AMPs, the "Work Horse" in an Electric Motor

As discussed in our previous article, E-bikes and Voltage, Why It Matters, Voltage and AMPs have a relationship in how your e-bike motor works.  If Volts are related to your expected top speed, then AMPs are related to the Torque your electrical motor and system will produce.  Where Voltage could be visualized as the speed of an electrical flow, which would lead to it's relation to top speed, think of AMPs as the depth of the electrical flow.  Similar to a wave hitting a wall.  If the wave is small it doesn't do much, but if it's a large wall of water, it could have enough force to move or even destroy the wall.  We'll get to why that's important too.  This depth of flow has the ability to "push" the motor around, and that motion is then translated into you and your electric vehicle moving forward.  

Sure, I guess, but in a later article we'll talk about how Wattage is a good general rule of thumb, but not the best reference.  Voltage and AMPs are calculated together to come up with Wattage.  For example, you might have a motor that is connected to a 48v battery.  They are then connected to a controller that has a certain rated Amperage capability and all of this is connected by wires that also have a certain ability to carry Amperage.  For the example, let's say it's a smaller 500w rated motor.  There's a 20A capable controller(the electrical "brainbox") and it's all wired for 15A.  Don't freak out, it's normal to "under-wire" an electrical system so you don't overheat the components.  In this case we're all good, check it out below.

Here's the fun math part:

48v X 15A = 720w Peak Output

As you can see, the above wired system will be able to provide more than enough wattage to meet or exceed the draw capability of the motor @500w rating.  We can adjust the number of AMPs in the displays/controllers as well.  Most of the motors are made to exceed their rating for short periods.  That's why you may find some motors that say, they "go up to" the next level of motor wattage rating.  Like our 500w motor mentioned being able to handle the potential 720w we may push to it.  What most companies are doing when they say it goes "up to" is upping the AMPs in a burst or turbo mode to give you more usable wattage from the motor.  

Keeping all of the above in mind, it's important to understand how and with what gauge your e-bike, e-scooter or e-motorcycle is wired.  You can have high capacity, high output controllers and motors, but if you have them wired to low flow power wiring, you'll be choking them off from the performance you expect.   

It's also important to understand the relationship above because you will notice it when you're riding and your voltage drains.  With e-bikes, e-scooters, e-motorcycles and to some degree all electric vehicles, there's a range of Voltage at which the motors can operate.  Your new electric vehicle or micro-mobility might be full speed when you take off for the day with a full charge.  When you're on your way home, you might notice, it doesn't get all the way to the top speed it did earlier.  This is due to that range of voltage operation.  As your battery drains down, that formula above also gets smaller.  Where before your battery was putting our 48v@15A, by the end of your riding, it might only be pushing 40v@15A=600w.

Now that's still more than our example motor would be rated for, but you will notice the reduced performance as the motor is now getting a lower overall wattage.  

Across all of that voltage and wattage drop off, the one thing that remains constant is the Amperage available.  This does fluctuate with your specific need at the time, you might only use 5A-8A at a moment to maintain speed vs. the full 15A to accelerate from a dead stop, but the electrical system is always ready to give you 100% of the torque generated by the AMPs flow at all Voltages the motor and controller can operate under.  Translated from tech speak: You get all the available torque all the time, no matter what your electric vehicle voltage at the time.  

As an additional note, don't be confused over the AMPs a motor or controller can handle and the AMP capability of which the whole system is rated.  You could have a super duper motor and controller, being held back by limited wiring.  Ask what AMP flow or Ampacity the wiring has going to the components and how that matches up with the capabilities of the respective components.

Now, for most of you, that should be good.  You should be able to go out in the world and ask, "How many AMPs is my new e-bike capable of?" and actually know what the salesperson is telling you.  Or maybe you just stumped them.  Good for you!  

But, if you want to get in the mind of our resident "Mad Scientist" and Founder (I'm not actually a scientist and I've never played one on TV, why do you think me "mad"?) keep reading below.  

