Salvaging rechargeable 18650 batteries for power projects

Hi Folks,

I have recently got an ebike and have been investigating assembling DIY battery packs. I don't think I have ever seen a really good thread on this here, and from my onw research I had underestimated how accessible this process was.

18650 Lithium Ion batteries are in pretty much every battery powered item these days, and can be bought new but also salvaged from old electronics (defunct battery tools, electric vehicle power packs, e-cigarettes etc...). The skills involved look time consuming, but technically simple, and there are videos on youtube of people using this for everything from ebike batteries to massive powerwall battery installations to go with home solar installations.

Here are a few of the many excellent videos I have found. I'm yet to put any of this in to practice myself, but will be stockpiling any old 18650 batteries I can get my hands on. My end goal is an ebike battery pack for long distance summer cruising to take me to the beach and on adventures - an upgrade over my smaller battery for commuting.

Great stuff!  I really think this seems doable!

You might like to check out what the crazy russians are doing over on the Kreosan youtube channel.  
They have several interesting ebike builds and experiments.  (Including taking a homemade battery pack UNDERWATER!)
https://www.youtube.com/playlist?list=PLKcrtC0fsVC1aPv88k0H4QcLddfA9rY_j

Also ProjectFarm did a review of different battery brands.  It seems that the specs on a lot of brands are "exaggerated"... to the point where one might start calling them a bald-faced lie.
Therefore, either factor that in and scale up accordingly, or stick with a reputable name brand like Samsung, Panasonic, or LG.
https://www.youtube.com/watch?v=qMZuHMlRw_0

I’ve been looking into salvaging cells. It looks like you can test the capacity of “found” cells with simple testers. They run the cell through a charge/discharge cycle to calculate capacity of each cell.

Then when building a pack you balance the overall pack using the capacities. It looks neat.

Battery Management Systems

These little gizmos protect your battery pack by making sure that the cells within the overall system stay balanced with each other while charging and discharging. It looks like they are pretty much essential for safe charging and use, and prolong the life of the battery pack.

Fortunately they are cheap!

Example BMS circuit board for a 14s battery pack (565V nominal)

DIY packs are fine, just P-L-E-A-S-E be careful.

Lithium Ion battery carelessness is shocking (@ 1:01 min)... https://www.youtube.com/watch?v=JrlLe6PRhyo  

1. A fire extinguisher should be your first purchase - an infrared thermometer for monitoring cell temps during charging AND discharging testing.  
2. Do NOT charge or discharge any salvaged batteries in your home - preferably outside and in a secure area.
3. Parallel connected cells should be the same chemistry and AH capacity - and ideally the same age.

The best source for EV's and batteries (I have been a member there for over 10 years): https://endless-sphere.com/forums/

 At the University I work at there was a fire in a dorm from a kids kit made electric skateboard.
No one died but it was a near thing.
As far as I know,  he used new cells,  so there is that.

Mind you,  fire can happen  wherever electricity is involved.
One Christmas at my Mom's house, we had a fire happen from a malfunctioning laptop charger.

For what it's worth,  there is a lithium battery pack/ charger at Harbor Freight for around 20 bucks.
I've been looking in to it for powering old dead nicad tools.

My understanding is that cheap cells - even if new - are more prone to failure and fires.

Michael Cox wrote:My understanding is that cheap cells - even if new - are more prone to failure and fires.

In the 9 or so years I've been harvesting 18650's, admittedly, I'm still unsure what a "cheap" cell is supposed to look like... or if there even is such a thing as a cheap cell. Many of those salvaged cells I harvested were labelled to easily identify the manufacturer (and capacity & chemistry), but many have no identifiable markings at all, making it extremely risky to combine them with cells from different sources... so I don't.  The unlabelled cells I reserve for flashlights and other single cell devices.

But to me, it really doesn't matter... ALL cells IMHO, need to be handled, tested and treated with the same level of respect and caution.

