Hello
Im trying to build a proper on off switch, but im struggling a bit, wonder if anybody has actually measured the inrush curre t from battery when two large motors start up?
Thank you
what type of motor and batteryare you using?
Also what vesc are you using.
Well it was a genral question lets say 12s, 5p and 2 large motors, and a vesc capable of 60 amps, think there is a new one out rat3d at 60 amps ? I really want to know highest current draw possible using 2 motors really.
Thanks
Is there any reason you think it wouldn’t be 120A battery?
Imo batteries usually end up being the current draw issue, I have never managed to max out the current in my motors. However, I am not very heavy so that contributes.
The motors I use are rated for 80A max each from the vesc, while the BMS I run discharge through is 60A at the battery, limit. So for me it would be 60A max that would go through something like that
Ok yes didnt think of it that way, its the capacity of the battery that govens everything.
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Essentially the motors are rated for a certain max amperage but they will only ever be able to pull what is given to them. This is further determined by the max amperage the VESC can provide.
The 4.12 VESC can’t take more than 50 battery amps each. So theoretically the max battery amps possible to pull with two VESCS without breaking the electronics is 100A. This is quite large but I know for a fact that some people are able to easily pull this much, especially offroad.
you can use a vesc monitor - metr, ackmaniac’s, davega - what have you, and it gives you motor and batt amp draw.
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When you input the battery and motor current limits into the vesc, it will use these input values along with throttle inputs as command instructions to adjust the duty cycle control parameter to vary the pwm (pulse width modulated) effective voltage applied to the motor, in so doing maintaining the motor and battery currents below the programmed limits. Just because a motor or battery is rated for certain limits doesn’t mean the vesc won’t exceed these if you program it do otherwise. Some BMS may be capable of limiting the battery current independently of the vesc. Many vescs won’t exceed 60a current battery or 120a current motor due to firmware limits. When the motor current is higher than the battery current it is because the “pwm effective voltage” to the motor at that moment in time is proportionately lower than the battery voltage, but they are both always the same watts.
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Inrush current has nothing to do with motors and etc, it depends on capacitance at power stage on ESC. When you power on the ESC because of super low resistance in the capacitors current in rush to charge them. In my previous calculations I don’t remember now exact but I think inrush without any limiting can be up to 1.5kA - 2kA for less than 100ms. That is time when switches die because of mosfets working in out of SOA (Safe operating area) range.
You can simulate this by using any spice
EDIT: I lied it can reach even 5kA 
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Does BMS limit and maintain the 60A current?? or It just cuts off the supply when current goes above 60A?? please help
I’m not sure, it was difficult with that setup for me to hit 60A, and to look at it while fully accelerating isn’t very easy.