Yeah I know the information about the back EMF a motor generate.
But then, there are some guys with over voltage protections on the bms etc. Some brands had the same issue about a voltage protection off the bms and they can’t brake anymore going off a steep hill. But why don’t kill those guys their esc?
It is almost certain that the very moment you touch the brakes slightly, the VESC goes up in smoke.
Even going from acceleration to neutral can be enough.
https://vesc-project.com/comment/2563#comment-2563#
If you are really lucky, the voltage rise will be slow enough for the VESC to detect it and protect itself.
A massive bank of capacitors will help with a slower rise time.
With no battery attached the voltage rises very fast! The VESC can’t protect itself and blows up.
Just to get the complete picture here, you are saying his VESC’s in this case blew up from bemf because it was as if there weren’t any batteries attached to the VESC’s which in your opinion is due to that his bms cut off the power to VESC’s?
Yes, I think what Frank means is that the inductive load doesn’t have anywhere to go when the battery isnt in the loop so the result is the voltage rising to infinity long enough to explode some components. Theres a very easy way to verify this tho. Just put the same system together and do the same thing, if it blows up. Its probably the BMS, if they dont blow up. Well, its probably not the BMS. Economically this test is pretty expensive tho 
That is almost certain. If you see over voltage damage, but you do not run a 13S or 14S pack or mega long battery cables, the over voltage can only be produced by the VESC itself. And that over voltage incident is only happening when there is no battery attached. It happened a few times in the past. Some cases because of user error (forgetting to plug in battery on a bike), other VESCs blew because a Mosfet switch shut off. The voltage rise time is so fast, you are lucky if the VESC manages to shut down before it blows up.
As much as I understand your point it doesn’t quite add up.
This would mean any esc would blow up when you would be riding when a bms detects an overvoltage.
I have personally had bms overvoltage cut off and my esc’s were just fine.
If your BMS cuts the connection and you can`t feed back into the battery, the VESC is dead the very moment it generates energy that can’t be stored somewhere. In rare cases it manages to shut down before it blows up. But don’t rely on this!
I don’t get it. You’re saying any bms with voltage cut off capabilities will blow up your VESC with bemf when cut off happens.
Yes, if the BMS decouples the VESC from the battery, the VESC is likely to blow up.
You feed energy in one end, the energy can’t be stored, the energy blows up your VESC.
If the VESC manages to detect the voltage swell fast enough there is a slim chance of VESC survival.
@pjotr47 whats the data refresh rate on the BMS app?
The BMS has his own storage where it saves his logs. App is only to check that.
cool. do you know how often the log is saved per minute/second?
I can ask the manufacturer. Good thing to know.
Find pout if it logs the switch. Over voltage does not happen in this case.
Let’s say in those conditions what happens when the VESC cuts off? Where does the bemf go then?
In that case the VESC will let the motor free roll. The VESC is powered but the motor does not act as a generator. The problem are the voltage spikes on load changes and when you push the brake.
Just spinning the motor when rolling is not an issue. But this scenario is only realistic if you pedal an e-bike without ever touching the throttle lever or brake lever.
This is a contradiction to your earlier statement.
Now you’re saying free rolling is fine without a battery.
Before you were stating otherwise.
Please don’t mention braking in your next post. I don’t in mine.
I honestly feel you are trying your best to avoid admitting that the VESC sold here were faulty which is understandable as a business, but I think in this case it’s he says vs he says situation and best resolve would be to replace under warranty.
Should Pjotr have this happen again afterwards with replaced VESC then we can definitely say for sure it’s not the VESC.
We are not trying to get free replacements to scam you by not admitting it was user fault. We are sure it wasn’t ours. That’s all. His VESC’s out of nowhere blew up and all other components are showing to work as normal.
You don’t understand the matter, so please inform yourself first. This is a very old problem that has been debated many times on various forums. A lot of users have killed their ESCs this way.
The problem are load changes and braking.
If you do not apply these, there is no issue. If you ride and suddenly loos the battery connection, you have a problem.