C-rateing on batteries

[Dewey H Lee]

I've been noticing that on a couple of batteries that I have that they are beginning to puff some. Not alot but are becoming squishy. One that is only 1month old and charged only 3 times. It is a kinexsis 3s 11.1 2200mah 30c. I always charge at 1c and always balance charge. I always storage charge my batteries to 3.80 when I don't get a chance to fly them down or if they are b aelow 3.80. I was just wondering what the c factor is for on the battery. I know it's has been explained in the past but on a lot of different areas. I just didn't Know if maybe the c is to low for the plane or I've been doing something wrong. Other batteries seem to be holding up fine. But not the kinexsis.

[Grossman56]

Hey Dewey, Weed snagger is on line about the P51, go get him!!

Grossman56

[Dewey H Lee]

Dang Dan I guess I missed him. I hope not left him a message at the classifieds.

[F106DeltaDart]

C rating is a rating of max discharge current. Take your battery mah (in Amps) and multiply it by this rating to find max discharge current. As an example, your 2200 mah battery would (2.2 A) x 30 = 66 A maximum current draw. Any current above this will damage the battery. However, it is also entirely important to note that many manufacturers overstate the C rating of their batteries, so try to use batteries with a good margin over the current required. So if you are pulling 66A continuously, it might be a good idea to use a 50C battery or so. Even if you are not using the high current capability of a high C rate battery, they tend to last longer and hold better charge compared to low C rate batteries. This is essentially because they are put through lower stresses during discharge and charge cycles.

[KJD]

"C" rating is a marketing thing as there is no objective measure for what that is. But what one is looking for are batteries that have the lowest impedance usually measured in milli ohms. The problem with impedance measurements is that so many variable have to be controlled that to get accurate consistent meaningful results is very difficult.

But if using the "C" rating use the formula Delta Dart is showing. Use the lowest rating shown of the battery, the 25 in the 25c to 75c rating you see on the battery. And then use 80% of that number as the max value for your continuos current draw.

Now this is counter intuitive but the higher "C" rated cells are prone to higher deterioration rates. This is because the chemistry and construction that allows the high current rates also allows for the faster break down of the battery internals.

Most Lipos are only good for about 2 years even if taken care of properly. This is defined as being able to extract 80% of the rated capacity.

Are you aware that Thunder Power has all their batteries and chargers on sale for the 4th of July at 30% off?

[Dewey H Lee]

No I didn't. I've heard alot about thunder power but never used one. All I have are admiral, elite, mad dog and kinexsis. How are they and where is the sale.

[Dewey H Lee]

If things work out I'll need some 6s soon I hope.

[KJD]

Here you go.

http://www.thunderpowerrc.com/Contact_Us/Thunder-Power-RC-USA

They are a USA based company their largest Customer is the USA government. While they don't make the cell there/here (That might change with Musk) they do have a strict cell acceptance criteria that meets "six sigma" criteria. And for those that do fail they are the best when it comes to support!

I need to be fair they are not the best value. Rarely is the best product also the best value. But at the 30% off sale they are getting close. Take a good look at the TP-820HVC that is the future of our power system, the 4.35v cell!

I do like the high "C" rated Admiral for my sport ship. They are a perfect fit for the entry and mid sport level of product (foamy aircraft) that MotionRC markets.

[Dewey H Lee]

Understanding Everything you need to for electrics is mind boggling. Just when I think I'm getting a good hold on things something else rears its ugly head. Before I started flying electric planes I was use to nitro. Fueling tuning and flying. So much less it seemed to keep up with. But Dang the mess. Most guys would just do a simple wipe down of the plane but I would actually wash my planes later after I got them home after the wipe down. And then during the off season remove the engines and reseal the firewalls. Shoot now I'm keeping my eye on lips as well trying to make sure I get the. Best possible service. Thanks for the information guys. It will be taken to heart and good use.

[KJD]

Glow is far more complicated, head spacing, glow plug heat range, non-linear power curves, guessing the fuel need as the engine unloads in the air. Then there is the issue of design limitations with piston speed (actually piston acceleration) be it a ringed engine, ABC, ABN or iron piston. Then if you use pipes even more dynamic variables. Glow to do it right is far more complicated than electrics. Electrics with her almost linear power curve and fairly flat efficiency curve is a piece of cake. You can also modify the electric motor without needing a $500,000 dollar machine shop!

Believe me I know, I built glow racing engines that won the USA Nats for FAI F3D Pylon. I also started flying electrics in the late 70's/80's. Electrics to qoute Mr. Magoo; "Is the only way to fly".

[Dewey H Lee]

Wow that is impressive KJD. I was never that far in.

[KJD]

Most folks aren't and they don't need to be, ether for Glow or Electric. 99% of folks are just happy with an OS 40FP on the glow side or a Sunray Outrunner on 4 cells on the electric. There is no "need" to know more. But oh what fun it is knowing more!

