# Is this 3 KW motor good enough?



## kingzilla (Sep 12, 2016)

Hello all,

I am new to this forum for pardon if some of the rules for posting were not followed. My friends and I recently build a custom reverse trike EV. It weighed at around 400-450 kgs, which includes the space frame, four 12V lead acid batteries rated at 100 Ah, seats, motor, etc.
Our motor was a 3 KW BLDC motor which has been used on other golf carts or EV builds. With our calculations we were expecting a top speed of roughly 60-70 km/hr. Our gear ratio was 1:4 (motor sprocket had ten teeth, rear sprocket had 40 teeth). However, the performance of the EV trike was really poor. The acceleration was slow and the top speed achieved was only 10 mph (roughly 16 km/hr). We did a lot of calculations, and obviously we went wrong somewhere. But theoretically could a 3 KW BLDC motor drive an EV trike that weighs around 500 kgs with a passenger to at least 35-40 mph or is that too much to ask? I've seen electric rickshaws in Asian countries going up to 25-30 mph on a 1 KW motor, 48 V, and carrying 4-5 passengers with them!

Any suggestions or replies would be greatly appreciated. 
Thank You!


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## Yabert (Feb 7, 2010)

With 3 Kw on flat road, you should reach at least 40-50 km/h.
Your problem is probably that you don't have 3Kw at the motor shaft.
You will need to monitor voltage and Amps at the battery output.

Also, maybe your ratio isn't adequate for this small motor. What is your wheels diameter and give more details about the motor.


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## kingzilla (Sep 12, 2016)

The motor specifications are listed below:

1. Voltages: 48
2. Rated power: 3KW
3. Peak power: 6KW
4. Speed: 3000-5000rpm
5. Rated torque: 10 Nm
6. Peak torque: 25 Nm
7. Efficiency: >90%

My rear wheel which is connected to the motor is 24 inches in diameter.
If you need any further questions please let me know.


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## Yabert (Feb 7, 2010)

Your drive ratio is a bit low (5 or 6:1 should be better), but it don't explain your poor performance result.

Problem is somewhere else. Controller adjustment? Battery voltage sag very low under load? Brake drag?
I suggest you to monitor power output of the battery. I guess you only have few hundred watt of power.


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## MalibuMan (Feb 28, 2015)

If you are using the GoldenMotor 3KW BLDC I am highly interested as I plan to use the same motor, also at 48V.

Differences between us:

1. My kart will be lighter ~300 kg with me in it.

2. I also want to go 50 km/h but I calculated a much bigger reduction, I plan to use 2 sets of 20/60 tooth gears to reduce the motor RPM by 9x. Each set of 20 to 60 teeth lowers the RPM by 1/3rd


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