EZGO PDS (2004) Upgrade Paths

[MattCarp]

I've purchased my first cart, a 2004 EZ Go TXT PDS. It's powered by three deep cycle marine batteries (36V).
I've played with the different performance plugs and it seems to be performing fine.

I'm afraid that it might not have enough power for a monster hill I need to climb (paved, maybe 0.25 miles, 10-15 degree grade).

So, I'm starting to think about upgrades.

It seems that an AC conversion is the top of the line, with the Navitas TAC controller. While I'm capable of installing that myself, that's a major expense. Plus, this is not going to be a frequently used "suburban scooter". So what are the intermediate upgrade paths?

Is there a benefit to just upgrading the controller to a Navitas TSX over the stock?

After that, it seems that I need to go to 48V DC, with new motor, new solenoid, another battery, new charger, new charging port, and, new charge meter.

I think the 48V conversion cost would be rather close to the AC conversion?

....It seems there is little actual performance data published on these different options. I know it can depend on a lot of things, but it would be helpful if someone took a cart, demonstrated performance with a specific load, then re-tested with each different configuration...

Does anyone here have the experience they can share?

Thank you!

 

[Golf Cart Wizard]

I've purchased my first cart, a 2004 EZ Go TXT PDS. It's powered by three deep cycle marine batteries (36V).
After that, it seems that I need to go to 48V DC, with new motor, new solenoid, another battery, new charger, new charging port, and, new charge meter.

This isn’t a good idea if you are trying to upgrade the controller/motor, those batteries barely have enough current to power the stock system. Not to mention adding another battery in with 3 old batteries will create an imbalance. Going to 6x 6 volt golf cart batteries with the stock system would be a better option for climbing the hill, or if you want to convert to 48v get 6x 8 volt at least. Or go to lithium (real golf cart lithium, not 3x amazon 12v lithium in series)

 

[MattCarp]

Interesting.

So a good path for me would be to install a better battery system on my 36V cart, before I change controllers or go to 48V?

A lithium setup seems like a good idea, due to the weight savings..

 

[Golf Cart Wizard]

I would decide if you want 36v or 48v before you buy the battery, don't want to have to buy another if you want to upgrade later. Can the golf cart climb the hill now? Do you care about how fast it goes up the hill or you just need it to get to the top?

 

[MattCarp]

I just checked the air pressure on the 23" tires. A little low. Max inflation pressure is 20, so I brought them up to 19 psi.

Using the Waze app on my phone, I was able to get it up to 22 mph, which was plenty fast for me on this cart. The cart is lifted (not sure how high, but it's not too high).

Regarding the monster hill...I don't need to go that fast, just get up it. I'd say I'd need to be between 5-10 mph on the hill.

I looked at some lithium costs - wow, you're right, I'd want to make that purchase carefully!

I suppose I don't know what happens to a [DC] motor in this type of a heavy, sustained load. I can guess that as the rotor slows down, we have heavy current flows, which, puts big demands on the battery system. If I'm right about this, this explains why you've suggested lithium as a first step?

Once the batteries are able to supply the power, I would guess the next concern would be heat? That said, the hill, at 0.25 mi at 5 mph, would be 3 minutes. So, I'd assume 3-6 minutes of heavy load.

I also guess that higher voltages allow for higher power delivery...As we discuss this, it seems that this might not be necessary for my usage scenario...

[thank you for letting me tap into your knowledge here!]

 

[Golf Cart Wizard]

I suppose I don't know what happens to a [DC] motor in this type of a heavy, sustained load. I can guess that as the rotor slows down, we have heavy current flows, which, puts big demands on the battery system. If I'm right about this, this explains why you've suggested lithium as a first step?

Yes the DC motor will be drawing substantially more current under the load. An AC motor is more efficient and won't have nearly the current spike as DC.

Lithium batteries don't have the same voltage drop as lead so they will supply higher voltage under load and therefore more power to the motor. If you go lithium make sure the BMS has a high enough capacity, if the amperage is below what the motor draws the battery will shut down. Don't forget your big tires greatly increase the current draw.

A 36v lead system will probably struggle to do that hill especially loaded up, the lack of voltage drop with 36v lithium would help. A 48v lead system plus an AC conversion would have no problem climbing the hill and make the golf cart much faster. Depends whether you value the lifespan and easy maintenance of lithium or the higher performance and efficiency of an AC drive what to do as both options would have similar price tags

To the original question I have done upgraded TSX controllers with stock motors in 48v club cars as well as TAC, both with identical lead batteries. The DC was barely noticeable improvement over stock maybe a little more low end torque but not any more speed. The AC upgrade will blow DC out of the water. Top speed is over 50% higher and you have torque throughout the entire RPM range unlike DC which only has down low torque. That is why DC slows down so much going up hills the motor cannot produce sufficient torque at high RPMs. See these current charts for DC then AC, the current is pretty much equivalent to torque output. DC falls off way quicker:



Also AC will be much more efficient. I measured current draw at steady speed and AC is up to 50% less current drawn from the batteries driving the same speed

 

[HotRodCarts]

Good info @Golf Cart Wizard thanks for posting it.

 

[MattCarp]

Exactly the experience I was hoping to find!

So summarizing: it would seem that a first step would be to upgrade the battery to golf cart lithium.

If that doesn't do it, the 48V DC probably isn't a good next step, since the higher voltage DC primarily helps with higher speeds, and may only offer an incremental improvement on a sustained load? Then, I would go to the AC system.

From a cost standpoint, since the AC upgrade would require the replacing a 36V battery and associated components, I should consider making the jump to AC from the beginning. AC: a more efficient system (longer run time on a charge), less maintenance (no motor brushes!), and, as you said, torque is throughout the rpm range.

 

[Golf Cart Wizard]

Higher voltage will increase torque too not just speed. And will be more efficient since you draw less amps to do the same work, watts (work) = amps x volts. Which means less energy wasted as heat, also with lead batteries specifically the more amps you draw the less useable capacity. I would go AC first, you can always upgrade to lithium in 5 years when the lead batteries die vs. starting with lithium now you’re locked into the voltage you started with unless you want to buy another battery. Some people do say you can run the AC kits on 36v but considering it was not designed for that it’s probably not a good idea and will likely void the warranty.

 

[MattCarp]

Super thanks!