[Dewey H Lee]

Amen. And I'm trying to learn.

[xviper]

I need to be fair they are not the best value. Rarely is the best product also the best value. But at the 30% off sale they are getting close.
I do like the high "C" rated Admiral for my sport ship. They are a perfect fit for the entry and mid sport level of product (foamy aircraft) that MotionRC markets.

There's a few guys at one of my flying fields that swear by T.P. and that's all they buy and they even pay a premium for them at this one LHS that charges way more than anyone else. Personally, I've seen enough reports by various "testers" that show they are vastly over-rated for what you pay. I consider 30% to still be twice as much as they're worth. I doubt I will ever buy T.P. or Hyperion batteries, especially, when we've got Admiral batteries from Motion as an easy and reputable choice.

[F106DeltaDart]

I agree with Xviper. I bought 2 TP batteries when they were 50% off to compare with my other batteries. A friend kept telling me that the performance difference would be easily visible between them and other batteries. Exact same top speed and flight time as my admiral pro battery that was over a year old.. I might drop money on a TP battery if I ran really high current setups (eg 160A continuous) but otherwise they just aren't worth the price difference. Between the Admiral batteries, and a few Revolectrix batteries for some of my jets, I am happy. Even the Zippy Compact 35C batteries have worked well for me in my 3S planes.

[KJD]

I agree with Xviper. I bought 2 TP batteries when they were 50% off to compare with my other batteries. A friend kept telling me that the performance difference would be easily visible between them and other batteries. Exact same top speed and flight time as my admiral pro battery that was over a year old.. I might drop money on a TP battery if I ran really high current setups (eg 160A continuous) but otherwise they just aren't worth the price difference. Between the Admiral batteries, and a few Revolectrix batteries for some of my jets, I am happy. Even the Zippy Compact 35C batteries have worked well for me in my 3S planes.

Maybe you have some limit set in the ESC. The new chemistry is night and day between the 4.2v and 4.35v. I too like to use the Zippy in my sport jets, the very thing Motion RC sells. My ME 262 runs fine and for a long time on the 30c 5800 mAh 6 cell (98 amps). The TP is about consistency in the cell selection process. (I don't think TP actually manufactures the cells and definitely not in the USA.) Of the 200 or so cells I've purchased I've only had the one high impedance cell. TP took care of that along with the connector. Most of my TP are in competition type ships were one can see performance differences in man on man racing. I too am constantly looking for value and am often trying out "New" battery OEMs. Such as this http://dinogylipos.com/4-cell-30c/201-3300mah-4s-ef-1
While the $5 price difference was nice the way the cells performed (6 batteries x 4=24 cells) was disappointing (did like the $5 x 6=$30 savings). The old 55"C" TP Lighting series 2700mAh cells held their voltage (flatter discharge curve) where more consistent (milli ohm reading) and offered over a once in weight savings. All are what one needs to be competitive, along with some other stuff :rolleyes:. And then there is the support. Would MotionRC (any other vendor) credit you for the cost of the connector (I don't use what MotionRC markets).

Yes, on the face of it TP are too expensive, No they are not the best value for the sport pilot if you are willing to except a higher failure rate. In my sport ships a 25% higher failure rate in the battery is often worth the 50% price discount in the HK type batteries. Do other vendors have a buy back program? Do other vendor credit the connector should you have an issue?

What I hear is that TP is not for everybody. I agree, they are for the discriminating consumer and those that know how to ascertain the best value and performance for the battery (Usually this means competition). Even I don't use TP in my low value sport planes, the realm of most of what MotionRC sells, Foam. But nether do I cry of premature cell failure in the lower cost/higher value sport cells sold by HK and the like. (Actually a failed HK battery is not a good value!)

Question what does the "3S" have to do with the issue. My understanding is that the cell is stressed more by the current draw not the voltage. The voltage issue is based on the individual cell discharge level and is not predicated on the pack voltage.

All the above is assuming proper care and operation of the cells.

Look at what Thunder Power is offering at 30% off. Also look at the "TP820 HVC" charger again at 30% off as this is the direction of the future, the 4.35 cell.

[KJD]

Something else I've learned when dealing with the Chinese. They don't make scrap! That is, things that fail one level of QC with be rebranded to a lower standard. If it fails that it will again be sold at a lower and lower price points under another brands. There is a very strong correlation with quality and price. This has proven to be true of foods, servo, paints ESC's batteries just about any commodity. Yes, you can find great deals, but as the product gets a proven track record the price will climb!

[F106DeltaDart]

I agree that the 4.35 versions will certainly give more performance. I got several HV lipos from Revolectrix and they do have some extra punch. The TP packs I bought were the old chemistry, I bought them back before they introduced the high voltage series.

[KJD]

Glad to hear you too have seen the improved performance of the HV Revolectrix cell.
As of today TP HV cells are not suitable for high power. That is they still have a low "C" rating.