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Topic: Shorting 18650 batteries...help! (Read 1 time) previous topic - next topic

mauried

I hope you didnt pay much for the batteries.
Ultrafire have a bad record for selling fake batteries.
Lots of people have been burnt.
Buying 18650 batteries on the Net especially from China is a big risk, unless you are sure the supplier is genuine.
http://lightsngear.com/beware-fake-ultrafire-18650-batteries/

Ive been burnt too, so now I only buy Panasonic NCR18650Bs , but they are not cheap.
They are also real, and a genuine 3.4 AH.



Boardburner2

I am not sure that paralleling these is a good idea, at least without series diodes.

Slight differences in terminal voltage may cause circulating currents assuming they are charged seperately.

DrAzzy

#17
May 15, 2016, 06:02 pm Last Edit: May 15, 2016, 06:04 pm by DrAzzy
You got some lousy batteries - *most* of the 18650's, even crappy ones under the ultrafire brand, have short circuit protection (in my experience).

I've shorted them a number of times, you see a big spark, all your fuses blow, and then the output voltage of the battery drops to zero. And they come back on a few minutes later (that's happened to me with multiple batches - I was scared to death for an instant when I shorted out a stack of 24 of them.

You can parallel them just fine if you charge them both up to full, and then immediately put them in. It makes it easier to charge them in place, since you can just use a cheap single cell charging IC.

I'm not sure if Ultrafire is actually a brand, or just something that every second rate battery maker puts on their batteries. The capacity never meets spec (sometimes only off 2:1, other times more like 10:1), but they're often still more cost effective. I can't afford the panasonics - I would have had to spend close to a thousand bucks on batteries in the past year if I used panasonic brand....
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Whandall

You got some lousy batteries - *most* of the 18650's, even crappy ones under the ultrafire brand, have short circuit protection (in my experience).
I think there are two types of 18650 cells, with and without protection.
Often a small board mounted on top, which makes the cell slightly longer.

The 'industry standard' cells don't have protection and are often welded together to build laptop powerpacks and the like.

Some holders take the bigger ones, some don't.
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)

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