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Comment by swader999 | Hacker News Reader

This is a great idea. Would be wild if they could support switching on the fly between 32 and 48v for a range/speed option. That gets complicated though.

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Most e-bike providers will buy their switching logic based on the voltage in use, a driver for 48V would be substantially more expensive than one for 32V. There is also the whole charger setup to consider so yes, that gets complicated.

Doesn't need to. Power is power.

This guy is right, the premise of switching doesn’t make sense, power is power.

I only remember when I built my own batteries, I would get more range at lower volts because at about 40+km/hr you end up pushing wind and range goes way down. So yeah, technically power is power, but it's fun to go 50km/hr if you don't have far to go.

There probably aren't many EVs that can't regulate voltage across motor poles between 0 to +battery pack(or -1/2 to +1/2 pack) voltage...

Did your controller only have one power setting?

Yeah it did. It was fairly burly to begin with and I modified it with a stronger mossfett. This was back in 2007 when ebikes were very fringe. I would get packs of defective DeWalt drill batteries on eBay to harvest the good cells and build my own packs. I spent almost as much time building the bike as I did riding it. Ebikes.ca and endless sphere forums were full of help.

Cue Bob Parr meme...

Changing the voltage doesn’t change the amount of power being used, the only thing that would change is the ampacity (which only impacts conductor size, in this case).

480 watts == 10 amps @ 48V == 15 amps @ 32V

An electrically commutated motor (brushless DC) in an e-bike will almost certainly have a speed controllee, if you want more range you simply have to go slower ;)

Reconfiguring a battery pack with the same number of cells doesn't change the power contained in the pack. However lowering the voltage will lower your top speed (if not already artificially limited by the controller) and raising the ampacity of the pack may allow you to get more torque from the motor if you haven't saturated the motor and you change the controller settings to pull more amps from the battery.

Ah yes, DC motor speed is controlled by voltage. Glad to see Cunningham’s Law still holds true, thanks :)

I’m much more familiar with three-phase AC induction motors from my day job and the speed on those are (most commonly) controlled by adjusting the frequency with a variable frequency drive while maintaining the same voltage instead of directly controlling the voltage like on a DC motor.

Yeah but the wind kills range much more so at the higher speed 48v gives you and you tend to never run at half throttle.

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