Controller Type/ Amperage

[JohnnieB]

Originally Posted by Brozzyb

Thank you, I suppose that would be an upgrade from stock ( stock is what 275 or 300?) MPH is no problem, with the speed chip and 23” tires I’m at 18-19MPH Flat land. My main reason for wanting to know was reading that the pds carts don’t like lifted/ big tires + speed chip, so assuming all 3 of those hurt the controller I was curious where I was at and if I should upgrade. Seems folks recommend the 400amp for this setup. Hopefully the 350 buys me more time than stock before it goes.
Also trying to troubleshoot low runtime ( about 5 miles with significant power drop after 2-3) Batteries 2yrs old and year and test good so trying to understand what the tire/controller / freedom chip combo is attributing to this. I might try the hill chip for some regen and to not hurt motor when I’m doing 30mph downhill.

With 23" tires, you will very likely need to replace the motor, controller and solenoid, eventually.

By adding a couple of switches in the jumpers on the speed chip you already have, you can get all four PDS modes by opening and closing the jumpers. When I was run a more or less stock PDS, I had a switch in the short jumper between pins 2 & 3 and could select either Freedom or Mild Hill to run in. (Have to toggle Run/Tow switch to change modes, so can't do it on the fly)

The difference between the modes is the max RPM the controller allows the motor to spin at and the amount of regen braking applied when you lift your foot off the pedal.

Even with 23" tires, I'm not sure if your cart will do 30MPH downhill. The max RPM the controller allows the motor to reach on level ground is 4400RPM and no matter what mode it is in, it uses regen braking to keep from exceeding the max RPM for the mode it is in. Mathematically, your cart should reach 24.2MPH on level ground and about 26MPH max going downhill.

You are only getting 18-19 MPH so something is holding the cart back. Possibly you have low pressure tires (<10PSI max inflation pressure), which take a lot of torque to turn and you've lost about 22% of the stock PDS torque where rubber meets road due to increased tire height.

The first upgrade I did was installing 2Ga cables (all ten of them) and got a noticeable improvement in acceleration from a standstill. Cart was fresh off a 3 year lease when I got it and I replace the cables a couple months after I got it.

Part of the short run time can be attributed to the tall tires, but it is most likely due to low battery capacity. A Powertron P2000 is only a 210AH battery while the standard 6V battery used to make a 36V battery pack is 225AH, so the storage capacity was slightly lower than the standard to start with.

Automotive type battery testers don't accurately check deep cycle batteries. To load test them, you need a device that places a 75A load on the batteries and measures the time it takes to drain them down to 1.75VPC (Volts per Cell), which would be 31.5V for a 36V pack.

[Brozzyb]

Thanks for the very thorough feedback. I am surprised to hear that all PDS modes Have some level of regen, my cart doesn’t seem to hold back at all going downhill w/ the freedom chip. I’ll have to gps it, it much faster than flat. Also heard of folks saying they have blown out their motors by going to fast downhill, so not sure where the discrepancy is. I’m still confused, what is the beat “chip” to use if I just want to extend runtime, or no real effect?. Do higher speeds of freedom mode reduce Runtime?

As I continue to learn about my new cart I just checked the batteries based on your comment. They are only 186 AH, which appears to be a low end budget type rating. Only 2 years old and all Voltage checks are all good but that low AH rating likely leading to low run time, especially with these tires?

Also checked tire pressure and all tires are at 14 PSI, states 22 MAX on the tire, so they are low but not under 10psi. I don’t care as much about top speed as I do about protecting the controller/motor so if inflating to 22 would help I could certainly do so.

[JohnnieB]

I know that stock PDS controllers turn on the regen braking when the motor's rpm exceed the max RPM for the mode selected by the J2 plug. With a modified 1206MX controller, I don't know, but I don't know why (or how) that feature could be disabled.

My stock PDS maxed out at about 19MPH on level pavement in freedom mode and regen braking keep it to about 22MPH going down a steep hill, with or without the pedal pushed. In mild hill mode, it'd do 14.5MPH on level ground and 16MPH going downhill.

The 23" tires reduce the amount of regen braking felt and it cuts off at a higher speed. With 18" tall tires, the regen shuts off at 8MPH, which is about 1850RPM at the motor, which in turn is 10.2MPH on 23" tires. So in the hill modes, you won't have pedal up regen braking below about 10.2MPH.

