Laptop pack teardown, testing, and pack building


Since the direction of this project has changed a good amount since I started the thread I though I would update the original post a bit.

I am now going to be using this thread to post updates on my cells and the packs I build from them. I have something like 400 cells now and am about 10% done testing them. I want to try sorting them not only by MAH but also looking at the WHR that each cell can do in order to avoid having cells whose voltage sags too much under load in the packs. If you simply take WHR/MAH it gives you the nominal or average voltage for that discharge , in my case 2A. In the 50 or so cells I have done so far, it is interesting to look at how the three correlate. Most high MAH cells have a high WHR which means a good nominal voltage but a few cells will have similar MAH but the nominal voltage is around 3.5v instead of 3.6v which would cause uneven discharge if those two cells where placed in parallel.

So I came across a set of laptop packs and took them apart within about 10 minutes of getting them home.

So I ended up with about 80 cells, mostly still had good voltages, a few under 2v, and some others at 0v

All the Gateway packs had Sanyo cells and the rest where a mix of Lg and Samsung

I started to cycle the batteries but with only one discharger it is taking awhile. The Sanyo cells seem to be the best so far, even when I discharge them at 3.0 amps they are getting around 2100mah when I terminate at 3.0v

So my question for you guys is what should I all do to test these batteries? Just discharge tests? what current?

Also what should I do with them? I have a few lights and might solder a few into a pack but need some ideas for them.

That is a lot of batteries and seems most are good.

Start an Electric Company perhaps :slight_smile:

start building a spare pack for a tesla?
no buy a bunch of stuff that uses them and convert what you have that doesn’t.
lots of lights that take 18650 and are low enough drain that laptop pulls are fine.
and welcome to blf!

Buy some empty external power banks then build up your own then give them as xmas presents.

Has anyone perfected a way to get the weld nibs off of the ends of these?

Rotary multitool (like a Dremel) plus a grinding bit: problem solved. :laughing:


P.S. to the OP: if would be a good idea to attach a sticker to each of the tested cells with the gathered information (binning). That could allow you to use matched cells for in-series configuration, and even make in-parallel compensated groups (high/low bins) for an even bigger (scary) nSxP BIG balanced battery. :crown:

Build yourself an electric or hybrid motorcycle?

Thanks Barkuti. The Dremel is a good idea.

Mmm, if at least 64 cells are all right, build a balanced 8S8P monster (and maybe attach a balancing circuitry to it). Keeping a close total capacity for each 8P block and about even brand/overall discharge performance distribution should do fine. 28’8V at 16A, 460’8W sustained output for (maybe) close to an hour…
How about this?

Cheers :blush:

What I said above, plus:

200W Neutral White 4800K Led Module Cree XT-E XTE Chip Light 42-46V 4.5A 16800LM
Which, in fact, seems conservatively rated, and those are not chinese lumens… :wink:

DC-DC 600W 10-60V to 12-80V Boost Converter Step-up Module car Power Supply
High efficiency CC/CV driver/supply.

For the rest of the components, ¿suggestions? :innocent: :smiling_imp:

Cheers :partying_face:

P.S.: if sufficiently well cooled, my suggested 8S8P beast could feed the boost driver well enough for it to feed that Cree 14S3P multi-chip @#$% around 9A at… 46V? Maybe some extra heat sinking would be required for the driver… better run 2 drivers in parallel, LOL!

Hey thanks for the welcome!

Yes I will be doing this, I am just giving them a first round of cycling (I think a few sat for 2 years) before I give each cell its “official” capacity test and ensure they don’t self discharge too quickly.

While that big Cree panel looks very nice, I might have to wait a little while to build it properly, but I do have access to CNC lathes and mills (currently machining new fog lights) so I could build something nice if I ever get the time to design it.

With the power bank cases, is there a good way to know if the circuits inside are proper or is a crapshoot like some Ebay items?

FastTech has a good deal of power-bank PCBs and complementary cases. Price may not be the best but it is possible to find a lot of user reports and other information.
I recently got this one:

SC-0176B 1A+2A DIY Dual USB Mobile Power Bank PCB Module

I myself added a nice thread under “Discussions” where I inadvertently ended up reviewing it while I was building that cafe bank for a friend.

A few days ago I ordered this:
Dual USB 5V 1A 2.1A Mobile Power Bank 18650 Battery Charger PCB Power Module Accessories For Phone DIY New
I’ll couple it with 3×NCR18650Bs and another custom box, for a someone who got a bit jealous after seeing what I had built in the hands of my good old friend. Gonna use some 5mm superbright leds to give some light to that LCD.

Hope this helps. :slight_smile:


Could you post up a pic of your charger/discharger and some details? Is that it in the background???

For charging I mostly use TP4056 boards off Ebay, seem to do a decent job.

the discharger is a dedicated unit than do up to 10A or 60W, it does pretty good, measures voltage and current accurately.

also this happened…

That’s 41 more laptop packs
So who needs a cell or two?

I will have to look into that discharger… does it do USB out by any chance.

41 more laptop packs?

How much for shipping to the land of the bullfighters?


It does not, just dissipates as heat.

I have to look into shipping regulations on lithium batteries, or if any of you know

Figured I would give a bit of an update

I have been slowly going through and charging/discharging all the cells to sort them into performance categories.

Current plan is to use some of them to experiment with a small scale solar setup. Looking at a 7s8p pack with a hopeful total of 500 whr of capacity. What exactly I power with it yet is to be seen.

My desk is still a mess with all the cells

And as a side project I machined a die for the plastic injection molders at school

It doesn’t work too bad, I use it for my discharging rig now.