Determining optimal motor and battery currents

ESK8 Electronics
1

So I’ve recently finished my first build, and got everything working using mostly the defaults in VESC Tool and its FOC Wizard. Now, I’d like to tune my parameters and use my board’s full potential.

My motors are dual hub motors from Meepo (link) I know basically nothing about the specs of these motors, except that they are 540w and I can count 20 motor poles from spinning the wheel and feeling the “snaps”

My battery is a 10s2p of P42A Molicel cells. Each cell is rated for 45A continuous discharge and 4.2A charge current. With two in parallel, that sould should be 90A discharge and 8.4A charge. (datasheet)

My ESC is a Maker-x DV4S. It can handle “100A phase current on each side” (link)

Initially, I ran through the VESC Tool Motor Wizard using medium outrunner as my motor type, because the VESC Tool docs says “If you want to use the VESC ESC as a controller for your electric skateboard or scooter, the 750g Medium Outrunner is 99% chance your motor to choose.” The default max power loss for this option is 120W. After completing the wizard, my motor max current and max brake current are set to (+/-) 27.44A.

So, here are my questions:

  1. Is medium outrunner the appropriate choice for my motors?
  2. What does the 120W max power loss refer to? Should I set it higher?
  3. Are my motor currents appropriate? If not, how do I determine appropriate values? Does having a dual ESC affect these values?
  4. Since my ESC is dual channel, should I set my battery max current to half of its total for 45A on each channel?

I feel a bit in over my head, so some help would be greatly appreciated. Thanks!

2

I am right there with you. I however, am a snowflake, so my thrusts, and braking actions are mild, so I opt for safety in settings. All while retaining a torque capable of throwing me on my keister. I am angry they do not have a step by step guide to setting up vesc.

In reality, leaving us to wonder a lot leads to fire risk. Future of PEVs in general. We neeeeeed to step up our games.

3

Hi!

I used another “540W” version of Meepo hubmotors for an build I did in 2019. After some testing I set 40A for each motor (motor max) but oly 20A battery max because I did use some old 18650GA cells that are not powerful at all. (12S3P) My new battery is made of Molicel P42a 12S3P. (Building it right now)

I have used that board for comuting to work for 3 years (during summer) so it worked just fine, but a bit underpowered battery that shows its weaknes when riding fast.

P42a cells are specified as 45A cells, but real test shows that they are best used at 30A max continuous. But you can of course push them harder in shorter bursts as long as they dont get to hot. So 2P battery = 60A continuous :+1: or battery max 30A per motor. I would test that, then rise it a bit if I find that the battery wont get to hot. Do you use a smart bms so you can se info about your battery through an app?

This is my setup on that board with Meepo 540W hubs: Meepohub setup 18650GA battery. 40A - Motor Current Max -33A - Motor Current Max Brake 130A - Absolute Maximum Current 20A - Battery Current Max -8A - Battery Current Max Regen 36V - Battery Voltage Cutoff Start 33V - Battery Voltage Cutoff End 8V - Minimum Input Voltage 57V - Maximum Input Voltage 20 - Motor Poles 1 - Gear Ratio 100 - mm Wheel Diameter Li-ion - Battery Type 12 - Battery Cells 10Ah - Battery Capacity 1200 - rpm Sensorless ERPM (900rpm på den kassa sidan) Max - Maximum Wattage

4

Hi!

I only have the BMS which came with my battery. It’s very basic and is only there for charging through a charge port (I bypass it for discharge). I don’t think theres a temperature sensor in my battery, so I’m gonna put my max discharge current to 30A per motor to be safe. What is too hot? Would I be able to feel it though my plastic enclosure? Thanks for providing your parameters - I lowered my max regen current from -4.2A to -8A. Is this okay? At high speed, the braking is not very strong at -4.2A.