Difference between pages "Premade or DIY" and "Volts and Amps"

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(Created page with "Premade or DIY, the decision can be tough. Most people don't have any experience in assembling mechanical devices or electrical work. Overall, DIY seems to be the way to go if you can. Many premade bikes use proprietary batteries controllers/shapes and some even use controllers that won't work without the exact same brand battery. a DIY bike can be repaired with off the shelf bike parts and the battery/controller/motor can be replaced with pretty much any other batter...")
 
(Created page with "Volts, Amp, Amp hours, watts and watt hours, what do they mean for an e-bike? These are the units of measurements for batteries, controllers and motors. Lets dive into what each means in detail: ==Volts== Volts is directly related to max RPM for a given motor. For a given battery voltage will slowly decrease as it discharges (See https://cdn.discordapp.com/attachments/593205534862082075/620503053178503181/1545991790982-png.png for chart). ==Current== Current (measure...")
 
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Premade or DIY, the decision can be tough. Most people don't have any experience in assembling mechanical devices or electrical work.
Volts, Amp, Amp hours, watts and watt hours, what do they mean for an e-bike?


Overall, DIY seems to be the way to go if you can. Many premade bikes use proprietary batteries controllers/shapes and some even use controllers that won't work without the exact same brand battery.
These are the units of  measurements for batteries, controllers and motors. Lets dive into what each means in detail:


a DIY bike can be repaired with off the shelf bike parts and the battery/controller/motor can be replaced with pretty much any other battery/controller/motor of similar spec. In the event of damage/failure of the frame the entire electrical kit can be swapped to a new bike. This gives you incredible flexibility to repair your vehicle should any particular company shut down in the future or have excessively high prices for some parts.  
==Volts==
Volts is directly related to max RPM for a given motor. For a given battery voltage will slowly decrease as it discharges (See https://cdn.discordapp.com/attachments/593205534862082075/620503053178503181/1545991790982-png.png for chart).


You can also make sure your batteries are from a name brand battery manufacture with DIY. Most prebuilds give little to no indication on who makes their batteries or who makes their cells.  
==Current==
Current (measured in amps) is directly related to the torque of your motor. You will often see a controller specify its 'battery amps' and 'phase amps'. Phase amps are your peak torque at lower RPM, where the controller can exchange voltage for amps to give you extra torque at low speed. Battery amps are what will be drawn from the battery. You absolutely must have a battery rated for the same or more amps then your controller is rated to use or you will damage your battery when the controller draws too much.
==Watts==
Voltage * battery Amps = Watts. Watts are your power. In fact it takes 745.7watts to make one horsepower. While voltage determins your absolute max RPM, without more watts you won't go any faster unless you where limited by the motor reaching its max RPM before you ran out of watts.
==Amp Hours==
Amp hours are how many amps your battery can give for one hour. For example if it was 10 amp hours, it could give 10amps for one hour, or 20 amps for 30 minutes, or 5amps for 2 hours. You might be mistaken into thinking that amp hours are equal to range, but that is only true for a given voltage as watt hours are the true unit of energy storage.
==Watt Hours==
Watt hours are Amp hours * Voltage. They tell you the true power capacity of a battery. In fact you will often find electric vehicles energy efficency expressed in watt hours per KM or mile. (wh/km or wh/mi). For a very rough idea, you can assume about 10wh/km for very slow riding at 25kph or below on flat ground, 20wh/km for fast riding up to 45kph or on slightly hilly ground, and up to 40wh/km for very fast riding at up to 60kph or on very hilly ground.  Exact figures vary greatly but this gives you a rough idea.
==C Rating==
Cells have what is known as a C rating, this is basically how quickly they can be discharged, with 1C being the current needed to fully discharge the cell in exactly 1 hour. You can calculate the peak discharge current by multiplying the AH rating and C rating hence for a 3.3Ah cell, 1C would be 3.3A and take 1 hour to discharge at that current. For a 2.5Ah cell, 1C would be 2.5A and also take one hour to discharge. a 2.5AH cell at 2C would fully discharge the cell in 30 minutes and at 5A current, 4C is the rate that would fully discharge the cell in 15 minutes at 10A for a 2.5AH cell, and so forth.


That said, it is a lot easier to just buy a product and ride it. Due to the high currents involved in e-bikes it can be dangerous to DIY if the electrical work is incorrectly done. Same with the mechnical work. We highly recommend you not convert 'department store' bikes such as Walmart, Canadian tire, etc due to their low part and assembly quality and instead stick to bicycles sold by bike shops or 2nd hand bikes.
Note that the C rating is only the maximum you can safely draw from the cell, if you only draw at a lower current the cell will take as long to discharge as a lower C rated cell of the same Ah value

Revision as of 08:19, 15 January 2022

Volts, Amp, Amp hours, watts and watt hours, what do they mean for an e-bike?

These are the units of measurements for batteries, controllers and motors. Lets dive into what each means in detail:

Volts

Volts is directly related to max RPM for a given motor. For a given battery voltage will slowly decrease as it discharges (See https://cdn.discordapp.com/attachments/593205534862082075/620503053178503181/1545991790982-png.png for chart).

Current

Current (measured in amps) is directly related to the torque of your motor. You will often see a controller specify its 'battery amps' and 'phase amps'. Phase amps are your peak torque at lower RPM, where the controller can exchange voltage for amps to give you extra torque at low speed. Battery amps are what will be drawn from the battery. You absolutely must have a battery rated for the same or more amps then your controller is rated to use or you will damage your battery when the controller draws too much.

Watts

Voltage * battery Amps = Watts. Watts are your power. In fact it takes 745.7watts to make one horsepower. While voltage determins your absolute max RPM, without more watts you won't go any faster unless you where limited by the motor reaching its max RPM before you ran out of watts.

Amp Hours

Amp hours are how many amps your battery can give for one hour. For example if it was 10 amp hours, it could give 10amps for one hour, or 20 amps for 30 minutes, or 5amps for 2 hours. You might be mistaken into thinking that amp hours are equal to range, but that is only true for a given voltage as watt hours are the true unit of energy storage.

Watt Hours

Watt hours are Amp hours * Voltage. They tell you the true power capacity of a battery. In fact you will often find electric vehicles energy efficency expressed in watt hours per KM or mile. (wh/km or wh/mi). For a very rough idea, you can assume about 10wh/km for very slow riding at 25kph or below on flat ground, 20wh/km for fast riding up to 45kph or on slightly hilly ground, and up to 40wh/km for very fast riding at up to 60kph or on very hilly ground. Exact figures vary greatly but this gives you a rough idea.

C Rating

Cells have what is known as a C rating, this is basically how quickly they can be discharged, with 1C being the current needed to fully discharge the cell in exactly 1 hour. You can calculate the peak discharge current by multiplying the AH rating and C rating hence for a 3.3Ah cell, 1C would be 3.3A and take 1 hour to discharge at that current. For a 2.5Ah cell, 1C would be 2.5A and also take one hour to discharge. a 2.5AH cell at 2C would fully discharge the cell in 30 minutes and at 5A current, 4C is the rate that would fully discharge the cell in 15 minutes at 10A for a 2.5AH cell, and so forth.

Note that the C rating is only the maximum you can safely draw from the cell, if you only draw at a lower current the cell will take as long to discharge as a lower C rated cell of the same Ah value

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