RANGE THAT THE BIKE CAN COVER...

[Nick]

Hi ,

I bought the 500W kit, and I am intended to use 12V 17Ah SLA batteries. I want to be able to cover a distance of 35km (21miles) without pedaling on a flat terrain is that OK?

[OneEye]

As long as the wind isn't blowing you should come close.

At 20mph you will need about 360W, one hour at that rate will be 360 Wh.  360Wh/36V = 10Ah of delivered power.  Note that SLA's lose much of their "nominal" capacity based on draining faster than 20hours (0.05C).  So a 17Ah battery rated at 0.05C will only get you about 10Ah when drained at 1C (one hour).  I assumed a 1.2 peukert exponent.

Note, however, this represents fully draining the battery, which will significantly reduce the cycle-life of the batteries.

To play around with the numbers yourself, visit http://www.kreuzotter.de/english/espeed.htm to get an estimate of power requirements at a given speed.  Look up Peukert to figure out how much power a battery will give at a given draw rate.

[waynebw]

As another practical example to help comparisons etc,..

I have the 500W Kit, and 3x12v SLA batteries @ 7.2AH each.
I pedal very little, and I get close to a 20km distance, on flat, with light breezes.

I've done a 25km trip with light pedal assist along the way and still had some power reserved.

Hope this helps!