Volts, watts and amp hours

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May 9, 2021
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Hello, just curious about watts and volts an amp hours.
I have an E bike the Motor is 250 watts and the battery is 21AH and the whole System is 48 volts.
So just wondering what part does what, I think the 250 watts is the strength of the motor and that the volts helps the motor to be able to produce 250 watts and that the 21AH is to do with how long the battery can provide the volts to power the wheel at 250 watts.
I am 72 kg my bike is 34kg, I ride 52 kms a day on my commute to work, the ride includes a long steep hill that is ridden down and up and a couple of shorter steep hills up and down with many flat sections (all Paved road and Bike Path). My bike battery gauge has 5 segments and the battery goes from 54.6v down to 42v
The first segment lasts for about 49 kms or down to about 49 - 50v The most I have travelled on one battery is 80km but I have never ran it dry.
If all things were equal and the same bike, given that we are (legally limited) to 25kph, which combination would give best performance..... between 36v 48v and 52v ..... would It be worth getting a 52 v system with 250 watts, would the extra weight cancel out the benefit or would 36 v be adequate ?
Just wondering how much each component influences the performance the most ?
What confuses me most is that the Battery voltage it goes from 54.6 v to 42v why? it has a range of 12.6v ... am I reading it wrong why doesn't it go from 12.6 to 0 or something similar?
 
Quick answer for the battery part.Your 48V battery is made with 13 groups of lithium cells, with a nominal voltage of 3.7, And 13 x3.7 is close enough to 48V. Those lithium cells are operated strictly between 4.2V and 3.0V. Anything higher or lower can cause them to fail and maybe catch on fire. You have circuitry in the battery, charger and bike to keep the voltage in range. So it can't go much lower than 40V or higher than 54.6V. Don't think the battery is dead when it stops running your bike. It's been shut off, and if you went inside and start poking at it, it might surpirse you with sparks and fire.
 
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