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Old Sep 12, 2011, 11:07 PM
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How much should I charge my 11.1V battery?

I (very) recently go into the whole RC plane hobby and I'm curious about my battery. I ordered a new SuperTigre LiPo 11.1V 1500mAh 15C 17Wh battery, and when it came in, I checked the voltage with a voltmeter and it read 11.7 Volts. I plugged it into the charger just to see if it would indicate that it was "done charging", but it didn't... I took it back off the charger anyways because I didn't want to overcharge it. Should I have left it plugged into the charger until it indicated that it was done?

Kinda confused, as this is my first RC plane. If my charger is screwed up (it's brand new, so it shouldn't be), then how much of a charge should I put in my 11.1V battery?
Thanks
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Old Sep 12, 2011, 11:17 PM
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An 11.1 V battery will charge at 12.6 volts. LiPo cells are rated at 3.7 nominal volts and they charge at 4.2 volts per cell.

So put it on the charger and let it charge all the way up. If you measure the voltage right off the charger, it should be about 12.6 V. During its discharge it will eventually get down to 11.1 volts for much of the discharge process. And of course it will eventually get all the way to zero if you keep discharging it. But you should never discharge it below 9 volts or you can ruin it.

So the 11.1 volts is sort of an average voltage that the pack will put out throughout its useful discharge cycle.
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Old Sep 12, 2011, 11:40 PM
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Great info. Thanks so much for the help!
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Old Sep 13, 2011, 08:44 AM
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LiPo Cell Capacity versus voltage =

http://www.rcgroups.com/forums/showp...1&postcount=11
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Old Sep 13, 2011, 11:48 AM
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Caution: it sounds like you do not have a LiPo capable charger. While LiPo's are quite safe to use if properly stored and charged and not discharged to deeply, if charged with a charger that does not automatically terminate the charge when the cells reach 4.2 volts, you run the risk of fire. Do yourself a favor and check into the proper care and use of LiPo's. For safety, a proper charger is almost a necessity.
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Old Sep 13, 2011, 06:05 PM
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I agree, it sounds to me that your not using a Li-Po Balance charger. If you use a balance charger, then you don't need to worry about overcharging as the charger will only charge until the correct voltage, then cut off.

Be sure to use a Li-Po capable charger as stated above, Li-Po's handled incorrectly can effectively ruin more than just the battery mate

Happy RCing
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Old Jan 20, 2012, 04:42 PM
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Hi.

Is there a way to charge the Lipo battery with a normal DC supply? Or the Lipo charger is mandatory?
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Old Jan 20, 2012, 08:16 PM
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You can charge them with a standard DC power supply, but i wouldn't recommend it, you can get a cheap charger for $50 that does the job safely.
If you want to charge them on your DC supply, you want to charge them with a CC/CV scheme, that is, Constant Current / Constant Voltage - in that order!

Your battery is rated with a recommended charge current of 1,5A (or 1C as we call it) so you want to set up your current limiting at 1,5A maximum. After charging at 1,5A the pack voltage will slowly rise to 4,2V per cell (12,6V in total for 3S pack) and at this point the charge current is to be turned down to zero gradually. Charging a cell over 4,2V is very unsafe and dangerous, so you do not want to do this. Better charge them at 4,1V for some safe margin. - But still, doing this you have no means of balancing the cells in the pack. Even if a single cell gets a couple of mV lower that the oters, you can quickly overcharge it to more than 4,2V, and that's bad news!

I would not recommend it unless you sit a watch the whole process....

I only charge single cells directly on a power supply (when i do not have access to a charger), because then i have no balancing issues.

// Per.
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Old Jan 20, 2012, 08:42 PM
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Originally Posted by Syed Saad View Post
Hi.

Is there a way to charge the Lipo battery with a normal DC supply? Or the Lipo charger is mandatory?
Use a dedicated lipo charger!

It is mandatory for safety purposes. Don't cut corners here as a fire is a very possible result of improper charging.
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Old Jan 21, 2012, 08:38 AM
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Originally Posted by Zapro View Post
You can charge them with a standard DC power supply, but i wouldn't recommend it, .... CUT!
This ranks right up there with the worst information I've ever seen someone give a newcomer. The truth of the matter is it's the worst information I've ever seen someone give anyone.

I'll tell you what, //Per: You deserve to live in an apartment with Syed Saad living below you.

Pete
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Old Jan 21, 2012, 08:54 AM
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There is no practical way to manually charge a Lipo battery pack. Please get a Lipo balance charger for your Lipo battery packs. The Lipo Balance charger is needed for safety reasons and to help prevent fires. Never leave the battery pack unattended while it is charging. Also charge the pack so that the charger and pack is away from anything flammable, preferably outside, as they can generate a lot of toxic smoke if something goes wrong. The Lipo balance charger does everything automatically for you, it stops charging when the pack is charged. Overcharging causes a fire. The Lipo Balance chargers have a computer inside and a set of calibrated voltmeters built in to monitor, measure, and charge the battery pack for you automatically.

So there is no practical way to manually charge a Lipo battery pack. It is nearly impossible for a person to manually charge a Lipo pack and ensure that all the cells are balanced. You need to measure voltages to a thousandth of a volt (.001v) and a voltmeter that accurate is very expensive, plus you need a voltmeter for each cell too. So then you have to sit there and monitor each cell constantly and stop charging the instant one cell reaches the full charge voltage. Then you have to discharge the strong cells a little to balance them out with the weak cell, and then repeat the charge process. But if you screw up and overcharge a cell, the cell may go off and smoke or burst into flames on you. You need to measure the cell voltages many times a second too. So there is no practical way to manually charge a Lipo battery pack.

Now we did do this at first in a laboratory setting, before Lipo Chargers existed as we were building and designing chargers for the Lipo packs at the time. Even then it was a pain, as it was so easy to miss the cutoff and overcharge a cell. I had to charge each cell one at a time and then put the pack together for use. Also I never really tried to go for a peak charge on the cell. I would just get close. Later after we got some early design prototype chargers built, we quit doing it manually. Yes we did smoke a number of battery packs too.
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Old Jan 21, 2012, 11:28 AM
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I had momentary flashbacks of Hall Woo silliness when perusing this thread!

Mark
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Old Jan 21, 2012, 11:50 AM
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I had momentary flashbacks of Hall Woo silliness when perusing this thread!
Heh ..

That's precisely why I said the info ranks right up there with the worst information I've ever seen someone give a newcomer.

Pete
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Old Jan 21, 2012, 01:29 PM
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In a way, I miss him.

In other ways, not so much...

-m.
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Old Jan 21, 2012, 05:35 PM
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Originally Posted by PGR View Post
This ranks right up there with the worst information I've ever seen someone give a newcomer. The truth of the matter is it's the worst information I've ever seen someone give anyone.

I'll tell you what, //Per: You deserve to live in an apartment with Syed Saad living below you.

Pete
Wow, that's a personal attack, why that ? I work with electronics every day and it's my living, that's why i answer like that.

The user asks if it's possible and i give him an answer, simple as that! Sorry to bug you - you kind make me wonder of i should even be here on this forum.
Sigh....

// Per.
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