I'm gonna be building a long range quad this spring so I'm getting all my parts in order currently. I know that I want to make 2 6s 4000mAh li-ion packs. I decided I didn't wanna buy the pre made packs because it's more expensive and it's nice to get the experience. I was wondering how do you actually know what type of mAh you'll be getting when wiring them up and how to go about picking the right cells.

Frankly its a lot of soldering to items that don't respond well to heat sinking into them, and increased risk to the expensive quad from a failed joint or damaged cell, so I'd advise against doing your own thing, but................

http://everythingfpv.com/how-to-make-a-6...tery-pack/

Picking Cells

You will need to choose the highest current capability you can get, as this is the limitation of Li-ion cells.  They will need to be "balanced", that is all the same quality/capacity, something the respectable pack makers do as part of the process.  So at minimum buy same make/model/batch.

I use SONY cells, and be aware there are "fakes" out there, so if it seems too good a deal, it probably is!


I'm very VERY experienced at soldering, but I repeat, I'd not do it, its simply not worth the risk measured to the loss of the quad, let alone who or what it might hit, but YMMV.

Also............

https://www.ebay.co.uk/itm/254152649672

For soldering, you need a very powerful soldering iron to solder quickly and not overheat the batteries. I always bought real original batteries here: https://www.nkon.nl/

Getting a cheap spot welder is a good way to reduce the risk involved in making your own packs. As for cells, I tend to get the Sony/Murata VTC6, Molicel P42A, or Samsung 50S. Just make sure to keep your amp target below 50% of what those cells will crank out continuously, or the energy density will be wasted on efficiency losses. If you need more amps in your voltage target, do them in parallel.

Molicel P42A has a 45A CDR and if you are in the US can be purchased here:

https://liionwholesale.com/products/moli...3210675294


And a good site if you want to compare discharge curves if you are considering different options.

https://lygte-info.dk/review/batteries20...arator.php

Simple Spot Welder tutorial that might be of use.

(25-Feb-2023, 11:31 AM)StSV Wrote: For soldering, you need a very powerful soldering iron to solder quickly and not overheat the batteries. I always bought real original batteries here: https://www.nkon.nl/

Also, use flux on the cells, it speeds up soldering process a lot. I haven't tried spot welding myself yet, looks interesting but for the sole purpose of making li-Ion packs for quads I'm fine with just soldering.

+1 for nkon.nl for Europe. I only buy from them.

I have soldered like the video shows with nicads,nimh,A123, and 18650,21700,etc…
  


   

Very easy to make if you are competent with soldering. If not, best to leave it to someone else, or buy them ready made.

Figured I should probably update, on this. I did end up making my own and it was pretty easy. I used the nickel strips to keep everything nice and flat. I used the soldering method and the number one thing that made it easy was roughing up the surface of the batteries. I just used a dremmel to rough it up and that makes the solder stick really easily and really well, then I just tinned the nickel strips and pressed them onto eachother. Wasn't able to break the joint with any amount of force after that. 

Will definitely make more lithium ion packs in the future!