I can get brand new 6 cell 4400mAh laptop batteries for $12 each which = $2 per cell.
I’ve no idea what cells they contain - what do you reckon, should I take a punt or am I just throwing my money away?
If they are genuine manufacturers replacement battery packs, then you are pretty much guaranteed to get decent branded cells so probably a fair deal
You can pretty much work out what the capacity of each cell will be from the number of cells and the capacity of the pack from the total mah written on the battery pack.
If it’s a generic aftermarket pack, then I wouldn’t bother at that price or probably any price, unless free, even then they probably won’t be great, as they are normally unbranded cells and all the ones I’ve ever found in aftermarket laptop batteries weight half the amount of a branded 18650 cell, so I didn’t even bother with testing them
They are not OEM (i.e. Toshiba, Dell etc) but manufactured by a company called Lenoge. They mostly have good reviews as laptop batteries but I haven’t been able to find out what cells they use. I’ll take a chance and buy one to find out.
Stick to the ones that made for brand name laptop… such as toshiba or acer or sony… I found good batteries in them… usually samsung 2600 mAh. Go for the laptop battery that advertised 5600 mAh, they usually contained samsung batteries 
I have bought my share of aftermarket laptop batteries for a name brand laptop. I found that the “branded” replacement battery had poor reviews, but still commanded a premium price. The original warranty for the “branded” battery was 12 months. In this case the price was $100 for 12 months. I bought some of the cheaper “non-branded” batteries, and found them to last about 6 months. The math tells me that it was prudent to buy the “mystery” batteries.
I do try to find sellers that at least claim to have “premium cells” in the battery. Sometimes they will claim to be made with Samsung cells. I am currently running a 12 cell battery (instead of the 6 cell original equipment). This gives me longer runtime. The life of this battery is also pretty good so far. I keep a 6 cell cheap battery on hand so that I have something to keep me going if the 12 cell freaks out (which it did once).
Think I stripped one of these, name sounds familiar, was just unbranded blue cells.
I bought a few new ones of various makes I’d never heard of from a Chinese ebay seller for 99 pence each including shipping to the UK.
(Maybe their way of getting rid of toxic waste 
)
Would take the reviews with a pinch of salt, as it’s
worth remembering, often when people have changed the oem genuine manufacturers battery pack out of their laptop, it’s normally because it is a few years old and probably holding a lot less capacity than when it was new.
so when they put in a new generic aftermarket battery even if it’s poor quality it’s probably (in the short term) far better at retaining a charge than their old battery pack, so of course they suddenly they think wow this is much better than my old battery and give it a corresponding good review
Anyway if yo do get one, post up what you find inside
I should have it in a couple of days - I’ll post pics of the cells that come out of it.
I would not go for anything except original brand battery packs.
Not much of a guess but I am going to say 3S2P = 2200 per cell nominal the quality of which you will have to test. like others have said if it is not OEM battery pack then you can count on lower cost cells.
This is what I got:
Anyone want to guess what capacity I’ll end up with after a charge/discharge cycle :quest:
I’ll guess 2000
edit
I see the label says 5200mAh? Wasn’t it advertised as 4400? Inspires confidence.
I’ll revise my guess to 1800
Between 1600mAh and 1900mAh @ 2A discharge is my guess.
Around 2000mAh maybe?
However, I have a feeling the IR will be high and the capacity and voltage will drop quite quickly if a lot of current is drawn.
Charged them up….
.
…then discharged at 1 amp - max temp reached 45degC ….
.
…after 2 hours they’d delivered 2000mAh and were down to 3.4v ….
.
… they were spent after about 2hrs 15min and all had provided over 2200mAh
.
The resistance doesn’t look too bad to me:
.
Well, what do you think - is it worth buying another pack :quest:
look like generic bak china cells.
fine for less demanding lights.
i have several srk sets running these.
most of the long barcode cells are bak.
the i r test in the opus is only good to spot really bad cells.
its contact resistance is too unpredictible.
i use a dick smith esr.
its test method is recomended by most battery datasheets i have read.
I’d say it’s up to you, yourself. If it were me, the two questions I would ask myself are whether 2200mAH is enough for my purposes, and whether $2USD each is a decent deal for cheap, unproven, Chinese, 2200mAh cells that might not have the stamina measured in years that we are used to in better cells. And before I decided that, I would test them more thoroughly in real world usage in my favorite lights. I would research the laptop pack brand, looking for reviews from long time users, professional product testers, etc. I would also find out what brand of cells are used and research that brand in the same way. When I was thoroughly convinced that they are worth the money I paid for them, I would consider getting more. If they turned out to be a gold mine, I’d get LOTS more! A “cheap” cell that pans out well in safety, reliability, and long term viability would make a great “gift” cell, to go with lights that you pass on to others.