I see this comment a lot and while not totally incorrect it should be noted that this assumes constant or equal power. For DC the equation p=IE is used but note that we are not assuming power is constant with the motor. So really what we are looking at is P = (e/r)*E where I = E/R. And this is actually much simpler that what is really going on because the R number is not constant in an we are actually dealing with a inverter that is converting DC to a stepped AC signal so there is a power factor in there too. Anyway, the point being is that load (R) is not changed just the input voltage which actually makes the amp draw higher as the input voltage increases.

Oh yay theory! All testing and development says otherwise. Speed control "X" running a 2wd modified buggy on 2s will run hotter than same speed control "X" running a 1/8 buggy on 4s. Speed control "X" will not even handle a 4wd SCT running 2s with a 550 motor, even though it's a smaller motor on a lighter chassis than the 1/8 setup.

On an 8lb 600 class 3D heli running 25.2v you need a 100-120amp controller, on the same heli running 50.4v you run a 55-80amp controller.

1/12 modified... everyone's esc's are always overheating running 1/12 modified running the very same motors and esc's as modified tc. What is the difference? Well the cars weigh HALF as much, there's less than 1/4 of the rotating mass being driven by the motor, and they run 1s lipo.

My guess would've been... it's because the esc's are switching more.
1/12 mod are fast little suckers and with really small wheels. That combined with being lighter means that the motors a more free to rev to the skies. This equates to the escs switching more... hence more heat.
If you suspect increased amp draw , are you seeing an increase in battery temps as well?
If not, I postulate the theory below...(assuming all else remains the same)

Higher voltage only equates to less amp draw if the output is the same. ie gearing for the same speed and acceleration.
If your gearing remains the same, but you increase voltage, your amp draw will be the same and your car will go faster. The ESC will get hotter as it will be doing more work switching faster.
Vice versa, if your voltage goes down, gearing stays the same, amp draw will stay the same but your car goes slower. ESC will be cooler as it will be doing less switching

So i'm thinking that with 1/12 Pan cars, their lower weight and lower rotating mass will offset some of the amp draw required to make them run faster. But being able to run faster with lower voltage means that they must be geared taller and the motors must have a higher Kv or the load on the motor is such that it is allowed to reach a higher RPM = more switching = more ESC heat


Just a thought...

PS. I don't doubt your knowledge in electronics especially when it comes to RC ESCs, but in this partcular case, the point you make doesn't really add up.;)

Esc MOSFETSs operate much more efficiently as you approach full throttle. They are very inefficiently at lower throttle percentages which is why on helicopters we try to always have the setup such that your throttle curve level is 70% or greater. The esc will be most efficient and run the coolest if it's setup so proper headspeed is achieved at 80-100% throttle.

This may be part of the reason we often see higher temps on the esc in 2wd mod than many onroad conditions. Even though in onroad you can drive it much harder and use a lot more throttle, causing higher current draw, the esc may run cooler because the FETs are switching more efficiently in the higher power band. You don't spend much time in the top of your power band with a 2wd mod buggy, so the FETs create more heat.

In 1/12 mod cars we see an increase in esc, battery, and wire temp. Current draw is getting so high with 1/12 mod that 16ga wire often cant handle the task anymore. We've seen cases, no pun intended, where the battery lead melted the lipo hard case from resting on it. Batteries now are such high C rating, often too high C rating for cars in fact, that the batteries often don't even get warm enough to work most effectively. That besides the point, only reason I bring that up is we don't pay a whole lot of attention how warm the packs are after a run, unless they're not warm at all.

A 3.5t motor in a 1/12 car will be spinning roughly half the rpm than a 3.5t in a sedan. So from your theory this would mean the esc will actually run cooler in a 1/12 than a sedan.

FETs operate like a gate and they open/close most efficiently the more they stay open, such as at high throttle levels. I don't believe the rate at which the esc is flipping the rotor has much to do with efficiency and heat. The FETs should open and close just as efficiently turning a 17.5 at full throttle as a 6.5 at full throttle, though of course the current draw will be greater on the 6.5 which will add heat, but not due to the switching rate.

i think i just went to class.. i mean my brain hurts a little bit but under neath it all there was knowledge

I was a little wrong last night. The theory of my equations is correct but I was not taking into account for the actual load on the motor. Which effects the amount of field flux required to move the rotor. If power output is constant then the current draw has to increase. It also must be noted that if you run at the torque limit of any motor. ie cause it to stall while applying power you will fry it as the motor becomes like a dead short and will over heat rapidly. The flux created in the motor spinning opposes the current form the battery and limits your max speed based on the size of the windings. We play with this quite a bit by adjusting the dynamic timing in the ESC but if left alone the motor even under no load has a point that it will stop accelerating. This has the effect of lowering the current draw towards the end of the RPM range.

This is why I went with a flux capacitor, and a posi-trac. How does it work? "I don't know it just does!". Haha!

any way some of you factory guys could post pics of how you have your wires soldered? ups just dropped mine off :) i'm guessing it works best with the wires in the vertical position.... thanks

i have min laying down.. if you are running 12 gauge wire.. cut a little bit off after you coat it with solder, that way its easy to get into the little cup.

I can throw up a couple pics in a little over an hour when I get home.

thanks

you can do both - I laid down my motor ones and stood up my battery (this is with Viper 12ga wire).

Yes I use a combination of laying them down and standing them up. Those tabs are awesome and very easy to solder. But they are tightly spaced so keep an eye on the gap to make sure nothing is crossing over!

22 - motor wires flat, battery vertical
b4.1 - all flat
T3 - all vertical
SC10 - all flat

Under the often tight confines of a 2wd body having them flat will give you more clearance :)

VTX10R costmetic quality issue
 

We have realized the first production run of VTX10R and VTX10R-Lite esc's suffer from a cosmetic problem on the plastic end caps and V-port housing. The factory did not catch the issue because it developed several hours after the esc construction was complete. This in no way affects the performance, function, or durability of the esc, but it does not meet our standards of high quality. If you have already received or ordered your VTX10R or VTX10R-Lite please send me an email at [email protected] to resolve or compensate the issue in the best manner for you. We greatly apologize for any inconvenience this may cause and want to do right by our customers. Thank you for your understanding and support!

Please note the VTX10 and VTX10-Lite do not suffer from this cosmetic problem.

Thanks!

Great support as always! Thanks Willie, Weylin, and the rest of the Viper crew!