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Old 01-10-2012, 09:55 AM   #13 (permalink)
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A fully charged 12v battery is going to be closer to 13 or even 13.4 if it just came off the charger.
I would also opt for a higher amp controller then 450 amps if you are only running 72v then you end up with 32,000 watts that you can pull, I only say this because people complain about their EV being a bit sluggish or slow when their controller is to small, my EV is 1,400 pounds and has the Altrax 4865 in it, so even tho it's a 48v controller I can put 650 amps or 31,000 watts to the motor when needed and I've seen it happen, not for very long but for long enough that I was glad that I had a controller that could handle that many total watts.
As for running the motor at a higher voltage, pretty much everyone says it's fine to do, that over speeding the motor and over heating it are the main things you need to worry about and both of those are easy to prevent/control, for the over speeding of the motor just figure out how fast it's spinning in each gear, and for over heating, a small squirrel cage fan and a short piece of heater duct from the auto part store should force cool it, add an air filter in there and your motor will be really happy, if you want to keep your motor under a set voltage then figure out what voltage it takes to go the speed you want and don't go faster then that! you could have a 300v battery pack but if you only ever drive 45mph and it only takes 60v to drive that speed then the speed controller is limiting the voltage to the motor to only allow it to spin fast enough to go that speed, the advantage of that higher voltage battery pack at that point is that your line loss in all of your wiring and battery interconnects is less, so popular opinion is that the highest voltage battery pack that you can get away with tends to be the best option as long as the batteries are not getting so small that they can't handle the load.
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