Could installing a higher C rating battery damage the ESC?

[Bluebird]

I have been flying my Carbon Z Cub with the stock ESC, 60 amp, and all else the same except for a wooden Xoar prop and E-flite aluminum spinner. Maximum draw at full power with this setup was about 62.5 amps so I have been limiting my full power bursts to 10 seconds or less to not overload the ESC.
I have always used a 4000mah battery, 40c. Today I flew with a 5000mah, 50 c and on the second flight the ESC died. I could have lost the plane as I had been flying very high but she landed in a corn field with minimal damage. Whew! I flew my normal routine of a few loops and half Imelmans.

Would the higher C rating allow the motor to draw even more currant at full power and thus overload the ESC?
Thanks for your response!!

[WintrSol]

While the higher C rating was probably not the reason, the extra weight of the bigger battery could be. You were likely operating closer to the maximum 60A, possibly just over, just lifting the extra weight, and since you already know the motor draws more current than the ESC rating, you very likely pushed it over the limit. IMO, you should never have a power setup that exceeds the rating of the ESC at full power; in fact, it should be less than the maximum by about 10%, to give a margin of safety. Either use a smaller prop, or replace the ESC with one capable of about 70A, or more.

[OV10]

Bluebird,
No, you were already able to allow the motor to reach its potential max amperage with the 40C battery.
The burst current available from a battery is C x Ah .
40C 4000mAh battery is 40 times x 4 = 160amps
Am assuming that you did the full power burst for 10 seconds or less have been done more than once or twice whereas repetitive stressing of the ESC occurred enough to finally cause it to fail. Having measured the setup to draw more amps than the ESC rating should have been an indicator to upgrade to a higher amperage rated device. The amperage draw higher than the provided stock ESC was most likely induced by the change to the Xoar prop which I am going to speculate was different from the stock props pitch and/or diameter. A good rule of thumb is to have a 10-15% higher rated ESC in your system than the max current draw.
Best of luck on the airframe repair and power upgrade.

[Bluebird]

Hi there WintrSol & OV10 Thanks for your reply to my question. I think you have both helped me to understand the problem. I have been flying for about a year with this plane and the Xoar prop which is more effective & efficient than the stock one. My amp meter told me I was pushing the envelope with the ESC. Not only have I used max power repeatedly for short bursts, but I also have the heavier Dubro inflatable tires and sometimes carry a GoPro camera. Funny thing is I had already bought a Castle Talon 90 ESC to replace the stock one but I was waiting till winter to put it in. I guess my luck ran out today.
I am happy to know that the higher C rating was not the issue, however it makes sense to point to the extra battery weight as a contributing factor as well as the repeated use of max power.
There is another lesson here as well. It's easy to ignore the details sometimes when things seem to be going well enough. That's when you can get rude surprises by something you knew darn well you should have fixed a long time ago.
Thanks guys!
Bluebird

[Bluebird]

OV10 I have a question for you re your calculation of 40c X 4amps = 160 max. burst current. That means then that if the motor demanded it the battery could deliver that much. If the ESC isn't up to the task then it will get fried. Am I on the right track? Just trying to understand the dynamics. If this is the case then obviously the batteries are capable of way more than the motor or ESC could or should ever be demanding of them. Assuming everything has been matched correctly.
Thanks, Bluebird.

[OV10]

You've got the gist of it now!! With that knowledge you can now maybe save yourself some money on batteries by not buying 40 or 50 C ratings when a 20 to 30 C can very easily get the job done on most prop driven applications. Those higher C's are usually in the troughs of the EDF current sucking hogs :p

[Bluebird]

Thank you OV10, I appreciate your reply. Yes the EDF's do suck the power, that's why I own the 5000mah 50C battery. Thought I might as well give it a try in the Cub as I already own it for powering the FW ME262. 4 minutes flight time with enough left over for two go arounds. That's about all you get. But what a rush!
Cheers! Bluebird.

