Talk About A Tease!!! Expertise Needed...

[TheGriz]

I was all excited about getting my four 280Ah 3.2V prismatic aluminum cells today. Got FedEx text at 5:30am this morning that they were on vehicle for delivery!!! Then an hour ago, I get another text that delivery is rescheduled for tomorrow. Certainly need to exercise extreme patience during these crazy times.

Expertise needed for this noobie please:

1. From watching Will's vids and others, it looks like I need to "bound" the four cells together. I see different methods: hose clamps which I am not crazy about; using tape of differing varieties. What is the brain trust out there using to bound the cells together?

2. Do I bound all four cells tightly together? Or leave a small gap between each for air circulation?

3. Suggestions for case to enclose the four cell pack. I do have some fabrication capabilities/abilities. I am figuring the finished dimensions of the cell pack "Cube" (if bound tightly together) will be roughly 8.5"(H) X 6.85(W)" X 11.36"(L). Height includes the buss bars, and Length presumes four cells bound together with no air space between cells. The case will also need to enclose the Chargery BMS8T and an insulating panel of some sort on top of terminals and buss bars. I am estimating the "pack" to weigh approximately 50 pounds not including whatever the case is going be.

4. Is ventilation needed for the case, and if so how much and how to ventilate?

5. The manufacturer of these cells in EVE Energy. I looked in depth at the 8 page spec sheets. But didn't see any guidance on cell orientation, e.g. Upright, on side, on edge. Any insight on orientation limitations of these cells?

FYI...I am trying to keep this cell pack portable for multiple uses: ham radio field use; RV boondocking; home use during power outage with 2000w/4000w pure sine wave inverter; and who knows what else. Already have a 100w solar panel/SCC for use when needed.

I look forward to this brain trust's insight!!!
Mike

P.S. - Hope all are well out there. Please remember to social distance and self-quarantine where required! We all need to act responsibly for the sake of ourselves, family, friends, and the world.

 

[Steve_S]

A-1 & 2) There are two lines of thought on this, Generally the accepted rule is to bid then together SNUG not "tight". Metal Strapping is so/so there is potential in metal right. I have seen assembled packs with that Polyester Strapping like these: https://www.uline.ca/Grp_57/Polyester-Strapping

A-3) a 24V "Square Packs" dimensions (footprint) is 13-3/4" wide by 11-3/3 long, standing height to screw top is 9". This leaves a little room so you can drop the cells in. I am building boxes with lids out of 3/4" Ply which will be eurathaned. My own "specific" design is for a base of 14" Wide x 15" deep, allowing for a 3" space & blocker between the cells & front. I will be putting the BMS Control module in that space. If using a metal box of some sort, ensure there is a non-metallic liner. The "Long" 8S pack is a beast to manage for me and my space. Also having a longer Lead from one cell terminal to Batt Post does NOT appeal to me, I am finicky (It's a Type A, Virgo thing) about keeping wire lengths as evenly matched as possible.

A-4) Ventilation isn't needed for the cells BUT the BMS Control unit does warm up, does not get terribly hot though.

A-5) You can put them on side but NOT upside down !

8S-24V Square Pack.

 

[TheGriz]

A-1 & 2) There are two lines of thought on this, Generally the accepted rule is to bid then together SNUG not "tight". Metal Strapping is so/so there is potential in metal right. I have seen assembled packs with that Polyester Strapping like these: https://www.uline.ca/Grp_57/Polyester-Strapping

A-3) a 24V "Square Packs" dimensions (footprint) is 13-3/4" wide by 11-3/3 long, standing height to screw top is 9". This leaves a little room so you can drop the cells in. I am building boxes with lids out of 3/4" Ply which will be eurathaned. My own "specific" design is for a base of 14" Wide x 15" deep, allowing for a 3" space & blocker between the cells & front. I will be putting the BMS Control module in that space. If using a metal box of some sort, ensure there is a non-metallic liner. The "Long" 8S pack is a beast to manage for me and my space. Also having a longer Lead from one cell terminal to Batt Post does NOT appeal to me, I am finicky (It's a Type A, Virgo thing) about keeping wire lengths as evenly matched as possible.

