Am I right that hybrid is recommended because the sensors aren’t needed and can get wonky at higher speeds?
I’ve only run sensored and sensorless, never hybrid, but I noticed no weirdness at speed either way. Still curious on opinions though.
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Yeah I’ve never seen or consciously set hybrid before, but I have set the sensor less RPM setting, I had assumed that already made it a “hybrid” setup but maybe those are only active if you tell it explicitly to use hybrid
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I’ve always read/heard here that even in sensored mode, the sensors aren’t really used after a bit of speed.
My sensors were acting up on my main board a few months back so I turned it to sensorless. I’m sure the gearing ratio and big tires helps but even a tiny hip flick gets the motor positioned very quickly and then it feels identical to sensors otherwise.
I’ll have to try it out on another board with good sensors.
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Yeah I’m in the same boat, never dug too deep into it before but had heard they switch themselves off.
To further complicate this it looks like sensored/sensorless/hybrid is only available for BLDC for me, which would be why I’d never seen it before. In FOC I get sensorless/encoder/hall/HFI instead, on VESC tool 3.0. Also lol I just realised I haven’t been very diligent with my installed tools because when I search vesc tool to find the .exe, the default one it loads is V1.25. I may be using veeery out of date FW
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Sorry for the longer post, its just a couple of things that i have had on my mind for a long time and just wanted to know…
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The power to my motors goes out very temporarily and comes back up within 0.1/0.2s but only when at max load (speeding up/braking). I have an 80A BMS so I set my motors to take 38A/-37A(Issue occurred inbetween 40 and 55) and that seemed to resolve the issue and it does seem apparent that this would be why, its just that on my previous motors, this didn’t necessarily happen, but i guess they were bigger motors so they might not have needed the same amount of amps ig. Switched from the chinese 6374 170kv to FS BH 6354 190kv motors today.
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The esk8 calc shows a 58km/h top speed with my current set up but I only get 46 max. Is it because of the low max motor amps (38a)? I mean that IS pretty low, but still, when the motors reach max rotation, they don’t really draw a ton of amps so… dunno. The amps should dictate torque in my opinion, not speed. Any advice as to where the difference might be coming from?
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The remote’s (VX1) throttle for some reason isn’t 100% responsive. The board will reach full speed on 75-80% throttle and when I push the throttle over that, the board doesn’t go faster/push harder and there is a clear cut off where it just doesn’t go faster the more i push the throttle. I am using UART, no possibility to use PPM.
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The board battery indicator on my remote (VX1) started doing weird things. When I go up hills, the battery indicator can go down 2 lights (~50%). I understand that it is supposed to show a bit of a lower battery because more is drained when uphill because it needs more power, but that wasn’t the case previously. When i initially built the board, there wouldn’t be such drastic misreports of the battery levels of the board. It would go down 1 bar/light/led, probably when it the charge was inbetween lights, but it never went down by two lights up a hill (moderate hill) only for them to come back after the hill or when i stop.
Sounds like you might be getting controller faults. You can check this through vesc tool, but the faults are cleared every time power is lost so you’ll have to reproduce the issue, then connect to vesc tool and read the faults in the terminal without powering off the vesc in between.
This is normal. The throttle is controlling motor amps (torque), so if you don’t need 100% torque to reach full speed, then you will reach full speed without full throttle. You should still see an increase in acceleration, but the top speed is not affected.
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Ok bunch of things here, mostly clarifications rather than suggestions
You clarified later in the post you mean 38 motor amps, but that’s not at all the same as 38 battery amps. For motor you can set it to 100 and floor it, and won’t necessarily pull more than 20A each from the battery if you’re not at a high speed. This is related to what was said above, speed≠power, and torque≠speed. Search battery amps for a fuller explanation, but basically motor amps is torque - ability to accelerate, or to maintain speed against resistance like extra weight or a hill - and battery amps is (percentage of current speed to top speed) x (motor amps). Accelerating hard from 5km/h is only 10% of your top speed so it doesn’t push the battery as hard as accelerating from 25km/h, which is 50% of your top speed.
