Question of Controller

[WindriderAU]

Hi Team,

Getting the bike together.

Settled on a Crystalit 408
48V LiFePo 20AH Batteries

What differences will the 20A controller be compared to going with the 35A controller. I understand the 35A controller will flatten my batteries quicker, but how much quicker, will I expect an overall reduction in range? etc, etc.

Any assistance would be greatly appreciated.

Thanks

 

[safe]

The first chart is an unrestricted motor.

The second chart is a motor with a current limit.

Basically the higher the current limit the lower down in the powerband you can go and still get a lot of power. There is a point of diminishing returns if you go below the parabola in the first chart. The power peak (black line) is a parabola... the current limit is usually set so that you are forced to stay closer to the efficiency peak over on the right. (blue line)

Note: The scaling on those charts is different, so don't try to compare exact values with each other, just try to pick up on the theory and learn what the shapes are about.

The "bottom line" is that a higher current limit means more power and that means more heat and more battery drain. However, you always have the option of "throttle twiddling" (a derogatory term I invented :wink: ) which is the act of carefully managing partial throttle so as to simulate your own current limit. All a controller really does is establish what percentage of time the switch is open... the duty cycle... and you can outsmart the controller if you "under" throttle most of the time. When the throttle is low enough the controller is not allowed to deliver the peak current limit and so you save energy.

It's a lot like driving a car... if you gas it all the time (full throttle) then you will use up more fuel. If you lean out the carburator (like deciding on a lower current limit controller) then you lose a little power.

Dragsters tend to not want to limit fuel intake... :wink:

 

[xyster]

Hi Team,

Getting the bike together.

Settled on a Crystalit 408
48V LiFePo 20AH Batteries

What differences will the 20A controller be compared to going with the 35A controller. I understand the 35A controller will flatten my batteries quicker, but how much quicker, will I expect an overall reduction in range? etc, etc.

Any assistance would be greatly appreciated.

Thanks

The 35A controller will give you almost twice as much power for accelerating quicker, and climbing steep hills better. Depending on the type of bike, the 35A won't increase your bike's top speed by very much compared to the 20A.

You don't have to use the extra power though -- that's what the throttle is for. So the 35A controller won't necessarily drain your batteries any faster. But that extra power is hard to avoid using; if you tend to ride fast and hard, you will burn through your pack's capacity almost twice as fast; if you tend to ride at a steady, moderate speed, you won't notice much if any loss of range.

A 48v 20ah LiFePO4 pack has a lot of capacity by typical ebike standards anyway. Unless the higher price is a problem, I'd choose the 35A controller.

 

[DHarris894]

Hi,

I am new to the group and just wondering which battery supplier you chose for the 48v 20ah battery? How much will it cost?

Thanks

 

[WindriderAU]

Still waiting on final costs including shipping so don't know exactly yet. They are getting back to me with the final price. Will post once I get it. Hopefully know over the next day or so.

http://www.gmbattery.com/English/Main.asp