maybe they can chime in. Would be good to know if there is a difference between the racerstar motors, APS etc. It’s not all about KV.
WOW, just did a kv calculation on @JLabs motors and they’re WAY off.
The 6355 208kv motors I got tested at 171kv, though a small disclaimer, I did test this in FOC, I’m sure it’d be closer to the 208 advertised value if I ran BLDC.
46799 / 41.09 / 7 / .95 = 171kv
EDIT: redid it in BLDC and got 181kv!
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How does the “turns” of a motor correlate to kv . I only have rc car experience from when I was a kid. We never worried about kv, it was all about turns. Maybe they are similar or proportional. Stock motors had like 21 turn s and gave long run times. And 18 turns gave more top end speed with the sacrifice of a shorter run time. These were all brushed motors though. With brushless it seems to be not about the turns but about kv. I just bought some tacon 160 bigfoot motors and did notice in the specs that they are 8turn and can handle 14s. Has anybody tested the true kv of these yet. Just intrerested
Turns determine kV is all. Basically the same thing. Vesc have the 60k ERPM or higher depending on which one you buy. Lower kV higher TQ. The concern is blowing drv chips above 60k ERPM on high kV and voltage builds. But everyone here uses various voltage and motor size based on range, speed, budget, ect of each build.
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So knowing the tru kv of a motor is probably more important for motors and battery combinations that max out the 60k limit. So inputting an advertised kv spec that is off will destroy the drv b/c of the edrpm. I mean some of these kv ratings are way off and there needs to be a comprehensive list to correct these bogus advertised ratings. I just don’t see why they would give specs that are rounded off and not dead on. Testing the tru kv of a motor should be #1 thing before vesc setup and battery choice. Before I stumbled upon this I would have just plugged in factory specs for kv when my vesc came in the mail.
Actually… if the KV is lower than stated and you do the calculations based on the stated KV the following will happen:
- the board will be slower than anticipated and a little more torquey than expected
- the board will be far, far less likely to come anywhere NEAR the ERPM limit so blowing up DRVs isn’t going to be an issue unless you do something silly.
@Jinra Do one of my motors. They’re stated at 3100 watts and 190KV. Its a standard sensored 6355 from Maytech. I would do it myself but for posterity and purity it would be better if somebody else did it.
I’ve never done it but i suspect theyr’e somewhere in the realm of 170 actual KV as well, which is why i can use them with such wild success at 12S on FocBoxes and VESC 4.12s because they’re nowhere near the ERPM limit even at full throttle, yet they deliver monstrous power at all ratios.
No skateboard motor is the actual advertised KV. ITs all horseshit. Find the motor that looks like it can handle your shit. Specs are all marketing garbage. You have to open the shit up and see the copper and feel it. Smell it. Roll the stator around on your chest sensually and absorb the magnetic chi. Don’t let anyone see you do that, they’ll laugh and post it on youtube.
or just get the big fucking motor with the mountain of copper and iron in it.
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I measured kV on my APS 8085’s and they were slightly above their stated rating but almost dead on at 350
My @chaka motors were actually only a couple kv off, but I’ve seen them vary wildly between vendors.
@longhairedboy i can test your motors when they (and their mounts) arrive. Shouldn’t be until next year but hey that’s not so far away!
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I think if a list is made we can see which ones are way off and we can have faster more efficient setups
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Maytech (eskating 190kv) Messured kv 160kv, quite a bit off whats advertised haha.
38788/ 36.5 / 7 / .95 = 159kv
Tested in FOC
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you should run the kv command in terminal for a more accurate calculation
This is what I got when running bldc
yep thats 187-197 kv
Thats weird. My max speed is 42km/h on full charge and the esk8 calc says it should be 47km/h with 190kv motors. If i put in 170kv in the calc the calculated speed seems spot on!
6374 motors with 10s battery 16/36 and 97mm wheels.
Cant do the kv calculation in the terminal when using FOC…weird.
Edit: With the maytech 190 KV motor, 10S battery on full charge, 16/38 ratio and 97 mm wheels I get around 44-45 km/h top speed.
I never managed to get a KV read in BLDC-tool terminal either (in FOC mode).
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you need to run a bldc detection before using the kv command.
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