First I have to say, I'm not mad, maybe a little crazy, but I like to think we all are in our own way.  As long as that crazy doesn't hurt anyone, who cares if I have a wild head of poofy mad scientist hair and live in a castle on the hill.   I don't like in a castle on the hill, but the hair thing is true.  More so, I just look at things a little differently and that's the same here at E-Powersport.  Enough about me, let's talk about AMPs.  So you kept reading and want to get deeper on Amperage and what you need to look for in your next purchase.  Yes or No?  

Yes, good, let's climb in this rabbit hole......

We already gave you a lot to work with above, what more can I say?  Well, to start with, Gauges!  No not like the speedometer, but I like how you think.  The gauges of the wires being used as well as the connectors and battery BMS.  That right, to really get to the beginning in all this, we need to go directly to the power source, the freaking battery and BMS.  These are both rated at certain Ampacities.  They will normally have 2 ratings, one that is nominal or normal functioning AMP rating and one that's the MAX, normally expected for very short periods of time.  The wiring coming from the battery pack, is rated for a certain Ampacity and stated at its MAX AMP Rating, but wait, there's more....

The connector used to connect the battery pack to the motor has, what?  That's right, a certain Ampacity.  And so on and so on and so on, till we finally get to the motor that turns all the AMPs that finally made it into mechanical energy.    Woohoo!  Now go raise some heck with your new knowledge!  

Still there?  OK, what else can I say about AMPs and how freaking important it is to know the overall Ampacity of your e-bike, e-scooter, e-motorcycle or other electric vehicle?  From my perspective, Voltage and AMPs are a much better way to think about your new transportation's capabilities.  Wattage is a fluffy bunny # that doesn't mean much when you start adding things like weight into the equations or by that I mean real world use.  As we had shown above, those short burst can be as high as 50% increase in total power consumption.  Forget Wattage and Watt Hours, that's for home use.  On these, you want to focus on Voltage and how many AMPs are being delivered to the motor over what time period.  Are they giving you an AMP boost capability, like we talked about and how will that effect your distance, or are these nominally functional AMPs for a steady AMP flow?  Don't get me wrong, I think Wattage has it's place, but it's more about usage than a scaled rating.  

Another important aspect of AMPs and AMP flow is how that can relate to usage and distance.  As the AMP flow usage fluctuates it takes certain amounts of the Batteries Ampacity or as batteries are rated, Amp Hours or AH.  This could be used to calculate "time x amps used" to display remaining Amp Hours available in the battery pack.  There's already the ability to view Volts left in a battery on most e-bikes, e-scooters, e-motorcycles, but knowing how many AMPs are left for draw could be a more accurate indicator of time/miles left on a charge.  And I guess, you could always slap the two together and give a remaining wattage level of the battery.  But I think the more discerning or power user, will want to know the Volt/AMPs too.

Here's a crazy thing to think about:

1 Joule = 1W per Sec = 1NM (Newton Meter)

Do we really need three of the same metric?  What the What?!?!

When motors are measured for Wattage it's in hours.  Our previous 500w motor example would be expected to use 500w an hour, not per second.  Keep that in mind, now the Newton Meter is a normal measurement for Torque of an Electric Motor.  Most 500w motors are rated @60nm.  That means a 500w motor is using 60nm, or 60watts per second, or 60 joules to propel you at its top power usage.  Even crazier is there's no rated Watt.  A Watt is as Watt, but a Watt can be applied to a measurement of time, there hasn't been a standardization across the Electric Vehicle or other electric industries.  However, both a Joule and a NM have been set in ratings.  Speaking of wheels and ratings, one of my favorite teams to reference for knowledge are the team at GRIN Technologies in Canada.  Rather than reinvent what they've already defined in both a deeply technical and eloquent way, I'm going to provide a link to their related article here.  

They get so deep, I use their tools, just awesome stuff:

Futility of Motor Power Ratings

There's more we can cover, we could talk about how electricity doesn't actually flow in a wire, but is a wireless transmission being provided by a series of magnetic fields generated across the wire.  But we'll save that for later....