Don’t forget that the max charge current for the cell found on the datasheet is for a full cycle from empty to full.
It’s not a problem for a short time to exceed this values
Did understood why the duty cycle should make the motor amps high and the bat amps low during low speed?
If you have high motor amps your motor voltage will drop, that does not affect the battery amps and voltage (besides the voltage sag for sure)
Or did I get something wrong?
As I said, a short injection of high currents is not so much of a problem for the battery. The rated amps for charging are for longer charge periods. In the end yo want the brakes to work when you need them.
The Battery MAX Regen is the value that defines brakes at speed, assuming that the Motor MAX Regen is matched.
When you go slow the motor generates at lower voltage, which will be scaled up to charge voltage, while the currents will be scaled down on the battery side.
25V x 50A (Motor side) equals 50Vx 25A (Battery side).
If you generate at 25V you can have -50A braking, while the battery only sees 25A of Regen current.
Here’s a video with real-time overlay of what the VESC is doing. Input current is another name for battery current in this case.
You’ll notice during the video that battery amps are always lower than motor amps, and the two approach each other as the duty cycle approaches 100% (during higher speeds). During low speeds, battery amps are low and motor amps are much higher. At around 0:35, you can see braking does the exact same thing.
I guess a way to think of it is in power. The power (watts) that the battery provides will be directly equally to the power that the motor provides to the wheels (ignoring effeciencies). Let’s say the battery and motor see 700W during acceleration. The difference is that the motor is doing 70a at 10v, while the battery is doing 14a and 50 volts, yet they are both using 700W. This large difference between motor and battery amps happens during acceleration from standstill or when the wheels aren’t spinning very fast (when duty cycle is low).
During acceleration, having a high motor amp value will give more punch. If both the battery and motor amps were set the same, during acceleration the motor will pull 35 amps, but the battery will only pull 10 amps wasting so much potential.
Kinda felt like I was talking in circles there. Hopefully that clears things up
Still don’t get it.
The thing with the input output watt is what I meant and in your first post thought you was saying wrong, but understood now that we mean the same
I thought the duty cycle never can‘t exceed 95%.
I thought you just set max values, so why you should I lose potential if I set motor and bat amps close to each other?
If I set my bat max to 50a and my motor Max to 60a, why I can’t get 50 b, 55m amps with just a Duty cycle of 95% out?
From what depends the duty cycle? From how hard I push the trigger or from the speed?
The duty cycle is directly related to the speed of your wheels. Let’s say your boards top speed is 20 mph. At 10mph your board is using a duty cycle of 50%, at 20mph its 100% (well 95% to protect the FETs), and 5mph its 25%. It doesn’t have to do with how hard you push the trigger, just your current speed.
If you set your battery to 50a and motor to 60a, you will get the most power at a high duty cycle. But when you are accelerating from a stand still (wheels aren’t rolling very fast = low duty cycle). Your motor amps will be limited to 60a at let’s say 25v, so 1500W. But your battery can produce 50a at 50v or 2500W. So you’re only accelerating with 1500W. But if you set your motor to 80a, you’ll be able to accelerate at 2250W and your battery still isn’t exceeding its set 50a.
This is hard to explain… Lol
So yes, at 95% duty cycle your motor and battery amps will be the same. But you aren’t always riding at top speed. For slowing speeds motor amps will always be higher than battery amps. Just watch the video, you’ll notice that they are rarely equal and the motor amps can be twice as much as battery amps for most of his ride. Just set these values to what your motor and battery can handle. If anything multiply the manufacture recommendation by 0.8 if you want to be conservative. But don’t make them equal!
If one of your wheels was spinning randomly then one of the hall sensors, or sensor wires was making bad contact, if you force the wheels pushing the throttle is this situation a large rush of current with flow into your VESC and surely will blow the DRV.
If you have studering on one wheel do not push the throttle all the way on the bench ever, disassemble the enclosure and make an inspection