My FOFF is a motor killer

[undercoveraddict]

My FOFF is 1/8 buggy based with a steel cage and it's heavy! I keep burning up motors when I gear it for the speed I like. I've been running 4074-4092 size motors, but they eventually get too hot and die. All these ranged from 2150KV down to 1400KV. I ordered the Castle 1717 from the XO-1 to see how that works, but I'm curious about also getting a 5692 size motor in 1000-1300kv range. Will running a larger motor pull more amps, if I run a lower KV? I know it's safer to run lower KV with two motors of the same size, but what about a larger motor?

If I'm running 6s max, can I use a 150a car ESC with a 5692 motor? I don't want to switch from burning up motors to burning up ESC's.

[Olle P]

A physically larger motor with the same watt per volt output should be more efficient (and thus draw less current).

What you need is better power efficiency at the your target speed, and motor cooling.
One way to increase efficiency is, as you're pointing at, to increase the voltage rather than the raw motor power.
This motor for example, doesn't draw more than 88A (at 30V), so an ESC rated for 150A should be fine.
It's still a 2.6kW input, so a lot of heat will be generated in the motor!

Spreading the load as well as the generated heat over multiple motors is a straightforward way to reach the goal.

[undercoveraddict]

I was under the impression the listed 88A or 2600W is the MAX it can take. At 30V, this would pull more than 88A if you tried to use it on a full size car, correct? Let's say I'm not sure of the watt per volt output. Pretend there are 2 motors of the same brand, same quality, same model type, same KV, etc. One motor is 4092 size, but the other is 5692... is it safe to say the 5692 will pull equal or less amps on the same voltage?

[Olle P]

Originally Posted by undercoveraddict

I was under the impression the listed 88A or 2600W is the MAX it can take. At 30V, this would pull more than 88A if you tried to use it on a full size car, correct?

You might be correct.
It's quite vague and not listed as the stall current.

Originally Posted by undercoveraddict

... is it safe to say the 5692 will pull equal or less amps on the same voltage?

It's not that simple...
Since they're the same Kv my somewhat educated guess would be that the bigger motor would use more current at the same voltage while loaded to run at the same speed.
The bigger motor would use less current and run faster at the same power output.

[Johnnysplits]

Originally Posted by undercoveraddict

I was under the impression the listed 88A or 2600W is the MAX it can take

It's the max that it will PULL from the battery.

[Johnnysplits]

Originally Posted by undercoveraddict

One motor is 4092 size, but the other is 5692... is it safe to say the 5692 will pull equal or less amps on the same voltage?

Less

[Johnnysplits]

Originally Posted by undercoveraddict

My FOFF is 1/8 buggy based with a steel cage and it's heavy! I keep burning up motors when I gear it for the speed I like.

You must be overgearing the shit out of it. If you can get a 5692 in there, do it and run it on 12s (2-6s in series) How heavy is this thing?

[Johnnysplits]

Here's the ultimate Products-LEOPARD POWER MODEL Co.,LTD

[Olle P]

Originally Posted by undercoveraddict

... Pretend there are 2 motors of the same brand, same quality, same model type, same KV, etc. One motor is 4092 size, but the other is 5692... is it safe to say the 5692 will pull equal or less amps on the same voltage?

Originally Posted by Johnnysplits

Less

How can you be so categorical?
Just look at the Leopard line you refer to, and compare it to their equivalent 4092-series:
5692, 950Kv:
Resistance: 0.0055 ohm. It has a no load current of 4.3A at 15V. Will pull 210A at 36V and stall.
4092, 930Kv:
Resistance: 0.0165 ohm. It has a no load current of 1.5A at 7.4V (equivalent to 3.05A at 15V). Will pull 80A at 37V and stall.

So given the same relative load (percent of the motor output) the bigger motor will draw more power all the way!
It will also deliver more power, so for a given absolute load the bigger motor will likely use less power, especially at loads where the smaller motor struggles.

[undercoveraddict]

Thanks for the info guys! In the simplest terms, it seems that larger motors are safer for the ESC and the motor. The downfall is that it's harder on the batteries?
The car is 12-13lbs, so it was "overgeared" for the motor size. The ESC is fine with the gearing. I purchased a castle 1717 xo-1 motor that I will try out this evening. Also bought a 5692(or 5698?) TP Power 1100kv if the Castle runs too hot. I'm only running 6s, because my batteries get too hot if I use under 5000mah... And 5000mah batteries aren't small. Also, the Hw 150a ESC can only run 6s safely.

[Olle P]

Originally Posted by undercoveraddict

... larger motors are safer ... The downfall is that it's harder on the batteries?

For a given output power (read: vehicle speed) a bigger motor is easier on the batteries!

It's just that the bigger motor is usually capable of delivering more power, which in tur will make it harder on the battery if (ab)used.