Buy from these Ali Express/Amazon sellers at your own risk

Ya’akov

Joined Jan 27, 2019
8,505
For anyone that might stumble on this thread because they are searching for high capacity 18650 cells…

At the time of this post, the maximum legitimate capacity for an 18650 cell is 3500mAh.


High quality, reliable cells with this capacity are available from manufacturers like Molicel and Samsung. It is important to consider that capacity is affected by discharge rate and the A (discharge current) rating of a cell must be considered along with the mAh (capacity) rating to determine the best cell for your application.

Increased capacity and discharge current mean increased cost, and you can save some money if you buy cells with reduced discharge current ratings if your focus is battery life and your application doesn’t require maximum current. For example if you are rebuilding a pack for a cordless drill, you might want to choose the more expensive, high current options—but if you are building a pack to run a microcontroller for a long time at low power, you can save money by not choosing something you will never actually use.

Examples of top-end cells are listed in the table below. These are meant to be exemplars only, there are other brands with good reputations—though Molicel and Samsung are common safe bets.

ManufacturerModelStyleCapacity (mAh)Discharge (A)Price (USD)¹
MolicelM35AFT, NP3500107.99
MolicelM35ABT, P3500109.99
Samsung35EFT, NP350087.99
Samsung35EBT, P350089.99
Samsung35EBT, NP350089.99
Samsung30QBT, NP3000157.99
1. Street price from a reputable dealer at the time of this post.

STYLE KEY

FTFlat Top—suitable for building batteries
BTButton Top—for devices with replaceable cells²
PProtected—includes protection circuitry
NPNot Protected—does not include protection circuitry
2. Please note that a button top is no guarantee of protection being present as in the Samsung 35E and 30Q. Such cells should not be used in devices that don’t have their own over-voltage, under-voltage, and over-current protection for the cells—this is a potentially dangerous thing to do and a fire hazard which may not show up until you attempt to charge the cell.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,120
I know they do not have 9900mAh capacity. I used to order such items and used to open disputes with test videos. So I used to get a partial refund and the final cost was too cheap.
I'm actually trying to find some batteries that offer close to the advertised capacity. Now, I send messages before I buy about capacity verification and no-return 100% refunds for batteries that don't actually have much capacity.

The 9900mAh battery I tested had 125mAh capacity. Unfortunately, I didn't know at the time that I needed to test capacity and didn't ask for a refund. I did buy some 18500 1600mAh at the same time that turned out to be accurate (1.59-1.66Ah for the 3 I tested).

The 88800mAh 18650's would have made great 2Ah batteries.

I've been asking for, and getting, 100% no-return refunds. I have no patience or sympathy for sellers who are selling batteries with less than 10% of the advertised capacities. I bought some "real capacity" 2.5Ah 18650's that had about 2Ah of capacity and I'm letting the seller get away with that.

I have some 1.2-2.8Ah 16340's that a member gave me. They test at 5-50mAh. He used them to power a homemade experimenter. I'm looking for some 16340's that would make the experimenter "work". In the meantime, I added a power jack so I can use an adapter for power.

I ended up buying a capacity tester for the last two sets of batteries I purchased because the method I initially used isn't as accurate and I adjusted the discharge current to discharge the batteries in an hour (once I determined the ballpark for the actual capacity). I used one of the cameras from my surveillance system to record battery voltage because it puts the time in the upper left corner. But it breaks up the video every hour; and I didn't want to have to upload videos as evidence that were larger than a few hundred MB.
 
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SamR

Joined Mar 19, 2019
4,911
didn't want to have to upload videos as evidence that were larger than a few hundred MB.
There was a limit on file size and I kept having to convert images from png to jpeg or gif and in some cases edit the image in order to upload them below their limit. Not sure if an hour long mov file would fit within their limits. Can't find any info online. It just pops up as an error when trying to upload to their report software function.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,120
There was a limit on file size and I kept having to convert images from png to jpeg or gif and in some cases edit the image in order to upload them below their limit. Not sure if an hour long mov file would fit within their limits. Can't find any info online. It just pops up as an error when trying to upload to their report software function.
I think their limit is in the GB range for videos, but I have slow DSL. My surveillance videos are .mp4 with decent compression. An hour is under 300MB.

The problem for me is that I could never upload videos to the AliExpress website. After complaining many times in the midst of a dispute, they said I could upload to YouTube and post the URL. YouTube was much more accommodating of my extremely slow (<1Mpbs) upload speed.
 

SamR

Joined Mar 19, 2019
4,911
They've mentioned movies to me but I have no desire to do so. Pics are a pain in the ass enough for my lack of patience and I fought them hard about them needing one before I sent the first one to them. FWIW
 

SamR

Joined Mar 19, 2019
4,911
Flipping through news articles and this little ad popped up...
1696033449729.png
Now even with the $230 delivery that doesn't sound too bad for a sit-down auto-balancing powered unicycle. See that little "Color: wheelbarrow" near the bottom of the ad? Here is what you are actually buying...
1696033660015.png
The real deal is...
1696033732815.png
Caveat Emptor!
 

Thread Starter

dl324

Joined Mar 30, 2015
16,120
I was going to use those 9V lithium replacements but I don't know their self-discharge i.e. would it be OK 3 months from now or would it be dead, boost converter running all the time I think.
Didn't get around to checking the batteries until now; 7 of 8 read 0.0 and the other is around 1.3V. No point in doing a discharge test. All completely discharged in less than 3 months.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,120
I find buying from the whole amazon and Ali express risky. No warranty. Only luck.
You can add eBay to your list.

I'm not looking for the highest quality when I buy from Ali Express. Just something that good enough and will get the job done without having to pay the high prices from "reputable" sources. Like the item in the first post in this thread. Those level shifters from Sparkfun:
1698505989910.png
You can get them for 10% of that on AliExpress. I got 20 for $5 before buying the ones that weren't packaged correctly.

This PEX tool was $100 at Home Depot:
1698506335756.png
I got the second on AliExpress when I lost a screw on the "good" one.

Bare semiconductors are a real crap shoot and I resort to testing enough to ease fears of counterfeits that aren't even the part being sold. It isn't feasible for consumers to do comprehensive testing, but DORA is sufficient to know that it wasn't a bait-and-switch transaction.

Even then, I'm hesitant to spend much money on any single transaction.
 
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Ian0

Joined Aug 7, 2020
8,941
I found this welder on Ebay
https://www.ebay.co.uk/itm/33506575...id=TYOgoELnSrG&widget_ver=artemis&media=EMAIL
I'd always fancied having a go at TIG welding, so I asked a few questions as the price was too good to be true:
"Is it supplied with the tungsten electrode?
Where does the gas connect?"
and got this reply:

"Sorry for the late reply,It does not have a tungsten electrode and cannot be connected to gas, otherwise it will explode.
If you have any problems or questions, you could contact us, we would be glad to help you, have a nice day ^-^
Sincerely
Doris"​

A machine that can make argon explode? What can it do with 78% nitrogen? It could make a useful weapon. . .
 
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