GoldenMotor.com Forum
General Category => General Discussions => Topic started by: Nick on March 27, 2008, 03:29:30 PM
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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?
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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.
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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!