Making a 12v 4s battery pack from 18650

[msacco]

Hi, I have around 20 18650 battery just sitting around, so I thought of making a 4s 12v(well more like 12-16v battery depends on charge).

That should be fairly easy overall, just looking for some advices to make it as good as I can.
One thing I would like to try is avoiding soldering as much as I can, especially with the 18650 batteries themselves, I'm not sure where I've heard that, but if I remember correctly soldering straight onto a 18650 is not very healthy for the battery due to the heat(like here for example: https://www.youtube.com/watch?v=0sj5DvG-qPI)

Now I believe that with the proper soldering skills and tools, soldering the 18650 batteries might not be an issue, but in my case both my soldering skills and soldering tools are fairly bad, and that's mainly why I'd like to avoid that if possible.

I thought about a solution for that, and thought about getting 5 of these 4 slots holder:
https://www.aliexpress.com/item/32823843782.html?spm=a2g0o.productlist.0.0.35fe766eyozMp5&algo_pvid=5b1f4838-a84d-496d-af65-0576353aaedd&algo_expid=5b1f4838-a84d-496d-af65-0576353aaedd-2&btsid=a7dcb7f3-87c0-4713-8752-c13d9fff40db&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_52

The wires are very very thin, so I believe I'll replace that, but the general idea here is that I'll simply get 5 of these, and then wire them up in parallel, so each slot holder is going to be ~12v(more like 14-16), and when wiring them in parallel each cell will increase the amps.

What do you guys think? Will that do the job? Would that be a good idea?

I'm also plan on using a bms for that, I already own the following 4s bms:
https://www.aliexpress.com/item/32961705432.html?spm=a2g0s.9042311.0.0.27424c4dbx6fs0

That's probably a bit of an overkill, but that seems like it should work just fine.

Are there any other recommendations? Something I'm not doing properly?
Thanks for the help!

[Michele Scotti]

The casing for the 18650 is a great alternative to soldering. I'm in the process to convert an hand drill - this is an fairly informative YT

https://www.youtube.com/watch?v=flNBEeG5KmQ&t=5s

 It adds a buzzer on top of the BMS. I'm planning to use a laptop charger instead of a 12v+step-up (who doesn't have a spare charger now!) 

 

[pete_l]

I don't know much about Li-ion battery packs. But it seems to me that the charge controller needs to have access to each individual cell to ensure that each one is being charged correctly. You will therefore have to modify those plastic battery holders to conform to this.
 

Edited September 22, 2019 by pete_l

[martinl]

It should work. A few comments:

1. If your 18650s have built-in protection circuits they are slightly longer than standard 18650s. My protected cells wouldn’t fit in a similar case. 

2. That BMS is for LiPos. You’ll want to double check that the over/under voltages are ok for Li-ion.

3. Charge all cells fully before before installing them to make sure they are balanced and give the BMS an easier job.