Higher C rated Lipos?

[Eric Miller]

I would really like to see some higher C rated batteries. The ones in stock are awesome and are always balanced in storage mode when received. They perform great, especially for the price. But, I have a couple of planes that are begging for higher C lipos. Especially my RocHobby F-16 and my A-10. I've been using 3s 2200mah 30C lipos and they seem to get super hot when ran. My P-51D has been using the 3s 1300mah 25C and it gets pretty warm when flown. I have tried a friend of mines 60-120C lipos in them and they didn't get so hot or puffy right after flight. The puffing goes away once it cools off, but it worries me a little. The 60-120C lipos didn't get so hot and didn't swell up. If you guys decide to bring higher C lipos in, I'd buy them pretty quickly (on the first day of every month)......

[Tom]

Re: Higher C rated Lipos?

Hi Eric,

We want to do some sort of a video on this subject. First, I'd like to mention the work we put in looking for a good battery manufacturer. We have one of the best. We did a lot of testing and found most battery brands overstate the C rating by a lot. Most 30C batteries are actually 15C to 20C. Most 60C batteries are 30C to 40C. Our batteries have a true C rating. If I were to test a battery claiming 120C, it will be 50C at best and likely even less.

60C to 120C is pure marketing. Manufacturers have no capability to produce a battery with his C rating. I've been to the factories, I've talked to the engineers, and I've seen the manufacturing process. The highest possible C rating is about 50C on a large size battery such as a 5000mAh while mid size batteries such as a 2200mAh have trouble reaching 40C.

I use an 1800mAh LiPo in my F-16. The F-16 has a 35A ESC. If the plane draws 30A, we simply need a battery capable of delivering 30A. An 1800 mAh battery is 1.8 Ah (divide by 1000 to convert from milli amps to amps). The Amperage the battery can deliver is 1.8 Ah x 30C = 54A. A battery which can deliver 54A is more than capable of powering a plane which only needs 30A. A higher C rated battery will only add more weight to the plane while lowering the weight of your wallet. Performance difference will not be notable.

If a battery is puffing, it has likely been run down too far. I run my batteries hard (especially in the F-16) but I always aim for a resting voltage of 3.75V per cell. In other words, I check the battery 5 min or so after landing and I want it to read 3.75V per cell in any plane. I've never had a battery puff unless I run it down lower than 3.75V per cell. Batteries will get warm in the F-16 because of a lack of ventilation. My 1800 mAh 30C battery comes down a little warm and never puffy. If you have run your battery down too far a few times, your battery may have higher IR (internal resistance) at this point. This effectively lowers the C rating of the battery which may be contributing to your issue.

I'd like to give one last example. I'd like to use the FMS P-51 mustang. It draws a bit less than 60A but I will use 60A for the sake of easy math. Many use our Admiral 3600mAh 40C battery in this plane. 3.6 Ah x 40C = 144A. Using a battery which can deliver 144A in a plane which draws 60A is already complete overkill.

I'm not opposed to ordering some higher C rated batteries if there is an application which calls for this. We have a 5000Ah 6S battery for some of our larger EDF jets. Please realize we will never have anything more than 50C because we want our batteries to have true C ratings. We will only have higher C ratings when/if new manufacturing process are developed. You can always count on Motion RC to have battery packs with true C ratings.

I'd go into construction and the process to make a higher C rated battery but I think I'd bore everyone to tears. Hopefully people are still reading at this point.

This is my 2 cents.

[Eric Miller]

Re: Higher C rated Lipos?

thank you for breaking it down for me a bit. i have put a couple of small holes at the front of the battery compartment to try and get some airflow. it is getting a small amount of air. i only run my lipos to 3.8v in my RocHobby F-16. they come out really hot and swollen pretty badly, but when cooled off, the swelling goes down. the batteries are really good and havent had any sort of issue with them since i started using the lipos you guys provide. they are the best lipos for the price in the market anywhere i found within the specs they have. my P-51 is from Parkzone and it is upgraded. it has a turnigy G10 1100kv motor, 60amp esc, and is spinning a 10x8 master airscrew. it is more powerful than the 1400mm series FMS P-51s. it is fast ( it will run over 80mph easily on 3s) and will climb 90degrees verticle unlimited at a little over half throttle. if i am easy on the throttle, the 30C is a little hot when they come out. but, thats to be expected for 3s 30C. 4s will break the wings in two from the speed. with 4s it will go over 100mph easy but the motor gets hot. so to stay in balance, i have to use 3s. if there was an option for a little higher C 3s, i will buy some. i just want to get the best power balance i can out of my planes and its always good to have the options for other customers as well. i think they will sell pretty well....

[Bogietrim]

Re: Higher C rated Lipos?

First of all I am not an expert when it comes to a lot of the numbers here. I just like to fly! LOL! I read this thread awhile back and decided to to a little test of my own. I have several of the Admiral's from MRC and so far am very satisfied with them. I do have several other different brands of batteries ranging from 1s to 6s with varying C ratings. I have 4 different C rated 6s...30, 40, 45 and 65. I hooked up my watt meter to my Freewing F-18 with the stock motor. The 30c battery gave me about 1150 watts on average. The other 3 all gave me exactly the same reading of about 1300 watts. I tried it a couple of times with fresh charges on all of them. The amps were all within about 3-4 of each other. The airplane definitely flies a little slower on the 30c than the others with no noticeable difference between the other 3. So, I would tend to believe that the higher C rating is hype and is pure marketing to charge a higher price.

Just thought I would share my experience.

[Tom]

Re: Higher C rated Lipos?

Some of our larger jets do require more than 30C so we do have all larger batteries in 40C and 50C for these planes. I don't recall the amp draw of the F-18 off the top of my head but I'm going to guess about 80A. A 3700mAh 30C would not be enough in this case. Ideally, you want at least 50% overhead which means you need 80A + (80A x .5) = 120A. So ideally you need a battery capable of delivering 120A for the Freewing F-18. If you use a 3700mAh 30C battery, it will only deliver 111A (3.7Ah x 30C). In addition, recall most batteries are not labelled correctly which is likely why you saw the lower wattage with 30C. This is why we carry 40C and above batteries for this plane. We make sure we have the appropriate batteries for every plane we sell.