Are Cell Spacers Necessary?

[kudos]

For my next battery build I’ll be looking to stuff as many cells in an EEB frame as possible.

I used the standard 21700 cell spacers in my last build but obviously not using spacers would allow a lot more cells in total.

I’ve seen people hot glue cells together, then fish tape parallel groups. A few other methods too.

The obvious concern is heating of the cells in the centre of the pack, but if the pack iis big enough and the cells are capable,it shouldn’t be an issue?

Can anyone’s who has actually made a pack without spacers comment on the pros and cons?

 

[fechter]

What C rate are you planning to discharge at? Cell heating is usually only an issue at higher C rates. I have a couple of packs I built without spacers and they barely get warm. I did design the pack so that the one end of the cells is directly against the housing and I filled the space with silicone to allow better heat transfer to the outside. This has worked well.
Good insulation between parallel groups is important. For sure I wouldn't suggest gluing cells from different groups directly together. I used fiberglass tape between groups on one build and heavy Nomex fish paper on the other one.

 

[honya96]

Simply said, heating is not an issue. If you don't plan to have a fan pushing air through, just glue them on top of each other as you want.. let me know what capacity you got in

 

[From-A-To-B]

I've never built a pack without spacers, so I cannot comment on the OP's question. But it seems to me that heating isn't the primary concern unless you're starting to push your cells to the edge of their ratings. I, personally, would be more concerned about vibration and would want to make sure cells aren't going to rub through their insulation as your bike rattles down the road for 10,000 miles.

 

[kudos]

would want to make sure cells aren't going to rub through their insulation as your bike rattles down the road for 10,000 miles.

You make a valid point.

Has anyone used cell wraps:

21700 PVC Wraps

21700 PVC battery shrink wraps, perfect for re-wrapping cells with damaged wraps. Fast delivery | Quality Products | Order now - Fogstar UK.

www.fogstar.co.uk

How loose are they initially? Can you fit them over a cell that is already wrapped before you shrink them?
(To double wrap them)

 

[From-A-To-B]

You can double wrap a cell, yes. From memory, I’d think that the wraps would fit over top of an already wrapped cell.

This is still not nearly as much protection as using a cell spacer. Insulating your parallel groups with fish paper is likely better than double wrapping them, but spacers are still better.

Unless one has space constraints that won’t allow for spacers, I see no reason to omit them. And even then, I’d opt for a smaller battery capacity than build without spacers.

Every OEM battery I’ve taken apart (and I’ve worked on a hundred batteries for other people) have used cell spacers. Omitting them seems neglegent to me, and the threat of a fire makes a 1-in-1000 chance too much risk for me.

Cell spacers don’t preclude other failure methods, but let’s reduce risk where we can, eh?

 

[batteryGOLD]

For my next battery build I’ll be looking to stuff as many cells in an EEB frame as possible.
I used the standard 21700 cell spacers in my last build but obviously not using spacers would allow a lot more cells in total.
Can anyone’s who has actually made a pack without spacers comment on the pros and cons?

Sir, ther r some dirty tricks to save space (more cells per sq meter)

1st- cell plastic spacers not necessary at all.. some extra mm multiplied by number cells P & S give an extra payload space..
instead holders use insulator card to separate S elements. if a 10S 36/42V battery, u will need x8 insulator cardboard.

2nd- build battery based at "honeycomb" architecture. this will save more space.
make sure to use also insulator cardboards between S elements.

gluing cells together with hot glue, is a very dirty and maybe danger idea..
since P cells at different voltage are very near. at beginning all ok, and seems a perfect battery design, easy diy.. butt remember that goes on electric veicule on roads/offroad, so you need to include variable vibrations/mechanical pressures transmitted to battery structure, P elements could do friction at next P element until metal cases of two S elements touch..
at this point better U to run way from your electric veicule, since the battery will sure catch on fire!!

PS: not all bad news, just build your new battery based on simple safety rules you learned. Trust your own learning & work!
always put a middle separator at different voltage elements!! at any electronic elements!!
would you touch a cable powered w 230V AC ? is more safe to touch the copper or the insulation?
butt worst, U are dealing w/ lithium fire pyrotechnics, once it triggered, THE END!!