LiPo battery recommendation

[Rolex]

I opened up one of my scale helis to use the battery pack in another heli and found that one side of the pack looked and felt like it was inflated. I can press it down and it comes right back up. It feels like an inner tube. Good pressure. This pack doesn't even have 4 full flights on it, but it has been in storage in the heli (disconnected) for 5 or 6 months. None of my chargers will work on it. They all show a battery error.
Is there a proper way to store them?

I need 2 11.1V, 20c packs, preferably 2200mAH or higher.
What brands and dealers do you recommend? Price and reliability.

 

[slowngreen]

Best price and from my experience, hard to beat reliability comes with Turnigy packs.

Hobbyking.com has them.

http://hobbyking.com/hobbyking/stor...me=Turnigy+Lipoly&idCategory=317&ParentCat=85


http://hobbyking.com/hobbyking/stor...Turnigy+nano-tech&idCategory=378&ParentCat=85

 

[Rolex]

Great prices. If I now have the 1800mAH 11.1V, 20c, 3s. What difference would the c rating make. I've found 2200 3s, 25c, but none of them are showing voltage. How do I know it's 11.1?

If it makes a difference, it's a rather heavy heli. Fiberglass scale body, 4 blade rotor head, full lighting and retracts, plus it's dealing with the additional drain of extra electronics to support the flybarless system of the scale rotor.

 

[Rolex]

Found a major stash of information:

Originally Posted by Shawn_Palmer from RC Car Action Forum Voltage
The # of cells in the pack determines voltage. Each cell is 4.2v fully charged. Most folks are comfortable with the fact that each cell in a NiMH/NiCad pack is around 1.5v fully charged, and the same principles apply to lipos.

6 NiXX cells = around 9.0v fully peaked, and pack rated as 7.2v (1.2v/cell) as its "nominal" voltage. 2 lipo cells = 8.4v fully charged, and pack rated as 7.4v (3.7v/cell) as its "nominal" voltage. 3 lipo cells = 12.6v fully charged, and pack rated as 11.1v (3.7v/cell) as its "nominal" voltage.

As you can see, "nominal" voltage is fairly arbitrary in both cases, as it's neither the fully charged voltage, nor the fully discharged voltage, but somewhere in the middle.

Current output capability
Lipos are commonly rated as "10C" or "15C" or "20C". The "C" stands for the capacity of the pack in Mah (milliamp hours). The "10, 15, and 20" stand for how many times of the capacity the pack can deliver continuously in amps.

So a 3800mah pack rated at 10C can deliver 38A continuously. A 3800mah pack rated at 20C can deliver 76A continuously.

"Ratings" can be misleading however. Apogee, Kokam, Orion, Peak and Tanic all have an impeccable record of their products standing up to what they SAY they will deliver.

So what does this have to do with anything? Well, lipos are subject to the same rules of performance as any other battery. They are still an electron storage device - just in a different package and configuration than you're used to seeing. The main parameter controlling a battery's performance is internal resistance. The lower the internal resistance, the more amps (speed/punch) it can deliver, the higher the voltage (speed/punch) it will maintain during that delivery and the cooler it will be at the end of the delivery.

So the above "10C" 3800mah pack would give lower top speed, less punch, and be hotter at the end of a run than the "20C" 3800mah pack. The exact same run will also use more mah from the 10C pack than it would from the 20C pack.

So the (actual) "C" rating of a battery is important to know, but what else affects performance?

Mah Capacity
One of the most interesting things about lipos is that as the Mah of the pack goes up - so does the output performance. As above - a 10C 3800mah pack can do 38A. If we parallel two of those packs together to make one 7600mah pack, we can then get 76A from it. From the above, we know that the more amps the pack is capable of, the more speed and punch are available, and at a lower pack temperature. So ideally, we'd want to run the most mah that can fit in the car, and have that pack be "rated" for the highest reliable "C" rating we can find. This maximizes speed and punch, and minimizes heat within the pack.

Just like you wouldn't want to run the GP1100 pack from your 18th scale car in your 10th scale car, you wouldn't want to run too small of a lipo for the performance that you want.

 

[speedingbulletbp]

I opened up one of my scale helis to use the battery pack in another heli and found that one side of the pack looked and felt like it was inflated. I can press it down and it comes right back up. It feels like an inner tube. Good pressure. This pack doesn't even have 4 full flights on it, but it has been in storage in the heli (disconnected) for 5 or 6 months. None of my chargers will work on it. They all show a battery error.
Is there a proper way to store them?

I need 2 11.1V, 20c packs, preferably 2200mAH or higher.
What brands and dealers do you recommend? Price and reliability.

If you have a normal NAMH charger that shows how many volts are charged in the battery, you can hook up your lipo battery to it and charge it until the voltage gets to what it should be or until it stops dropping. It only takes seconds to do this so you need to watch it closely. I had to that with my Losi box starter battery and it works just fine now. My lipo charger works with it too.

Now I have a lipo question, I have a Thunder Power RC 5200mAh 2 cell/2S battery and I'm not sure what current to set to charge it at.

 

[slowngreen]

Set it at up to 5.2A to charge. ^^^


And yeah Ralph, the packs you were looking at from hobbyking that say 3s are 11.1v.

 

[hamz9561]

You could easily charge it at the 5200 mah (5.2 amps). Again if it's a 20c pack it can be charged at 10 amps with no effects. Personally I charge them at the rated current.

 

[speedingbulletbp]

I have the Bantam e-station lp6 and the highest current setting I can use is 4

 

[Rolex]

I disposed of the one that had the swelling on one side. I think I'm just lucky that I caught it when I did, rather than have it explode and take out a thousand dollar chopper and whatever else catches fire.
LiPos are scary, so I played it safe and got it out of the house.
I'll probably be getting Turnigys.

 

[Rolex]

Thanks to the sng links and a little extra research, I went with this one:

Zippy Rhino, 2250 mAH, 25c, 3s. These also come with the deans connector already installed for heavy helis. I checked on my heli forums, and found no complaints on these whatsoever. $17.50 each, but almost $10 postage.
I only got one, for now, but if I'm satisfied with it, it will probably be the brand of choice.

 

[slowngreen]

Rhino's, Zippy's and Turnigy's are all awesome lipo's. They could easily be priced at tripple what they are and still be worth it. I find that the people that complain about them, havent ever even had any!

 

[Rolex]

From what I read, the Turnigys are using Zippy cells. I found several complaints about Turnigy having bad cells or dead cells, but no complaints about the Rhinos. For a few bucks more, I went for this one, and my next one might be a Turnigy for comparison.