Battery Configuration E-Scooter

[dineshmdes]

Hi All,

I am a technology enthusiast residing in India. I joined the forum after a few years searching and gathering knowledge.
I am prototyping a vehicle with following configuration :
• Vehicle Weight : 110 Kg
• Motor 2000W 120 70H Mid Drive Motor
• Motor Type: BLDC Permanent Magnet Inner Rotor Motor With Hall Sensor
• Motor Design: Single axle
• Wheel: 12inch Wheel (as default)
• Rated Power: 2000W (peak power, pending)
• Rated Voltage: 72V as default
• Speed: 70KPH
• No-load rpm: 2800rpm without flux weakening, 4400RPM with flux weakening.

I need to decide on the battery pack for to achieve a range of 60Km and a max speed of 60kmph
Can you please help me define the li-ion battery pack for the same.

I have researched an calculated a few parameters :
• Battery Pack Capacity : 72V 28Ah
• Battery Cell : 3.6V 2.7Ah
• Battery Module : 18650

How can I calculate the rest of the parameters like :
• Discharge Current (Constant)
• Discharge Current (Peak)
• Discharge Peak Current Time (PWM)
• Nominal Voltage
• Cut-Off Voltage
• Peak Continuous Current, etc

Thanks in advance.

[eee291]

The rest of the parameters are based on the Cell you use.

Let's use Samsung 25r cells for example.

Max. continuous discharge current: 20A
Safe pulse discharge ratings: 95A < 0.5 sec, 65A < 1 sec, 40A < 5 sec, 30A < 6 sec
Nominal capacity: 2500 mAh
Nominal voltage: 3.6 V
Discharge end voltage: 2.5 V
Charging voltage: 4.20 +/- 0.05 V
Standard charging current: 1.25 A

So if you put 11 Cells in Parallel you will get 27.5Ah, and then put 20 rows of cells In Series (72V) for a total of 220 Cells.

And now you can calculate your battery specs simply by multiplying every value by 20 (Cells in series)

For example:

Discharge cutoff 50V (I would recommend 60V though)
Nominal Voltage 72V
Charge cutoff 84V

As for the other parameters, those will be multiplied by 11 (Cells in Parallel)

Max Cont. Discharge current 220A
Discharge current 6 sec. 330A
Nominal Capacity 27.5Ah
Standard Charging current 13.75A


If you have anymore questions I'll gladly try to help

[dineshmdes]

Hi,

Thanks eee291, appreciate it. This is really helpful.
I am looking for a off the shelf BMS (which can be programmed and connected to an IoT platform).
Can you please guide me on this. Also if there is something for a custom connected dashboard (which can be used for the electric bike to start with. OR are there any DIY on raspberry pi or arduino that can be referred. I extensively searched but couldn't find a comprehensive one.

Thanks in advance.

[eee291]

There is a thread about Bluetooth BMS and BMS with displays right here:viewtopic.php?f=14&t=88676


I personally use Bestech BMS 90% of the time, so I have no experience with those Bluetooth BMS. But I plan on buying some in the future.

But there are a bunch of talented and experienced people on this forum, I'd expect some decent answers if you create another Post or rename the Title of this one.

[dineshmdes]

Hi,

Thanks again eee291, appreciate it. Sorry for my late replies been busy with my first prototype.
The Bluetooth BMS thread is helpful, I will surely create a thread though.
Currently I will be using a outsourced battery pack with 20S protection circuit.

Thanks.