[xviper]

Most manufacturers select equipment that will work adequately for any given application. This is true for ESCs. Having said that, most ESCs have a bit of "extra" (or burst as some may call it) that will allow for some "overage" for a few seconds. Lots of things can contribute to a power system exhibiting more amps, more volts, etc than what was originally designed for. If you change the size, pitch or efficiency of the prop or change the motor type or KV or change the weight or aerodynamics of the plane itself (more or less resistance to the flying situation) other components of the drivetrain may change (either work harder or less hard).
Without all the fancy calculations, I look at batteries using the analogy of a car's fuel system, primarily, the gas tank. The "mah" of a battery is like the size of the gas tank. (3000mah is like 30 gallons; 5000mah is like 50 gallons). The "C" rating is like the diameter (and length) of the fuel line. (30C is like having a 3mm diameter fuel line; 50C is like having a 5mm fuel line.) The more mah the battery has, the more fuel you have. You can fly longer, given the same kind of circumstances. The bigger the "C", the easier it is for the engine to draw the fuel. Of course, you get to a point where it's pointless to increase "C" as the motor simply can't draw any more fuel anyway. Same goes for the size of the gas tank. Keep increasing it and the weight of it gets be too heavy and the vehicle starts to work harder to carry it. Imagine putting a 100 gal tank into a Fiat 500. Similarly, if the Fiat has a 1/4" diameter fuel line, increasing it to 1" won't necessarily benefit the car.
The kind of prop you put on your T-28 has the ability to pull the plane through the air faster and better. This can tax the motor, ESC, motor mounts, etc, more. I've got a Master Air Screw 3-blader on my big T-28 and I used to limit my max throttle runs to a few seconds at a time. Now that I've put in a slightly larger ESC, I can fly max throttle (if I want to) the whole flight without worry of anything getting over-amped and/or getting too hot. Over-amping an ESC builds up heat and heat is cumulative. IE, it builds up and takes time to shed it. It takes longer to shed the heat than it does to build it up again. If you don't allow for it to completely lose all the heat it built up, the next time you load it up, it can get to it's limit much faster with less effort. This is likely why on your subsequent flight, the ESC cut out. It may very well have cut out even if you stayed with a smaller C battery.
HINT: sometimes if you over-draw the ESC and it hits it's "cut-off" and shuts down, you can bring it back if you close the throttle completely for even a couple of seconds. The ESC can reset and you can have power again. Just don't max it out again for the rest of that flight.

[Bluebird]

Hmmmm xviper2, Good tip about shutting down the throttle momentarily to possibly restore some of the ESC. I didn't know that! In my case it was a gradual failure over 20 or 30 seconds but it allowed me to at least bring the plane within 10' or so of the ground at which point I lost all control and she nosed into a muddy corn field. Fortunately no critical damage.
Great explanation of how the battery systems work,with a good analogy to a gas tank and fuel line. Its so well done I hope other folks read it as well.

Thanks for your valuable input! Regards, Bluebird

[gooniac33]

In a word.... YES. You increased the discharge rate by quite a bit going up to that battery. You were already over the rating of the esc with the other set up. Going higher will draw more amps and when that happens you get more heat. I have seen this and argued with people about it before. The best thing to do is get a watt meter or an clamp meter to check the draws on your systems. The other battery that you used could have delivered quite a bit more amps than you were expecting which will in turn burn it up. A pack of the same capacity that you had with a higher C rating would have delivered more amps but going up in capacity and discharge rate for sure did. You most likely had already pushed the esc's limits and just went over the edge with the bigger pack...

[gooniac33]

one thing that you guys need to think about with higher C batteries. They have lower resistance which means that they are able to deliver more current and more current will actually reduce flight time as well. it may not be a lot but it will still be less. Watt meters and clamp meters will help a lot with seeing this stuff. I always match the battery to the load. In most cases the higher C packs are totally not needed. even with the higher performance edfs. Just do the math with the discharge rates and you will be fine. I usually use 20-30c packs. Rarely will I go higher because it isn't needed for the load...

