the cells whether or not springs are used.
My problem is my motorhome is a 22 foot and they used every square foot in it and with only two outside storage spaces, I had to use the smaller of the two which is only 13" high and I can't use the original battery shelf because it in exposed and under the stairs.
So I have to be as space conscious as possible.
you could call it a ultra mini winnie.
 

Bob B

Photon Sorcerer
Joined
Sep 21, 2019
Messages
4,372
Very nice engineering, has anyone tried use shipping straps?
you know the nylon woven straps you’ll see on some heavy items in cardboard boxes they don’t want to break open. I have access to a strapping machine at work and I’m going to try it out on my 280ah when they arrive and post.
They just seem a little cleaner look with a lot of tension ability.
I tried using a couple different kinds of ratchet strapping when I first assembled my pack ..... what I found was that the strapping stretches over time. Also, unlike spring tension, the pressure on the pack could vary significantly with SOC.
 

OnTheRoadAgain

Solar Addict
Joined
Feb 22, 2021
Messages
643
3 months later and this is still amazing work.

I would say I am going to duplicate this....but I'm not sure I have the required skills to pull it off.

I wonder what kind of wood working equipment he has?
 
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kpw

New Member
Joined
May 7, 2021
Messages
46
Thanks guys! Fun little project!

Got the braided copper from Ebay.

We smashed the copper pipe some first and then put in the braid. Final smash from there! After that, I cleaned up the ends with a sanding disk and sanded everything flat using 120-220-400 grit paper on a flat table.
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nice Job! where did you get the springs?
 

T3TRIS

Solar Enthusiast
Joined
Feb 22, 2022
Messages
14
Hey so I'm late to the party here, but I've been browsing this site looking for inspiration for compression boxes.
Your build is one of the cleanest I've found and resembles what I had in my mind (albeit with 4 larger cells). I've got the sides and springs figured out, but am still working on the bottom plate. I kept looking at your design and I'm a little curious about the thoughts with the aluminum L brackets. It looks to me like the way you have it would prevent any movement from happening between the side plates since they are tied to the bottom plate (except they might flex at the top). Have you addressed this or does it work just fine as is?
Here's my version so far:
LiFePO4 compression box WIP.jpg
The best idea I've come up with so far is having the bottom tray completely free from the sides. You can see the angle bracket at the bottom that supports that bottom plate and the weight of the batteries when the assembly is lifted (not that it would happen that often anyway). I plan on putting rubber feet on the bottom plate and a lip on the edge so the assembly doesn't slide sideways. Anyhow, still a work in progress but maybe it'll help someone come up with an even better idea.
 

Mike Jordan

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Joined
Jun 15, 2020
Messages
414
Hey so I'm late to the party here, but I've been browsing this site looking for inspiration for compression boxes.
Your build is one of the cleanest I've found and resembles what I had in my mind (albeit with 4 larger cells). I've got the sides and springs figured out, but am still working on the bottom plate. I kept looking at your design and I'm a little curious about the thoughts with the aluminum L brackets. It looks to me like the way you have it would prevent any movement from happening between the side plates since they are tied to the bottom plate (except they might flex at the top). Have you addressed this or does it work just fine as is?
Here's my version so far:
View attachment 85826
The best idea I've come up with so far is having the bottom tray completely free from the sides. You can see the angle bracket at the bottom that supports that bottom plate and the weight of the batteries when the assembly is lifted (not that it would happen that often anyway). I plan on putting rubber feet on the bottom plate and a lip on the edge so the assembly doesn't slide sideways. Anyhow, still a work in progress but maybe it'll help someone come up with an even better idea.
What are your end plates made out of?
 

