Vesc lvc and braking downhill

General topics and discussions about the VESC and its development.
Hummie
Posts: 105
Joined: 10 May 2016, 04:05

Re: Vesc lvc and braking downhill

Postby Hummie » 12 Sep 2016, 17:13

no one has said where the energy goes! there seems to be confusion. I believe there is power being created by the coasting wheel no!? obviously so as it'll destroy the vesc if there are no batteries. yet the batteries dont get charged unless going fast enough. where does the power go!? that's a fair question and no one has answered it.
a voltage is produced. magnets fly past coils. i can get zapped if i put my mouth to the wires. I can make my other motor move if i connect the 6 six wires and turn one of the motors by hand. it will blow up the vesc if the batteries aren't connected....BUT it wont go to the batteries??? just trying to understand where the energy is going. maybe the esc can disconnect from the incoming energy somehow. I dont know. I'm not asking the same question that has been answered. maybe there's a misunderstanding on my part about power being produced but i thought it was unavoidable if the motor wires are connected to something there has to be energy going somewhere if the motor is spinning.

maybe it just spins around in the vesc or something i dont know.

pf26
Posts: 283
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Vesc lvc and braking downhill

Postby pf26 » 13 Sep 2016, 06:35

While there is a voltage produced by the spinning motor, there is no power generated or absorbed unless there is also a current flowing (P = u x i).
And energy is the accumulation of power over time. Re reading the basis of power/energy laws in physics may help ?
You don't need much energy to kill a Vesc, a high enough voltage and a little current will do in a very short time.

rew
Posts: 914
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Vesc lvc and braking downhill

Postby rew » 13 Sep 2016, 09:51

Do you actually READ any of the replies you get?
Hummie wrote:no one has said where the energy goes! .
That happens to be because everybody is saying that there /is/ no energy being generated.

@pf: There is a minimum amount of energy required to break anything (try breaking your leg falling off a sidewalk). The mosfets are actually documented to be able to handle 0.5J when overvolted. Most other devices (notably the DRV) do not document that number.

pf26
Posts: 283
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Vesc lvc and braking downhill

Postby pf26 » 16 Sep 2016, 17:36

You have 0.5J released while breaking 70kg from 36km/h down to 35.997km/h... - Or just 50V, 10A during 0.01second
And probably the DRV can be destroyed with a lot less than this...

Hummie
Posts: 105
Joined: 10 May 2016, 04:05

Re: Vesc lvc and braking downhill

Postby Hummie » 13 Oct 2016, 17:42

ok...ok..
but....
there is some power being generated as the lights on the vesc go on when batteries aren't connected and you ride downhill. there is a complete circuit in there

rew
Posts: 914
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Vesc lvc and braking downhill

Postby rew » 14 Oct 2016, 17:05

Correct! :-)

Hummie
Posts: 105
Joined: 10 May 2016, 04:05

Re: Vesc lvc and braking downhill

Postby Hummie » 14 Oct 2016, 20:13

everyone so far has been saying theres no power being created?

just trying to find out how it works. it creates power but how is the amount produced limited or determined?

rew
Posts: 914
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Vesc lvc and braking downhill

Postby rew » 15 Oct 2016, 07:05

Last try.

Just like the power outlets in your home, the motor can generate a voltage that nobody needs to use. If you see the VESC power up, that uses some power, enough to light those few leds (and run the CPU). This is totally insignificant compared to when you command the VESC to brake the motor. My VESC currently uses 0.5W at 24V. Whereas commanding a 10A brake current at 24V would mean 240W of power being extracted from the motor and put into the battery (minus that 0.5W and some losses in the power-conversion).

Hummie
Posts: 105
Joined: 10 May 2016, 04:05

Re: Vesc lvc and braking downhill

Postby Hummie » 15 Oct 2016, 15:22

How can a circuit be made so current flows in the vesc and lights come on with no battery, yet if the full current were to flow it would destroy the vesc?
The difference between what could be generated and what is...how is that happening?

rew
Posts: 914
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Vesc lvc and braking downhill

Postby rew » 17 Oct 2016, 18:49

Yes.


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