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Originally Posted by Spaghetti Man
If I want 10kw of power (my current 125cc motorcycle's power) and I use 4.5 litres of fuel to travel 160km (35km per litre). I would need at least 4.5 x 2.5kw 11.4kw of power in my batteries to make the example 160km trip.
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10 kw is over 13 HP. Do you need that continuously (for cruising at 100 kph) or for short bursts of acceleration?
I think the forklift motors that have been used in budget conversions put out that sort of power to move small cars (at maybe 50 kph).
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If a Panasonic 18650 is 3.7 volts and 3.4 amp
3.7 volt x 3.4 amp x 1 = 12.58 watt hour.
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12.58 w-h per battery is right if 3.7 is your average voltage during discharge.
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I need 30 Panasonic 18650 batteries.
3.7 volt x 3.4 amp x 30
= 111 volt x 102 amp = 11,322 watt hour
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111 volts is 30 cells in series at 3.7V each. Good for calculating your capacity. At 4.2, your charger would be putting out 126V to get to 100% charge for the 30 cells in series. At 0% charge, your batteries would be 2.75V - 2.50V, for a pack voltage of 82.5V - 75V.
10 KW (your desired output) / 111V is 90 amps. The panasonic batteries can do 2C output, or 2X rated capacity. So about 6.8A for each cell. To get 90 amps, you need 13 cells in parallel.
That's 13 batteries wired in a parallel set, and 30 sets of batteries wired in series to get 111V. 390 batteries.
That's part of why you need to know if you need 10 KW continuous, or just for a few seconds to accelerate up to cruising speed, when your power consumption goes down.
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30 batteries
Is this correct?
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I don't think so
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At a weight of 46 grams each the total 30 batteries will weigh 1.380kg which is lighter than my current lead acid motorcycle battery.
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30 * 12.68 w-h is 380 w-h. That may work for electric assist on a pedal bike.
I think you need 13 times that if you want 10 kw.
You also need to know how long you drive at 10 kw. 160 km is a fair distance, so maybe 2 hours? (average of 80 kph including stops and acceleration). If you use 10,000 watts all the time, times 2 hours of driving, that's 20 kw-h.
20 kw-h is the size of a Nissan LEAF battery pack, so it's likely too big. But if you DO need 20 kw-h, at 12.68 w-h per battery, that means you need 1577 batteries(!!)
A quick search gives this (2009) article/blog at DIYelectriccar
Step 1: How to plan a DIY Electric Motorcycle - DIY Electric Car Forums
Perhaps some reading will help you get a handle on what power you need for cruising, depending on your chosen conversion.
There are motorcycle projects at ecomodder, but I'm not familiar with them
Looking forward to reading about your project!