18650 cell holders instead of soldering

raccooon

raccooon

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Nov 25, 2018
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Hi everyone,

i'm on my way to build a 3S20P , with proper copper busbar and 2A glass fuses on both side, but if one cell go wild, i will need to desolder everything, so since idc about the size of my pack, i was thinking if these instead would work

https://www.aliexpress.com/item/New-18650-Battery-3-7V-Clip-Holder-Box-Case

i could buy 100 of them, but do you think i would increase a lot the losses in my pack due to this extra layer of connectivity?

I checked vruzzend battery kit but its too expensive for me :/

Thanks a lot :)
 
The linked are total crap.

Do Like this
 
daromer said:
The linked are total crap.

Do Like this
Click to expand...

I know i've seen this video, i think i've seen all this guy's channel awesome videos ! :)
but still when you have to change a cell, you need to brake the corner and
unsolder some part, i mean, its not exactly plug&play :)But if its the only way to go, then...
 
How often do you expect till change cells? I have not changed a single One in 2 years
 
If you get the cell holder, do "not" get any with spiral springs. They are monster energy leaks. You want to get the ones with bronze or the other type of tabs, if possible. The cost is around $2 per 4x holder, if I remember correctly.
You can go with the tabs that are nickel coated, but they won't be as good. The tedious task of soldering an independent wire on each tab isn't worth it. The wire would be copper/tinned to give the least amount of resistance possible.

Spiral springs have 'lots' of losses, and will loose strength over time. The tab style will hold a lot longer.
 
@daromer: I dunno, but my cells goes from 1900 to 2320 mAh, and many different brands, so i'm not sure if they would cohabit happily together, a bit like how human from different origin try to cohabit together , u know what i mean ;) as a first pack, i would have like for the easy plug&play style ;)

@Korishan : thanks a lot, that's why i was afraid about without being sure if or if not ;) so i won't order those ones, let's see if i found some good ones with bronze ;)


ps: just realised i put so many smileys everywhere ...
 
we like smileys :D
 
Curly spring holders are the worst type ....

If you want to go the cell holderroute these are the only choice ...

s-l225.jpg

But you would be much better spot welding this makes a secure connection but is also easily removed for dismantling ... but since you have already soldered these cells , I would stick to that method for them.
 
I have over 30000 cells... And they are all mixed.... I got 1200 to 2600 IF i include the life cells that are between 1200 to 1400. Liion 2000 to 2600
 
One thing you can do is actually this:


image_zdrkki.jpg


I've actually made it myself, and I've tested it up to 20A with capable cells, and the springs do not warm up much at all. You can make one 20 cells wide if you want, and then you've got something very nice. It's only a prototype though.

I've used these parts to make it:

0,2mmx10mm copper strip(use 0,5mm strips if you want to make a 20P setup for higher current)
4mmx1,5mm brass buttons/beads: https://www.aliexpress.com/item/50pcs-lot-4-5-6-7-8-10m
Phosphor bronze springs: http://kaidomain.com/S027428-DIY-Br...upport-Springs-10mm-x-12mm-5pcs?search=bronze
4x battery holder
High temperature epoxy
XT60 connector
Some thick wire, thick as you like.
I used solder paste to actually solder the parts. Was easy as pie :)


image_yphqrb.jpg
 
That design still uses wire springs. I have tried to do same layout but using the tab style 3 cell holders
 
Well, since they're made of phosphor bronze and much thicker wire than the ones used in the cheap holders, they can sustain much more current.

One advantage of using these types of spring holders is the fact that you can directly bypass the springs for absolute maximum conductivity with 20AWG wire, and that they support multiple sizes of cells.
 
BlueSwordM said:
they're made of phosphor bronze
Click to expand...

This is what I was thinking of earlier. Couldn't remember what they were. Thanks BlueSwordM :)
 
No problem.

What was surprising during my BeCu spring groupbuy on BLF is how cheap they are when you buy them in bulk.

For example, 2000pcs of nickel plated Beryllium Copper springs would cost 335$ including express shipping, so about 0,20$US/spring.

For 4000pcs, it would cost about 460$US to make the springs, so 0,12$US/spring.

And so on and so forth.

Phosphor bronze C54400 would be even cheaper.

And knowing how many springs we would need in our battery holders, I think we could get down the price to 0,05$US/spring for 6A+ capable springs, unlike the steel nickel plated trash that can barely do 2A without massive power losses.
 
BlueSwordM said:
And knowing how many springs we would need in our battery holders, I think we could get down the price to 0,05$US/spring for 6A+ capable springs, unlike the steel nickel plated trash that can barely do 2A without massive power losses.
Click to expand...

Perhaps add the info needed in the Marketplace and see how many people would be interested. You could probably do a poll along with it. List the prices, pictures, quantity, shipping areas, etc. Don't forget to put "Group Buy" in the title so people will know what it's about to get more attention on it.
 
Shouldn't be too difficult to do, as I already have experience in this regard :) :
http://budgetlightforum.com/node/61145

I've learned a ton of stuff about it, along with 9 pages of math, and created a ton of data in this regard

And I just wouldn't be selling the springs alone though. I have an idea to incorporate 3S-4S-5S setups in the battery holders. It would stupidly good if I could manufacture battery holders like spcified that would be a fully integrated system. You'd only need a BMS at this point.

That would mean, for good amperage, we would need to make a 6 cell 3S holder, an 8 cell 4S holder, and a 10 cell 5S holder.

That would be golden, and we would be able to draw 130W from the 6 cell holder at peak, 170W from the 8 cell holder at peak, and 210W from the 10 cell holder at peak.

And you'd easily be able to connect in parallel via a direct connection, and series the packs just by flipping the battery packs sideways.

The only problem to correct at the design stage would be reverse polarity protection between each pack.

TLDR: Only need to find a manufacturer to make solid battery holders to hold the cells with springs compressed, and I'm golden.
 
I went back and reviewed the info on the group buy. I was not aware of magnitude of this previous effort. Impressive.

It seams like everyone was happy with the quality and performance but maybe more time is needed?

What is time frame for a second group buy?

Tks

Mike
 
@Chablis_m, yeah, there was a huge effort involved in my part. I had to do quite a bit material research, try to find a trustworthy spring manufacturer, and about 7-8 pages of math to design my own spring. A lot of work was put in. I learned a lot of stuff though.

There's not much more testing to be needed, even over time. The spring wire thickness/diameter is quite high, meaning it can resist to plastic deformation extremely well for a copper alloy spring, and it has very high conductivity and yield strength relatively speaking compared to phosphor bronze and BeCu C17500.

And since it has low resistance, it has no thermal sag resulting in a higher chance of plastic deformation at high compression levels, and while you do need to apply a lot of force to compress it compared to a normal steel spring, contact resistance is minimized, even with a hard nickel electroplate.
 
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