CharlesK

Solar Enthusiast
Joined
Jan 31, 2021
Messages
37
Location
NE Florida
The best idea I've come up with so far is having the bottom tray completely free from the sides. You can see the angle bracket at the bottom that supports that bottom plate and the weight of the batteries when the assembly is lifted (not that it would happen that often anyway). I plan on putting rubber feet on the bottom plate and a lip on the edge so the assembly doesn't slide sideways. Anyhow, still a work in progress but maybe it'll help someone come up with an even better idea.
I am working on a design for my DIY batteries as well. I am using springs as part of the design. So, I need to have the cells move independently of the case.
I found a video that gave me an idea. I can attach the rods to one end of the case, but not the other. To illustrate this, let me point to a you-tube video by "Ray Builds Cool Stuff" titled "My Lifepo4 Battery Final Assembly..." Link:
Stop the video at 0:09 (nine seconds from the beginning). He is not using springs, but I would put the springs at the end of the rods nearest the camera. He puts the BMS, Class T Fuse, and Anderson connector inside the case. In one of his videos he adds hinged covers, etc.

The idea that I garnered from this is that only ONE end of the battery is hard-fixed to the case. The other end can "float" inside the case.
Hope this helps.
 

T3TRIS

Solar Enthusiast
Joined
Feb 22, 2022
Messages
14
What are your end plates made out of?
Very fancy Costco polypropylene and polyethylene cutting boards... turns out they flex a tiny bit, I'm about to reinforce them with some strategically placed extruded aluminum. I'll share photos when I'm done with that part.
I am working on a design for my DIY batteries as well. I am using springs as part of the design. So, I need to have the cells move independently of the case.
I found a video that gave me an idea. I can attach the rods to one end of the case, but not the other. To illustrate this, let me point to a you-tube video by "Ray Builds Cool Stuff" titled "My Lifepo4 Battery Final Assembly..." Link:
Stop the video at 0:09 (nine seconds from the beginning). He is not using springs, but I would put the springs at the end of the rods nearest the camera. He puts the BMS, Class T Fuse, and Anderson connector inside the case. In one of his videos he adds hinged covers, etc.

The idea that I garnered from this is that only ONE end of the battery is hard-fixed to the case. The other end can "float" inside the case.
Hope this helps.
Thanks for sharing those ideas. I'll take a look at the video. I think I've seen a setup with the bottom plate attached to just one side plate. I was thinking of having our bottom plate free from either side but I'm thinking it should be attached to one side. This will be installed in a camper van with which we do some pretty heavy off-roading so I need to make sure the pack is tightly secured.
 

CharlesK

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Joined
Jan 31, 2021
Messages
37
Location
NE Florida
Very fancy Costco polypropylene and polyethylene cutting boards... turns out they flex a tiny bit, I'm about to reinforce them with some strategically placed extruded aluminum. I'll share photos when I'm done with that part.

Thanks for sharing those ideas. I'll take a look at the video. I think I've seen a setup with the bottom plate attached to just one side plate. I was thinking of having our bottom plate free from either side but I'm thinking it should be attached to one side. This will be installed in a camper van with which we do some pretty heavy off-roading so I need to make sure the pack is tightly secured.
I just remembered I have a photo from an intermediate stage of my prototype design. This shows the end plates at the spring end. Using the idea I mentioned above, the far end (not shown) would be the case itself. And, the rods in the photo would be shortened, of course.

I am also considering an aluminum plate underneath the cells as a heat conductor (insulated from the cells of course). The batteries are going into a motorhome that may travel in some cold regions during the winter months. Referring back to Ray's battery box, add some insulation around the cells (maybe outside the box?), and some PTC heating pads under the aluminum plate. Then, control the heat with a simple thermostat to keep the cells above 40F at all times. BMS, Fuse, thermostat, heat pad, etc. would all be inside the box.
 

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T3TRIS

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Joined
Feb 22, 2022
Messages
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Oh I see, that's cool! Just to add a wrench in there, I'm also keeping in mind that we're talking about compressing to get 3,500 life cycles instead of 2,500 uncompressed... These batteries will most likely never be cycled fully more than 5 times month (averaged over an entire year). Even uncompressed, that's more than 8 years of use (theoretically). And by then, they should still be at 80% capacity which is still plenty in our case... But it's fun to build the right box :)
 

pellicle

retired ex-professional dingbat
Joined
Feb 8, 2022
Messages
123
Location
Queensland, OzTrayLiYa
After searching the forum, robbing ideas, asking questions, and learning a couple things the hard way, this is what I came up with for my first DIY solar boat batteries. Is this the best way? Highly doubtful. This is just how I did it and I feel like it will work great for me. Maybe this will give you some ideas and hopefully something to improve on....

