How to Know a Fake 18650 Battery

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Introduction: How to Know a Fake 18650 Battery

About: Tech nerd like web technologies and gadgets. Kitesurf on weekends and recently got involved in 3D printing technology.

An average genuine 18650 batteries will weigh about 45g and no nothing less than 42g. You can see I have a fake 18650 battery in the pic weigh 32g only and the genuine 18650 battery weight 45g. Some genuine 18650 battery can weigh more than 50g. Good brands will tell you the weight of the battery.

You can use a digital kitchen scale.

Why fake 18650 battery weigh less?
That is because inside is a smaller battery with step up circuit which wrap in layers of paper and stuffed inside a 18650 battery size case then heat shrink in a tight plastic label sheet to make it look real.

Genuine sellers will specify battery weight in their product description/sheet.

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30 Discussions

1
Big Texun
Big Texun

17 days ago

Fake is the wrong word. A fake battery would be one that is not a battery at all. In fact, there are "empty" cells made that are not fake, they are simply sold as empty to fill a mechanical void for battery packs with odd numbers of cells, and are used to fill a space mechanically for the structure of tha pack, without unbalancing the individual strings of cells. This is common in higher density packs that have staggered string sizes, or a pack with a specific shape, but wanting to maintain the fullness of the pack within that shape.

There are a lot of different capacity cells sold, and each weigh a different amount. There are a lot of reasons for using smaller cell sizes, ranging from reducing the cost of the cell for marketing or cost reasons, to safety regulations for a particular regulated application. There are safety standards for appliances used in critical or hazardous environments that might limit how much lithium is present, or have containment requirements that reduce how much you can put in a cell and still meet the safety spec. A cell that is integrated as a backup of short duration might be made for one application, and find it's way to the surplus market where it is sold on ebay... Nothing fake going on there, as long as no lies are being told.

If the battery has a rating that matches it's actual capacity, any capacity or weight is valid. That is a big IF as exaggerations and rip-offs are common. Anyone can cut the shrink wrap off a cell, and replace it with a new wrap, with whatever markings they want. These repackaged cells can simply be remarketed cells, or actual forgeries of popular brands. Some flashlight makers rebrand all batteries they sell. Some are honest and some are not.

And besides capacity specifications, there are safety features, and the absence or presence of cell protection circuitry that has an impact as well.

When evaluating a cell from a new vendor, you should perform a capacity test where you drain a cell to the rated cutoff voltage, then test the charge cycle to see how much charge it takes, then perform a discharge at both slow and fast rates to see the results from thos tests. Discharge rates matter! The slower you discharge a storage cell, the more power in total you get from it. And that affects the cell rating for a given application. So the same cell can have a different capacity depending on what it is used for.

And a sand filled cell sounds fishy, and probably is... Unless there are weight requirements that need to be met coupled with a lower capacity requirement. The buyer of a manufacturer's production run is responsible for the specifications of that run, and their reasons and final product markings could be honest or dishonest. While I would agree in principle that dishonestly market batteries are somewhat fake in nature, the word fake is not an accurate word in most cases. A buyer will always do capacity spot checks as part of the qa of the incoming parts, as most parts have a certain percentage of bad units, and for a product build there will need to be some way to accommodate for the occasional bad part, especially from a new manufacturer or from a surplus supplier. Even "new" chips might be remanufactured pulls from scrap electronics, so the incoming QA team is there to keep suppliers honest.

So you are right that there is more to a battery than the claims printed on the shrink wrap cover. But the QA process is so much more than just weighing the cell.

0
lnxpro
lnxpro

1 year ago on Introduction

You are forgetting about the sand filled fake 18650 cells to make them weigh more.
Lots of chinese shenanigans going on over there.

1
aleggert52
aleggert52

2 years ago

A good article weight of 45g or more is the easiest clue to a fake 18650 battery! Generally speaking most batteries made in China that are labeled over 2600mAh are fakes as to there mAh rating. China's highest capacity for 18650 is 2600mAh as a rule of thumb. There are a lot of fake labeled and fake 18650 batteries being manufactured in China these days. Be sure what you are buying from China. It is worth it to get a confirmation from the manufacture as to the 18650 batteries weight and real capacity in mAh, not peak capacity!