What battery amps have you set? You can increase the motor amps quite a bit as long as the battery is set correctly. Also is your BMS set up as a discharge BMS? If not you don’t need to consider its current rating and only the cells’ ratings. Finally, is that 80A continuous or pulsed, what BMS is it?
Bigger motors don’t produce more torque with the same or fewer amps, if anything they may produce slightly less. The exception is if the smaller motors overheat - which they’re more likely to do because less copper and less mass - but it doesn’t sound like that’s the scenario here
As above, torque is your ability to accelerate, or to maintain speed against a resistance. If I’m dragging a trailer it’ll take more torque to run at 30km/h than it would if I was unburdened. To tie this in to your top speed, consider air resistance. Drag increases a LOT with higher speed, roughly the square of speed (more if you account for rolling resistance and other stuff but let’s go with this). So air resistance you can count as an amount of power and torque required to not slow down. These numbers are made up but if it’s 100W at 10km/h then it’s 900W at 30km/h. So torque and therefore motor current can definitely become the limiting factor for top speed, especially when it’s very low. Usually it’s something else like the duty cycle - ie that calculated electrical top speed - but if the current is low or you’re really heavy or you’re riding up a hill, current becomes the limiting factor first.
Battery % is calculated by battery voltage. When you draw a load of current, the voltage sags down, so the calculated percentage drops if the measuring device isn’t smart enough to compensate. If the indicator is dropping more than in the past it means the voltage is dropping more, which is definitely possible if 1. The pack is ageing or 2. You’re riding more aggressively because you’re more experienced. I presume it’s case 1, but 2 is worth considering too.
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Currently, my motor current max/break max are 38a/-37a and the battery current max is 40a per motor. The battery is a 10s3p molicels, but the limiting factor is the Bestech d596 BMS which is 80A discharge. I didn’t test TOO much but it seemed it would cut off at times where i’d expect the most power to be needed, like when accelerating hard, or braking hard. I mostly resolved this by just lowering my motor max from 40a to 38a. It is doing it now as well during the braking but only at the very end of the braking, when i’ve mostly stopped already. Accelerating doesn’t seem to be affected, whereas it does cut off as well when the motor current is 40, instead of 38.
Regarding the speed, I just don’t understand what might be causing it. I am taking the “weighted” number from the calculator and I know it is just a suggestive number, but still. I tested it at half battery power, on a very flat road and I weigh 80kg/175lbs, which is definitely not the heaviest. I was looking at my vesc tool’s real-time data and it wasn’t really pulling the full 38a it had at its disposal when at full speed. If we add the 20% from the lack of acceleration from the remote’s throttle, it comes to about 55km/h which is something that i’d expect.
What we call sensored is usually actually hybrid mode.
Ah yes, the next post. This is hybrid mode you’ve described.
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Nope that’s not how that works, if it’s showing you 38A then there’s obviously no extra 20% available. The 20% only looks like it’s “unused” if you’re not fully loading the current budget and are hitting another limit (duty cycle)
The battery amps taken can never be higher than the motor, I’m not saying it shouldn’t for safety reasons or anything I’m saying it’s not possible. Set your battery amps as high as is safe and useful based on your pack, and set your motor as high as you want for acceleration. Crank the motor amps, you’ll have a better time and the battery will be fine
Power available to accelerate is equal to input power minus resistance (from air, weight, rolling, etc). Resistance increases with speed, if power input isn’t high enough to overcome resistance then it won’t be able to accelerate. You set the motor amps very low, so it doesn’t have the power to overcome drag, so as I said above that is why you can’t hit theoretical top speed. That, or the calculation is done wrong or the motor Kv isn’t exactly as advertised, but IMO it’s the current
I guess I will do more testing maybe tomorrow. My BMS is considered to be 80A cont., so I presume it can spike to at least 100+ for short periods. That being said, should I set the battery current max higher? I have set it to 40 as that makes a total of 80 for the two motors and that is just the rated continuous discharge of the BMS, the battery can handle more than that, but the BMS won’t really let it.
