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Author Topic: charging lithium ion batteries  (Read 1828 times)

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Offline blackbeardTopic starter

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charging lithium ion batteries
« on: August 08, 2009, 05:27:28 PM »
so i have a bunch of trustfire 18650 lithium ion batteries that i want to use but i havn't the faintest idea how to charge them. if i solder 3 of them together in series can i still charge them with the charger i use to charge my single cell camera battery?
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #1 on: August 08, 2009, 10:14:01 PM »
can you say house fire?
when charging Li-on batteries, more precautions need be taken than with other batteries...
i wouldn't try charging them with a charger not meant for them...
rather buy a dedicated charger for that type of cell.
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Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #2 on: August 08, 2009, 11:00:32 PM »
the camera uses a single 3.7v cell and i've used it to charge indevidual cells before but i was wondering if it can charge them in series
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #3 on: August 08, 2009, 11:12:44 PM »
nah, if its meant to charge 3.7V single cells, thats what it should charge...
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Offline Joker94

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Re: charging lithium ion batteries
« Reply #4 on: August 09, 2009, 06:30:17 AM »
make a board so you can plug them for use but charge the cells seperatly. And remember if a fire occurs make sure you don't throw water on them to ty and put them out. Use dry chemical or CO2

Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #5 on: August 10, 2009, 08:04:29 PM »
now uh... hypothetical if i already soldered them together is there some way i could still charge them without disconnecting them?
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #6 on: August 11, 2009, 12:46:20 AM »
not unless you soldered some switches in between them?
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Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #7 on: August 11, 2009, 06:40:31 AM »
ok i guess i better get out soldering iron again
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #8 on: August 11, 2009, 03:52:09 PM »
yeah... you probably should :P
they had tabs or something that you soldered to right?
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Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #9 on: August 11, 2009, 03:57:11 PM »
nope just the flat
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Offline Trumpkin

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Re: charging lithium ion batteries
« Reply #10 on: August 11, 2009, 03:58:42 PM »
make sure you don't get the batteries too hot while soldering!
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #11 on: August 11, 2009, 04:03:13 PM »
hell yeah! try to use a high wattage iron for short periods of time!
damn, i dont even want to think of bad soldering with li-on's!
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Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #12 on: August 11, 2009, 04:25:35 PM »
yep i'm really cautious around these guys. my 35w iron seems to do a good enough job though
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Offline blackbeardTopic starter

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Re: charging lithium ion batteries
« Reply #13 on: August 12, 2009, 12:04:03 AM »
while we're at it does anyone know if you can charge them in parallel? it wouldn't be so bad if i added a switch that disconnects them and puts them in parallel for charging
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Offline SmAsH

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Re: charging lithium ion batteries
« Reply #14 on: August 12, 2009, 12:34:24 AM »
im not too sure, with li-ons, they have a "smart circuit" inside that says when they are charged.
wiring them in parallel may screw up this circuit and make them over/undercharge.
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Offline Razor Concepts

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Re: charging lithium ion batteries
« Reply #15 on: August 12, 2009, 12:54:35 AM »
im not too sure, with li-ons, they have a "smart circuit" inside that says when they are charged.
wiring them in parallel may screw up this circuit and make them over/undercharge.


Thats is with pre-built battery devices like in cell phones and such. Since he is using individual cells, they do not have any protection circuitry built in.

You don't need any switches or anything, just solder wires from each cell in to a connector, this forms a balance tap. This way you can charge each cell individually.

See this picture here:

The red connector is the "standard" connector for powering devices. The battery is the 3 cell lipo, so out of that standard connecter you get the 11.1v nominal out. However, to charge it, the white connector is used. The white connector has connections for each of the individual cells, so that each cell is charged to their max potential.

I would greatly avoid using your camera's battery charger, if the cameras battery has built in circuitry, the charger will not be able to charge your batteries properly. You can buy chargers for your batteries for cheap on dealextreme, just look for flashlight battery chargers (since the li-ions you are using are usually meant for flashlights)

Offline SmAsH

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Re: charging lithium ion batteries
« Reply #16 on: August 12, 2009, 04:40:01 AM »
i meant the charger having the smart circuit...
but anyway, be sure to check out ebay too, they tend to have lots of direct sellers which have very cheap electronics.
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