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ArcticMyst Security by Avery

16340 ---> 18650 adapter

Joined
Aug 13, 2010
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839
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I know the 18650s have a massive capacity compared to the 16340s but I wanted to be able to charge them both with the same (cheap) charger.
I just got a lathe 2 days ago so this was a nice bit of practice ^_^
PA140335.jpg


Pretty simple to make, its a little thin around the battery but actually quite tough.
PA140336.jpg

Simple to get them the same length but good to get some practice working "down hole" :crackup:
PA140337.jpg


I just charged 2 of these little batteries in an hour, they worked fine in the charger and both came out to exactly 4.2V
The 18650s like to "pop out" but the adapter didn't have any of that trouble.
I just got an idea on how to polish aluminum in one easy step so I'll likely try it out on these lol.
Just learned how to embed images so there will be a 1.495mA 445 build guide coming soon (it's under the phone in the 1st pic)
 





Joined
Dec 14, 2009
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Cute little adapter. There is really no need to have the 16340 battery in an adapter, you simply need any conductive chunk of metal to act a spacer between the charger and one of the batteries terminals. Yours actually has a potential to slice the battery wrapper and short out the lead running between the anode and the protection circuit.

But, more importantly just because you can make a connection to charge a 16340 size battery in that charger it does not mean the charger is appropriate for that cell.

I am not sure on the specs for your particular charger, but that looks to me like the 1 amp or 500max2 charger I have seen.

If charging 1 16340 cell in that charger you are nearing 2C charge rate, or at the very least 1.5C (I know many of these Chinese 16340 claim 880 mAh capacity, but trust me, it is much closer 2 600) So, that is potentially dangerous, a bomb even. At the very least, it will dramaticaly shorten the life of your battery.

Also, you need to be very careful charging cells of differing capacity at the same time. In your case, because I see 2 indicator leds, there is a good chance your charger has two independant channels. If it didn't, and was simply charging in parallel, the charger wouldn't terminate the charge properly and the 16340 would be severely over charged potentially venting with flames.
 
Joined
Sep 12, 2007
Messages
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2C charge rate is not enough to overheat it.

There are plenty of chargers that charge both 16340s and 18650s using the same circuitry.
 
Joined
Dec 14, 2009
Messages
66
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If you look at the white papers from most any large battery manufacturer, lithium cobalt cells nearly ALWAYS have a charge rate of .7 to 1 C. I have never seen a manufacturer suggest other wise.

The temperature of the cell by the way is dependant on the internal resistance of the cell, and that will vary from battery to battery, and also will increase with age, abuse, condition of the cell etc. As the internal resistance increases the heat created while charging will increase exponentially depending on the charge rate. Also, by charging at a SLOWER rate, the battery will spend less time in the danger zone near 4.2V. If charging at .2 C during the constant current stage, when the battery reaches near 4.2V and the charger enters the constant voltage stage, it will already be very nearly full.

There are plenty of consumer battery chargers available that charge multiple size cells, as you say. Everything from 10440 up to 26650 cells. That is not one of them however. None of them I am familiar with charge higher than 500 mA.

In the case of a hobby charger even more so than a consumer charger, the end user is expected to understand how to safely charge a particular chemistry of battery before use.

My concern here is for the safety of the original poster and for the safety of other hobbyists that read this, so I would like to point out documentation that backs up what I am saying.
http://battery.sanyo.com/en/spec/ion/UR18650F.pdf <--- Sanyo 18650 white papers
How to charge Lithium Batteries. Power streams lithium ion charging page
Charging lithium-ion batteries Battery universitys page about charging li-co. The very bottom under "hints to long battery life" pertains to this discussion.
Lithium-ion battery - Wikipedia, the free encyclopedia Look under "Charging procedure"
Warnings for Using Batteries Look about 3/4 of the way down under "Charging Process"

Honestly, I could point to many more white pages, sales pages etc that say never charge li-co at higher than 1C but I think you get the point. I honestly am not trying to get into a flame war or something, but just for safetys sake I want all to understand these numbers aren't something I just made up, they are very well documented.
 
Joined
Aug 13, 2010
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I appreciate the input, I always charge on a welding bench in the shop.
I don't really care about shortening the life of the batteries, this charger model has done fine so far. It might be charging a little quick (500ma) but I'm not about to buy a 16340 specific charger.
I always check the voltage when I pull any of the li-ions and this charger has always given exactly 4.2V every time.
It still takes about an hour and 3/4 to charge the 16340s and a little more than 4 to charge the 18650s.
The little guys also have pcbs so I can only use the unprotected 18650s as a gauge to how well the charger works to shut down at 4.2v
It's a good idea to always charge your batteries in a reasonably safe place and set a timer just in case you forget about them ;)
 
Joined
Aug 13, 2010
Messages
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Yes, that is what it is labeled as but it is only 500mA per channel (average)
Oh wait, DX never makes mistakes like that do they? NO WAY :crackup:
Actually, this charger will initially charge at 1A but levels off to about 500mA pretty quick. I think it has to do with the draw of the battery because the 18650s draw about an amp for 20+ seconds and the 16340 only draws max for a couple of seconds.
It must be similar to the way an electrolyte battery (car batt) can have a HUGE draw for the first 15 minutes of charging but levels off to a slower rate.
Kinda glad it doesn't have the constant 1A output, I have more time to wait for charging batteries than I do money to buy new ones ;)
 




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