Proper voltage for 18650 battery build?

[Synon]

I'm in the process of building an 18650 battery pack for my 48v 1000w hub motor. The batteries are used laptop batteries, I've tested them all and I'm working on the final configuration of the pack. I built a triangle that can fit a max of 185 batteries so my question is this... I can either build a 12s15p (180 cells) pack or a 13s14p (182 cells) pack. Maybe I'm splitting hairs here, but am I correct in that this is simply a trade off in power vs. range? I have a 13s charger so that is not an issue. Would the 12s15p configuration be slightly gentler on the batteries since they are not designed for high discharge? Anything else I need to consider?

 

[izeman]

Maybe I'm splitting hairs here, but am I correct in that this is simply a trade off in power vs. range?

no it's not. it's speed vs max power. 13s14p is faster but can't deliver as much amps as 12s15p.
depending on your batteries this makes sense or not. as these are low discharge cells as you said, more parallel cells can make sense as voltage sag will be lower. and if voltage sag for the 14p pack is higher than for the 15p pack it could even be that the 15p pack is faster. but the opposite can happen as well so: correct answer: it depends
range should be the same as you need the same energy for the same range if speed is equal. and energy is voltage * capacity per cell * number of parallel cells. so 13s = 48.1V nominal, and let's say you have 2,500mAh batteries, this is 48.1 * 2,5Ah * 14 = 1.7kWh which is almost the same as 12s15p.

Would the 12s15p configuration be slightly gentler on the batteries since they are not designed for high discharge?

correct.

 

[fesanand]

I ran 14S 8P for 500km and then 14s 9p used laptop batteries in a 40A controller. Only issue I had was doing steep hills 13% and the remaining battery being below 50%... you could feel a big loss of power, sometimes I had to pedal hard to do the hill.

If your battery is 14S13P I guess you wont have any problem at all. Also is better to run 14s instead of 13s if you're concern about top speed.
On the other hand 185cells is quite a big battery: 9.3 kg of battery. I hope you don't have to remove the battery every time you need to recharge it

 

[Synon]

Thanks for the clarification, that makes more sense! I think I may just go with the 15P, I guess if I really want a little more speed I can make a separate little booster pack.

9.3kg doesn't sound too bad considering I was using 23kg of lead acid batteries initially. I'd like to charge on the bike, but if I do need to take it out I won't have to move it very far.