Heat Shrink and Padding Battery Pack - Why?

[YoshiMoshi]

I'm building a power tool battery pack. I see lots of people online use some sort of padding and put it around their battery pack, then they heat Shrink the whole thing, put it in their hard plastic case, and add additional padding as necessary.

My question is what exactly is the function of the heat Shrink and what purpose does it serve? Would heat shrinking the whole thing and putting padding all around it just cause the pack to heat up even more?

I have seen people take power tool battery packs apart online. I don't think I've ever seen a manufacturer (DeWalt, Milwaukee, Craftsman...) put heat Shrink or padding around their pack. I'm wondering why? As it seems common place for battery packs in other applications. Is it because battery tool packs are very compact and limited in space, so there's just simply not the room for hear shrinking the whole pack or any type of padding?

I get the battery padding just helps absorb shock, but at the cost of hearing the cells up more?

Thanks for the help!

 

[neptronix]

Physical trauma can cause some cells to blow up.
Whatever you do, you need a sealed case, which will cause the pack to be a little ez-bake oven if they are abused. Adding padding won't change the main thermal problem much.

Cells that are used conservatively relative to their maximum amp/C rating don't generate enough heat for a sealed environment to be a problem. Therefore, pad away, but pick your cells/amp hours well.

 

[gromike]

The shrink wrap is about trying to eliminate relative motion between cells, imho. I add foam padding to stifle any motion between the electrical parts.

 

[fechter]

Right. The heat shrink is what's holding the pack together and insulating the cell connections. Cheap and easy, but not ideal in many ways. A rigid box with some way to dissipate the heat is a better approach.

 

[YoshiMoshi]

Tha k you all. Is there a particular padding I should use?

 

[amberwolf]

Tha k you all. Is there a particular padding I should use?

Whichever type of padding you can get that compress under load but rebound afterward (like on a bump), and can take the weight on them, and are thick enough to handle the full compression under worst-case loading, and still have thickness beyond that so bumps are absorbed by it and not transferred to the battery (or whatever is being padded).

Closed-cell dense foams (like neoprene, often used for the better mousepads, scuba suits, etc) are often used for this. There are rubbery ones that are very flexible and heavy, and those have better recovery than the lightweight stiffer ones.

Open-cell foams don't recover well from loading, so I'd avoid those.

There are also thick heavy rubbers often used for mass-damping in acoustic systems, and those usually work well too, but they can tear easily so you don't want to put pokey or sharp edged things against them.

The main thing to remember is that you are trying to immobiilize the entire pack as a unit, so nothing in it moves relative ot anything else, and then also trying to prevent the unit from being banged around (into it's casing, etc).

If you've ever received packages that were thoroughly packed, you'll probably have noticed they tend to arrive undamaged, vs ones loosely packed (or no packing, loose in the box).

 

[Diggs]

Closed-cell dense foams (like neoprene, often used for the better mousepads, scuba suits, etc) are often used for this. There are rubbery ones that are very flexible and heavy, and those have better recovery than the lightweight stiffer ones.

All the packs I make that run on a rear rack sit on a sheet of 1/2" closed cell foam to dampen the shock. Sitting on the rack, space is not a huge issue. I also use a much heavier shrink tube than the shiny blue PVC stretch wrap tube. The blue stuff just does not hold up well.

 

[Chalo]

I use closed cell polypropylene or polyethylene foam from electronic gizmo boxes to cushion my batteries. I'm willing to use the open cell stuff that comes with my fake Pelican cases for padding the case lid, but I use the closed cell kind on all the other surfaces that see more shocks and vibrations.

 

[Zambam]

How about big semi truck tire inner tubes? Aren't they pretty thick? Double them or triple them up if needed. They're free.

 

[YoshiMoshi]

Thank you all.

Do you guys have like an Amazon link to recommended padding or foam, as well as a link to recommended heat Shrink for battery pack?

 

[docw009]

For inside a tool battery case, you could just do what the OEM maker did. The design should be more than adequate.

For heat shrink within a case, the blue stuff you can buy on amazon will work. There are different levels of quality, Amazon tends to sell the lowest quality, It develops holes if given too much heat,

For a stand alone brick battery, I also use the rubberized PVC that Diggs recommends, but underneath will be a coroplastic box and additional padding between that and the cells., I've used the rubber drawer liners sold by Rubbermaid as padding.

 

[aroundqube]

See post above by Diggs for heat shrink tube. Here is another one Shrink Wrap Tube Glossy Black Ebike Battery Pack (per foot)

 

[YoshiMoshi]

Would fish paper do the same thing as heat Shrink?

 

[Diggs]

Would fish paper do the same thing as heat Shrink?

No, I'm afraid not. You should watch some YouTube videos on the materials and processes used to heat shrink an ebike battery. The video below is using the heavier rubberized heat shrink tubing we discussed above.

 

[YoshiMoshi]

No, I'm afraid not. You should watch some YouTube videos on the materials and processes used to heat shrink an ebike battery. The video below is using the heavier rubberized heat shrink tubing we discussed above.

Thanks. I have watched a few videos.

