# Have a few question, starting a project bike

I’m going to build a electic motorbike.
But i’m confused by a few things when it come to the motors.
When i look at the motors specs it has constant current 110A and then max current 200A (5sec). the max current has a time next to it… what does this mean? can it only have max current for 5 seconds?

also would it help having an electric motor joined to a gear box so that the motor can stay at low rpm where all the torque is? I figure i can achieve better top speed with a gear box…

[QUOTE=albonator316;5107]what does this mean? can it only have max current for 5 seconds?[/QUOTE]

Electric power is delivered as a combination of voltage and current (amps). When you multiply the two together you get power in watts… which is what you are after. The problem with current is that heat is produced in direct proportion to the current, so a motor can only run at high current loads for a short period of time before it overheats.

So that’s why… current means heat.

Thinking a little more you realize pretty quickly that more voltage is going to give more power, but you need to be careful because there’s a bunch of other stuff that goes on that amplifies the heat at low rpms due to the PWM controllers we use.

The more you know, the more you realize there is more to know.

Some of the programmable controllers allow you to set a limit on the armature current (motor current) and that gives you more flexibility in voltage selection.

[QUOTE=albonator316;5107]I figure i can achieve better top speed with a gear box[/QUOTE]

Yes, however, there’s a limit to the advantages. From what I’ve been able to calculate there is a relationship of about two or three to one between motor power and it’s ability to be efficient and effective. More power covers a lot of deficiencies. Some people are using gears already with success. No gears is easier.