Quote:
Originally Posted by TurnNBurn
Regarding that link the guy used an Alltrax 450 controller and a ME1003 motor, the same motor I'm going with now. He achieved 100+ MPH. I was told 72V motors (depending on gearing) would max out around 75-85 MPH. How would he be able to achieve 100+ mph?
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It's hard to say, but Lithium batteries operate in a narrower voltage range then lead acid, a 72v lead acid battery pack could be over 90v when you pull it off the charger.
In terms of 12v batteries their voltage can range from 15.5v under an equalize charge and stay at that voltage for a few minutes dropping down to about 15v until you put a load on them, under high load that voltage can drop down as low as 10v.
So the 72v speed controller is designed to handle that peek voltage, but lead acid also sags a great deal under load, it could sag down to 60v under high load, a 72v lithium battery pack that just came off the charger should only be around 79v or even a little less, so a higher voltage lithium pack that is at 90v off the charger it will sag under load to around 82v and the 72v 450amp Alltrax should handle that just fine and allow the motor to put out around 49hp for two minutes (controller rated 450amps for two minutes) at that point you're going full speed and you could bypass the speed controller with a contactor that closes at full throttle.
So if you had lead acid batteries and an Alltrax 7245 controller your motor would put out a peek of 36hp because of voltage sag compared to that 49hp that the lithium batteries could pump out of that same motor.
You were asking why lithium batteries might be better then lead acid before, right?