Runtime in a ST with a 540S VS 380S

[MarNaDaKi]

Just would like to know how does the runtime compare between a 380S (400) size motor against a similar RPM/Volt 540S in a stadium truck on the same battery ?

[TheSteve]

I can't answer the question for a stadium truck but in a touring car I'd say you'd get atleast another 20%(if not more) runtime out of a 380 sized motor versus the 540 sized

[Andrewg]

The runtime depends on how much current you want to draw (gearing) and the motors efficiency.

The 380's are usually 5-10% less efficient than the 540 within any given brand
The motor will put out less torque. So for the same speed you will need more imput power to get the same output power. Runtime will be down and acceleration will be slower.

If you want a 400 to match a 540 you need to ensure it is geared to pull the same amps that means lower gearing and a higher revving 380 and more heat.

The issue with electric motors is not to get a smaller motor but to right size the motor for the current draw or runtime. This can make a huge difference to the runtime and performance you achieve.

[starluckrc]

Take at 380 and 540 with the same kv, and they will require the same amount of amps to get the same speed due to having the same torque constant. Like Andrewg said, you have to find which motor in going to be most efficient at the intended operation point. That's a tough one in cars with continuously varying throttle. Larger motors in general do have better efficiency.

[MarNaDaKi]

I have several off-road trucks plus my on-going MT2 electric conversion.

In my T4, I would be interested in the Nemesis/Feigao 540 8S instead of a Twist 47 or C40 9s.

[Andrewg]

MDN

the Kontronic Hacker and Lehner Basic are significantly more efficient than the Nemisis. The Basics are good value

Alternatively the Aveox 3624/1.5 have efficiency nearly as good as the European motors.

Mega have a very easy driving characteristic and seem to be able to pull a higher gear and are a snap to set up.

[starluckrc]

MDN

the Kontronic Hacker and Lehner Basic are significantly more efficient than the Nemisis. The Basics are good value

Alternatively the Aveox 3624/1.5 have efficiency nearly as good as the European motors.

Mega have a very easy driving characteristic and seem to be able to pull a higher gear and are a snap to set up.

I will have to disagree. Have you even tested one of the Feigao motors? They are constructed identically to the Hacker "B"series.

[MarNaDaKi]

starluck

Why if the Feigao/Nemesis 540S are built and perform like the Hackers, Fine Design list them as maximum 6-8 cells ?

[starluckrc]

He listed the Hackers the same. Remember, he is primarily a boat dealer. Boats generally run direct drive under a lot of drag dumping packs in a couple of minutes.

[Andrewg]

OK heres the oil

Feigao motors appear to copy Hackers. They are inexpensive.

However they are not constructed from the same materials - the stator is different and the windings are not made in the same way or with the same precision.

These motors have been dyno tested by Steve Neu. The results can be seen in recent issue of Quiet Flyer. Steve Neu is an international competitior in f5B - which use extreme power systems and probably the leading expert in USA on brushless motors

The feigao motors consistently test 10% less efficienct that Hacker Kontronik and Lehner. They also become less efficient as cells are added, whereas all other motors I have seen become more efficienct. The torque and power are well down on the hackers et al.

For electric motors the rules are the same regardes of the evironment you run in. Feigao may seem better but the fact is with other motors you will get more acceleration more power and longer runtime.

[TheSteve]

I have not used Feigao motors but I have used several hackers in touring cars. If you directly compare a c40 7s(5950Kv) and a B50 6s(6100Kv) the runtime difference is huge. The c40 will win hands down. You can gear for the same speed with both. The B50 may have a slight edge in the torque department but it is totally lost on a touring car. If you go with a c40 6s(6942Kv) versus a B50 6s and again gear for the same speed(or a little more with the c40) the c40 will win in the torque department as well and will again give more runtime then the B50 6s.(not as much as the c40 7s though)

Its clear to me the c40 series in a sedan is much better then any 540 sized motor, I do wonder though how much heavier the car would need to be before the 540 sized motor had the edge...

[starluckrc]

I'll have to check that out. What series of motors were tested? I've been contacted by a couple of well respected companies in the field of brushless who love the motors. Can't deny the value.

[Andrewg]

to get the right motor you need to state the runtime you want

Then the right motor can be worked out on the basis of the motors electrical characteristics

One issue which woudl make the c40 run long is that it simply cannot pull more amps in its midrange - so if you were racing circuit and accelerating often you runtime will be down but the 50 will acclerate harder

If you were running long open ovals the b50 with better efficeincy at a more constant amperage would run faster.

If it is for sport another way to make you car run longer is use more cells 7-8
and get a motor with a lower kv which will be more efficeint still.