Samsung 30Q 18650’s with 4.2 volt max and 3000mah. 12S?P configuration…
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Just for the first, say,10 seconds of the ride, with 12S configuration Battery Pack, How many fully-charged, brand new, Samsung 30Q’s would it take in Parallel to fully utilize the capability of 1 Hub Motor which is rated for 80Amps at 50 Volts?
4p of 30qs is 80A max
(20A per parallel group)
It is independent of voltage (10s vs 12s), they can both provide the same maximum “safe” amperage when the parallel groups and cell type are the same.
With 12s (Volts) you will generally send less amps (Current) for any given amount of power (Watts) when compared to 10s because:
Power = Current * Voltage
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That’s a pretty good answer. The “Linear” answer. I would tend to agree!
I just wonder like, if you tried 12S3P, then 12S4P, then 12S5P…
I’m pretty sure i’d feel a noticeable increase in the acceleration between a 12S3P and a 12S4P.
But would the 12S4P and the 12S5P feel the same?
When you consider the Maximum Surge Voltage of each Pack, I think the 12S4P would have enough power to saturate the capability of the Hub Motor, and thus the 12S5P would not make a difference, maybe even be slower due to the added mass.
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Another way to look at the problem to add on to what @Venom121212 said too is really you care about the Watts, how many Watts does the motor need and can your ESC and battery both supply those Watts to “saturate” the motor and “fully utilize” the capacity.
The problem with low count of cells in parallel is typically getting voltage sag where the batteries can’t sustain the current necessary. With a 10S 5P setup and warm weather my latest limitation has just been the ESC overheating 
I’d be curious what the goal/intent is though too, if looking to drag race it might make sense to try and do this but otherwise would see if the board has “enough” torque to keep you happy and not put you out on your butt every time you touch the throttle.
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Or maybe the 12S5P would accelerate faster, but would wear the Motor out faster since it would be operated above its specified max parameters…
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The voltage limits on motors for the most part I think don’t matter they are after all just coils of wire inside a metal case with magnets in there. So if you know the resistance in Ohms of the wire and you know the voltage you can calculate the current, the BLDC ESCs are opening/closing the gates pretty much constantly though so the current is only happening when gates are open (also percent of gate open time essentially creates an average voltage lower than the battery incoming voltage).
As current flows heat builds up if no air is flowing to take away the heat it just collects until enamel coating on wires or other things start to melt and then you have shorts and real issues with the current spiking and more things melting at that point. Voltage is the ‘pressure’ and will at high enough voltage jump across small air gaps (but talking thousands of volts for a cm air gap) but through a component it could be far less to make the jump/short out.
Yes, interesting.
I’m actually looking at a new battery solution for my next board after my trusty old DIY Board finally went up in flames towards the end of charging the other day.
It was a 4 wheel drive board with 2 electrically independent home made, 12S3P battery packs with no BMS. One 12S3P for front wheels and one for rear wheels.)
For this next board, I think I’m going to go with pre-fabricated Packs with BMS.
But I am trying to figure out if I can keep the board a little lighter than it was before with 2 Packs of 12S3P, or keep the power similar from a lower cost vendor on Alibaba or something like that. The best they seem to have are 30Amp nominal with 60Amp surge. But I was using Sony VTC5A before and I think they had quite a bit more amperage than that, especially with no BMS…
So that’s what is going on here : )
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heh okay gotcha just good to have some context sometime people just want to maximize numbers but don’t know what the big numbers mean good to hear you have some experience even if not 100% positive
I went with Lipo setup on my first deck (to keep it cheap) and that one is still rocking and pretty happy with it, took me like 2 sets of lipos to find ones that are a good compromise on size and max discharge but anyway that one is good for budget friendliness (I take apart two 5S batteries that are put in series to make it 10S and charge them separately or in parallel with a hobby balance charger)
More recently grabbed one of the batteries from metro-boards, I haven’t exactly stress tested them but will go take a quick ride here and post some datas for Science!
