Originally Posted by cliftonts
How do the voltages work? I've seen you can run at 12 for testing and people seem to be discussing many voltages as options for the same kit. So is it a case that I could use 3 lithium batteries to give me 12 volts with pathetic range and then add 1 more to run at 15v, 2 more to run at 18v? Or do we need to stick to the figures people are quoting? 48v, 72v, 96v, 144v etc. What's the maximum we can go to?
Although what I'm about to say does not answer your question directly (and in parts a bit off on a tangent), it is something to keep in mind when working things out.
There is a relationship between power (P), voltage (V) and amps (I) as expressed in this formula:
P = V * I
where P is measured in Watts (W)
V in volts (V)
I in amps (A).
So if for example, you have a 48 volt system and 200 amps is being pulled,
power is 48V * 200A = 9600 W = 9.6KW
If you double the voltage (and keep the amps), then 96V * 200A = 19600W = 19.6KW
Another thing to think about is that if hypothetically for arguments sake you only needed 9.6KW, by running 96 volts, then you only need 100 amps to get the same power as if you were running 48 volts at 200 amps.
ie. 48V * 200A = 96V * 100A = 9600W = 9.6KW
However, with the higher voltage and lower amps, the cables don't have to be as thick compared to lower voltage and higher amps.
Thick cables = more weight.
That is one reason why it is desirable to have higher voltages.
The maximum voltage you can go up to is dependent on things like how much voltage the controller, electric motor, etc can handle.
With an Electric Motor, I've been told the thickness of the winding determines the maximum current and the insulation of the winding governs the maximum voltage it can handle.
Keep in mind that motors and controllers typically have a continuous current rating and peak current rating which you need to keep in mind. They can only run at peak current for a very short time - need to look at documentation for controller and motor for what that time is.