Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: blackbeard 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?
-
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.
-
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
-
nah, if its meant to charge 3.7V single cells, thats what it should charge...
-
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
-
now uh... hypothetical if i already soldered them together is there some way i could still charge them without disconnecting them?
-
not unless you soldered some switches in between them?
-
ok i guess i better get out soldering iron again
-
yeah... you probably should :P
they had tabs or something that you soldered to right?
-
nope just the flat
-
make sure you don't get the batteries too hot while soldering!
-
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!
-
yep i'm really cautious around these guys. my 35w iron seems to do a good enough job though
-
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
-
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.
-
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:
(http://www.electric-rc-helicopter.com/pic/lipo_acro/EFLB0995.jpg)
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)
-
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.