Very interesting Setup from Mega Motors

[GriffinRU]

Originally Posted by BrianG

I too noticed increased runtime with more cells, but that turned out to be simply that you are into the throttle less to achieve the same speed. The max power with a higher voltage setup is higher, so you don't need to push the batts as hard to get the speed you want. There is some savings with higher rpm since there is a little more "resistance" so that helps too.

You will get better efficiency overall with higher voltages. All losses associated with resistance goes down with the current.

Power loss = Sum[I^2*R(x)],
where R(x) resistance of:
- motor
- wires
- connectors
- FET's
- Cap's
- Batteries
- ...

Going really high in Voltage is not good as well :) There are obvious reasons and electrical.

Artur

[BrianG]

Doh! How could I forget wiring losses! :007:

[glassdoctor]

Serum, I probably missed your post.. I skipped a few posts on the first page, sorry. I'm sure you tried to make the same point as me.

We are having some difficulty making it clear to sleebus and maybe some others....

Please guys, don't get this confused with changing motors, and/gearing with a change in voltage. That's a different subject.

Try again:

A motor DOES draw more amps with higher voltage, under the same load.

Sleebus, let's use that motor in the picture you talk about as an example. It doesn't have a built-in current limiter that forces the motor to only draw the rated 1hp, or 746 watts. That is only a rating on what the motor can do within spec, without self-destructing or stalling, etc. Each motor has a limit to what it can do, for both short cycles and continuous duty.

If that motor produces 1 hp at 110V, then it would indeed produce more power at higher voltage. But at some point it will burn up, literally. That is why we have different motors that are designed to run at higher voltage. They are a different wind, and draw less amps and turn a lower rpm per volt. So when this "high volt" motor is run at the higher voltage, it can produce the same hp at half the amps. It's a DIFFERENT motor.

I wish you were right sleebus, because we could have our cake and eat it too. :004:

[glassdoctor]

Let's not forget that a motor is designed for a certain range of voltage and won't work well if at all, if you go too extreme.

Please consider this, back to r/c stuff. I think this may clear things up:

Take a normal r/c car 540 brushed motor made for running on 6 cells and try running it with 3 cells, or 12 cells. What happens?

It will barely move a car on 3 cells, and it not draw twice the amps or produce equal speeds as it did on 6 cells. Under your arguments, we should be able to just gear up and have equal performance at double the amp draw, since the motor is a constant source of power under changing voltage.

It would be ballistic fast on 12 cells for a short time until it blows up, and will produce much more power, indicating much higher amp draw. No matter what you do with gearing, the increase in power will be dramatic.

Notice it doesn't magicly become a self-current-limiting device on 12 cells and only produce the exact same amount of power as it did on 6 cells, while drawing only half the amps and thus doubling runtime. Again, even changing the gearing will not make up the differences.

[starscream]

Originally Posted by glassdoctor

Serum, I probably missed your post.. I skipped a few posts on the first page, sorry. I'm sure you tried to make the same point as me.

We are having some difficulty making it clear to sleebus and maybe some others....

Please guys, don't get this confused with changing motors, and/gearing with a change in voltage. That's a different subject.

Try again:

A motor DOES draw more amps with higher voltage, under the same load.

Sleebus, let's use that motor in the picture you talk about as an example. It doesn't have a built-in current limiter that forces the motor to only draw the rated 1hp, or 746 watts. That is only a rating on what the motor can do within spec, without self-destructing or stalling, etc. Each motor has a limit to what it can do, for both short cycles and continuous duty.

If that motor produces 1 hp at 110V, then it would indeed produce more power at higher voltage. But at some point it will burn up, literally. That is why we have different motors that are designed to run at higher voltage. They are a different wind, and draw less amps and turn a lower rpm per volt. So when this "high volt" motor is run at the higher voltage, it can produce the same hp at half the amps. It's a DIFFERENT motor.

I wish you were right sleebus, because we could have our cake and eat it too. :004:

Well, I have been doing some testing lately. I do not have a watt meter but I can tell you this.
5S 3200mAh Lipo with 24/51 gearing = 14min runtime
6S 3200mAh Lipo with 24/51 gearing = 16min runtime
Just for a comparison:
6S 3200mAh Lipo with 20/51 gearing = 17+min runtime

These test cases are reproducable and, call me crazy but, they seem to indicate that a lower current is achieved at higher voltage with the SAME gear ratio.