A-4) Ventilation isn't needed for the cells BUT the BMS Control unit does warm up, does not get terribly hot though.

A-5) You can put them on side but NOT upside down !

8S-24V Square Pack.
View attachment 9945

Excellent input Steve. Roger on NO upsidedown...didn't intend that. I just have no means of tensioning polyester strapping...and not going to buy tool for a one or two time use. I was thinking wrap cell pack first in some type of non-adhesive "undertape", then two or three wraps of Gorilla tape or some other strong tape over the undertape...thoughts?

OH...also "Type A/Virgo" here too!!! So I understand!!!!! LOLOL Are you a Southpaw by chance (which is triple trouble)???

Thank you!
Mike

 

[Steve_S]

Excellent input Steve. Roger on NO upsidedown...didn't intend that. I just have no means of tensioning polyester strapping...and not going to buy tool for a one or two time use. I was thinking wrap cell pack first in some type of non-adhesive "undertape", then two or three wraps of Gorilla tape or some other strong tape over the undertape...thoughts?

OH...also "Type A/Virgo" here too!!! So I understand!!!!! LOLOL Are you a Southpaw by chance (which is triple trouble)???

Thank you!
Mike

Ohh, I suffer TWO handicaps that make it worse. I am an APEX Virgo apparently as my DOB put's me in the worst of the pickiest group. I'm Right Handed but before the injuries, I was ambidextrous, oh well, ces't la vie. I wondered about the strapping thing too, pondered if I could borrow one of those hand crimpers from a local shop (rural small towns, it's not hard to do things like that with businesses that know you).

The tape idea you have might work well, gorilla tape is good stuff and won't let go over time like a lot of others BUT you are right an undertape something so if you need to take it apart your not glued to the cells and making a massive mess...

 

[FilterGuy]

Aluminum cells tend to bulge a bit, so they don't fit up against each other well. To compensate for this I put 1/8" or so spacers on the outside edge between each cell. This is a design I did for a 24V pack.

The red blocks are the spacers. In this build I used some scrap 1/8" plastic for the spacers.

Edit: Added "and spacers" below
I build the box ever so slightly larger than the cells and spacers and then use tape to shim the batteries till it is a snug fit.

 

[FilterGuy]

I was ambidextrous,

I'd give my right arm to be ambidextrous!

 

[FilterGuy]

Aluminum cells tend to bulge a bit, so they don't fit up against each other well. Fo compensate for this I put 1/8" or so spacers on the outside edge between each cell. This is a design I did for a 24V pack.
View attachment 9948
The red blocks are the spacers. In this build I used some scrap 1/8" plastic for the spacers.

Edit: Added "and spacers" below
I build the box ever so slightly larger than the cells and spacers and then use tape to shim the batteries till it is a snug fit.

 

[TheGriz]

Ohh, I suffer TWO handicaps that make it worse. I am an APEX Virgo apparently as my DOB put's me in the worst of the pickiest group. I'm Right Handed but before the injuries, I was ambidextrous, oh well, ces't la vie. I wondered about the strapping thing too, pondered if I could borrow one of those hand crimpers from a local shop (rural small towns, it's not hard to do things like that with businesses that know you).

The tape idea you have might work well, gorilla tape is good stuff and won't let go over time like a lot of others BUT you are right an undertape something so if you need to take it apart your not glued to the cells and making a massive mess...

HAHA...APEX! I thought of this after I hit the post reply last message. The 'undertape' can simply be the first layer of Gorilla tape with adhesive side up and non-adhesive side toward battery. Then wrap another couple layers on top of the undertape conventionally. Put strapping right at top of cells and another strapping at bottom of cells...viola! I'm thinking that would do fine.

 

[TheGriz]

Aluminum cells tend to bulge a bit, so they don't fit up against each other well. To compensate for this I put 1/8" or so spacers on the outside edge between each cell. This is a design I did for a 24V pack.
View attachment 9948
The red blocks are the spacers. In this build I used some scrap 1/8" plastic for the spacers.