Regen braking also occurs if the cart start rolling with the pedal up. Its called Walkaway Safety. The beeper beeps rapidly and the regen braking is turned on at max, trying to keep cart speed under 2MPH, so you can catch up with it if it rolls away.

The Walkaway Safety feature is why you absolutely must put the Run/Tow switch in Tow if you ever have to push or pull cart. Otherwise there is a very high probability of burning out the motor and/or controller and maybe taking out some batteries also.

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I exploded my stock PDS motor when I was running it with an Alltrax DCX controller. The DCX was designed as a plug-n-play replacement for a DCS drive system and an PDS to DCX adapter was used. Neither the DCS nor the DCX used a speed sensor, so the motor was not RPM limited and was spinning at about 8,000RPM when I lifted my foot off the pedal to slow for the curve at the bottom of the long, steep hill. The motor was alread hot for running at top speed (about 28MPH on 17" tall tire) and climbing hills and when the regen braking kicked in, something let loose and the armature grew into the field winding, seizing the motor and locking the rear tires. I slid to a stop from about 34mph, but managed to stay out of the ditches and off the barbed wire fences. The DCX controller was smoking when I finally lifted the seat and I had heard sparking as I sat there shaking after come to a stop.

The Alltrax XCT48400-PDS I now run has user adjustable RPM limiting and I limit my motor to 6500RPM, which is roughly 25MPH with my 17" tall tires.

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Check you batteries under load while driving. Find out what the pack and individual battery voltages drop to going uphill.

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Upping the tire pressure will up the speed, but make the ride rougher.
Pump up to 22PSI and check speed for bragging rights, then lower it back to 14, or whatever, for comfort.

[Brozzyb]

Thanks again for the great feedback. I plan to test the batteries under load. One last question (I think), I just looked up the model of my solonoid and it appears to be stock 50amp. With the bigger tires, wires and 350a controller- does the solonoid “need” an upgrade as well. Aside from a new motor, Could this be a limiting factor to more speed/ torque. I understand it probably “should” be upgraded but not sure I understand what I will gain from that ( if anything ) or if it’s more that it’s bound to fail sooner with the 350a controller? Or does not ugrading the solonoid basically eliminate the any pros from the upgraded 350a controller?

[JohnnieB]

A 50A solenoid is way too small. Stock was 85A, which was only marginal for the stock series (275A) controllers and more so for the stock PDS (300A) controller. After a few years the contacts look like those shown in the attached pictures.

About the only time the motor will draw more than about 50 to 75 amps is when accelerating from a standstill, climbing a hill at low speeds or towing/hauling stuff at low speeds and possibly while running at top speed, so a 200A solenoid should do the job nicely with 23" tires. The motor runs slower for any given speed with 23" tires and the slower the motor runs, the more amps it can draw.

If you have the slightest suspicion you might go to a higher voltage battery pack (42V or 48V), go with a 48V MZJ400, which works at 36V, 42V and 48V, so you won't have to replace the solenoid when you up the pack voltage.

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The solenoid could be a bottle neck in the amp delivery system. If the contacts are pitted or burnt, they'll have more than normal resistance and will drop more voltage as amps pass through them. Same issue with the ten high current cables and their connections also.

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Measure across the solenoid's two large terminals while driving. If there is much of a voltage measured, the contacts have too much resistance and the solenoid should be replaced. Nominal voltage drop is 0.1V or less per 100A of current flow, so at most you shouldn't get more than about 0.35V with a 350A controller.

[cgtech]

That controller is (physically) so tiny, I didnt even know any "upgrade version" existed. It's small size makes claims of upgrades dubious in my mind. Just how could you get the heat out? That controller was something I considered "too small to upgrade".

And, I totally agree, all the 36v TXTs had a pathetic solenoid, and all should be replaced with anything better, even if it doesnt fit under the stock cover (any decent one wont fit as far as I've seen). Stock solenoid was really that bad!

Does a "better" Curtis/Albright fit under the cover? I'm sure a decent Trombetta, or a White/Rodgers does not fit under the stock cover. We usually cut the cover to allow a "umbrella" to remain.