Quote:
Originally Posted by MPaulHolmes
Current <==> Torque. Voltage <==> MAX RPM!
So, for a given power, you can have higher top speed but lower torque, or lower top speed and higher torque.
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You got it Paul.
Also, keep in mind that batteries, especially lead-acid, care a lot about how many AMPS are being pulled out of them. If you are pulling twice as many amps from a battery, you will get less than half the total energy out of it.
So, lets compare a 72V battery pack to a 144V battery pack.
If it takes about 10 horsepower to push your car down the road, that comes to 100 amps at 72 volts. But in a 144 volt pack, it's only 50 amps.
Since the only thing the batteries car about is amperage, line up lots of batteries in a row (series) to get the high voltage.
In fact, using twice as many batteries, which are each physically half as big, will get you more range without changing the weight of the car at all!
You can also use thinner cabling and lower power connections as well. Look at the 4 power cables going into the motor on this
AC Neon Conversion
The cables are about the thickness of a pencil, but the car will run at around 300 volts. At that voltage, the cables only need to carry 24 amps for the same 10 horsepower as the 72V car using 100 amps!