I have a 6374 140KV and a 6374 170KV but from what I can tell I am limited in voltage on those motors to 12S max. I’d like to use 12S packs but I don’t like running anything at max capacity. I found this one and it appears capable all the way up to 18S which would give me more headroom but at the cost of more current draw.
So my I figure my options are 6374 140KV or 7070 110KV. So question for the guys who understand these motor rating better than I do, which one will be produce the most power while drawing the least current? I’m thinking I want to use 12S packs because large capacity 6S (like 16 and 20 AH) are readily available and not expensive. If I went with the 6374 I could run 8 or 10S. The 6374 says max current of 85A and the 7070 says 100A. I would use a 150 or 200A ESC either way.
What do you guys think given the two motors above?
Motors aren’t limited in voltage like the chinese specs say and the ”specs” are often mixed with numbers that don’t go together. The 6374 motors will be able to take 12s if you want to use them. Outrunner motors will not explode like inrunners can so the limiting rpm will be when eddy current losses get too high and cause heating and loss of efficiency. The 80100 motors i’ve used could take up to 7000-8000rpm before eddy heating started to get noticeable.
Energy in equals energy out plus losses so these motors will both take roughly the same power to do the same task. The difference is the max torque and power potential which will be higher for the 7070 motor with its larger airgap area. It will also have a bit higher efficiency at the higher torque levels
If you plan to use it for an efoil then i would choose the 7070 to have a bit more power available to get up on foil. There are some people here that could get up on foil with the 6374 but i think they might have been lightweights😀
Then for the different kV figures, torque potential of motors are not set by kV but by the saturation and heating of the stator steel and your controller and battery max current so a 50kV motor fed with 100A phase current will create as much torque as a 100kV motor fed with 200A phase current (as long as we’re talking same motor only different kV)
it might seem like the higher kV motor is drawing more current to do the same task and would be less efficient but eventually there is only half as high voltage needed for the same speed and this evens out to a few percent in efficiency difference when motors are compared. Normally it’s best to choose the lowest kV you can reach your rpm goal with but you can get away with a lot if the system just is well balanced in motor-esc-battery capability.
Awesome explanation. Thank you. Do you think I’m asking for trouble running the Flipsky 75100 ESC close or at is rated continuous current of 100A? I have some cheap 120 and 150A ESC’s but they are not programmable. I like how the 75100 can be software limited on current. I’ve seen mountain board builds using the 75100 with 7070 motors and they seem be working.
I would like to build this so I can straight up efoil, but would more likely use it as an assist, but I’m a big guy on a big board and big foil, so more power won’t hurt.
The VESCS have temp limiting so running at 100A current will not break it immediately but you might get problems with thermal limiting. Good cooling will be needed. All components mean time beteeen failure go down when being run at high temperatures and if the 100A Flipsky is borderline to do 100A then there’s a risk for shorter life. I’d try it and note the temperature at the normal riding you plan to do.
I would probably do some sort of passive cooling, like sealing the ESC through a hole in the bottom of the box. When the control box hits the water, and I spend plenty of time in the water, the back of the esc would be exposed to water. Similar to how Foil Drive is doing it on the Assist Plus. I can also limit the current If need be. Specs say to make sure and limit max current to 200 (assume that means burst current) with a continuous capacity of 100A. Worth giving it a go for the price. Thanks again. Very helpful.