sl33py
10 kW
@fasser - what motor kv? I saw something here about >200kv on 12s could be a problem.
fasser said:Another thing is that when I was testing the VESC even if I set the motor current limit to 120A The realtime graph never showed more than 80A and it did not feel like it was more than 80A. Is there some type of limit I did not recognize yet? The limit was exactly 80A.
Best regards,
fasser
sl33py said:@fasser - what motor kv? I saw something here about >200kv on 12s could be a problem.
onloop said:The vesc also has temp limiting function.. I think the temp sensor is positioned near fets. What do you have it set at in BLDC
Hi fasser, that's quite the beast you have to drive there! Maybe I'm misunderstanding if it is the setting or real RPM but why do you want to spin the motor at 9k RPM? The VESC can handle >200KV motors but overspinning them is useless (you lose power) and frenquency of erpm can damage the DRV.fasser said:Hi everybody
Thanks for your answers.
The motor is an EMAX GT5345/09 with 170KV. The error occured at around 9000 ERPM in sensorless mode, so I don't think it's the reported KV limit.
I'm asking myself if maybe the batteries are limiting the current, but it would be strange that it is exactly at 80A. I'm using two Turnigy 5000mAh 6S 20C Lipos in series.
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=35828
They should have 150 Amps peak discharge. Does anybody have some experience with these? I think they're quite common.
Best regards
fasser
pf26 said:I think fasser said 9k ERPM. So that's maybe just 1285RPM for a motor with 7 pairs of poles (not sure this one actually is).
The motor voltage should then be around 8 volts (=1285/170), so 100Amps in the motor yields around 18Amps for the battery (assuming 44Volts), which is Okay for those Lipos. Or am I wrong somewhere ?
pf26 said:Hi,
I'm also using two Turnigy 5000mAh 6S 20C Lipos in series and 168kV motor. I had no issue so far (after some 100 kilometers now). The VESC works great for me.
But my current limit is set at 60A (discharge) and 40Amp charge (for mechanical reason, otherwise my timing belt might slip then). I also use a low amp limit on battery currents (10Amps, that is 2C for regen - but also against overvoltage).
I have a 1500uF/63V Nichicon capacitor (60mOhmESR / 3Amp ripple) + a transil1.5kW56V ( transil1.5kW56V) very near to the VESC.
In your case, I suspect an overvoltage killing DRV8302 chip.
Were the batteries fully charged ? Was the motor loaded ? Did the VESC fail upon deceleration ?
What capacitor did you use ? How near is the capacitor from the PCB ?
I wish there was a DRV with a higher max voltage, also because we could then use a more common 13s battery (possibly using other FETs).
silviasol said:My drv8302 died after one ride with my 270kv motor and 12s. After talking with vedder I found that you can not use more then 200kv with 12s. If you gave it alot of throttle at low speed would the vesc cut off then back on? That is what mine did, otherwise after about 15mph no issue's going WOT. I got home the next day and tested sensored and it cut off at high speeds then shortly after I got drv8302 errors. Might still be kinks that need to be worked out with 12s even with 200kv or lower. I am working on my 10s pack now, have my fingers crossed it will work well. No issue's with 6s right now. If you want me to replace your drv8302 message me.
Vanarian said:Hi fasser, that's quite the beast you have to drive there! Maybe I'm misunderstanding if it is the setting or real RPM but why do you want to spin the motor at 9k RPM? The VESC can handle >200KV motors but overspinning them is useless (you lose power) and frenquency of erpm can damage the DRV.
BTW if you want killer LiPos to get huge 150 discharge peaks, you can't go with Turnigy 6S 20C Lipo you are asking too much of only one pack of 5Ah. Either you parallel more packs or you get something with less internal resistance, but less internal resistance also equals more expensive. Though I wouldn't burst 150A on a RC sized motor, it is a LOT of heat to bear for the motor.
May I suggest that you look at a123 LiFepo4 cells? 26650 cells are rated for 70A continuous at 2,5Ah each for 3.3 nominal per cell. Stack 20 cells in 10S2p and you can have 33/36V 140A capable continuous current from your battery pack, but hey it costs more than Hobbyking lipos! Your choice is defined by how much you want to pay for your battery.
I'm not an expert but I think Vanarian is right, it's not the voltage that goes down if the motor isn't running at full speed, it's the efficiency, meaning more energy is converted into heat (in the motor).Vanarian said:pf26 said:I think fasser said 9k ERPM. So that's maybe just 1285RPM for a motor with 7 pairs of poles (not sure this one actually is).
The motor voltage should then be around 8 volts (=1285/170), so 100Amps in the motor yields around 18Amps for the battery (assuming 44Volts), which is Okay for those Lipos. Or am I wrong somewhere ?
