opinion needed on which Alltrax to order

[yurtle]

I did have one steep hill with two passengers that took a running start to climb, and it wasn't due to tires slipping. I had it set for 400 amp max. It may have climbed that one hill without a running start if I had already set it for 500 amps.

For me, I'm happy I went for 500, even though 400 is rarely exceeded.

[mazdawg(Mikey)]

just got off the phone with Scottyb and he was very very helpful in putting me in the right direction. I ended up ordering the dcx400 because he said that's all I really need. the cool thing is the $125 I saved ill add to it and order the brake kit from him in the near future.

[JohnnieB]

At zero RPM (stalled) the impedance of a series motor is the DC resistance of the wires in its windings, which isn't very much.
If the DC resistance was 0.05 Ohms, the stalled motor could draw 720A at 36V (25.92kW) or 960A at 48V (46.08kW).
The 400A controller would limit that to 14.4kW at 36V or 19.2kW at 48V, so the same motor has roughly 33.3% more torque off the line at 48V than it does at 36V.

As soon as the motor starts spinning, something called Back-EMF starts being generated and increases more or less linearly as RPM increases. Back-EMF effectively increase the motor's impedance, so the faster it spins, the fewer amps it can draw and the less torque is generated. At some RPM, the amount of amps the motor can draw will generate an amount of torque equal to the total of the drag factor of the cart and that will be the cart's top speed. Because 48V will force more amps through the same impedance than 36V will, the motor will reach a higher RPM before the torque generate equal the cart's drag, so the top speed will be higher. Perhaps not 33.3%, but something in that neighborhood.

As previously mentioned, the number of amps a motor can draw starts decreasing the moment it starts turning and at some RPM it is unable to draw as much as the controller will allow it to draw, so from that point up in RPM, it doesn't matter if it is being fed by a 300A, 400A, 500A or 600A controller.

Basically the difference in performance occurs in the first 30 feet or less from the starting line and when climbing a hill steep enough to bog the motor down to a few hundred RPM. On the other hand, the larger ampacity controllers are more robust and can take stresses that might kill a less ampacity controller.

The way a Sepex motor and controller work is a little more complex, but they follow about the same overall patterns.

[scottyb]

Originally Posted by JohnnieB

A zero RPM (stalled) the impedance of a series motor is the DC resistance of the wires in its windings, which isn't very much.
If the DC resistance was 0.05 Ohms, the stalled motor could draw 720A at 36V (25.92kW) or 960A at 48V (46.08kW).
The 400A controller would limit that to 14.4kW at 36V or 19.2kW at 48V, so the same motor has roughly 33.3% more torque off the line than at 48V than it does at 36V.

As soon as the motor starts spinning, something called Back-EMF starts being generated and increases more or less linearly as RPM increases. Back-EMF effectively increase the motor's impedance, so the faster it spins, the fewer amps it can draw and the less torque is generated. At some RPM, the amount of amps the motor can draw will generate an amount of torque equal to the total of the drag factor of the cart and that will be the cart's top speed. Because 48V will force more amps through the same impedance than 36V will, the motor will reach a higher RPM before the torque generate equal the cart's drag, so the top speed will be higher. Perhaps not 33.3%, but something in that neighborhood.

As previously mentioned, the number of amps a motor can draw starts decreasing the moment it starts turning and at some RPM it is unable to draw as much as the controller will allow it to draw, so from that point up in RPM, it doesn't matter if it is being fed by a 300A, 400A, 500A or 600A controller.

Basically the difference in performance occurs in the first 30 feet or less from the starting line and when climbing a hill steep enough to bog the motor down to a few hundred RPM. On the other hand, the larger ampacity controllers are more robust and can take stresses that might kill a less ampacity controller.

The way a Sepex motor and controller work is a little more complex, but they follow about the same overall patterns.

And that folks is the short answer
Thank you JohnnieB

[caokgafamily]

Nice explanation Johnnie B.

[financethis]

Originally Posted by JohnnieB

A zero RPM (stalled) the impedance of a series motor is the DC resistance of the wires in its windings, which isn't very much.
If the DC resistance was 0.05 Ohms, the stalled motor could draw 720A at 36V (25.92kW) or 960A at 48V (46.08kW).
The 400A controller would limit that to 14.4kW at 36V or 19.2kW at 48V, so the same motor has roughly 33.3% more torque off the line than at 48V than it does at 36V.

As soon as the motor starts spinning, something called Back-EMF starts being generated and increases more or less linearly as RPM increases. Back-EMF effectively increase the motor's impedance, so the faster it spins, the fewer amps it can draw and the less torque is generated. At some RPM, the amount of amps the motor can draw will generate an amount of torque equal to the total of the drag factor of the cart and that will be the cart's top speed. Because 48V will force more amps through the same impedance than 36V will, the motor will reach a higher RPM before the torque generate equal the cart's drag, so the top speed will be higher. Perhaps not 33.3%, but something in that neighborhood.

As previously mentioned, the number of amps a motor can draw starts decreasing the moment it starts turning and at some RPM it is unable to draw as much as the controller will allow it to draw, so from that point up in RPM, it doesn't matter if it is being fed by a 300A, 400A, 500A or 600A controller.

Basically the difference in performance occurs in the first 30 feet or less from the starting line and when climbing a hill steep enough to bog the motor down to a few hundred RPM. On the other hand, the larger ampacity controllers are more robust and can take stresses that might kill a less ampacity controller.

The way a Sepex motor and controller work is a little more complex, but they follow about the same overall patterns.

wow that really helped me to make my mind up as well.

[JohnnieB]

Originally Posted by financethis

wow that really helped me to make my mind up as well.

There are several more factors involved in picking the right ampacity controller for a cart.

Tall tires (over 22" diameter) and low pressure tires (under 15 PSI max inflation pressure) take a lot of amps to turn, so a 500A or larger controller may be needed. However, 500A is a bit much for a stock motor, so an aftermarket motor may be needed also.

High speed and high torque motors may also need a 500A controller for optimal performance.

A back seat or hilly terrain are other reasons for going with a higher ampacity controller.

Also, pack voltage has to be taken into consideration.

The list goes on and on, so the best bet is to consult with a competent vendor before deciding.

[720Deere]

Originally Posted by JohnnieB

There are several more factors involved in picking the right ampacity controller for a cart.

The list goes on and on, so the best bet is to consult with a competent vendor before deciding.

Enter Scottyb!