Problem with EZRun 5.5T/ESC combo

[83imp]

First off, I've been in the hobby for about 24 years and was really into it until about 2002 when I was racing 19T Touring Car at the local Hobbytown USA when 3300mah NiMh batteries and Trinity Chameleon were the hot thing. I'm not a newb, but I'm a newb when it comes to things like LiPo and brushless.

So, I've been sticking true to my old-school backround until I bought this EZRun set up. I took it out of the box and put it in my TT-01 BMW M3 with stock gearing and after about 2 minutes of run time that Ludicrous Speed, while intriguing, was pointless and uncontrollable.

I removed it from the TT-01 and put it in my Rustler as I thought it might be a better platform for this motor. I put it in the Rustler and it would run OK off the ground, but if you put it on the ground it couldn't pull itself. I checked it over and the next time I turned it on the fan came on but the ESC got hot to the touch within 30 seconds and all it would do is turn the motor at a very low RPM.

I'm guessing the ESC is fried, but I guess what I really want to know is that other than a manufacturing defect what could have caused this? I used to gear my brushed motors for 4 minute heats and things would get hot, but I never once fried an ESC then.

[Trubble]

Originally Posted by 83imp

First off, I've been in the hobby for about 24 years and was really into it until about 2002 when I was racing 19T Touring Car at the local Hobbytown USA when 3300mah NiMh batteries and Trinity Chameleon were the hot thing. I'm not a newb, but I'm a newb when it comes to things like LiPo and brushless.

I'm in the same boat, got out in the early 90's. Got back in a few years back and had to start learning all over again.

Originally Posted by 83imp

So, I've been sticking true to my old-school backround until I bought this EZRun set up. I removed it from the TT-01 and put it in my Rustler as I thought it might be a better platform for this motor. I put it in the Rustler and it would run OK off the ground, but if you put it on the ground it couldn't pull itself. I'm guessing the ESC is fried, but I guess what I really want to know is that other than a manufacturing defect what could have caused this? I used to gear my brushed motors for 4 minute heats and things would get hot, but I never once fried an ESC then.

A 6,000 kV motor? In a truck? Ouch.
Other than a manufacturing defect....... stuff proven to kill electronics would be

-Too high a kV rating (can be overcome by gearing lower)
-Too much voltage (* I'll explain at the bottom)
-Too heavy of a vehicle
-running in grass/sand/mud or other high drag surface
-gearing too tall (via gearing, or oversize wheels/tires)
-using low (amp) output batteries (NiCads,NiMhs, or LiPos w/too low a C rating)

Sounds like that combo you bought would make a killer on-road pan car combo w/ 4 cell NiXx or 1 cell LiPo, but in the applications you tried it in...... meh. Offroad, I'd be leery of reccomending anything hotter than 3,500 kV (roughly 10.5 turns), and a 2S LiPo. If you want to use your 6-7 cell NiXx packs, either gear rediculously low, or (better) go with a lower kV motor.





(*) Explanation of above
Please note: this is strictly opinion. Believe what want to.

I subscribe to the theory that wattage of an electrical appliance is the constant. The example I'm going to use is the CC BEC, 10 amp. Notice in their specs chart that at 12 volts, it can supply 7 amps, and moving up to 24 volts it can only produce 5 amps. Since wattage is simply volts times amps, it makes enough sense to me that if the wattage remains fairly level, and the voltage moves up, then for the formula to work, the amperage has to move down. (for those with accurate metering equipment, numbers don't need to be 100% accurate, just looking for proof of concept here.)
Thus, I firmly believe that in the above Motor ESC combo, the math looks something like 864 watts=7.2 volts (batt voltage) times 120 amps (ESC max). With the same load factor, moving up to 2S LiPo, 864W=7.4v X 116A. Moving up to a 3S LiPo, 864W=11.1V X 77A.
"so wut, ount care, those are jus numbers, 3S kicks ass, you're a jerk". Four unrelated but conveniently true facts. Anyway, it is also my belief that in a motor, the increased voltage is great for setting up magnetic lines of flux around the windings, and the more voltage, the quicker they get set up, and thus the more degrees of motor rotation you'll actually be pulling on the magnets. Ya but.... As demonstrated above, more voltage equals less amperage. I feel that the number of electrons in those magnetic lines of flux are what determines the actual strength of the pull on the magnets, less amps, less strength of pull. It'd be kinda like trying to start off your motorcycle in 4th gear, you could probably do it, but wouldn't it be smarter to downshift (ie, gear down)? So if somebody says "volt up, gear down", there might be some wisdom in those words.
"wul.... but.... on paper it says I cen get like 50% more rpm's, that's a lot. You're still a jerk" True on the calculus, but if you don't have the strength of pull, are you ever going to get to top rpms? (true enough, I guess, on the other part, too) I've had this discussion before with off-roaders, and I'm sure I'll be proven wrong someday, but right now, experience tells me I'm at least on the right track.
"dude, quit bein a jerk, if yer so smart tell me wut I cen do to stop blowin stuff up" How to get torque?
-Quit using high kV/ low # of turn motors in applications that require torque (like heavy off-road trucks lumbering around off road). More turns will put more wire in your electromagnets, which will carry more electrons, and should make your magnetic lines of flux stronger.
-Use a longer can, 550 instead of a 540 size, longer can, more wire, yada-yada.
-Gear down, give a hotter motor the mechanical advantage it needs to produce "percieved torque".
-I'm a big fan of using 2S and letting the motor have the amps it needs. If it runs cool, you can gear up to get the spur gear spinning faster. 3S is very popular in crawlers, but remember crawlers are typically lower geared than a Slash/'Pede/Rusty, the trans' aren't identical, but both are geared down there, and whereas your Traxxas comes off the trans and goes right to the wheels, crawlers have more gearing down in the R&P of the axles. That's why "just throwing in a 3S" into a crawler isn't much of a problem, the motor already has quite a bit of mechanical advantage, so they can afford to lose some amps (torque) and still hit top rpms. Pan cars don't need insane amounts of torque simply because they weigh a LOT less than off road trucks, and run into a LOT less rolling resistance, so they can run higher kV motors and lower voltage (usually as a result of race sanction rules to try and limit top speeds). Thus I'm not a big fan at all of running 3S LiPos or high kV motors in an off-road truck.

These are just the theories I subscribe to, and thus, what I believe. Therefore, I encourage counterpoints, and that anyone who bothers to read all this go out and do some learning, formulate your own point of view. Post up, Man! Mebbe I cen learn somethin off ya.

[majatra]

Sounds like a blown Mosfet to me.
I had the same symptoms on one of my brushless ESCs when a motor lead came off when I was driving. It blew out one mosfet and the motor would only go really slow and only if no load was on it or if I gave it a push.
It was totally my fault as I plugged in a connector that was quite loose.
I was new to brushless and I was used to brushed ESCs which can tolerate looser connections, but brushless ESCs are more vulnerable.
I emailed about getting it fixed, but it was cheaper to just buy a new one.

[83imp]

Thanks for the replies. I've got a Sidewider V2 on the way and the motor will be going into a new project that will have a build report on here in the on-road section.