Edit: Added "and spacers" below
I build the box ever so slightly larger than the cells and spacers and then use tape to shim the batteries till it is a snug fit.

More excellent input...thank you FilterGuy! I was thinking I could kill two birds with one stone. I have 1/2" VHB tape. I am thinking of using a small 1" long piece of VHB tape on the four corners between each cell. This would provide an every so slight space for airflow/bulge, but also keep cells from shifting side-to-side. I am throwing this out there thinking this is a good idea. If others know better, please speak up! I have never done this before, and open to all suggestions and criticisms (constructive I hope).

Regards,
Mike

 

[FilterGuy]

More excellent input...thank you FilterGuy! I was thinking I could kill two birds with one stone. I have 1/2" VHB tape. I am thinking of using a small 1" long piece of VHB tape on the four corners between each cell. This would provide an every so slight space for airflow/bulge, but also keep cells from shifting side-to-side. I am throwing this out there thinking this is a good idea. If others know better, please speak up! I have never done this before, and open to all suggestions and criticisms (constructive I hope).

Regards,
Mike

I have not done that, but it seems like it would work if it is thick enough and stiff enough. If the tape flexes, you are going to be putting some nasty stresses on the cell terminals.

BTW: what i did not mention about my spacers is that I use a touch of glue (or 2 sided tape) to hold them on the cell while I get them all snugged up in the box.

 

[Steve_S]

More excellent input...thank you FilterGuy! I was thinking I could kill two birds with one stone. I have 1/2" VHB tape. I am thinking of using a small 1" long piece of VHB tape on the four corners between each cell. This would provide an every so slight space for airflow/bulge, but also keep cells from shifting side-to-side. I am throwing this out there thinking this is a good idea. If others know better, please speak up! I have never done this before, and open to all suggestions and criticisms (constructive I hope).

Regards,
Mike

I don't remember which one(s) but Will does some battery builds and uses a 1x1 ? square piece of 3M 2-way tape on the facing corners to keep the cells from shifting. I think this makes especially good sense if the pack is being used in a mobile environment, for normal "home" storage system, I dunno, can't hurt.

 

[TheGriz]

I don't remember which one(s) but Will does some battery builds and uses a 1x1 ? square piece of 3M 2-way tape on the facing corners to keep the cells from shifting. I think this makes especially good sense if the pack is being used in a mobile environment, for normal "home" storage system, I dunno, can't hurt.

Yes...I believe he used the VHB tape in the video and is where I got the idea. I think VHB stands for 'very high bond'. Below is right off 3M's site:

• With 3M™ VHB™ Tapes, you can maintain consistency from sketch to construction, eliminating distracting, visible fasteners, like screws and bolts. These high-strength, double-sided acrylic foam tapes let you quickly and easily create a long-lasting bond that actually builds strength over time. With the ability to join a variety of materials including aluminum, steel, glass, plastics and painted and powder-coated surfaces, they provide resilient bonding solutions in just about anything you can dream up.
  

Here is link to the VHB tape: https://www.amazon.com/3M-Tape-RP32...Roll),Gray&qid=1585612662&s=hi&sr=1-1-catcorr

 

[JoeHam]

How about this

Robot Check

As a starting point? Add spacers to keep it snug.

 

[TheGriz]

How about this

Robot Check

As a starting point? Add spacers to keep it snug.

Yep...a KISS solution. And that is always good! Thanks.

 

[Bob B]

I've got some of THIS strapping but haven't tried it yet ..... still debating about spacers and ventilation.

 

[TheGriz]

I've got some of THIS strapping but haven't tried it yet ..... still debating about spacers and ventilation.

How would you tension the straps?

 

[Bob B]

How would you tension the straps?

Once you wrap it through the buckles you can pull both ends to tighten it up ..... I plan on getting it really tight by getting a pair of pliers on both ends to pull tight.
It's gonna be a week or 2 yet before I put it together ..... Maybe I'll try something as a sample to see how it works.