0
arvevans
arvevans

4 years ago

High cost Li-ion cells contain a MOSFET in one end that shuts off once the battery gets down to 3.2 volts. This is the MOSFET turn-on voltage and is used to protect the cell from discharge below that voltage. If you discharge it below that voltage (difficult but it is possible) it is very difficult to restart the charge process because the charging current is not adequate to force battery voltage high enough to turn on the MOSFET.
Since the MOSFET "ON" resistance is only a fraction of an ohm it does not significantly reduce battery maximum current to have it in series with the cell.

Many so-called "fake" Li-ion cells do not include this protection device. This lets them actually have more chargeable material inside, and thus their higher than normal current and capacity. But this high capacity comes with a caveat...if you discharge them below 3.2 volts (remember, there is no low voltage protection) the cell may be damaged. Typically these damaged cells will not retain a charge for as long as a virgin cell might, or they might even overheat and catch fire when charging or discharging at high current rates.

On higher cost (i.e. non-fake) Li-ion cells you can usually feel an insulated metal strip down the outside of the cell covering. This is the sensor lead that provides gate voltage to the internal MOSFET switch. So-called ":fake" cells do not have this strip.

0
DanieleT15
DanieleT15

Reply 2 years ago

3.2v? That is not correct at all. Just look at the datasheet of a LG Choco 18650 battery. It's cut-off voltage is 2.5v. Even most battery chargers like the IMAX B6 will discharge down to 3.0v when testing batteries.

0
mc172
mc172

Reply 4 years ago

Can you show me a datasheet of an 18650 cell, or any Li-ion cell which describes this built-in MOSFET?

0
texas hank
texas hank

Reply 3 years ago

If it's a single mosfet to disable discharge, its body diode would still allow charging of a deeply discharged cell. The safest way to attempt recovery of a deeply discharged cell is to attempt recharge at low current maybe 0.1C or 250mA max for an 18650 for up to 10 hours or so. If it's voltage recovers to normal minimum or more (but don't let it get over 4.2V) congratulations!!! If it doesn't, the cell is garbage now.

0
Douglas75
Douglas75

4 years ago

Yes, I to got caught purchasing FAKE UltraFire 18650 Batteries. I was able to go back to mu eBay purchase history and discover the FAKE 18650 battery sellers. THEY ARE: ebanlan, hksells, yallstock, led201314, laptopz-outlet, hkiron-aus. I reported this to eBay but received no responses. In total, I purchase 32 batteries which I must re-purchase. Need more info? Just ask.

Douglas

0
Chris TibbM
Chris TibbM

Reply 4 years ago

You must not know how many Battery manufacturers there are in the word for 18650's . There are ONLY 5. Aspire being the newest, with Sony, LG, Samsung and the Leader Panasonic the rest are simply rewraps of the subsequently lower grades on those 5 production lines Bins A-E A being the best and gets the company TM logo the rest as I mentioned are wrapped by those other companies that purchase from the B-D bins. So in other terms those FAKE Ultrafires are not even Ultrafires lol.

0
IceC3
IceC3

Reply 3 years ago

In the word? What "word"???

0
Eddieb1213
Eddieb1213

Reply 4 years ago

I don't know how other people haven't realized that yet. Or you can go to moochs 18650 battery results. He test and shows data to all the real 18650 and how many companies ly about the amp and MHz on 80% of 18650s.

0
danleow
danleow

Reply 4 years ago

Thanks Douglas, your information helps.

Daniel

0
Chui Lerhern
Chui Lerhern

4 years ago

Thanks for your advice, i got that my 4 batteries bought are fake. But anyway, if the battery is fake,how much is its capacity?

0
danleow
danleow

Reply 4 years ago

Is hard to tell, it can go as low as to 600mAh

0
M.J3
M.J3

4 years ago

From ebay. 4200mAh, but only 650mAh in use. I was wondering why:

https://plus.google.com/u/0/photos/104329020925538604658/albums/6220722228646169665

Do not try at home without knowledge AND protections

0
danp70
danp70

Reply 4 years ago

Thanks for your knowledge

0
wasteoinc
wasteoinc

4 years ago

another problem that the weight test wont catch is the used 18650 battery. You buy them as new but they are actually old laptop bateries with reduced capacity from time not from design..

0
nunyafb
nunyafb

5 years ago on Introduction

Maybe this is stating the obvious but to everyone who is complaining
about this Instructable just add this simple little step. use this as
your first step to determine if your battery is fake. Really this is
helpful to say otherwise is foolish. Thank You