More Voltage = Less Amp Draw?

[BP-Revo]

But with a 1530 - smaller motor than what Brian plans to run - he's running a full 19 series!

Anyway, reason behind 8S is because I was going to run 4, but then I decided they are small cells, and more voltage will require less current and I get more efficiency. On top of that, I need to pump a little extra out of the somewhat small 15 series motor.

So then I though of 6S. When I was looking for a controller to handle it - I saw the Pheonix HV series (Plane controller is fine since I'm using mechanical brakes) - and then figured, if I'm going to buy an ESC capable of 12S, might as well go higher. So I went to 8S, since my charger does 4S max, I do 4S per side - perfect!

Power should be PLENTY (if its too much, I can always go and wire the motor in Wye connection - which I just learned today! - which will reduce KV and thus reduce power).

So, there's a reason to the madness :)

[Serum]

Sounds perfectly healthy to me!

LMAO!!!!!! as long as theres vids i cant complain :D

[BP-Revo]

Originally Posted by Serum

Sounds perfectly healthy to me!

My thoughts exactly.

Don't worry, I won't hold out on you guys. Full build up with pictures and video's are planned.

Now, for the bad side...project will not start until May at the soonest :035:

lol now "THE WAIT" LOL

[BP-Revo]

Yea...no kidding

But only 8 days until GorillaMaxx re-opening...and then I get to have a bunch of ideas go through my head on my G2R.

thats true... i hope i dont buy something new from them lol, new stuff like that is always soo tempting lol

[captain harlock]

Oops! You almost got me wrong my friend. I've just tried to say that posting three threads in one day does not mean you have to get annoyed nor annoying the others around you.

It is annoying to you when you just come over here and do nothing but visit the forums without sharing info or seeking them.

You're doing just fine, really. No hard feelings whatsoever..:)

[starscream]

Did I miss something?
The last time I tried a HV110 on 8S, it was too buggy to use consistantly. (Unless you like having your truck take off WOT after applying the brakes)
I eventually unloaded the HV110 on the bay because it could not be tamed :007:
Hmm, wish they would release the MMM already...

[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.

[Serum]

Yes, but with a higher voltage you still aim for the 'sweet spot of a BL motor. Meaning it's not screaming at 65000 RPM. but rather at 25-30000 rpm.

If the KV of the motor stays the same (as well as the gearing), it would be obvious that the current will increase too.

But if you gear a vehicle at 40 mph on 2S with a certain motor and gear that same vehicle on 40 mph with 8S, the current will be significant lower with the 8S.

It takes a certain amount of power to accelerate a vehicle, and at a higher voltage with the same speed the P=U.I becomes relevant

The higher the voltage, the more efficient a setup runs, and the lower the voltage the more current is needed to get the same power (watts)

[BrianG]

I think the general assumption is that if you use high voltage, you also have to use a high turn motor to reduce amperage.

People using HV setups are trying to do one of two things: 1) Have a VERY high power setup without having a ridiculous amperage, or 2) be able to reduce current draw on a more typically-powered setup so that losses due to high currents are reduced.

[BP-Revo]

I'm still aiming for ~40K. Is this ok with a LMT 1530? This already requires a 1530/19 or so. Do I need to go with an even higher turn?

[Serum]

Yeah, these tiny motors seem to do nice on a higher RPM. 40k would be nice imo.