Group Build - 12v Battery Module (EVE 280AH)

zzyzx

Solar Enthusiast
After lurking for a few months around the forum, I have learned much and seen the incredible knowledge, technical skills and impressive battery builds of forum members. These have largely been purpose-built and size-constrained, and thus "one-offs", primarily due to their locations (yachts, RVs, etc). These builds have been time-consuming and labor-intensive. My interest is a bit different, as I await delivery of my eight EVE 280AH cells.

My goal is to build a DIY Modular, Scalable, Reconfigurable, and Serviceable system. With demand surging for battery systems and Value-Added Resellers (VARs) springing up worldwide, DIYers have distinct advantages. I will be one of them. While Zzyzx Ink will be my VAR to design / build my modules, customer Zzyzx (currently on vacation) will do the energy audit and configure the system.

Phase 1 for Zzyzx Ink is to design a 12v LiFePO4 battery module, capable of quick and easy assembly, duplication, configuration and tear-down for repair. One of those many VARs . . . Seplos . . . has a 48v kit, BUT is using a "plastic holder" to hold the cells together. It is this plastic holder that I think can be redesigned and produced for use by those forum members interested in a 12v (or whatever size) battery "building block".

The plastic holder between cells is the common part, requiring only the end plates to be different. If you view the video, take note of the plastic "fingers" on the four sides. When two holders contain a single cell, the fingers touch (under no real compression using tape). Consider making each finger length shorter by a couple of millimeters (or whatever), such as when the "all thread" rods are connected to the end plates and tightened (12-14psi), the fingers again touch, indicating sufficient compression.

In any event, I am interested in collaborating with those forum members with similar interests. What say you?
 

sshibly

Solar Enthusiast
I am interested, make one and ship it to me pls
I will be glad to do your testing.
:)
Lol, I think the one you linked is too bulky
Make sure you consider that, size matters.
 

zzyzx

Solar Enthusiast
@sshibly If you are referring to the entire rackmount module, I totally agree (for a 12v version). HOWEVER, at this time, I am only interested in the plastic holder, redesigned for the EVE 280AH cell size. Besides, if size does matter (and it does), I am suggesting shortening the plastic fingers ;), so that when the end plates are tightened, a 12-14psi compression can be visually determined when the fingers touch. Thus, no need for a torque wrench or springs.

I am interested in working with someone who can 3D model and print a prototype of this part. I am willing to fund the project.
 

sshibly

Solar Enthusiast
@sshibly If you are referring to the entire rackmount module, I totally agree (for a 12v version). HOWEVER, at this time, I am only interested in the plastic holder, redesigned for the EVE 280AH cell size. Besides, if size does matter (and it does), I am suggesting shortening the plastic fingers ;), so that when the end plates are tightened, a 12-14psi compression can be visually determined when the fingers touch. Thus, no need for a torque wrench or springs.

I am interested in working with someone who can 3D model and print a prototype of this part. I am willing to fund the project.
I have NO cad skills, I can braid hair very well though.

Compression - I have been following the discussion about compressing the cells,
I think a simple strap system with ratcheting thumb nuts might be good to set the compression on the cells. The end plates need to be STRONG to distribute the pressure evenly, else you will have strap fatigue.

Once you have a 3d cad design, you can feed it to a machine (around $700) to print samples.
 

MatWill

New Member
Better yet it would be great if someone could make an off the shelf full system that tied solar/alternators/chargers/relays etc with the battery.
 

zzyzx

Solar Enthusiast
Better yet it would be great if someone could make an off the shelf full system that tied solar/alternators/chargers/relays etc with the battery.
Yes. I decided to start with a 12v battery module (compressed), but scaleable to at least 24v. After that, solar and chargers. And then, . . . ? The battery is the key "building" block for what I have in mind.
maybe this is something
Great find. That is what I have in mind, but with some compression. In recent days, the compression discussion has evolved, as the Chinese translation of the word "fixture" has come into question as to what it means . . . exactly. My current "Occam's Razor" thinking is to hold-off on torque wrenches and springs and go with a "little" compression as opposed to "a lot" of no compression, until more is known. We'll see.
I have NO cad skills, I can braid hair very well though.

Compression - I have been following the discussion about compressing the cells,
I think a simple strap system with ratcheting thumb nuts might be good to set the compression on the cells. The end plates need to be STRONG to distribute the pressure evenly, else you will have strap fatigue.

Once you have a 3d cad design, you can feed it to a machine (around $700) to print samples.
I have friends with 3D printers, so getting a prototype should be fairly easy. With the lock-down continuing, the retired engineer in me yearns for another hobby activity . . . so, off I go. Looked at Fusion 360, but Autodesk is no longer hobby-friendly, so FreeCad got my attention, being a Linux guy. Anyway, I'll play with that until my EVE cells arrive.
 

lexio

feel the balance 3.65
Yes. I decided to start with a 12v battery module (compressed), but scaleable to at least 24v. After that, solar and chargers. And then, . . . ? The battery is the key "building" block for what I have in mind.

Great find. That is what I have in mind, but with some compression. In recent days, the compression discussion has evolved, as the Chinese translation of the word "fixture" has come into question as to what it means . . . exactly. My current "Occam's Razor" thinking is to hold-off on torque wrenches and springs and go with a "little" compression as opposed to "a lot" of no compression, until more is known. We'll see.

