How to charge a LiPo?? (Full Version)

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rs917 -> How to charge a LiPo?? (12/21/2012 12:38 AM)

Hi,

I posted here a couple weeks ago about needing a LiPo charger for my new plane. Well, I got one—an older Turnigy Accucel 6—and now I need to charge the battery.

I found a manual online, and it seems pretty straightforward, however it doesn't mention what to do with the cables coming out of the battery. It has two, one that looks like it connects to the ESC in the plane, and another one that is composed of four wires. There are places to plug both in on the charger, but is that really what I do? Does it charge through one and monitor the battery through the other?

I'm worried that I'm going to start a big fire not knowing what I'm doing, so if anyone wants to give me step by step directions for charging my battery (1800mAh 25-50C discharge 14.8v battery). It has a big "1.8" on it, which I have no idea what it means. It also has a sticker on it saying that it should not be charged over 5C, whatever that means. 

I'm assuming:
• That the "C" is the charge/discharge rating, with a larger discharge number meaning the battery puts out more power?
• That the 14.8v is the total capacity of the battery?

Any help or corrections are welcome. As is abundantly obvious, I'm new to LiPo. Last time I did this, NiMH and NiCad were the name of the game, and I didn't even know how to charge those properly. :)

Thanks in advance.



guver -> RE: How to charge a LiPo?? (12/21/2012 12:53 AM)

Yes, they both need plugged in. The main esc connection (2 wire) goes to the main output of charger. The other is the balance plug and allows balancing of lipo cells individually. Charging thru the main and monitoring thu the 4 wire tap is pretty good way to say it.

You'd have to set the battery for a 4 cell and the capacity (C) is 1800 mah. Since the label shows a max charge rate of 5C then that is 5 times 1.8 ah = 9 amps max. You can set your charger for a max of 5 or 6 amps depending upon how old it is. Since your charger is 50 watts max then even though it's set for 5 amps it will only put out 50 watts and this is going to be around 3 amps. Many insist upon a MAX of only 1C and that of course would be a 1.8 amp rate and take an hr.

"C" stands for capcity (with a multiplier before it) and can describe the charge and/or discharge rating of the pack and the 14.8 is the voltage, right? That is 4 cells in series.



rs917 -> RE: How to charge a LiPo?? (12/24/2012 3:30 PM)

Thanks guver. I'll see how it goes, though all these numbers and measurements have me very confused. I'm hesitant to fly because I don't want to burn my house down. ;)

I guess I can't go wrong if I just set the cell count right and charge slowly. Real slowly.



Goldenduff -> RE: How to charge a LiPo?? (12/24/2012 9:19 PM)

Don't charge at a rate less than 1/10th of the capacity as it may take forever. Either charge outside or supervised. Some have rigged a plastic bag over the battery full of sand. I it burns through the bag sand extinguished the fire. Personally I charge mine outside in an old cooker!



rs917 -> RE: How to charge a LiPo?? (12/28/2012 4:01 AM)

OK, sorry to be back here again, but I'm more confused than ever. 

Reading the responses above, and the naming conventions section in this thread....


....I'm completely stumped by all the abbreviations, their meanings, and how they relate. And I'm NOT going to try charging this innocent looking wannabe bomb until I have it all figured out! :D

What am I missing? Everyone else seems to have no problem with this. I never thought of myself as stupid, but I may have to reevaluate! :)



hugger-4641 -> RE: How to charge a LiPo?? (12/28/2012 4:07 AM)

Go to the Electric forum and there's a thread there called  "all you need to know about electric flight". I'll go find it and come back and copy the link here in a bit.



hugger-4641 -> RE: How to charge a LiPo?? (12/28/2012 4:09 AM)

Here it is: javascript:mox();



rs917 -> RE: How to charge a LiPo?? (2/8/2013 3:20 AM)

Thanks Jerry. That thread was amazingly helpful. Still a little hazy, but understand much better.

A quick question that I hope someone can answer.....I'm charging the battery right now. It's set for 4 cells (4S) and a 14.8V battery. I picked a charge rate of 5A. 

This correct, and if so, how long is it going to take to charge? I can do the math the one way, but not the other.



guver -> RE: How to charge a LiPo?? (2/8/2013 3:33 AM)

5 amps can be thought of as 5 ah (per hr)

If your pack is an 1800 and it was able to accept 1800 mah and the rate stayed at 5 amps then it would take .36 hrs.



rs917 -> RE: How to charge a LiPo?? (2/8/2013 4:01 AM)

That explains it perfectly. Thanks guver. 

Found this video quite helpful as well: http://www.youtube.com/watch?feature=fvwp&NR=1&v=kvr-25yGeVk



benlinus -> RE: How to charge a LiPo?? (3/1/2013 11:28 AM)

You shouldn't let any one cell of your battery fall below 3V to avoid damaging it. That means 9V is your lower limit on a 3S, 6V on a 2S. This is where balance charging becomes important. The whole battery may be at 9V, but if one cell started higher than the others, then one cell may dip below 3V. Most ESCs won't let the battery go below the 20% threshold previously mentioned, but other applications may not be so merciful. Each cell will discharge and charge at a slightly different rate than the other two, so balancing keeps the starting point the same for every use.

Charging rates is another fun topic. Dave recommends 50% of the mah, but you can charge at 100% of the mah without damaging the battery too. 50% will get you the max lifetime from the battery, but when you have a bunch of lipos to charge, 100% makes more sense. Quick charging at the field (if your charger will do it) will push that rate up even more, but once in a while won't kill a battery. The quick charge usually isn't a balance charge, either, so if you have an older battery it may not be a good idea.



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