pbert said:
He needs the high amps in order to produce more torque though, so i dont think upping the voltage and lowering amps fits the riding style. More amps equals more torque , more voltage equals more top speed. He needs torque, so more amps.
you are partially right. you are right in the aspect of power flow between the controller and the motor. there this rule applies.
this rule does NOT apply between the battery and the controller.
(this is a biginner mistake that happens a lot, so this is why i am asking basic questions.)
the controller always gets the battery voltage. the motor voltage is dependant on speed. so when stationary you only have a few volts in the motor so you need massive amps to get the watts you need to get moving. voltage x amps = power.
but the controller does not suffer from this. it always has the battery volts going in. so you can have a 100V from the battery and 100A draw wich means you get 10kW at the motor. with a 50V motor you would need 200A for the same power. the motor will accelerate the same.
torque is determend by the motor and the amps going into it, not the battery voltage. higher volts simply means you can reduce the current draw and possible get higher speed if the motor can take the power load. but that is simply limited with a rpm limit.
the trick here is to prevent sag in the battery so you can push as many watts into the motor side of the controller as possible.
pbert said:
I'm not looking at the wrong spec. I mentioned both the capacity and the discharge (30A per cell). The goal of this battery build is to build one able to put out 120 continuous and 300A peak and have a low amp hours in order to make the battery lighter. So i was saying if i use cells that output 30A continuous and i put 10 in parralell i can build a battery that outputs 300A continous but that it breaks the other goal of this build which is to build a smaller capacity battery. hope that is more clear.
those cells dont do 30A proper. you need serious high current cells (like the samsung 25R) that can deliver the load -constantly- without having massive voltage sag. so you need low capacity cells used in power tools. those dont heat up and can take high current abuse without wearing out in a few dozen cycles or burn your bike down due to overheating and dont sag under high loads. these cells can also be charged much more agressivly (up to 4A per cell!) without dying too fast. so 30 min full fast charge from 0% SoC is possible while staying within spec.
why are you guys saying the battery is not going to last ? For example if i use cells rated for 15A and 2C then i put 10 in parrallel it should be fine ? would give 150 at C and 300A at 2C, or am i not understanding something ?
