General upgrade Qs on 08 TXT PDS cart

[Great white north]

Might as well go 48 volt ... That's what I did , go with 8- 6 volt set up for max. Range ... I use mine for hunting no issues ... Will prob. Up grade motor at some point ..

[JohnnieB]

Originally Posted by g.schucks

1. Question about the limitation of the stock motor you listed there. When drawing that at walking speeds are you saying walking speed like trying to go up a hill that slows down the cart to that speed?

2. You might have talked me into the 42V addition as well. Just wish I didn't have to replace the charger as well, they are not cheap!

3. Any ideal knobby tires that would keep the stock 18" size that you could recommend? Had the cart out in the woods earlier today and I could have used something better than the turf tires I have now.

g.schucks

1. Accelerating from a standstill and when the cart bogs down to low speed while going up a hill (or carrying/towing a heavy load) are about the only times you'd have a wide open controller at low motor RPM.

A controller doesn't push amps through the motor, instead it allows the motor to draw whatever number of amps it capable of drawing from the battery pack, up to the maximum amp limit of the controller.

The maximum amps an electric motor is capable of drawing is at Zero RPM (Stalled) and due to a phenomena known as Back-EMF, as the motor RPM increases, the dynamic impedance increases, so the number of amps the motor is capable of drawing decreases. At some RPM the Back-EMF equals the applied voltage and the motor will no longer accelerate, that is called the No-Load RPM.

When a mechanical load is applied to the motor, the motor will slow until it is capable of drawing the amps needed to produce a torque value that is equal to the applied mechanical load. When motors are dyno tested, they are ran with a wide open throttle and loaded down mechanically to target torque values typically, but could be for RPM or HP or Amps or whatever. When the target torque value is reached, amps and RPM and other parameters are noted, producing what is known as a Torque vs RPM curve.

I don't have a Torque vs RPM curve for a stock PDS motor and the torque curves for SepEx (PDS and DCS) motors are more complex than series motors, but with 25A of field excitation, the motor I'm running, which produces about 30% more torque and about the same top speed as a stock PDS motor, cannot draw more the 400A at 48V when spinning faster than 2,000RPM. A little number crunching says the max RPM a stock PDS motor could draw 400A at 36V is about 1000RPM. which is 4.3 MPH with 18" tires and 12.44:1 gears.

2. Going to 42V up the RPM at witch a stock PDS motor can draw 400A to about 1200RPM, or 5.2 MPH. Of course, the gain is not perfectly linear, so it may be more than that.

The best bang for the buck for a 42V charger is the DPI Accusense. http://www.cartsunlimited.net/48v_Battery_Charger.html

It has user selectable charge profiles for different brand batteries and goes into float charge after the regular charge cycle finishes.

Another nice thing is that the 42V and 48V use the same transformer, so if you decide to go to 48V in the future, all you have to do is replace the control board, which is a lot cheaper than a completely new 48V charger.

3. I'm not up to speed on what is out there in the tire market. I had to stick with turf tires if I wanted to continue driving on the grass in my local parks, but the Carlisle Turf-Master tires I'm running have a lot better traction than the Carlisle Links tires the were on the cart when I got it.

Try to stay with tires that have a max inflation pressure of 15 PSI or more and be aware that the tire height stamped on the sidewall might be an inch or more off in either direction. (IE: My tires say 18" om the sidewall, Carlisle lists the mounted height as 18.3" on their website and they measure 17.04".)

[g.schucks]

To keep my options open for future upgrades if I think I will up my voltage in the future.. 42 or 48 maybe. What controller should i go with now? I might finish my 4G cables this weekend, stock motor, stock size tires and 1 year old batteries currently. I am going to go with the bigger solenoid that would work up to 48 volt, should I push up to the bigger controller as well instead of the alltrax 400? I am thinking WAY down the road this being lifted with bigger tires and actually driving it around the woods during off lake season. Well, it gets drove in the woods now, but not very well... Don't want to hurt it or anything, so I am not taking it places that I think will hurt it.

[JohnnieB]

Originally Posted by g.schucks

To keep my options open for future upgrades if I think I will up my voltage in the future.. 42 or 48 maybe. What controller should i go with now? I might finish my 4G cables this weekend, stock motor, stock size tires and 1 year old batteries currently. I am going to go with the bigger solenoid that would work up to 48 volt, should I push up to the bigger controller as well instead of the alltrax 400? I am thinking WAY down the road this being lifted with bigger tires and actually driving it around the woods during off lake season. Well, it gets drove in the woods now, but not very well... Don't want to hurt it or anything, so I am not taking it places that I think will hurt it.

The stock PDS motor can't handle much more than 400A, but the max amps on a DCX500 can turned down to 400A by setting the max current slider to 80%. The when you get a more robust motor that can handle 500A, you can crank it back up to 100%.

[Mrh20]

Wow, very good thread! Great information on how an when are motors draw Amps,

[g.schucks]

Originally Posted by Mrh20

Wow, very good thread! Great information on how an when are motors draw Amps,

Your signature sounds about like what I would like to do eventually... I figure I would bump the cables to 2G when I swap a motor. Should I go with the DCX500 over the 400?

You guys rock with all the help BTW, just wait till I get some parts and then have even more questions!

g.schucks

[JohnnieB]

Ask the questions before you get the parts.

You can turn a DCX500 down to 400A for use with a stock PDS motor, but you cannot turn a DCX400 up to 500A for an aftermarket motor.

FWIW: My first upgrade was a complete set (all 10 of them) of 2Ga cables.

[g.schucks]

Originally Posted by JohnnieB

Ask the questions before you get the parts.

You can turn a DCX500 down to 400A for use with a stock PDS motor, but you cannot turn a DCX400 up to 500A for an aftermarket motor.

FWIW: My first upgrade was a complete set (all 10 of them) of 2Ga cables.

I am thinking that I will have questions about the install once parts show. I may or may not have just been shot down by the warden on ordering parts... Still thinking ahead, is it better to have a 48 volt setup when adding 12 volt accessories? Possibly a winch and a stereo?

g.schucks

[JohnnieB]

Before I retired a few years ago, I had a knack for justifying non-budgeted expenditures to upper management, but the same techniques never worked with SWMBO (She Who Must Be Obeyed).

Fortunately, cart addiction is contagious and she caught a mild case of it.

As for going to 48V and adding 12V accessories, they are separate subjects, more or less.

You are at 36V now, but may increase the pack voltage to 42V or 48V in the future, so pick a Controller and Solenoid that will work at 36V, 42V and 48V.
The stock motor will work in that voltage range, so all that is needed to up the pack voltage at a later date is a set of batteries that adds up to the desired voltage and a matching battery charger for that voltage.

The high current cables are not voltage specific, but if you suspect you will be using 8V batteries to build a 48V pack, get the longer cables needed for 8V batteries. (Terminals on 8V batteries are on the same side while they are on opposite corners of 6V batteries, so the interconnecting cables have to be longer for 8V batteries.)

Tapping the main battery pack for 12V accessories is a bad idea and should be avoided. That leaves a DC-DC converter (aka Voltage Reducer) or a separate 12V accessory battery.

There are Voltage Reducers that will put out 30A at 12V with an input anywhere from 26V to 60V, so the entire main battery pack is discharged equally by the accessories.

A winch might draw more than 30A, so you'll probable need a separate 12V battery to run it.