recommendation for hot glue/padding of cells?

emaayan

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hi..
i was wondering if you found any particular hot glue which is more suitable then others to attaching cells
the same goes for any padding material like foams to withstand heat.

for example i was wondering if there is any "spary" i can use that would turn to foam and harden around the pack, so for example i would place the pack in a heat shrink spray inside the heat shrink ,and after foam hardens , close and heat the shrink so the battery would all nice and snugly and won't move anywhere.
 
no takers from the battery builders.

I would say if you do choose hot glue,, choose a higher temp stick at least.

The foam idea is interesting, but battery cells need to be able to cool themselves when they get hot during discharge. I would not want to make the cells in the center of the pack any hotter than usual with more insulation. Outer insulation then can keep a whole battery warm in winter, be removed in summer.

For winter,, you could shrink the pack, then wrap it in loose plastic. Add another layer of shrink, then foam it. Next summer the inner plastic would allow easy removal of the foam. Pretty easy though, to just take sheet foam and tape it around the pack in winter.

Summer or winter,, DO NOT insulate the bms. It needs to let the heat out.

Some go the opposite way, using some kind of special wax that is able to act as a heat sink. Allcell does that, and claims it helps cells stand more heat.

I've wondered if something like aluminum rods in the spaces between the cells could heat sink some. More weight of course, but the space is very small, so maybe not really that heavy. Not protruding past the end of the can though,, risk of a short.

Maybe just an epoxy could still heat sink a bit,, like a PC7 or JB weld and glue the cells together.
 
I like using a product called "quick grip" for gluing cells together. Yes you do need to wait for it to dry, but its a lot faster than hot glue and a lot cheaper as you dont need as much. Most of the time I actually glue the cells together then put some insulating gasket paper rings on top from one cell to the next to join them together that way while the glue is drying, works great and I can even weld the pack up while the glue is setting. Also I've seen a lot of packs where the hot glue just kind of falls off without bonding to the cell jacket. Quick grip sticks.
 
define "higher temperature" any brands?
 
Hot melt is commonly used on smaller packs I see in other applications. Not too hard to take apart if needed.
Regular Super Glue will make a bond so strong it rips the insulation off the cell if pulled hard enough. In a lot of packs, just the welded tabs provide enough support. Especially true if sheets are used instead of 8mm strips. Silicone works and has very high temp rating but takes a long time to cure.

I would highly recommend placing some additional insulation like Nomex paper or fish paper between series sections to prevent shorts from vibration or impact. It's pretty much only a matter of time before a bike gets tipped over or crashes. You want to provide protection against shorts (and resulting fires) in these events.
 
i'm looking for all sorts of protection against that.

even thought about using http://www.ebay.com/itm/1-4-x-24-x-60-HiDense-CLOSED-CELL-UpholFoam-G/192066578897?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D40757%26meid%3D9185054a72614d9bb1e1f18fb533c892%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D112224000750

but maybe it's too thick?

i have no intention on relying just on welds to keep them, as for regular super glue, ripping the insulation off, i understand that removing the welds itself safely is very very hard ( have a123 cell triangle battery with a dead cell inside somewhere which i'm afraid to touch because of it)

as for glue sticks? how about this one?
https://www.amazon.com/Adhesive-Technologies-220-11ZIP24-10-Inch-24-Pack/dp/B0018N9P22/ref=pd_bxgy_469_img_3?_encoding=UTF8&psc=1&refRID=7GTKJQZSXQZ4FEHV8R5P
 
The thing about Nomex or fish paper is it won't melt if a cell shorts and it has very high compressive strength. Fiberglass sheet is good but not flexible. The squishy kind of foam is better around the outside of the pack for cushioning. You want to avoid any movement between cells that would cause weld or insulation failures. Bouncing over pot holes can put some really high forces on things.

The hot melt there looks OK. If the glue is too hot, it can melt the battery wrapper.
 
define "too hot", i don't know much about hot glue, but i understand there are too kinds low temperature and high temperature kinds,
for example if i use this gun https://www.amazon.com/gp/product/B006IY359K/ref=od_aui_detailpages00?ie=UTF8&psc=1 will be too hot ?

if i use nomex paper around the paralalls that means i won't be able to bond them with glue, i won't the whole pack to be as rigid as bonded securely as possible.
 
I didn't see a temp specification. Most of those general purpose glue guns work fine. You can test it on a sacrificial cell by holding the nozzle against the cell wrapper for a second and see if it melts through. Even if it's a little hot, you can avoid problems with proper technique, like don't hold the tip on any spot for very long.
 
thanks i'll add to tests i'm planning to do like glueing 12 guage wires on single cell and use jutine's http://www.ebikes.ca/load-resistor-6-8.html on it, do a full discharge and see how hot it goes, and use soldier various strips onto the wires and see the amps before and after the strips ,as well as see the temps on the strips...
 
how about those

https://www.akkuteile.de/abstandshaeuelle-faeuer-18650-zellen/a-400301/ (just a drop of super glue inside)

and this (thinner)
moosgummi2.jpg


everything glued together with epoxy finally.

my last pack has been built with this mentioned paper things for each cell, a layer of 3mm foam between each cell, finally a layer of fibreglass mat soaked with 45min epoxy.

pro: still possible to maintain, the paper around each single cell makes it possible to push out a dead cell if needed
con: weight, worktime
 
what about heat?
 
I used a double sided tape called Gorilla mounting tape, its about 2mm thick and sticks instantly to anything but seems to want to peel OK if you get it wrong. I just cut a number of about 5mm wide strips, attach one side to a battery, take the protective tape off and push the two batteries together. As long as you don't push them together to hard you can re-position them. Leaves the batteries all about 2mm apart for the heat to dissipate.
IMG_1730.JPG
 
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