So you spend time opening 10k laptop batteries and then check every single one of them and end up with 1k usable ones? I guess you must value your time to absolute 0 dollars That must have taken months. I even already regret getting the 40 laptop packs that I got. It will take me 2-3 weeks to go through it. Definitely not worth my time, but as I already started, I will finish it. Anyways, thanks for your input. I appreciate it.Yep thats what needs to be done if you want a long lasting battery harvested from "laptop batteries".
In my case it took over 10,000 cells to come up with 1120 cells for my 14s80p Frankenstein Battery.
6000+ cells recorded in this spread sheet
Database Part Number and Color,Manufacture,Format or SKYRC Program,Wrap Color,Insulator Color,mAh Rating,Nominal V,Max V, Cutoff V,Standard Charging,Standard Dis Charging,Charge Cutout mA,Manufacturer IR (mΩ AC 1kHz) spec,Prefered IR (mΩ AC 1kHz) ,Max IR (mΩ AC 1kHz) APR18650M1A,A123Systems,...docs.google.com
After learning that IR is a perfect indicator of a cells SOH (State of Health) I was able to discard 4000 + (to the recycler) and giveaway a bunch of marginal cells as they would not (as you say) fit my criteria. I also saved a bunch of time by not testing these out of range /criteria cells.
I am not telling you how to build your battery as you can do whatever you like but you asked the question..............
So if you want to build a successful battery that requires little to no maintenance try to stay within the parameters. If this is not possible at least try to keep you cells SOH to > than 80% and avoid high IR >65mΩ cells. Which if you are pretty much using laptop cells( ICR chemistry) then that IR reading will be the very top margin for good cells as pretty much anything over 65mΩ will have a SOH below 80%. Except the occasional LG**S31865 which can have a reasonable result at 80mΩ The Sony US18650GR G* series cells also can have a very high IR but they do not play well with others so I would stay away from them.
These are my recommendations learned from experience, experiments and many other long evenings researching this.
My Frankenstein battery consists of these cells and their rated capacity as you can see between the highest and lowest there is an 800 mAh difference.
View attachment 26406
This is not tested capacity as by now you surely understand that most used cells will not give you 100% of rated capacity.
That being said if you take a 3000mAh cell at 80% SOH this = 2400mAh, likewise if you have a 2600mAh cell at 80% SOH it is 2080mAh you are within the 400mAh difference so it is not impossible. Does it take a little more work, some more cells, sure. Do you want to build a good battery or something that needs to be serviced on a regular basis. It matters none to me you are welcome to take the advice as you wish.