I have friends with 3D printers, so getting a prototype should be fairly easy. With the lock-down continuing, the retired engineer in me yearns for another hobby activity . . . so, off I go. Looked at Fusion 360, but Autodesk is no longer hobby-friendly, so FreeCad got my attention, being a Linux guy. Anyway, I'll play with that until my EVE cells arrive.
see what i can do tomorrow lets sharpen my cad skills again. normally drawing furniture
 

Mike Jordan

Solar Enthusiast
I am no help for you in development. But I might be among the first customers. I came across that Seplos video a little while back. I love the concept. Something along the same lines with the 280ah cells in 12v would be very nice
 

zzyzx

Solar Enthusiast
I am no help for you in development. But I might be among the first customers. I came across that Seplos video a little while back. I love the concept. Something along the same lines with the 280ah cells in 12v would be very nice
The Seplos video was my initial inspiration that got me thinking about this simple solution to bundling the EVE cells. The main problem (easily fixed) was it was not strong enough to support compression. Neither was the ebike bracket that @lexio shared. Thicker plastic should solve that issue. Add an appropriately thick plastic compression "wall" to each cell holder, which is between each cell and the compression should be uniform between all cells in the module. A properly sized end-plate at each end, fitted with four "all thread" rods and I should be ready to test.
 

Capt rick

New Member
After lurking for a few months around the forum, I have learned much and seen the incredible knowledge, technical skills and impressive battery builds of forum members. These have largely been purpose-built and size-constrained, and thus "one-offs", primarily due to their locations (yachts, RVs, etc). These builds have been time-consuming and labor-intensive. My interest is a bit different, as I await delivery of my eight EVE 280AH cells.

My goal is to build a DIY Modular, Scalable, Reconfigurable, and Serviceable system. With demand surging for battery systems and Value-Added Resellers (VARs) springing up worldwide, DIYers have distinct advantages. I will be one of them. While Zzyzx Ink will be my VAR to design / build my modules, customer Zzyzx (currently on vacation) will do the energy audit and configure the system.

Phase 1 for Zzyzx Ink is to design a 12v LiFePO4 battery module, capable of quick and easy assembly, duplication, configuration and tear-down for repair. One of those many VARs . . . Seplos . . . has a 48v kit, BUT is using a "plastic holder" to hold the cells together. It is this plastic holder that I think can be redesigned and produced for use by those forum members interested in a 12v (or whatever size) battery "building block".

The plastic holder between cells is the common part, requiring only the end plates to be different. If you view the video, take note of the plastic "fingers" on the four sides. When two holders contain a single cell, the fingers touch (under no real compression using tape). Consider making each finger length shorter by a couple of millimeters (or whatever), such as when the "all thread" rods are connected to the end plates and tightened (12-14psi), the fingers again touch, indicating sufficient compression.

In any event, I am interested in collaborating with those forum members with similar interests. What say you?
I just saw the seplos technology battery kits on YouTube. I am interested but have not been able to find any reviews about cell quality or bms Quality does anyone have any knowledge of thi product?
 

Seven30

New Member
I use Varicad on linux for design work. Mine is out of date but still works well.
On pack compression does a constant pressure need to be applied (springs) or a rigid fixture that tries to prevent any swelling (pressure can rise substantially if it swells) ?
 

vtx1029

Solar Enthusiast
Here's the problem with your idea. not everyone has a 3d printer to print something like this especially for a 280ah cell. Second the performance of PLA isn't up for the task. 3rd an injected molded part is going to be costly just because of the mold needed $20-30,000. Forth the cell variation is not consistent enough IMO to use a static cell with as your compression indicator. With a static load on cells you also have no give for expansion or contraction so with SOC and temp the compression could vary quite a bit.
You would be better off IMO in sourcing valve springs the correct spring force for your application they can be found cheaper than most other springs for the weight rating you need. I can send you the spring force calculator I made. With that calculator you can figure out an installed height range that you could make say a spring cup that was 3d printed to visually indicated the installed spring height range. Personally I would make the design around using wood because it can be available most all places in the world and most people have access to wood working tools. Second choice would be steel.
 

zzyzx

Solar Enthusiast
@vtx1029 Your comments are welcome and have value. Since a number of "fixture" and "compression" threads have been going on for some months, we are all still learning what the cell specs actually mean.

@HaldorEE is working with a load cell to try and accurately characterize the cell's compression "psi" at various SOC levels and by using Belleville washers may easily help set a fixture's compression. Because these washers can be configured in series and/or parallel (like cells), the idea intrigues me. Time will tell.

Unfortunately, my efforts for a fixture are on indefinite hold, as I have no cells to play with. It turns out my "overdue" EVE cells are currently in Japan, hopefully still aboard the ONE Apus container ship. During the end of last month, only 129 containers were removed from the ship over an 18-day span. I ordered replacements in early January and hope to get them aboard ship and out of port before the Chinese New Year work slowdown and stoppage. Then, new problems begin when the ship approaches the Port of Long Beach.

I'm going to spend my time planning how to build four, identical 4S (12v 272ah) batteries. These batteries can then be connected in series (24v) or parallel (544ah) and charged via solar, grid-tied, propane-based Honda generator or a car's alternator.
 
  • Like
Reactions: JCB
Top