maybe i worded it wrong?
battery will only push what the esc is telling the motors to pull
or maybe i just got the wrong thing goin here
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Yes your wording was shit, not gonna mince words.
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cock
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The ESC is the only “smart” thing in the system.
Battery is dumb, will put out as much power as it can until it explodes.
Motors are dumb, they will take as much power as they are given until they melt.
Only the ESC can control things.
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i think i fixed it
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Sort of… but you still used the word ‘pull’
Although I am quite fond of the word pull, its not an accurate term because the esc is ‘pushing’ to the motors.
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either way, if you wanna use a discharge bms (interesting choice), that will be the bottle neck,
seetings = ((battery current limit maybe - some headspace) / 2)
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that’s true,
it pulls from the battery then pulls to the motors tho? like a cunning middle man
it’s6am 
i should probably stop before i get worse
Think of a small water wheel connected to your faucet.
The municipal water supply is the battery.
The faucet is the ESC.
The water wheel is the motor.
If you broke the faucet off the pipe, water would just blast out - dumb battery.
If you stuck the water wheel straight on that, it would probably explode - dumb motor.
All that’s keeping either of those in check is the “smart” bit. You, with your hand on the faucet.
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if you got the motor current and the duty cycle you can roughly work out the battery amps.
100 motor amps at 60% duty is roughly 60 battery amps
on a side note vesc controls current, things like car escs control speed hence why batteries MUST be overrated for the esc or they will get hot and the esc must be overrated for the motor or it will fail by dumping more amps then it can handle.
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Not when you’re talking about VESC. You can run a 12s1p or a 12s100p battery with any vesc.
As long as your settings are made accordingly.
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How is everyone misunderstanding OP’s question? It works like this:
motor current = MAX(battery current setting in vesc tool, throttle value (between -1 and 1) X motor current setting in vesc tool X duty cycle (between 0 and 1))
So if you want to drive your motors with 85A all the way up to your max speed, then you need a battery that can supply 85A x2 = 170A or more. If you only care about that acceleration until 50% of your max speed, then your battery only needs to be able to supply 85A to drive the motors at 85A each. If your battery could do only 42A, then you could have full motor torque until 25% of your max speed.
However, remember that having full motor amps at the end of your speed range can suddenly throw you off once you reach max speed. That’s why we set our max duty cycle current limit start to 85%, and max duty cycle at 95% so that the ESC can still break in case we pass that value.
So with that in mind, if you want 85A x2 at 85% duty cycle, that will require a 144.5A draw from the battery. So to answer your question: for an electric skateboard a battery capable of delivering 144A or more will fully satisfy the needs of a dual motor board with each motor running at 85A.
P.S. Remember that voltage sag might not let you reach top speed while pulling that amount of current. So in reality, you might have to over-spec your battery regardless if you want that much power!
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Ideally, yes, but that completely misses the point of programmable ESCs, which is that you can program current limits to get around exactly this kind of thing.
If you’re using a dumb, shuntless, non-programmable ESC like a Hobbywing or any other RC-derived thing, yes the over-rating holds true. But with VESCs and their derivatives, that is no longer necessarily the case.
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While I agree that this does answer the question that OP asked, I submit to you that the OP is, in fact, asking the wrong question out of ignorance of how esk8 power systems work.
If the question is “How much power would I theoretically need to have zero bottlenecks between the cells and the motor?”, then that answer is great. But rarely if ever do most riders actually come anywhere near that level of power draw under any real-world conditions, and having that kind of potential explosive acceleration up near top speed is just a serious injury waiting to happen in the hands of anyone but a veteran rider.
Given that they’re a complete n00b on the forum with less than 20 minutes of read-time when I began my reply, and their questions, I’d say they are highly unlikely to need even half that level of power to have a blow-your-socks-off esk8 experience.
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uh no, motor can only receive how much amp the controller dump into it, they draw nothing on their own
they are not the same indeed
step down, yes, esc will drive the motor at any given lower voltage to achieve the speed it was told to do
wrong, see my first sentence
not sure if these help
Scanarios where vesc draws amps less than the set max batt amps.
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Here’s when vesc draws the set max battery amp. Bottlenecked but that’s the norm.
With 20A limit, vesc will only draw 960W from the battery. It would convert it to either high voltage low amp for speed or low voltage high amp for torque. This is how the battery amp is maxed out.
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Here’s when motor amps = batt amps. No bottleneck but… Not riding full speed on steep uphill all the time, arent’ya?
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Here’s an overspec battery.
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One thing to note is that batt amp has only litle to do with acceleration. Ya dun need to have op batt to accelerate hard.
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You can calculate it with the formula here:
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and here:
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You can get the bemf v by dividing the motor rpm by the kv, and you get the winding resistance by mutiplying the vesc detected resistance by 2 since it detects single phase resistance, but you need the 2 phase resistance, and that resistance has to be in ohms not milliohms. Those formulas are for BLDC not FOC.
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hence why i stated rc esc not VESC. VESCs are smart, you set the current limit and it will run upto that, a rc esc like (trackstar, quickrun, mamba, traxxas, hobbywing) are mostly dumb and will spin the motor to the desired speed amps be damned
i was just saying that for comparable dumb escs the parts must be overrated motor-battery to run properly. of course with smart/highly programmable escs like VESCs you can bottle neck it to prevent failure.
still don’t change the fact that if you got the motor amps and duty cycle you can work out the battery need for it.