Explain higher voltages like I'm a slug ( better power density at 1000 nominal 2000 peak?)

[uhmwpolyethylene]

I was looking at a bbshd 52v , or perhaps 72v but people say that's a bit wonky. But I have seen people running higher voltages on hub motors (and some mid drives? Any? ) it's hard to search for specific voltages about 72 because there are so many.

And I guess it's what, voltage x amps = watts? Idk. I don't understand electrically stuff. But besides the potentially heavier weight of some 2000-8000w qs etc motor, can I find some 96-144v batteries and controllers that look inconspicuous?


Instead of having like 1 52v 20ah downtube battery + another 1 or two in a rear rack basket to swap + extra chargers, it would be cool to have a very high powered downtube or triangle fabric bag battery if the power is... denser? Say I'm running mostly at 1000w and 2000w uphill.


And don't motors rated to 8000w dissipate this heat easily, and take higher voltages? Can I get vastly more range than a 52v if I'm running Mostly 1000w? Costs of higher output batteries? Common controller and hub motor models and their weights? Will their added weight offset battery savings? A second triangle battery in the rear rack would be interesting too, like 2 40ah batts etc. Do any hub motors have torque sensor crank installations, efficient connection to chain drive, or some gradual stepped power (without being geared I guess, maybe could use statorade idk? Do I want geared? Heavier? Lower max power?)


Whats a good hub motor and controller for a true stealth build on a regular hybrid/gravel/mtb bike that looks inconspicuous? Maybe I could engrave it at 750w or sticker it. Something that is either really long and narrow or tiny and wide that fits in the clearance I guess could work I've heard also a 10ah battery 52v for example can't put out as good energy as a 20ah , are 25/40/60ah significantly more efficient? Is a 96-144v 20ah/40ah small downtube battery or triangle bag battery a thing? Are there any hub motors sold/can be laced that are lightweight and do 1500-3000w but could take up to 144v or something?

by the way, is the 750w bbshd any different from the 1000w, I just wanna buy the former for the engraving

edit: I did learn cells top off around 3.7v so you need bigger battery for bigger voltage anyway

 

[scianiac]

This is way too many vague and general questions to answer any of them. Lets start with what are you trying to do? As in want to build an ebike but what do you want that ebike to do?

 

[Chalo]

What are you trying to do?

Volts give you RPMs; the higher the voltage the greater the RPM. Amps give you torque; the more amps, the more Nm. RPM times Nm equals power (measured in watts).

Thing is, to take advantage of more RPM, you have to have more torque to reach and maintain those RPM. So rearranging the same size battery for 72V as for 52V, 48V or whatever implies you'll have fewer amps available, which could mean poorer performance instead of better performance. Also, motors are most efficient at about 80% of their unloaded speed. If you raise the unloaded speed so high that you don't have enough power available to get there, efficiency and range will suffer a lot, and you'll be more likely to overheat.