Can battery configuration help with torque?

[laerciohj]

Using machine translator, strange things can appear

Hello guys!

I have a preference for extracting torque in my kit (Cyclone 3000W) as it is for urban use and I have to overcome slopes. I am riding a battery. I wonder if her setting helps in my goal.

I have 140 Samsung 35E cells https://lygte-info.dk/review/batteries2012/Samsung%20INR18650-35E%203500mAh%20%28Pink%29%20UK.html

Should I mount a lower voltage and longer battery life (48V ~ 32Ah) or longer voltage and shorter battery life (72V ~ 22Ah)?

I don't know if I'm right, but the higher the electric current, the greater the torque.

Since this motor is not suitable for continuous 3000W, but should have no problem for continuous 2000W, the 48V battery may be more cost effective for my purpose as I can maintain continuous 40A at 48V but not 72V.

What do you recommend?

 

[john61ct]

36 or 48V

higher volts only adds top speed

lower volts more efficient for torque

But that "longer life" is not a thing, no difference there

 

[fechter]

Torque is a function of motor current. But the current is limited by the controller. As long as your batteries can supply the current at the limit, it won't matter much what your battery configuration is. When the controller is less than 100% duty cycle, the current going to the motor will be higher than the battery current. This happens when starting from a stop or climbing a steep hill. Once the motor speeds up enough, you can get to 100% duty cycle and the motor and battery current will be equal.

To answer your question, if you are doing a lot of steep hills, you will probably be better off at the lower voltage.

Two packs with the same energy (kWh) but different voltages will give the same range if the bike is ridden at the same speed, but a higher voltage pack will allow higher top speed, which uses up the energy faster (less range).

 

[laerciohj]

Thanks for the confirmations!

I will work on building the 48V battery, following the recommendation.

But all this is intriguing. If it is the current that determines the torque, what is the need to work at low voltage? What is the difference in torque between 72V 40A and 48V 40A if both work with 40A? Why does high voltage reduce torque?

I will propose hypotheses, but your confirmation is more interesting:

1 - High voltage (V) and high electric current (A) result in higher power (W). This leads to rapid system heating and current control to reduce heating, which reduces torque.

2 - High voltage (V) requires lower electric current (A) to reach certain power (W), which results in lower touch.

 

[john61ct]

I'll try. Voltage is a function of rpm, just as current is a function of torque. So the higher voltage level does not give any advantage except when greater top speed is desired.

And since

A = W/V

at lower **motor** voltages, getting the amps required for high torque takes more power.

What is the difference in torque between 72V 40A and 48V 40A if both work with 40A?

Those are **battery** voltages

In the motor, neither of those voltages are reached until a high rpm.

Amps are what creates high levels of heat. So once rpm increases, higher voltages are an advantage - same power at lower amps - but only then, not in the earlier low rpm stage where greater torque is required.

The controller has "more work" (less efficiency) when the difference between battery and motor voltage is greater, as if it were a DCDC converter.