Regarding the top speed, I will have to double check, but i think i was NOT pulling the full 38A when at full speed, which in my understanding is that its not necessarily due to lack of power. I do understand that more speed = more resistance and 46/47kmh isn’t low at all, but I’d need to double check again. I didn’t reach “advertised” speeds with my previous motors either and they were 170kv, so more torque, less speed, less resistance, but I still hit only 40 I believe.
Edit : Can you clarify the “duty cycle” limit that you mentioned a couple of times? That is something I do not understand.
Ohhh sorry I misread and thought you said it was pulling 38
Righto @Nathraichean duty cycle; the motor is switched on and off very quickly, for the sake of illustration let’s say 1000 times a second. That means every full cycle of on to off to back on takes 1ms, that’s the period. Duty cycle is the ratio of how long in each cycle the motor is turned on vs off, expressed from 0.0 to 1.0. If it’s on 50% of the time in each period and off 50%, it has a duty cycle of 0.5.
When it’s “on” the motor gets full battery voltage, let’s pretend 50V, and “off” it gets 0V. Because the switching is very very quick (combined with the electromagnetic properties of big coils of wire) you can treat it like the motor getting an average voltage. So for 0.5 duty cycle it’s like the motor is getting 25V. Voltage controls speed, so this is where my statement about ratios and top speeds comes from, and also why 50 motor amps at high speed draws more from the battery than at low speed. 50A x 0.2 for flooring it at 10 km/h vs 50A x 0.6 for 30km/h.
You’re not actually able to go up to full 1.0 duty cycle because the MOSFETs that switch the power take a very small but finite amount of time to transition (plus one other more messy reason), and there are some safety settings in VESC where you can adjust what amount of buffer you want
I don’t think its a duty cycle thing as it drops the power for a noticeably long amount of time, its not intermittent and something that can be ignored by me, it definitely makes me jitter and if I am not aware of it i’d fall.
And how about my battery current max being set at 40? Given that the BMS is 80A cont. it only seems reasonable to put it at 40 per motor. It wouldn’t really matter if I put it on higher because the BMS (bestech d596) is a bit overbuilt and it wouldn’t really let anything happen to the battery, so it would only give it as much juice as it decides it can give and maybe it will deliver 100-110A if it wanted to for a short period when it might need it. I do not know how BMSes work exactly and they might be more strict about the “continuous” rating and it would make sense because if the battery cant let out more than 80A and the BMS lets it, it would be clearly dangerous, but… I will test once again but I am certainly confident that the motors/power cutting out intermittently at high amps was resolved by lowering the motor current max, which is very weird as it shouldn’t be like that given that the motors are rated for 65A and the vesc is rated for 50A
Hi, question about TRIGGER Remote:
I got a master cho GT2B remote and some mini remotes which still work 100% in my area.
After spending some time here researching for more updated and safe commercial TRIGGER remote solutions it seems to me that I have to keep using the ones I already have till somebody will finally proposes a truly reliable commercial trigger remote. Correct? Am I missing anything?
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You’re right it’s not a duty cycle thing, but I wasn’t suggesting that it was and it’s a sign of not fully understanding the answers above. I really do mean this respectfully because this stuff is complicated, but I think you should do more reading and googling for a bit and come back after.
Yup this sounds reasonable, the only small things are what you mean by “it” here?
And what specific Molicel cells are you using? You should set the battery current in VESC tool to 80 as you said, but it’s important to understand that the batteries also likely can’t do more than about 90A continuous (less if they’re not P42A). But you’re probably not gonna hit that anyway, the limit will almost definitely be elsewhere
What ESC is it?
What do you guys think of ground clearance? I was working on a droptrough deck and my clearance would be about 3cm (1 1/5 inch), would it be okey? Or do i need to topmount it. I would just ride normal roadways.
This entirely depends on your roads. The lower you are, the better, but the more issues you are likely to encounter, should there be any pot holes, drops of curbs, sticks, speed bumps etc…
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Hmm, indeed I want it as low as possible. I will not drive down curbs / not a lot of potholes. But sticks is something I do worry about…