So you should wrap fish paper around parallel groups if your not using a plastic divider to physically separate the cells?

Is it absolutely necessary to use fish paper around parallel groups if your not using a plastic divider?

I see people who don't use plastic dividers put fish paper all around parallel packs, to prevent parallel packs from touching.

Is the insulation wrap on the individual cells when you buy them new not enough insulation if your not using a plastic divider to hold the cells?

 

[Diggs]

Thanks. I have watched a few videos.

So you should wrap fish paper around parallel groups if your not using a plastic divider to physically separate the cells?

Is it absolutely necessary to use fish paper around parallel groups if your not using a plastic divider?

I see people who don't use plastic dividers put fish paper all around parallel packs, to prevent parallel packs from touching.

Is the insulation wrap on the individual cells when you buy them new not enough insulation if your not using a plastic divider to hold the cells?

I've always used these 18650 battery holders for all the batteries I have built. Common wisdom is not to let the cells be able to touch each other. If you can do that with fish paper and are sure they won't chafe?????? The results are pretty serious if you make a mistake.

 

[docw009]

Yosh, thought you're redoing tool pack batteries? Doesn't this constrain you to the original container? While I bet a lot of the really old ones glue their cells together, I looked up my Craftsman and Ryobi 40V and they use cell forms. Shrink wrap has no place in these units.

The bottom is what I would want to see in a tool pack that's going to fall on concrete, Wll, hopefully we don't drop the Ryobi's.



Ryobi 40V



Well, if you are doing custom battery shapes and glueing them together, that's old technology and more riskier. .

It would be safer to put at least one layer of fish paper between parallel groups. You would be surprised at how it takes up space, especially if you use an interlaced cell pattern,The fish paper is stiff and you would want to use wooden clamps to hold the cells together til the glue sets,





.

 

[aroundqube]

Yoshi , please try this for learning How To Build A DIY Electric Bicycle Lithium Battery From 18650 Cells

 

[YoshiMoshi]

I've always used these 18650 battery holders for all the batteries I have built. Common wisdom is not to let the cells be able to touch each other. If you can do that with fish paper and are sure they won't chafe?????? The results are pretty serious if you make a mistake.

I see what your saying. Is there a product like that, that is not meant to act as end caps? Essentially the same holder, except instead of being at the end of each cell it can sit in the middle of the cell, and not add extra height?

 

[YoshiMoshi]

Yosh, thought you're redoing tool pack batteries? Doesn't this constrain you to the original container? While I bet a lot of the really old ones glue their cells together, I looked up my Craftsman and Ryobi 40V and they use cell forms. Shrink wrap has no place in these units.

The bottom is what I would want to see in a tool pack that's going to fall on concrete, Wll, hopefully we don't drop the Ryobi's.


View attachment 362950
Ryobi 40V


View attachment 362947
Well, if you are doing custom battery shapes and glueing them together, that's old technology and more riskier. .

It would be safer to put at least one layer of fish paper between parallel groups. You would be surprised at how it takes up space, especially if you use an interlaced cell pattern,The fish paper is stiff and you would want to use wooden clamps to hold the cells together til the glue sets,





.

Yes something like that. Ok so no heat Shrink for power tool battery packs. Don't think I've ever seen one with it. Probably a reason why.

Yea so that black plastic holder, adds some height to the cells, so like the overall length of the cells is more, not allow for much room to weld nickel strips.

So I'm hoping there's something like that black piece, but sits on the middle of the cells and doesn't add any height to the cells? But I don't think such a product exists?

 

[Diggs]

So I'm hoping there's something like that black piece, but sits on the middle of the cells

Actually, those holders that I linked to you can nip off the four little tabs that hold them at the end of the cell and then you can slide then to any position on the cells.

 

[YoshiMoshi]

So my Makita BMS can support 30 A continuous discharge. Per matador's table, I would need at least three strips of 15 mm width by 0.2 mm thickness and one strip of 10 mm width by 0.1 mm thickness to carry the 30 A.

Those black plastic holders are meant to act as end caps. There is little to no room going the width of the battery pack when using the black plastic holders, meaning this way.

Add multiple layers of nickel strip, and it likely won't fit. 15 mm width nickel strip requries going over those black pieces, resulting in the nickel strips not laying perfectly flat, resulting in not good welds and hard to do.

But I like the idea of knipping off those four little black tabs so I can slide them down the length of the battery, so the nickel strips can lay perfectly flat, making them easier to weld, and more room for more thickness of the strips.

But I think I am understanding more now, and why the black plastic holder is safer.

So what exactly is the purpose of fish paper then?

 

[YoshiMoshi]

I see on that ebkiek site

They seem to be placing parallel packs together, without using a holder, and allowing them touch, but like you guys say that is not a good idea.

I tried kniping those four black pieces, and it seems a bit harder than I thought. I would need actual flush cutters, and it might take sometime. But I guess a commerical product with the four black tabs already missing doesn't exist, and I'll just have to deal with it

 

[Diggs]

I would need actual flush cutters,

Sorry, but you probably will. My favorites.

 

[Zambam]

After cutting, probably have to follow with a round file.