[bradl4648]

Hi guys
I guess I will jump in on this as well you may or may not agree which is fine. But I have this plane as well the Z-carbon cub and have had it 3 years now. I use either the admiral 40006's 60 c and the admiral 50006's 50 c. I have never had 1 issue with it at all for me I can do hover with it with the floats on it and any stunt I want to with out issues. Know if I use a 40'c I totally not caring for the plane in performance out of it. Know I do agree that I get the same flight time on both 40'c 50'c and 60'c but I get one heck of allot more power out of it. When flying my jets in 80 mm its the same results much much better power + higher speed. I have flown my A-6 intruder against another one he had a 40'c and I burnt him on take off roll out and in flight speed. To match his speed I had to go to half throttle he at full. We did have the same flight time but I smoked him. So to me and I mean to me the math thing is not a 100% correct I go by what I see in living proof just saying thanks.

[xviper]

Hi guys
I guess I will jump in on this as well you may or may not agree which is fine. But I have this plane as well the Z-carbon cub and have had it 3 years now. I use either the admiral 40006's 60 c and the admiral 50006's 50 c. I have never had 1 issue with it at all for me I can do hover with it with the floats on it and any stunt I want to with out issues. Know if I use a 40'c I totally not caring for the plane in performance out of it. Know I do agree that I get the same flight time on both 40'c 50'c and 60'c but I get one heck of allot more power out of it. When flying my jets in 80 mm its the same results much much better power + higher speed. I have flown my A-6 intruder against another one he had a 40'c and I burnt him on take off roll out and in flight speed. To match his speed I had to go to half throttle he at full. We did have the same flight time but I smoked him. So to me and I mean to me the math thing is not a 100% correct I go by what I see in living proof just saying thanks.

I completely agree. Most of the experienced flyers at all 3 clubs I fly at buy the highest C rated batteries they can justifiably afford. They just perform so much better - better "grunt", better speed, longer flight times in general. The first reaction to a flight with the Graphene (see below) is, "Holy Shat! Does this plane ever GO!"
As our original batteries get old and reaching the end of their lifespan, we are all replacing them with the new high C Graphenes from HobbyKing and the Admirals (preferably the Pro) from MotionRC. In fact, the high C Graphenes perform so well, an older, lower C rated 2200mah LiPo is being replaced with a high C Graphene that is only 1800mah. The 1800 Graphene (in both 3s and 4s) perform better and lasts about as long in flight time (maybe even a bit longer) as the old 2200mah. Nobody I fly with will ever buy low C batteries ever again. They just aren't worth the effort. After a whole season of flying with these Graphenes and a couple of seasons of Admiral Pros, nobody has fried anything (while keeping all other facters the same). This is for both props and EDFs. I won't shove more cells into them but I'll allow my motors and ESCs to draw what they want out of what cells they were designed for. Proof in in the pudding, calculations be damned.
NOTE: This is my experience and opinion only.

[StormyDog1962]

Also be sure to check the Bearings in the Motor as this can cause some current draw issues and lead to overheating of both the ESC and the Motor if they are going bad. The higher C Rating just allows the juice to flow more freely like the Pipe Analogy that was used. After 40C most won't even notice any difference but the EDF's will as these are juice hogs that need it now and as quickly as possible.

[bradl4648]

Hi xviper2

Thanks for chiming in I have the same feeling as well. Do not show me math show me proof. If the math was truly right then the 40 c should be the same as 50-60 c but its not correct. Plane for plane 40 c versus 60 c it does not have a chance. Plus the 40 c will be greatly hotter at full throttle versus the 60 c at half throttle to match the speed. I have not had a chance to try the graphene lipos yet but will make the step soon. One of the other CST mates has been using the graphene lipos and told me you have to try them you will love them.

