Black Beauty II - Pic Heavy

[scottyb]

A little quirk about the DCS turbo feature is this. Turbo on actually limits access at low rpm. Turbo off will allow the motor access to more amperage at low speeds. In either case 500a is too much for the stock sepex motor in my experience. Other people's experience may be different.

[JohnnieB]

Originally Posted by coosa

............

1. I am still confused about the settings I need, so I guess I really ought to read the manual before asking more dumb questions.

2. The thing that concerns me most is getting either of them to that point where the cart is barely creeping along on the steepest hill and blowing the motor. I just can't understand how changing controller settings will provide more torque in that situation. Can it?

3. From JohnnieB's response, it sounds like I need to limit the power to the motor in that situation so that I don't blow the motor.

4. The dealer that I bought the 2008 from indicated that they had it set for maximum torque, but I don't understand how controller settings could do that.

5. I suspect they just limited the top end speed, which might be a good thing if 500 amps is more than the stock motor can handle.

6. If the default settings allow 100% of power, then it looks like to me that the only way to increase torque is to put on smaller tires. Am I understanding it right?

7. Thanks for all the help. I'm thinking of taking it to a nearby mountain this afternoon and giving it a try.

1. The only dumb questions are the ones not asked. (But here is the manual.)

2. When a motor is stalled or when the armature is turning slowly, it will draw all the amps made available to it and all the amps not converted into motion (torque) are converted into heat. The controller is an electrical valve that LIMITS the number of amps the motor is allowed to draw.

By adjusting the number of amps the controller will allow the motor to draw to something less than the maximum rating for the controller, you are effectively reducing the maximum amount of torque the motor can generate while stalled or turning slowly. Conversely, if the controller's Max Output current (amps) is turned down, turning it up will increase the amount of low-end torque that can be generated, but there is a limit to how much heat the motor can withstand.

A motor and amps is akin to a drug addict and his drug of choice. He will take all he can get, even if it kills him.

3. It depends on how you drive the cart and where you drive it. Motor case temperature is the warning sign. The motor will get too hot to touch, so you'll need some way to measure temperatures in the boiling water range.
If it is staying below 239°F, you are okay. (Non-contact IR thermometer works. I have DMMs with temperature functions, so I use a thermocouple attached to my motor.)

4. He just set the Max Output Current slider to 100%.

5. Turning down the max amps does not change top speed, but there is a control that limits top speed.

6. Smaller tires isn't the only way. Changing the gear ratio in the differential is another way. As is installing a different motor, you can get them wound for low-end torque or high speed or something in between like the stock PDS motor is wound, but capable of handling more energy.

7. Check motor temperature about 10 minutes after getting to the top of the mountain. It is the wires in the windings that get hot, so it takes some time for the heat to conduct.

Also, check the temperature of all the high current cables. They shouldn't get much more than warm (about 10°F or so above air temperature) and all should feel about the same. Any that get hot need to be fixed or replaced.

[coosa]

>>>In either case 500a is too much for the stock sepex motor in my experience. Other people's experience may be different.<<<<

Scottyb, that's not particularly good news for a guy that owns 2 carts set up exactly that way.

Johnnieb, I love the way you are able to analyze a disjointed post and number it into something that kinda makes sense.

Thanks for the detailed reply. I am about to head to town and try to find a cable to hook the controller to the laptop. I'm starting to think that maybe the dealer I bought the first cart from knew more about it than I thought. He is limiting power in some way using the controller settings, and maybe that's to keep me from burning up the cart. It does have a warranty, so I'm not gonna mess with his settings until it expires. I will hook it up and see what they are.

A further question on this:

>>>A motor and amps is akin to a drug addict and his drug of choice. He will take all he can get, even if it kills him.<<<

So am I better off to let my motor have all the dope (power) he wants at that moment when its about to stall? If I limit the power and causes it to stall in a spot it could climb if I gave it full power, isn't that the worst thing that I can do?

My biggest problem is that I have controller carts and still have a resistor cart mind. After running a resistor cart 16 years, I'm sure aware of heat and the damage it can do. So far, I've not found my motors or cables to ever be hot, and I've checked them often when I thought they were under a strain. I suspect I'm controlling a lot of the possible problems by the fact that I seldom run either of them wide open.

When I said smaller tires were the only way to increase torque, I meant with my stock motor, differential, and this controller. But before I get more confused, I guess I'd better read the manual. Thanks again for the help!

[JohnnieB]

Originally Posted by scottyb

A little quirk about the DCS turbo feature is this. Turbo on actually limits access at low rpm. Turbo off will allow the motor access to more amperage at low speeds. In either case 500a is too much for the stock sepex motor in my experience. Other people's experience may be different.

It is a field mapping thing.

Normally the field mapping increase amps in the field windings at lower RPM (as sensed by throttle position and armature current) to generate more torque and reduces field current at higher RPM so the armature will spin faster for the voltage being applied. The turbo mode reduces the field current even further, to up the max speed, but when it kicks in at low RPM, you effectively end up with the low end torque of a high speed motor.

As far as I know, turbo kicks in after the the throttle has been at 100% for one second and the controller is not in current limit, so if your cart is slowing down on a long hill, try backing off on the throttle a little, it might speed up.

[JohnnieB]

Originally Posted by coosa

A further question on this:

>>>A motor and amps is akin to a drug addict and his drug of choice. He will take all he can get, even if it kills him.<<<

So am I better off to let my motor have all the dope (power) he wants at that moment when its about to stall? If I limit the power and causes it to stall in a spot it could climb if I gave it full power, isn't that the worst thing that I can do?

