This is for anyone present and future who might find it useful. I've been using a pair of Zefal lights from Walmart. Not expensive, provides a nice bath of light that's adjustable, though I always use them in their widest setting.

These run off 18650 rechargeables - the light comes with a 1200 mAh battery that works okay. I wanted to get something beefier so initially got Ultrafire batteries off Ebay, labeled as 5800 mAh. Clearly that 5800 mAh number is pure fantasy. I haven't tested them to see what they actually are but the lifespan on them isn't any better than the 1200's that came with the bike. Maybe not even as good. Mine say "Made In China" under the rest of it. The ones pictured don't.




Then I got some Nitecore NL189 3400 mAh batteries. Night and day difference in longevity. If you're looking for this kind of battery, these are the ones to get. Somewhat pricey but they're really robust. Also got a Nitecore smart charger.

5800 mAh? Nope. I think of all the cheap 18650s the BRCs are the worst. I think the max capacity of 18650s is 3500mAh. I buy Panasonic, LG, Samsung brand only and don't buy from Chinese sellsers. Mountain Electronics is where I buy my batts.

I think I read somewhere after I got the Nitecores that they're the same battery as the Panasonics.

I buy Panasonics off Amazon.

In general, for the Chinese ones off eBay, the closer they claim to 3000mAh, the better. The 5000+ ones tend to be complete junk with actual capacities at or below 1Ah. It's like the worse it is the bigger they lie.

Of course, the hype has become standardized to some extent anyway, with giving capacities >1Ah in mAh. Might as well completely throw out common sense and require them to be labeled in kmAh.

When I started R/C cars the standard sub-C nicad was 1200 mAh / 1.2V for 1.44 W-h. With a six-pack and a brushed electric motor we geared the cars to run flat out for four minutes plus a lap. There were 1700 cells but everyone agreed they were basically too finicky to use except for pro racing.

Now these cells are like 10 Wh and they're smaller! An R/C car can be run until you get bored or break it. Just amazing.

I'm seeing that the cells that don't live up to the rated capacity are actually fake and you can tell by weighing them.
Example: How to Know a Fake 18650 Battery - All

Interesting. Apparently even weighing them isn't always a reliable indicator.

I agree with you that you can take the ratings for many of the Chinese made lithium ion batteries with the same "grain of salt" that you can take the ratings for many CREE XML-T6 flashlights sold on eBay. The flashlights can't be more than a bit over 1000 lumens as that is what CREE says is the maximum output for the T6 bin.

I will speak out in defense of the cheap batteries. I've used them myself for a flashlights and some DIY LED bike light projects. If you want an inexpensive but workable battery, they are a very cheap alternative to the expensive throw-away alkaline batteries like Duracells. The Panasonic 18650 batteries on eBay run between $6 and $9 each including shipping. Most of the Ultrafire and Trustfire batteries I used or gave away as gifts with flashlights were around $1.50 each. Six bucks to make a 12V DIY battery pack sure beats $24. I don't expect them to last as long but for a buck fifty, who cares. Nobody has complained about being given bad batteries in the flashlights I gave to friends.

Even within the same brand (Ultrafire) there can be a pretty large difference between the weight of their batteries and it doesn't correlate with the mAh rating:
Ultrafire BRC 5800 mAh 27.8 grams
Ultrafire BRC 3600 mAh 31.9 grams
Ultrafire JYD 5800 mAh 27.6 grams
Ultrafire BRC 4000 mAh 37.3 grams
Unbranded INR 18650 2000 mAh 42.6 grams
Unbranded purple case 4900 mAh 40.9 grams

Several years ago I was perusing web sites that evaluated 18650 cells, and one of them tore apart some very-poorly performing samples to find they were really worn-out batteries salvaged from laptops, covered in new casings.

They look like AA cells to me, I might be missing something.

From what I've been seeing there's more to the bogus battery issue than just fake performance numbers, apparently the real batteries have protection circuitry in them that keep the battery from overdischarging and overheating when charging that the fakes lack.

There are protected and unprotected cells. Sometimes you want unprotected cells. I suppose it's possible that someone is selling batteries as protected that are not. eBay sellers do a lot of stuff. I haven't seen it. I have gotten unprotected cells but that's because that's what I ordered.

Interesting, I want to take apart one of these crappy Ultrafires to see if it's actually a tiny battery embedded in flour as in the one video. To drain it down before taking it apart I put it in one of my lights on high. I thought for sure it would be flat dead in an hour or two. 12 hours later it's still putting out a weak beam of light.

I went through a similar process of culling batteries for my DSLR. I have a West Mountain Radio CBA II upgraded to a model III (older, current version is CBA IV) and built a custom holder for the DSLR batteries using a disassembled cheap Chinese battery charger. I then proceded to buy from various Chinese sellers and eBay every battery I could find to compare with the OEM Pentax batteries. I could measure the actual capacity of the batteries both brand new and after several charge and discharge cycles and graph the results. I could not find a single Chinese battery that exceeded the Pentax OEM batteries for performance, many of them matched, most were much weaker. Not a single of the cheap Chinese batteries matched the advertised output, many falling far short of their ratings. I also did some long term retests and almost all of the clone batteries lost capacity at a much faster rate than the OEM batteries. I didn't publish any of those long term retests since they would not hold up to standard testing practices and there were no control specimens.

I am sure that in the 4 years that I did all those tests nothing has likely changed with cheap Chinese batteries in any form factor.

What you're missing is that they are 2 entirely different batteries.

Without a direct comparison it's hard to tell, and searching the internet didn't help.

Whenever I do searches I always check out the images. Like they say, a picture is worth a thousand words.

I did, the search was a dud. thanks for the help. Never heard of this cell until now. I use either Ds or AAAs.

Pretty sure thing that you use 18650s, you just don't know it. If you have a laptop, probably the battery is a bunch of 18650s (unless you have one of the fancy razor thin laptops). Electric and hybrid cars typically have a few hundred of them in too.

I believe they are so called because they are about 18mm in diameter and 65mm in length. I don't know what the 0 is for.

These are lithium polymer or lithium-something cells which produce much higher voltage than traditional batteries, so they are not at all interchangeable. That's why it's smart that they are not the same dimensions. If anyone ever made a lithium-something battery in a traditional shape, bad things would happen.

I don't bother with 18650's. My LED flashlights that can use 18650's came with an adapter that takes 3xAAA, and I just use no-name disposable alkalines that last a good long while before having to be replaced. It's likely not as environmentally friendly as rechargeables, but it's convenient and cheap. I think a 40 pack of AAA's costs somewhere around $20 at Costco, something like that.

I've always thought it was too much of a crap-shoot buying specialized rechargeable that aren't readily available due to the plethora of badly made imports and knock-offs.

Maybe input from a thread like this will inspire me to look into it again one day, but for now, the 3xAAA's just work for me without issue.

Cheers
TRJB

You're correct about the 18 and 65, the 0 stands for a round shape.

So is 1865# for the square kind?

The square kind are for those who just don't understand.



When bad things happen to good batteries?


Okay, I stand schooled, back to my 'D' cell.

Wait a minute!


We put lithium cells in the smoke alarms here...occasionally the alarms will chirp, although the voltage is nominal and the drain is negligible when I measure it. Could that be from it being COLD in the vicinity of the battery?