More Voltage = Less Amp Draw?

[BP-Revo]

captain - PHEW! :)

starscream -I don't know. Did you try messing with the programming?

There are so many throttle configurations and stuff on the Pheonix HV line its insane. You can adjust in hard cutoff, soft cutoff, current limiter (which cuts off when you draw too much for the ESC to support). You can set throttle type to remember your radio, automatically adjust endpoints each time you start it up, or have it "govern" where it translates throttle to a certain RPM and tries to hold that RPM regardless of load, etc. Then there is also start power, timing, etc. There is like 9 things you can program on that controller, vs like 5 on my little Mamba 25 (my only other CC controller).

I'm assuming it should work fine (hoping it will work fine - because there aren't many 8S controllers available for just 130 bucks!)

[VintageMA]

I think you guys are missing something in your calculations of high voltage = less amps. If you take the same motor with the same KV rating, higher volts will = higher amps.

If you take the equation V = R * I, if volts goes up for across the same amount of resistance then current has to go up proportionately.

To take an example, if you have a motor of 1000KV and a battery of 10V the max speed of the motor will be 10,000RPM. If you then double the source voltage the max speed of the motor will be 20,000RPM. Remember the concept that a BL motor will take as much power as it can to rev up to the RPMS it should hit for any given voltage. So if you hit the throttle to 50% on 10V, the motor will draw whatever amps it needs to get to 5,000 RPM. If you do the same with 20V it will try to rev up to 10,000RPM, doing this as fast as it can it will draw more current following along with Ohms law above.

I have seen this in action with a LMT 1950/7t connection up through a MGM 24160 in my LST2. I spec'ed out the system to run with 6S when I bought it, and it does so beautifully with very reasonable heat. I tried to put 8S in it (max S for the MGM controller) and in less than a few minutes the controller was up to 180 deg. and the motor hit around 140 deg.

In order to gain the benefit of higher voltage = less current, you need to take that into consideration when you are spec'ing out your project before you buy your motor. If you want to double the voltage of the source in order to get a lower current draw, you need to take this into account with the turns and KV of the motor you buy. For example, if you have spec'ed out a motor that is 2,000KV for a 4S setup, you can just go to 8S and say you'll get less amp draw because you're actually doubling your motor speed. If you want to go to 8S, you will have to lower your motor to a 1,000KV motor to stay in spec with your project and get the benefit of the lower amperage draw.

[glassdoctor]

Originally Posted by VintageMA

I think you guys are missing something in your calculations of high voltage = less amps. If you take the same motor with the same KV rating, higher volts will = higher amps.

I know I'm not missing it... :010: ...to increase the voltage you must reduce the kv accordingly. I assumed that would be assumed. :030: hee hee

[VintageMA]

Well it's just a point I wouldn't assume everybody reading these threads would know to make.

When I first got into this I would've just thought "Oooh, faster motor cool!!" Without first understanding that means higher current draw, lower starting torque, and generally a drop in source voltage as the resistance of the motor starts to drop to that of the internal resistance of the cells.

[starscream]

Originally Posted by BP-Revo

captain - PHEW! :)

starscream -I don't know. Did you try messing with the programming?

There are so many throttle configurations and stuff on the Pheonix HV line its insane. You can adjust in hard cutoff, soft cutoff, current limiter (which cuts off when you draw too much for the ESC to support). You can set throttle type to remember your radio, automatically adjust endpoints each time you start it up, or have it "govern" where it translates throttle to a certain RPM and tries to hold that RPM regardless of load, etc. Then there is also start power, timing, etc. There is like 9 things you can program on that controller, vs like 5 on my little Mamba 25 (my only other CC controller).

I'm assuming it should work fine (hoping it will work fine - because there aren't many 8S controllers available for just 130 bucks!)

I wish I could say it was as easy as changing esc settings but it wasn't. The HV line of controllers are configured with a safety feature which requires the user to arm the esc every time it's powered up. In order to arm the esc you must advance the throttle to full brake. I was able to "trick" the esc with my JR XS3 by basically letting the initial programming timeout during the full brake setting thus setting full brake to the nuetral position of the trigger. This worked fine for me as I disabled braking and used mech brakes however, the esc had a nasty little caviate to this "trick"...
Randomly, during a run, the esc would "reset" when the throttle was advanced past nuetral toward reverse (while I was applying the brakes). This "reset" resulted in setting the throttle nuetral position to half throttle and viola my MT was out of control. The only way to stop the truck was to apply full brakes and even full brakes was not always enough to fully stop the motor...
The nuetral position trick only worked with my JR radio. I could never get my Nomadio Sensor to perform this same "trick"
In my opinion, the HV line of esc's are more than adequate to handle a car but because of the esc arming functionality, the esc becomes more of a hassle than its worth.
If you decide to go this route and figure out how to tame this arming feature, PLEASE share with us your secret :017: