I can help with some of the technical details. For instance, from the weight of the vehicle and the inclines you need to climb and the speeds you need, and the gear ratios from the motor to the driving wheels (and their outside diameter), I can determine the motor torque and power. This translates to a certain size motor with a certain number of poles or nominal RPM. Then you need to determine your average driving needs in terms of watts/mile, and the maximum range you need before recharging.
From this you can find the total energy needed for your battery pack. There are pros and cons to lead-acid vs lithium and generally the LiPo is the best choice for long-term cost and performance.
You also have a choice as to what motor and controller you want to use. I prefer 3-phase standard induction motors which can be controlled with a standard industrial VFD, and require a battery voltage of at least 300 VDC. Or you can use a DC-DC converter to get the voltage from a smaller number of batteries. That is also my choice and I am working on a design that can do that economically and reliably.
The ultracapacitors can be very helpful for short-term surge power and efficient regeneration for braking. AFAIK this is not possible with series-wound brushed motors but other motors can also work as generators and dynamic brakes. The energy in ultracaps is determined by the formula:
E=0.5C*V^2
This is in watt-seconds, or joules. So your 2000F 2.5V capacitor can store 6250 W-seconds. or about 2 W-hrs. Generally about 300W-hr per mile is used, so to get a 30 mile range you need 9000 W-hrs. This would require 4500 of these capacitors and 60*4500=270,000 RMB = $46,000. You would need to connect them in banks of about 120 each for 300 VDC. This expense is probably 10 times that of LiPo, but they will last 20 times longer.
These are rough calculations. You need to factor in efficiencies and how much of the potential energy in the batteries and/or ultracaps you can extract. Batteries tend to have a fairly level voltage until maybe 50-60% of capacity has been used and then the voltage drops and impedance rises so you can't get much more out. Capacitors have a logarithmic discharge into constant power load so the voltage is 1/2 when 3/4 of the energy has been used. And most controllers will not operate below about 70% of their nominal input voltage, so a VFD that normally operates on 320 VDC will shut down below 200VDC.
You should be able to work out these calculations for your own needs, or there are spreadsheets and calculators that can help. Let me know more, and good luck!
From this you can find the total energy needed for your battery pack. There are pros and cons to lead-acid vs lithium and generally the LiPo is the best choice for long-term cost and performance.
You also have a choice as to what motor and controller you want to use. I prefer 3-phase standard induction motors which can be controlled with a standard industrial VFD, and require a battery voltage of at least 300 VDC. Or you can use a DC-DC converter to get the voltage from a smaller number of batteries. That is also my choice and I am working on a design that can do that economically and reliably.
The ultracapacitors can be very helpful for short-term surge power and efficient regeneration for braking. AFAIK this is not possible with series-wound brushed motors but other motors can also work as generators and dynamic brakes. The energy in ultracaps is determined by the formula:
E=0.5C*V^2
This is in watt-seconds, or joules. So your 2000F 2.5V capacitor can store 6250 W-seconds. or about 2 W-hrs. Generally about 300W-hr per mile is used, so to get a 30 mile range you need 9000 W-hrs. This would require 4500 of these capacitors and 60*4500=270,000 RMB = $46,000. You would need to connect them in banks of about 120 each for 300 VDC. This expense is probably 10 times that of LiPo, but they will last 20 times longer.
These are rough calculations. You need to factor in efficiencies and how much of the potential energy in the batteries and/or ultracaps you can extract. Batteries tend to have a fairly level voltage until maybe 50-60% of capacity has been used and then the voltage drops and impedance rises so you can't get much more out. Capacitors have a logarithmic discharge into constant power load so the voltage is 1/2 when 3/4 of the energy has been used. And most controllers will not operate below about 70% of their nominal input voltage, so a VFD that normally operates on 320 VDC will shut down below 200VDC.
You should be able to work out these calculations for your own needs, or there are spreadsheets and calculators that can help. Let me know more, and good luck!