That said... It's safe to assume that I personally, couldn't/wouldn't feel at all 'warm'n fuzzy' about building, what some are referring to,.. as a "Power Wall"... with used cells. All it takes is just ONE questionable cell... to shed an abundance of light on the party. But that's just my cautious nature.  As always...YMMV

Safety points above duly noted, thanks.

I have sourced a job lot of old laptop batteries to salvage. Approximately 300 cells all told I think.

Aside from the time and labour involved in salvaging them, and getting them tested, I'm thinking ahead to a first project. Something smaller and straightforward to get used to the process and tools. I'm currently thinking about setting up some outdoor lighting in a remote shed that has no fixed power, but access is frequently needed at night. Yet to sort out details, but likely a strip of LED lights and switch fixed in place, with a removable battery pack that can be take to power to charge up. I think it will be a good first test of our skills, and a useful end result as well.

My 8 year old is incredibly excited about having a project he can help with. (safety etc.. yes, I know.)

Lithium-Ion batteries have poor low temperature (< 10°C) performance. Their discharge (and charge) current will be a fraction of the normal one.

Sebastian Köln wrote:Lithium-Ion batteries have poor low temperature (< 10°C) performance. Their discharge (and charge) current will be a fraction of the normal one.

Quite true for many Li-ion chemistrys, but not all.  FLA's and SLA's suffer from the same temperature deficiency, but at a fraction of the cost. If you seek rechargeable Li-ion cells that endure the lower temps... then sample Lithium Titanium Oxide (LTO) cells.  Unfortunately, LTO's have a much low energy density, but longer life span.

Eugene Kenny wrote:If you seek rechargeable Li-ion cells that endure the lower temps... then sample Lithium Titanium Oxide (LTO) cells.  Unfortunately, LTO's have a much low energy density, but longer life span.

Or Lithium-Iron-Phosphate – also much lower energy density. I build a nighlight using a 10Ah LiFePo4 cell, a resistor and a white LED… last charged 2018.

I'm still plodding along with this. My little charger/tester is working well.

I have a handful of cells in excellent condition (2800mAh, low internal resistance), some in moderate to poor condition (1500 to 2500 mAh, higher IR) and some dead ones.

I'm going to be dismantling some powertool packs tonight. I opened up one earlier to see what the insides were like. Makita brand, 8 cells, on the outside it says 6Ah which would suggest high capacity cells. When I got it open the cells inside were only rated to half that! The original owner got stiffed on that deal.

Michael Cox wrote:... Makita brand, 8 cells, on the outside it says 6Ah which would suggest high capacity cells. When I got it open the cells inside were only rated to half that!...

All of my Makita lithium 1.5Ah packs are 5 cells in series = 18.4V nominal. The Makita 3Ah packs use the same 1.5Ah cells but have 10 cells arranged in 5S 2P, to achieve 18.4V but double the Ah.  I've Never seen an 18V Makita pack with 8 cells???

You are correct - it was 10 cells, not 8 cells.

Hi,

I started with 18650 cells, but have been moving on to Electric Vehicle batteries.

Started with a Tesla model S battery but now I have moved up to some LG batteries over 14 KWH


Here is my progress from getting the batteries till now fully in use.
https://diysolarforum.com/threads/lg-chem-batteries-from-battery-hookup-5-94-kwh.4592/


I have been converting over to 18650s for all my flash lights, and my clocks.    Life is so much better when you can go several months before changing batteries or charging them.


I also run a group on MeWe for lithium batteries,    it appears Tesla's new batteries are going to be a game changer.


https://mewe.com/join/lithiumbatteries18650diyevpowerwalls


Cheers

So it's important when using salvaged cells to capacity test and balance the pack using a battery packing tool like this. You can also test IR or internal resistance and add that into the calculation for packing which will help make a super balanced pack.

And: it's important to recognize that you don't know how these cells have been treated, what stresses they have previously seen, and where their failure point really is. Caveat emptor. Don't burn down anything you can't afford to replace. My 2c.