7s2p Vs 14s1p battery pack

[amadeok]

hello
I'm trying to assemble a DIY lithium ion battery pack for an electric bike with a DC motor of 24 250w that can be used at 36v 350v as well.
For now I'll be only using it at 24v 250 as it is the legal limit, so a 7s2p 24v 7Ah pack would be enough. But say if instead of that I make a pack of 14 single cells in series, 48v 3.5Ah, would there be any difference if I don't use more than 24v with either battery?
Thanks

 

[gophert]

...would there be any difference if I don't use more than 24v with either battery?
Thanks

how will you limit the 48v of the battery to 24v? Either I am confused or you are.

 

[amadeok]

how will you limit the 48v of the battery to 24v? Either I am confused or you are.

Sorry let me explain better.
With 14 18650 lithium ion cells i can make either a 7s2p pack or a 14s1p (meaning just connect them all in series). I would then connect that to a motor controller that can take up to 60v 20A. With either case, 14s or 7s2p, i would use PWM to feed maximum 24v to the motor.
I thought that i could use the 14s configuration to eventually reach 36v, if i ever need, which i cannot do with the 7s2p setup. So the question is there would be any difference by using the 14 cells in series at 50% duty ratio(24v) rather than the 7s2p pack at 100% duty ratio (also 24)?

 

[gophert]

No difference except you will have more trouble balancing the charge on the 48 v stack from battery life point of view.

Also, a 48v at 50% duty cycle is an average of 24v over time - it is ACTUALLY 48v 49-50% of the time and 0V for 49 to 50% of the time. Somewhere in between for 0-2% of the time (hear losses from switching).

Good luck