Ok I understand better for the ERPM But if I'm not wrong, 100 amps in the motor means 100 amps from the battery, because even when dividing all amps between each poles you must have the total amps from the start... so 100 amps from a pack of 5Ah 20C is asking too much of it IMHO ?
lizard said:Here are some load tests with different "R/C-grade" lipos:
http://www.elektromodellflug.de/hobby-king-40-65c.html (german, but the load diagrams on the right are in english).
http://www.rcgroups.com/forums/showthread.php?t=1767093
But apart from all those numbers, as far as I understand, it's pretty easy to find out if your lipos are up to the task:
- Check if single cells drop below 3.3 or 3.2v under load ( can be checked with a cheap lipo warner buzzer connected to the balancer leads)
- Check how warm they get. Opinions differ on this, but I'd say if they go over 50 degrees Celsius regularly it's too much for them.
Yes, maybe overvoltage is the problem. I had a 2000uF/63V Nichicon capacitor placed in the same way as on the Onloop BETA batch. So approx 2-3cm away from pcb connecting points.
The VESC failed at full throttle in current mode and was still accelerating. It felt a bit like cogging in the last moment, but it's hard to say if this was the reason for the VESC to fail or if this was the result of the failed VESC.
Maybe I should add a second capacitor or a transil 1.5kW56V.
Concerning the transil1.5kW56V: I am right that this is a diode that shorts the circuit if the voltage rises over 56V?
fasser said:Hi everybody
Thanks for your answers.
sl33py said:@fasser - what motor kv? I saw something here about >200kv on 12s could be a problem.
The motor is an EMAX GT5345/09 with 170KV. The error occured at around 9000 ERPM in sensorless mode, so I don't think it's the reported KV limit.
onloop said:The vesc also has temp limiting function.. I think the temp sensor is positioned near fets. What do you have it set at in BLDC
I left the temp limit as default at 80°C start and 100°C end for the current limiting. But as mentioned the temperature was not reported near this limits when the VESC died.
I'm asking myself if maybe the batteries are limiting the current, but it would be strange that it is exactly at 80A. I'm using two Turnigy 5000mAh 6S 20C Lipos in series.
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=35828
They should have 150 Amps peak discharge. Does anybody have some experience with these? I think they're quite common.
Best regards
fasser
lizard said:Connected the VESC to a PC now. Looks like the DRV is toast again.
vedder said:Hi fasser,
Is it this motor?
http://www.agmhobby.com/item/outrunner-motor-emax-gt534509-170kv-for-900013000g-plane-p-648.html
You should not set the current limit way higher than in the specification. If you do that, the back-emf gets distorted and tracking the motor won't work properly. I don't recommend more than 80A at most for that motor. With a too high current limit, the protection features will also not work properly and components can fail easily. What happens when you the realltime graph (which shows a filtered version of the current) shows much lower current than you set and you run far from maximum speed is that the current rises above the set limit and the hard current limiting feature kick in all the time, which is very bad condition to operate in (notice that this can also can happen if you have the wrong motor parameters).
If you'd like, you can send me your VESC and I can try to repair it.
lizard said:No worries, thanks for your help Benjamin, I really appreciate it
Hmm, why are the DRVs such divas?
I am using an external BEC that is wired like this:
The steering servo is plugged into the receiver also.
Can this cause ground loops? I'm not that electrically savvy, but in R/C car forums and in Castle's manuals it is explicitly stated that the ground wire from the ESC to the receiver is needed because otherwise the ESC may not be able to read the throttle signal correctly and strange things and glitches may happen (If I understand correctly, because it doesn't have a ground reference then). I run it like that in my other cars too (including the twin 1717 car with 2 ESCs) and never had problems.
lizard said:The settings I used are the ones that it came back with from you. Only settings changed are related to PPM pulse duration. I'll pull the XML file from it when I get home later.
lizard said:Regarding putting the 1717 in your car: That would be really cool, but I'm a little afraid that would be asking too much from you:
It has M4 mounting threads and is 50mm in diameter, it will probably not fit in an 1/8th scale buggy motor mount, most of them have M3 holes and allow for a maximum diameter of around 45mm. Gearing will also be a problem, with most 1/8th scale buggies you can't gear to 160kph without modifications to the motor mount, you'd need to mount a 30t or bigger pinion with common 1/8 buggy spurs and diffs (the Traxxas Slash is nice in that regard because it can use spurs down to 34t and has a 2.85:1 diff ratio ...).
lizard said:I also have a TPPower 56x92mm 6-pole sensored inrunner for testing if you want, but I'm not sure if the VESC can do enough ERPM for it, it's 1130KV and was originally intended to be run with 8s.
erwincoumans said:Does anyone know how can you configure a Linux serial terminal program, such as 'screen' or 'minicom' to communicate with VESC, similar to BLDC_Tool? The BLDC_Tool connects fine to /dev/ttyACM0
I tried running screen /dev/ttyACM0 115200 but there is no feedback, when typing 'help'.
chuttney1 said:Who here has issues uploading firmware to the VESC. I'm stuck since I arrive an openocd init failed problem.