Thanks,

Brad

[xviper]

Hi xviper2

Thanks for chiming in I have the same feeling as well. Do not show me math show me proof. If the math was truly right then the 40 c should be the same as 50-60 c but its not correct. Plane for plane 40 c versus 60 c it does not have a chance. Plus the 40 c will be greatly hotter at full throttle versus the 60 c at half throttle to match the speed. I have not had a chance to try the graphene lipos yet but will make the step soon. One of the other CST mates has been using the graphene lipos and told me you have to try them you will love them.

Thanks,

Brad

One word of caution about the Graphene. Those units that were on the shelf when the new transport regulations came into effect, have been known to have had a bad cell or two. I think HobbyKing went into "panic" mode when LiPos had to be reduced in what voltage each cell could have for shipping. Up until that point, they were all manufactured with a storage voltage of ~3.85v. The regs indicated that voltage couldn't be above ~3.75. I believe HK was very careless and rushed when they discharged them to meet the new regs and some of the cells were inadvertently reduced way too low and some customers got the odd battery that had a "dead" cell or 2. They immediately replaced them without question when a picture was sent of the voltage tester showing the readings. A couple of us got replacements immediately. The later batches haven't had a problem but there's always a chance you could get one that has been on the shelf since those earlier days. With all LiPos, make sure you put them on a tester as soon as they get unpacked and document any that are too low. You may be able to bring them back on a slow charge using NiCd setting but they are likely to never balance evenly again. Some of ours came from the US West warehouse and some of them came from Int. warehouse.

[WintrSol]

The ONLY real effect the higher C rated battery will have is to make the model heavier, not cause a big increase in current. Some years ago, the lower-C rated batteries could limit the current, but newer batteries have much lower IR now and, at around 60A, that wasn't happening, since the OP was only drawing a bit over 15C from the 40C battery. A battery can NOT force current into a motor, the motor demands what it needs to turn the prop, so, if it draws 62A with a 40C battery, it will be very nearly the same with a 50C or 60C battery. The lower IR will only cause a slightly smaller drop in Voltage, therefore a slightly higher current, maybe another Amp, at most.

I've been measuring IR with a quality meter for about a year, now, and batteries labeled higher than 30C show very little difference in IR; I have 65C batteries that measure within 0.1mOhm of those labeled 45C. Insignificant, since a change of 10 degrees F will make a bigger change in IR. The exception is the Graphene 65C batteries; these measure about 1.5mOhms less than similar size batteries rated 40C. Still, that is a change of about 90mV per cell at 60A - not enough to significantly increase the current. The Graphene is a LOT heaver though, so the model will draw more power to fly the same.

[OV10]

Lets see.......... math and science proven perspective(I'm in that camp) versus speculative and subjective opinions.

[xviper]

I think the problem with LiPos is that we can't always believe the ratings that are stamped on the label. When we buy a 30C bat, is it really 30C? It might barely put out 15C. When we buy a "super duper" 65-130C Turnigy Heavy Duty bat, it might just put out 40C, if that. That's where the math and science get dumb founded. If the numbers aren't true, then the math doesn't work. That's the reason why I buy the highest C rated LiPos I can justify. I can only hope I get a battery that puts out 1/2 of what it says. Even the former "almighty" Thunder Power and Hyperion batteries have been tested to be NOT always what's on the label. Battery "experts" (you can find them all over the net) have indicated that anything over a stated C of 40 - 50, is just dreaming and a tall tale by the manufacturer.

[WintrSol]

My IR meter was built by Wayne Giles, and uses a proven algorithm to estimate a true C rating for a battery; it is rare for a battery of ANY printed rating to exceed 35C. The '65C' Turnigy Graphene 1300mAh and 2200mAh batteries rate between 28C and 31C, and most of my 30-40C rated batteries show up in the 23C-28C range. This was at a stable temperature of 76F, BTW. Of course, if you actually used 65C from a battery, continously, it would last all of 44 seconds (assuming 80% usage), and swell up.