^^ maybe worth a look/comparison too, it has some sort of balance circuitry built in from what they tell me but couldn’t get details on the BMS and they sell a power supply for charging them (about $50-60 for that but you need it as far as I can tell)
Nice, sounds familiar. I saw some good looking LiPo Batteries and was thinking of trying those. They were specified as delivering great Maximum discharge Amperage, but had low Milliamp Hour ratings. Was thinking this would be OK since my rides are typically brief. I’m thinking i’m going to try Alibaba for the first time, will post some info if anything notable occurs…
Will check back in days and weeks ahead and hope to see some info about your new Metro Boards Battery performance!
Have a Marvelous Day ; )
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Thanks will definitely get out and try my hexacopter to test out the GPS I’m sure that will be memorable 
Would focus in on the dark blue line that is voltage there and the yellowish line that is esc temp. I was just going a few blocks here 1/4 mile basically with couple intersections in between. Can see how much the voltage is dipping as I ask for more current, can also use the arrow on the graph to turn on ppm/pwm display to show the control input and corresponding amperage over time.
Thanks Ryan 
really eloquently explained.
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Something that comes up repeatedly that I don’t really get is how motor amps can be greater than battery amps. Surely if I limit my battery to 60A, the motor cannot draw more than 60A no matter what. I’m not sure how this is implemented in the VESC but I would imagine it would be like a regular constant-current supply that just uses PWM to create an average current flow.
The only thing I can think is that maybe motor amps is a measure of the instantaneous current flow during a period of “on” time? But that would make no sense since a) we only care about average current flow through the motors, not current flow during an “on” period, and b) the current flow during an “on” period would be a natural result of voltage and motor resistance; the duty cycle is the control.
In my mind the only use for a battery amps limit is if you’re driving two motors on a single-MCU dual-output VESC. Otherwise battery amps and motor amps have identical function and only the lower of the two would be taken into account.
What am I missing?
Duty Cycle is the missing piece. Battery amps limits total power (watts) to the system.
Battery = fixed voltage, variable amps
Motor = fixed amps, variable voltage
Some explanations here:
The graph really helps put it together
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Essentially the motors are only drawing that current for half the time, so effectively the battery only sends half of that current to the VESC and the VESC sends 2x that current half the time to the motors.
Honestly that graph did nothing but increase my confusion lol. My problem is that it shouldn’t be possible for motor amps to be higher than battery amps (where is the extra current coming from??)… but then I saw this explanation by @MysticalDork:
In this way, the ESC’s switching, combined with the inductance of the motor winding, acts as a buck converter to drop the battery voltage down, while at the same time increasing the current to the motor.
This is how you can have 100A flowing through the motor, but only be pulling 12.5A (P=I*V, 100A * 5v = 500W, and 500W / 40v = 12.5A) from the battery.
So the motor becomes a buck converter. That explains everything. Not really sure why that’s not the first thing people say when they explain this; would make it a lot easier to understand.
Yeah but on its own that doesn’t explain it. For instance, if I have an LED running at 50% duty cycle, it will be dimmer than if it were running at 100% duty cycle. The LED will never have more current flowing through it than the battery can supply.
Intuitively, if I run the motor at 100% duty cycle, it will have no more than the maximum battery current flowing through it (because the VESC would actually reduce the duty cycle to maintain the battery current). Then the faster the motor spins, the less current would flow because the less the effective phase voltage becomes due to back-EMF. This is what I was confused about.
That seems like an awkward way to think about it. The battery only supplies variable amps because the ESC varies the duty cycle to the load (the motor). The ESC can’t control the amps coming out of the battery except by changing the load duty cycle.
The vesc is the buck converter, not the motor.
Not by itself though, surely? It would rely on the motor’s inductance right? I’m far from an expert on switched-mode power supplies so maybe I don’t know what I’m talking about.
I am also not an expert, i just like breaking shit.
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