PDS cart, stock motor, how fast can I go?

sportcoupe

If I take a stock PDS cart, add Alltrax DCX 500, upgrade to 48v and add 23" tires can I get 26-29 mph with stock motor?

BGW

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JohnnieB

A stock PDS controller limits the motor RPM to about 4.4k in freedom mode, which is about 19MPH on stock height (18") tires.
Using a controller that doesn't limit motor rpm, allows it to spin at about 5.5k at 36V, which is about 24MPH on stock height tires.
Upping the tire diameter from 18" to 23" increases the speed by 22%, or about 30MPH at 36V if the controller and cables will pass the amps need to turn the tall tires that fast and the battery pack can provide the amps.

I'm not sure how much the speed will increase going from 36V to 48V, but the 33% higher voltage will reduce the amps need to turn the tall tires by 33%, so amp load on the batteries and cables will be lower, so my guess is at least 30MPH, maybe more.

A 500A controller being fed by a healthy 48V battery pack can hit the motor with about 25.4kW, which is pushing the limits on a stock PDS motor, so I'd either back the controller's max amps down to 400A (~15.3kW) or ship the motor to Plum Quick and let them do their magic on it.

FWIW: A Stock PDS controller (300A) and 36V battery pack hits the motor with 11.5kW.
My 42V 400A system will deliver about 17.8kW (55% increase), so I feel pretty comfortable with a stock PDS motor, but I'll still keep a close eye on motor temperature.

sportcoupe

Perfect, thanks Johnnie.

sportcoupe

I noticed a PDS motor has smaller gauge wires for F1 and F2. When I replace A1 and A2 with 4 gauge wiring do F1 and F2 need to be 4 gauge or leave them alone?

ScottyB is going to get a call Monday for my controller package order.

JohnnieB

Unlike a series wound motor, the current though the armature and stator (field) windings in a sepex motor can be different.
In fact that is what sepex means. (SEParately EXcited)

In a PDS cart, the F1 & F2 wires only carry about 1/10 the amps that the A1 & A2 cables do, so stock size is okay.

Just make sure the connections are clean and tight and the insulation isn't worn where they are routed around the battery box. See Picture.

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Worn field wire insulation.jpg (593.6 KB, 0 views)

sportcoupe

PDS 48v conversion has started, parts are coming in. With JohnnieB's estimate of 30mph here is my first upgrade. I believe I'll need these.

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sportcoupe

Today I answered my own question: how fast can a stock PDS motor go.

Alltrax 500A + 23" tires + 48v conversion = 29 mph

Very cool! Now, how can I go 35 mph?

rib33024

8.1 gears will get you there, read this



http://www.buggiesgonewild.com/road-...o-build-2.html



http://www.buggiesgonewild.com/elect...tml#post662427

sportcoupe

I don't know if it's better to do 8:1 gears and keep the stock motor or just upgrade the stock motor to a D&D and leave the 12:1 gears.

Decisions.....

JohnnieB

Looks like my guesstimate of 30MPH wasn't all that far off.

If the tire height is truly 23", the motor is spinning at 5,272RPM, but how tall a tire actually is vs the size stamped on the sidewall is at best + or - about an inch and sometimes more.

Does the tire manufacture list the MTD (mounted) height on their website?
Or have you measured the height or circumference?
Also, what is the max air pressure rating and what pressure are you running them at?

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Is the 29MPH in Turbo mode?
How many amps and at what voltage are being drawn when cruising at 29MPH?

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I'm asking so many questions because I'm trying to figure out why some people running DCX400 controllers at 36V with tall tires are not getting anywhere near the theoretical speed I think they should be getting.