I originally was going to do a few rounds of electrical tape, throw them in a plastic container and call it a day. All was good until I came across the cell compression with springs thread...

I'm all for saving money and using whatever I have on hand if possible, so a lot of this stuff is just leftovers or saved from the dumpster. I'm just a hillbilly with a small garage and a big dream of having a cheap boat that never runs out of fuel and never breaks down.:p

I started with cutting up some 1/2" Douglas Fir plywood 1" larger than the cell dimensions.
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Ordered up some stainless hardware including 5/16-24 threaded rods. Also 10ft of 8mm ID silicone hose. I still have quite a bit left over...
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Saved some .030 plexiglass from old picture frames and cut them to cell size. These are insulators to go between the cells.
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Decided to round the top corners because..... it looks better?
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I saved a UTV/SXS windshield from the dumpster(6mm thick plexiglass) and cut that up for the baseplates and top covers. Also, ordered a couple small stainless hinges from Amazon...

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Also from Amazon, these small cast aluminum L brackets. I sanded them for a nicer look...
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Next up was sealing/strengthening both sides of the wood with fiberglass cloth and just a touch of tint to make them black.
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I had some carbon fiber scraps that have been sitting here for a while. Hmmmmm.... I had just BARELY enough to pull it off! No point in doing this at all but it looks cool and added that much more strength so.....
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Getting there...
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Ordered up some 135lb springs to hit our goal of 12psi of compression. Also, drilled holes for BMS wiring and used some of that silicone tubing as grommets.
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Time for some flexible bus bars! I robbed this idea from member upnorthandpersonal and made my own from 3/4" wide braided copper and 1/2" copper pipe. Very cool! DIY tin plating is on the list BTW.
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Made the handles with paracord and spare vacuum tubing. Also, used 1/2" adhesive backed closed cell foam on the bottom to keep vibration down and not scratch my boat!
xmbjZuR.jpg


I know, a lot I'm leaving out. This is all of the pictures for now at least. I'll come back and post links/details ASAP. There's still a few small things I want to do before we call these "done" but they are ready to put in work as is.
quite simply >very nice work<

thanks for sharing this
 

Electro Dan-O

Current Situation
Joined
Nov 15, 2020
Messages
40
Location
Middle TN
Hey so I'm late to the party here, but I've been browsing this site looking for inspiration for compression boxes.
Your build is one of the cleanest I've found and resembles what I had in my mind (albeit with 4 larger cells). I've got the sides and springs figured out, but am still working on the bottom plate. I kept looking at your design and I'm a little curious about the thoughts with the aluminum L brackets. It looks to me like the way you have it would prevent any movement from happening between the side plates since they are tied to the bottom plate (except they might flex at the top). Have you addressed this or does it work just fine as is?
Here's my version so far:
View attachment 85826
The best idea I've come up with so far is having the bottom tray completely free from the sides. You can see the angle bracket at the bottom that supports that bottom plate and the weight of the batteries when the assembly is lifted (not that it would happen that often anyway). I plan on putting rubber feet on the bottom plate and a lip on the edge so the assembly doesn't slide sideways. Anyhow, still a work in progress but maybe it'll help someone come up with an even better idea.
Yeah, I guess I left that part out.😬 I elongated the bottom bracket holes on one end and used lock nuts, left loose enough for the plate to slide back and forth.👍

I like your idea better. Looks awesome! 😎
 

Electro Dan-O

Current Situation
Joined
Nov 15, 2020
Messages
40
Location
Middle TN
@Electro Dan-O how did you get the springs to the correct compression?
nice Job! where did you get the springs?

The springs came from WB Jones. PN-283

To find the correct spring tension, there's a couple of math problems to do with the cell area and spring specs. Nothing crazy. I can't find it in my notes at the moment. These need to be compressed .187" each and .813" installed height is checked with a basic caliper tool. Easy done and doesn't have to be perfect. 😉
 
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