Good deal? Used 18650s

Hey guys!

I´m living in Greece, and I´ve been searching everywhere for used 18650 Lithium cells with minimal luck.
Today in a shop I came across an old battery pack with a blown BMS (due to water damage), that the owner had kept at hand for 1 year.
It's from an old Xiaomi scooter.
The pack has 280Wh according to the label.
When measured with a volt metre it reads close to zero volts, altho it could potentially by a broken connection, as the individual cells were not accessible.
He wanted 40 euro for that, and I said it´s way too much, and he immediately agreed to 20 euros (something like 24 dollars). But I left it there, not knowing whether or not this was worth the risk.
As I suppose it could amount to nothing. The battery has been sitting in the shop with a very low voltage for 1 year.

What do you guys think? I was looking for free cells. But this is the only one I´ve come across.
I don´t have much experience, and I´m eager to try things out. I´m thinking I would take it apart and solder it back together into something if the cells are good.

Thanks!

EDIT: It should be worth mentioning that he said the scooter had been used for 6 months.

If any of the Cells are below 2.5 volts I'd avoid it --- no telling how long they've been in that state

chops728 said:

If any of the Cells are below 2.5 volts I'd avoid it --- no telling how long they've been in that state

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right, meaning that if a cell is stored below 2.5 volts it is quickly destroyed, correct?

Correct --- That's what I do --- I've seen some crazy things where people revive very low cells -- too much risk for me

chops728 said:

Correct --- That's what I do --- I've seen some crazy things where people revive very low cells -- too much risk for me

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and by risk you are referring to the potential loss of investment, or safety wise? thanks for your feedback

Both -- Safety first ---besides they aren't worth saving at that point -- If he would let you open it up to check individual cells that would be good
Some of those scooter packs aren't very good cells to start off with --some are -- if you can get it cheap --Go for it
I always go by --How much am I will to pay for a Paper Weight (total loss)

right, so I've seen some videos as well, on reviving cells with minimal charge. Safety wise, what are your concerns about that? I did some research just now, and could not determine what the consequence could be?

BOOM!!! Li-ion cells are Dangerous to start off with ( Overcharging ETC ) -- I originated in the Flashlight world --- there you practiced safety first--Besides you don't want to build a battery with questionable cells

Jehu has a ton of videos talking about how to recycle old 18650's

he has several videos where he talks about how to evaluate old cells and determine if and how to use them in new rebuilt packs.

chops728 said:

BOOM!!! Li-ion cells are Dangerous to start off with ( Overcharging ETC ) -- I originated in the Flashlight world --- there you practiced safety first--Besides you don't want to build a battery with questionable cells

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hahaha. Appreciate the graphic talk!
Right, so I know there's always a potential risk that lithium batteries can explode. As far as I've understood at least with over charge, high heat, and rupture. But if I recycle undercharged cells, bring them back to life, and install a BMS and charge and discharge them within an accepted range, is that still to be considered particularly dangerous you think?

You need a way to check these cells --capacity/resistance --- anytime you're using recycled cells you need to check them
You don't want to use cells that are diminished to much -- I recently bought several Mobius packs ( 27 Panasonic Cells each)
I have had good luck with them in the past --- One pack 27 cells tested under 1500mah --when a new cell test 2900mah +
All those cells were recycled --- you never now what you have without testing them

chops728 said:

You need a way to check these cells --capacity/resistance --- anytime you're using recycled cells you need to check them
You don't want to use cells that are diminished to much --

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right, but when you say that - is that meant to be an answer to my question/clarification on the safety?
thanks for hitting me up with replies man, your feedback is gold!

I don't have any means of testing besides a voltmetre btw -- which I know isn't considered testing per say.
As of now I don't have the means to invest in such equipment, and intend to go ahead with what I have available.
So at the end of the day I guess I'll see if I can check individual cell charge, and make my assumption of their state from there.

On the internet it reads that Xiaomi 365 batteries are made up of high security LG cells, whatever that means.

Vega said:

So at the end of the day I guess I'll see if I can check individual cell charge, and make my assumption of their state from there.

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100% Does not work. The batteries need to be charged/discharged (tested) to track the capacity of each cell. Internal resistance as well as capacity all matter when building packs out of used cells.

schmism said:

100% Does not work. The batteries need to be charged/discharged (tested) to track the capacity of each cell. Internal resistance as well as capacity all matter when building packs out of used cells.

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even if all the batteries i'd use were from the same original pack? In other words, produced at the same time at the same place, and used all in the exact same way?

Vega said:

even if all the batteries i'd use were from the same original pack? In other words, produced at the same time at the same place, and used all in the exact same way?

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There are 2 reasons these ebike or scooter packs are taken out of service
1) they scrap the bike/program in which case the battery may be 100% good
2) they scrap the battery because it no longer holds charge well.

You dont know which is the case. You can put the cells directly into use but when they dont perform like you expect the only way to determine which cells are bringing down the pack is to test them all. most people do the testing on the front end because the dont want to put all the time into building a pack only to find out it doesnt perform and half to tear it all down, THEN test it, THEN build it again.

There is no "free lunch" option here ( a phrase used to mean you get it all for free)
1) you find used laptop batteries that people are throwing out for free. Have to take them apart and test them all (lots of time and effort but almost no cost
2) you find used ebike/scooter packs and gamble on them (could be costly, may have to spend the time to test them all anyway)
3) you buy new cells that you know are good. (will be costly but don't have to test them, buy them and use them)

You really should spend some time watching the Jehu videos. He covers all this in detail in his videos.

I test new cells also --- makes a better more even pack