It is a juggling act. If you allow the motor to draw too many amps it may burn out and there is a good chance it will take the controller with it.

IIRC, a stock PDS motor is rated for about 3.0kW continuous and with a 400A controller, you can hit the motor with about 15.3kW peak. With a 500A controller it is about 19.1kW. It will take it, but the question is how long will it take it.

Heat damage is cumulative, so each time the motor is taken to its max temperature limit, the sooner it is going to fail.

The trick is not trying to climb hills that slows the cart down below walking speed (3-4 MPH) and if you find yourself in that situation, try to back out of it and find another route.

It depends on the tire height and tread pattern, but your tires may loose traction before the motor stalls on a hill.

Bottom-Line: The entire drive train (Batteries, cables, motor, controller, solenoid, gears and tires) should match each other. And the entire system should match the application it is being used in.

With tall tires climbing steep hills, you probably need a more robust motor.

[coosa]

Thanks for all the good info!

>>>With tall tires climbing steep hills, you probably need a more robust motor.<<<

The thing about BB2 is that she is gonna live in a place that doesn't have really steep hills. I have already put her on some hills around my house that are steeper than anything she will face at the farm, and she had no problems at all.

But I'm about to load her up and take her to the mountain. If she can climb it, I'm gonna be satisfied to try her with the stock motor. If she blows up the motor and controller, I'll be back to beg for advice. :)

I just picked up a cable; the smart thing would be to hook it up and check the settings before going, but that would kill too much time and I wouldn't get to go to the mountain. Nobody ever accused me of being smart anyway. I'll report back. :)

[coosa]

Just to report back, BB2 climbed the mountain without breaking a sweat. The road is pretty rough and very steep in places, so I was usually running it half or 3/4 throttle and it climbed the worst places with ease. I did put it to the floor over one steep stretch where the road was fairly smooth just to see what it would do; it climbed it with good speed.

I checked the motor for heat a dozen or more times and it never got beyond warm. I could put my hand flat on the motor and leave it there with no discomfort. None of the cables ever got beyond slightly warm.

I'll try to hook up both carts to the laptop and see where they are set now. I'm sure I'll be back with more questions.

One thing I did find - though BB2 handles fine in the woods, she sure doesn't trailer very well. The combination of a 6" lift and stock springs and shocks with low pressure tires just doesn't do very well on a trailer. There is a lot of up and down movement, and going too fast on a bad road could result in a big problem. If I were gonna trailer it often, I'd have to put some HD springs on it. Since I'm planning to take it to one place and leave it there, I'll try to get by without that expense.

[JohnnieB]

When hauling BB2 on a trailer, run a tie-down strap from side to side on the floorboard in front of the seat and cinch the body down.

Great news about motor and cable temperatures. BB2 may serve you as long and as well a BB1 did.

[coosa]

Thanks JohnnieB, I had one winch strap around it and tightened the front tires against the front of the trailer. I was planning to put a 2nd strap on it next time to try to pull it down further and eliminate some of that bouncing.

If I didn't know about the problems others have had with the 500 amp controller and the stock motor I wouldn't be concerned at all. I don't think that I will ever drive it in a way to get it too hot, but I know others will drive the cart too, and I know they won't pay any attention to my warnings.

I'm really not sure of the ideal way to drive this cart. On ScottyB's web page, he warns against creeping thru the woods at a slow speed for a long time with this PDS motor. That was also a terrible way to drive the old Marathon; it ran best wide open.

So what's the best way to run this cart? Is a steady 3/4 throttle better than running it wide open for an extended time? Is it better to vary the speed or better to keep it at one speed?

[JohnnieB]

Nearly fifty ago when I was in the 3rd Mob (Third Mobile Communication Group - USAF), we had to chain the bodies of our vans and vehicles down as well as the wheels, when we airlifted them. When we hit downdrafts, those things could get a foot taller and do bad things to wire and pipes above them in the ceiling of the aircraft. Same laws of motion apply to a cart on a trailer.


If you don't need/want the extra speed, turn the Turbo off. (Un-check the Turbo box in the program)
Turbo give you a few more MPH at the top end, but generates a lot of motor heat doing it.
It also reduces torque if it comes on while traveling at lower speeds.

With Turbo turn off, running steady at 1/2 or 3/4 or full throttle is about the same motor heat wise.
It is at the lower RPM stuff that generates more motor heat.
The reason why motors get hot is roughly the same at any RPM, but the motor simply cannot draw as many amps at higher RPM, so there are fewer excess amps being turned into heat.

On a brake-dynamometer and powered by 48V, when loaded down to 1450 RPM, my motor can only draw 400A through the Armature (with 20A flowing through the Field), but when it loaded down to 2900 RPM, the Armature can only draw 90A (with 5A through the Field). A stock PDS motor will not draw that many amps at those RPM's, but the pattern will be roughly the same, the higher the RPM, the lower the max amp draw.


I try to keep my motor above 500RPM when I'm on rough terrain, and for my cart that is about 2 MPH. You have taller tires, so your cart will be moving faster at 500RPM. (IE: If your tire height is 22", the cart speed at 500 RPM is 3.4 MPH - walking speed)

If you can keep the other drivers from stalling the motor trying to climb over logs and such, or inching along the trails, you ought to be okay.