so i used many Lipo batteries in the past , and i use a lipo battery charger for them , the thing is , now i recently got a 7.4 2C lipo battery but it does not come with the conventional plugs it only has two wires ?? a red one and a black one .. how can i charge this thing without damaging it ?
it's exactly like that one :
You can buy 2S (two cell) LiPo chargers.
jremington:
You can buy 2S (two cell) LiPo chargers.
i have one but i will not charge that one . that one only has the power wires and does not have the extra wires for charging that the other lipos have .
A 2-wire lithium battery probably has the charge/discharge controller and protection circuits built into the battery. Does it have a lump on the side like there's a circuit board alongside the cells?
You could try plugging it into a dumb charger and seeing what current it takes as it charges up. If you see a sudden drop in current, that would indicate an active circuit has disconnected the battery instead of the battery becoming "full" slowly with a smooth drop in current over a long time. For example, I have a large battery that charges at 17A, slowly dropping to about 1.5A, then it cuts off to zero when the onboard computer decides that it's fully charged.
It looks to me as though you just need to buy/make some type of adapter to enable you to connect your existing charger to the battery.
You haven't given us any information about your charger, so i cannot say what this adapter will look like / be called..
The battery pack shown at www.robotshop.com/en/dfrobot-7-4v-lipo-2200mah-battery.html is not very well suited for Arduino. There is no safety electronics in that pack, so it can deliver 100s of amps and smoke everything if you fuck something up.
Leaving the battery pack plugged into the Arduino will end with a over-discharged pack and sooner or later an unbalanced pack. Not so smart.
// Per.
the only thing i can do , is to supply a continuous current to the battery , but if it has no internal circuit to do the charging then i would probably end up overcharging it .
i know about the balance of Lipos since i did work with them for a long time before though the dischrage rate of that battery is 1C i think it's safe . though the best part about these batteries is that you do not need a Lipo charger , you only need a 9v to 7.5v wall adapter that's it . like Morgan said , it has an internal circuit .
amine2:
the only thing i can do , is to supply a continuous current to the battery , but if it has no internal circuit to do the charging then i would probably end up overcharging it .
i know about the balance of Lipos since i did work with them for a long time before though the dischrage rate of that battery is 1C i think it's safe . though the best part about these batteries is that you do not need a Lipo charger , you only need a 9v to 7.5v wall adapter that's it . like Morgan said , it has an internal circuit .
Well, the problem is, plugging this into a 9V power supply would make it a bomb ...
// Per.
Zapro:
Well, the problem is, plugging this into a 9V power supply would make it a bomb ...// Per.
why ? it has an internal circuit for balancing as far as i understand
amine2:
why ? it has an internal circuit for balancing as far as i understand
Where do you see that? It doesn't look like there is any safety circuits in that pack.
// Per.
as Zapro says, I don't think there is any circuit in this pack - It is just 2 cells pack, nothing more.
charging it requires a LiPo charger, at least the one in DFRobot link will do the minimal protection job .
And, by the way, "1C continuous discharge rate" doesn't mean it cannot source more than 2,2A , it just means that it can safely source 2.2A - If you ask more, it will get (very) hot, and if you short it, it will burn very fast, and probably quickly turn into flames
be very careful with LiPo batteries, they are very good.... if properly used , very very bad if not 
alnath:
as Zapro says, I don't think there is any circuit in this pack - It is just 2 cells pack, nothing more.
charging it requires a LiPo charger, at least the one in DFRobot link will do the minimal protection job .
And, by the way, "1C continuous discharge rate" doesn't mean it cannot source more than 2,2A , it just means that it can safely source 2.2A - If you ask more, it will get (very) hot, and if you short it, it will burn very fast, and probably quickly turn into flames
be very careful with LiPo batteries, they are very good.... if properly used , very very bad if not
i know . though what i don't understand why can't they provide the conventional plug for charging like the one i used to find in Lipos . i am thinking about constructing a charger or programming one for this , but i still cannot figure how to do it . with the usual plug it's not that hard . but with this one ... meeeh
amine2:
i am thinking about constructing a charger or programming one for this , but i still cannot figure how to do it . with the usual plug it's not that hard . but with this one ... meeeh
You could always resort to removing the wrapping.
You could probably find out if there's a PCB included or not. You might be able to add your own balancing port.
As I'm sure you know, if you have access to a balancing connector, you can charge a multi cell LiPo one cell at a time with a single cell charger.
FWIW, I've heard good things about this charger.
mingdaiyu:
just see your battery ,7.4V LIPO Battery, just use rc toys charger- 7.4V Charger is ok
I certainly hope that OP no longer needs advise after 2 years. And it was already solved