Now, before you call me crazy, understand that I realize every motor has its limits but if you run the motor within its efficiency range, it seems the higher the voltage, the better. My motor is rated for 6S and it seems that 6S is the most efficient as well.

[coolhandcountry]

The problem I see star scream. You probably couldn't run the motor at a wide open or as much throttle as you did with 5s as you did with 6s.
By adding the extra cell. You accually added more watts to be drawn.
If each cell is capable of making or running 1000 watts a piece of run time.
Then you have 5000 with 5s and 6000 with 6s. Just an example.

[starscream]

Originally Posted by coolhandcountry

The problem I see star scream. You probably couldn't run the motor at a wide open or as much throttle as you did with 5s as you did with 6s.
By adding the extra cell. You accually added more current to be drawn.
If each cell is capable of making or running 1000 watts a piece of run time.
Then you have 5000 with 5s and 6000 with 6s. Just an example.

My testing area is only so big so I can only drive the truck at a certain max speed without losing control. The test runs are as consistant as I can make them. The advantage of 6S is the truck reaches the max speed faster than with 5S. With that said, it seems that I am at WOT more on 5S than with 6S so maybe that is playing into this discrepancy in runtime :030:
None the less, the discrepency is there so it seems to be an advantage in a racing scenerio.

[glassdoctor]

Come on guys.... :) you keep throwing in variables.... just focus on the laws of physics, a theoretical setup. You can't just say you got more run time bashing your car therefore the setup is draws less amps. It shows that it draws less "average amps" for your car the way you drive it etc etc, but not as an absolute.

Although this is an interesting observation in it's own right, and valuable information for you to have for your setup.

What would be a true test is a dyno that records exact amps etc with an exact specific load every time. Run the same motor on the 4s,5s,6s on the dyno and it would pull more amps on 5s and 6s...

When running a car, you are using a constantly variable speed control, and variable load, etc etc.... that doesn't do anything to argue the point either way. I know it's somewhat repeateable, but not to the degree you can base anything off of to change the basic motor theory that's already established.

hee hee

[glassdoctor]

For what it's worth to the naysayers:

When I had my data recorder in my 1/8, I ran a 3s lipo pack once with the same gearing as I have done on 4s, and the amps were less. I'm sure the graphs are on my laptop if anyone would like to see them. Speeds and amps are higher on 4s.

Now if I were to run 4s and try to baby the throttle and mimick the speeds of the 3s (and/or change the gearing) then maybe I could make the 4s draw the same of less amps than the 3s... but that's not the point of the discussion.

[Serum]

That's for mounting the motor Nick...

[coolhandcountry]

Originally Posted by starscream

My testing area is only so big so I can only drive the truck at a certain max speed without losing control. The test runs are as consistant as I can make them. The advantage of 6S is the truck reaches the max speed faster than with 5S. With that said, it seems that I am at WOT more on 5S than with 6S so maybe that is playing into this discrepancy in runtime :030:
None the less, the discrepency is there so it seems to be an advantage in a racing scenerio.

I like the 6s more than 5s or 4s. As long as the truck can take it.

[neweuser]

Originally Posted by coolhandcountry

I like the 6s more than 5s or 4s. As long as the truck can take it.

More juice more fun! After reading that whole thread, this is what I got out of it......HEADACHE! you guys are all nutz! I plug, play, and run the crap out of it. Although I learned some from here, most will come in due time. I like stats, but for me, i need the results to prove what I'm saying. An eagletree for me would be in order to understand much of what you guys are all saying.:032:

[glassdoctor]

It's really not that complicated... just difficult to get on the same page I think.

It's just the basics here, and it's simple math. I'm not an EE, but this is pretty easy.... W=VxA

[coolhandcountry]

Think of it as a hole in a pipe. volts is like water pressure. internal resistance
is like the size of the hole. The more pressure you put the more water going
to come out. If you put a restriction like the esc that can limit the which
would be like a vavle. No matter how much you put on it if you cut the vavle
back you won't get more water out. Even though you have more pressure.

[crazyjr]

Originally Posted by coolhandcountry

The problem I see star scream. You probably couldn't run the motor at a wide open or as much throttle as you did with 5s as you did with 6s.
By adding the extra cell. You accually added more current to be drawn.
If each cell is capable of making or running 1000 watts a piece of run time.
Then you have 5000 with 5s and 6000 with 6s. Just an example.

I believe you are wrong there, if it was parallel you would add amp capacity, not in series. In series you add voltage and not amp capacity, but the wattage would still go up like you were saying, just not on amps but voltage