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Electric Motorcycles

by Burak KAZAR | April 25, 2020 at 6:13 pm

In Reply to: Batteries for motorcycle conversion

Hi, first of all i wish you good luck on your new project! You have a serious performance targets for an e-motorcycle. It will be something like e-superbike. I am currently working on my own electric conversion project of 93′ Vespa PX200E electrification project. I am going to use a 2kw hub electric motor and my target is 50km/h max speed and 50km’s range which is enough to go to work or weekend activities.

Let’s discuss about your case.

Your electric motor link is not working but i did a small research and found out that;
it’s a 12kW mid-drive electric motor and can operate between 24-96V.

There are many decisions to make before choosing your battery capacity but i’ll make some assumptions to explain it.

Voltage: Higher voltage is better because you will need lower amount of current (amps) to reach the required power output (watts). More amps=more heat=lower efficiency. Usually you will find 48,52, 60 and 72V systems. Let’s say that your motor will be operated with 72V.
Battery Type: creating packs using Li-Ion 18650 type batteries are industry standard now. Also you are going to use a powerful motor, needs high quality volts so let’s stick with this type. Each battery has it’s own Amps/h capacity. you can find nice 18650 type batteries rated 3000mAh or higher.
***Since i don’t know your plans about gears, i assume it’ll be 1-1 ratio, though my calculation will be very basic. The gear size will effect the performance massively.

Firstly let’s convert your range to “usage time”. If you use your motorcycle 90mph for 50miles, you are going to use it for 0,6 hours.

Secondly let’s calculate your current needs to full power;

Our formula for calculation will be ; Watts=Amps x Volts
So if we want to calculate required amps to use full capacity of the motor in theory (without efficiency) 12.000W=Amps x 72V
Amps = 166.7

So you need to feed your motor 166.7amps for 0.6 hours. so your battery pack should be “minimum”; 166.7×0.6 = 100Ah

So you need to create a 72V 100Ah battery pack (with %100 efficiency which is impossible. you need to multiply it with 0.8 at least to be safe).

As i said in the beginning, 18650 batteries are an industry standard. You can find many variations from many different brands.

I used “INR18650HG2 LG Chem” batteries for calculations.

3.6V
3000mAh
20A
47g/piece

To reach 72V, which is your operating voltage, you need to connect “20 batteries in series”.
To reach 100Ah, which is your power capacity/h, you need to connect “34 of 20 batteries packs(which gives 72V) in parallel”

In total you’ll need to create a battery pack which includes 680pieces of 18650 batteries, supplying 7,344kWh (12kW*~0,6h), weighing 32kg without any casing.

This is a serious amount of battery and serious amount of voltage&current. If you are going to do this project that powerful, please be careful about the electricity.

To sum up;

I tried to show you the calculation method for battery selection. But to calculate it more precisely, you need to decide many other design topics. If you want to play around about different possibilities, there are many websites and phone applications for this. I am using “Battery Package Calculator”.

If you want to check my project, please don’t hesitate to check my youtube channel;

https://youtube.com/220garage

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