Explaining Terminology Used In Electric Motorcycles

If you are learning about how to tune a Surron, Segway, Talaria or other eMX bike and need a Tuning for Dummies guide, this can help you understand some of the terminology you are finding out there as related to electric motorcycles and EV's in general.  Take a look and hopefully you'll learn something new about your eMX bike!

EV Terminology

This is "the brains" of your bike.  It is essentially a computer programmed to operate the electrical system of your bike and take inputs from components like your throttle and output the correct voltage and amps to your motor at the right time as well as provide safety thresholds to protect the electronics (and the rider) if something isn't within spec.
The tune is basically a software file full of values that is loaded into your controller which sets all of the parameters needed for your bike to operate properly.  There are 100's of settings that can be applied and therefore tuning should be left to those with a lot of experience and know what these values mean...aka the professionals who do this for a living.  Many of the items below have settings within the tune and this is how your bike is programmed to operate.  
Watts is how you measure power and it's calculated based of volts and amps.  1W = 1v * 1A

Volts is the amount of electromotive force.  Think of this as water pressure in a hose and how fast the water shoots out of the hose.


A measure of how much current is flowing through a circuit.  Think of amps as the size of the hose that the water flows through.  

AmpHours (ah)
You will see this as the primary spec on aftermarket batteries to tell you how "big" the battery is, or how much energy it contains.  Amp hours is how much how much amperage the battery can provide for one hour.  However to understand the actual battery capacity you must convert it to Watts. (see below)
Kilowatts (kW)
This is the "15kw tune" number that you often see and it means this tune has a maximum output of 15,000 watts, this is burst and not sustained power.
Phase Amps
The maximum amps output by the tune, think of this as torque.  Amps are related to voltage, when you run 400amps at 60v it is less power than 400amps at 72v.  Amps also produce heat which can damage your motor or electronics.
Field Weakening
A tune setting that allows the electric motor to essentially "over-rev" at higher RPM's which results in a higher top speed.  If your motor is only rated for 5000RPM field weakening can in gas terms change the timing on the motor to allow it to spin past 5000rpm and over-rev.  You loose torque and efficiency when this happens.  Most tuners limit field weakening to a maximum of 20-25% because this can damage your motor.
Battery bypass
This is a physical process where the battery is opened up and the discharge circuit is cut from the BMS and discharge now "bypasses" the BMS directly into the controller.  This allows full battery discharge rates, but without a BMS controlling the discharge you can now reduce the life of your battery if the tune is asking too much from the battery.  The purpose of the BMS is to manage the charge and discharge of the battery within the specification of the manufacturer to ensure reliability and safety.  Most battery bypasses only affect the discharge, not charging, the BMS is still able to balance cells and manage the charge of the battery.  This procedure is dangerous and will void warranties and is not recommended.
Battery Voltage

Surron and Talaria are 60v from the factory and some people upgrade to 72v.  One interesting thing about batteries is the actual voltage varies based on how much energy is in the battery.  A 60v at full charge will be around 67v and it's considered dead 0% at 48v.  This is why your bike looses power as your battery drains.  Voltage Sag described below will also lower battery voltage while riding.  

Battery Voltage Sag
This is caused by drawing power (amps) from the battery at high loads the voltage will be lowered in your battery.  If you have a bypassed OEM battery this can be very dramatic below 40% because your voltage might drop below 48v which causes your tune to cut power so that you do not damage your battery, motor, or controller which have 48v protection limits.  Aftermarket batteries also have voltage sag, but were designed for higher amps and sag less than an OEM battery.
Almost all electric vehicles implement regen to harvest energy from your braking and put it back into your battery.  Heavy regen will harvest more energy than light regen.  While riding the bike you can feel this when you completely let off on the throttle and it feels like you are using your brakes, this is regen acting like a brake and harvesting energy.  If you are a motocross guy/gal heavy regen feels like a 4-stroke and light regen feels like a 2-stroke when you let off the gas.  If you're a pedal biker, they feel like regen is turned off!
Throttle Voltage
The way your electronic throttle works is by outputting voltage to your controller.  When your bike is idle with your hand off the throttle it's outputting a low voltage signal to the controller to tell it not to accelerate, as you twist the throttle the voltage increases telling the controller to accelerate the bike.  The voltages are usually around 0-5 volts and this is how your controller knows how "fast" you want to go.  If you have an aftermarket throttle like a Domino or Magura the voltages are different than your OEM throttle and it requires a throttle tuning session by a technician who has access to the controller or if your controller has a companion app you can usually tune the throttle yourself in the app.
Hall Sensor
If you're familiar with gas engines it's essentially what sets the timing on your motor.  If it's out of alignment with the controller tune value  you can have odd behavior such as slow or jerky acceleration, excess power drain, or an overheating motor.  A tuning app for your controller will allow you to run a test to set the proper hall sensor alignment which will optimize your motor efficiency and power.
An app from ASI that is only accessible to authorized dealers and it is used to load tune files into the BAC controllers, make adjustments to parameters, calibrate, and view errors among other things.  The general public does not have access to this app because without proper training you can easily destroy your bike with the wrong settings.


Helpful Mathematics (aka Myth Busters)

To compare two batteries together with different voltages to understand how "big" they are you'll need this formula to convert the batteries to watts which tells you how much energy is available within the battery. 

Watts = Amps * Volts 

This is important to understand when shopping for batteries, because a common mistake is that the battery with the most "ah" will have the longest range, however this is only true if both batteries are the same volts.  Let's look at a common example where some think a 72v battery will have less range than a 60v:

60v * 50ah = 3000 Watts

72v * 42ah = 3024 Watts 

By converting to watts we can see that these batteries are nearly identical in capacity and the 60v is not going to have more range than the 72v.


This article covers some of the most common settings that are often discussed and we hope you found it helpful.  If you have suggestions on additional information post it in the comments below and teach us all something new!

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