Batteries do not improve torque. Batteries are like gasoline for your car. You need bigger motors, controllers, and lower gears for more torque. eCargo bikes like that are geared much slower for the torque they require. The Rad Burro has a motor that puts out 200N.m of torque.
Thank you, and exactly. Higher voltage, nor battery amphours, by themselves will do a thing to help motor torque. Its in the design of the motor itself and its gear ratios, and magnetic fields, and current fed into it.
But frankly, Ecargo bikes often don't need higher torque motors to pull heavy loads, are often set up with and optimized around direct drive motors, where you are dealing purely with magnetic fields and no internal gears, which substantially improves motor reliability and longevity, though not acceleration. They can haul a very heavy load though, and it has nothing to do with torque, but rather the current you can supply, at the given wheel rpm. You can pull amazingly heavy loads with a 40 nm torque rated motor, but its going to take a while, or more of your effort (if you want to go faster) to get up to speed. Won't hurt the motor one bit, but you will suck lot of current. usually OEMS will really jack up the controller amperage with the direct drive motors. Grin tech specializes in this area. The direct drives will be largely 'bullet proof' in a heavy load situation.
Now if you want BOTH acceleration and pulling a heavy load, You'd want two hub motors. (or preferably a single mid drive) Geared hub motors even with 70 to 90 nm of torque are going to present a lot of reliability and operational issues with heavy loads at lower speeds (say when you are starting out and staying below 8 mph), and sooner than you want you will shred the gear teeth, especially if you get stuck in the wrong gear on a hill, and force the motor into doing nearly all the work, at a less than ideal speed. If your speed is too low with an internally geared hub motor, you will also very likely, and rather quickly burn up your controller. The amp draw by the motor will want go through the roof, and internal controller current limiters dont like that sort of situation either.
Many cargo ebikes are using mid drives now, and with torque sensing it substantially moderates the instantaneous amp draw, and with mid drives they are already spinning at far higher rpms than hub drives, (a hub drive which is stuck to only 200 to 300 rpm, which is your rear wheel RPM, and its obviously much lower rpm when you are first starting out from a dead stop- and imagine starting out from a dead stop with a heavy load. Just not good at all for a internal geared hub drive.).
However, A Bosch mid drive motor (choose your favorite mid drive brand as I am just using their name for example) is spinning at a ratio of 35 to 1 of your crank cadence, and peak torque is going to occur over 3000 RPM, enabled and leveraged by its internal gears that are between the motor and your crank arm. Don't confuse cadence RPM with the motor RPM. You want that high rpm, as that is creating the magnetic field you need to get the torque and a decent amount of acceleration throughout the power/rpm curve.
Heres a visualization of the guts of a Bosch, that might help you to see how they get the 35 to 1 ratio.
Whereas a geared internal hub motor is going to typically have a 5 to 1 ratio. So its going to need much higher current, usually helped by higher voltage (often 48 volts if its at least a 500 watt motor), to achieve similar torque levels as the mid drive. Its tough to reach 90 nm with an internally geared hub drive, so usually you will see them in the 40 nm to 65 nm range. With 500 watts, and 48 volts, a 65 NM hub drive motor is going to accelerate very nicely with the average weighted single rider.
But I
would not want to use that geared hub motor for heavy cargo loads, as again (as mentioned above) you will run the risk of tearing up the internal planetary gears (teeth) rather sooner than you'd want. (that won't have the same risk of happening with a mid drive though, because its spinning at rather high rpms already even at low bike speeds)
Choose the RIGHT motor type for your application, and you will be a much 'happier ebike camper.'
