Climb Every Mountain (or what I learned on my first commute)

[pwbset]

In this other thread I think fechter describes the whole thing power thing well:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=4940#p73744

Using a 36v, 20ah battery vs. a 72v, 10ah gives you the same total energy. Since your controller is limiting you to 20 amps, you could get twice the running time at 36v.

The other piece of it is that at 36v, your motor will only go half as fast as it could at 72v. Your top speed will be much lower, which reduces wind resistance, so your range would actually be more than doubled at the lower speed.

If you rode at exactly the same speed with either setup, the range would be nearly the same.

Another weirdness is that at the higher voltage, the motor will get more current at low speeds even though the input current to the controller is the same. This results in more available torque on takeoff and hill climbing.

 

[monster]

at 36v (28ah) it feels like i am reaching the LVC point of my X5 controller and i switch to 72v (14ah) for the rest of the journey in order to get the most out of the batteries. is this a LVC problem or a low SOC thing?

 

[pwbset]

at 36v (28ah) it feels like i am reaching the LVC point of my X5 controller and i switch to 72v (14ah) for the rest of the journey in order to get the most out of the batteries. is this a LVC problem or a low SOC thing?

Not sure. If I were to hazard a guess I'd bet that your controller is set to 29v, which seems to be a default for a lot of controllers, and that at 36v with battery sag you probably hit that a lot. At 72v not at all. Then again you're likely to get much more battery sag at 72v/14ah. Can you eliminate/lower the LVC on your controller?