36 volt upgrade

Shaunb914

It's time to replace the batteries in my 36 volt EZGO TXT series cart and this will be my first upgrade. I have a few questions for those more experienced than me on here. I am planning on upgrading to 48 volts and replacing the controller with a 500 amp controller. I am going to replace the solenoid as well as the FR switch. I will also upgrade to 2 gauge wires. The cart already has a lift and larger tires on it. Do I need to replace the motor also or can I leave the stock motor on? What kind of performance increase could I expect if I upgraded the motor? Is there anything else I am missing or should this cover it? What speed should I expect after the upgrades?

BGW

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rbuggies48IN

scottyb and/or johnnieb (spelling) should be able to respond in detail, but as you probably already know volts = speed and amps = torque. The percentage increase from original equipment volt & amp ratings vs. original 36volt and guessing 400 amp controller will approximate speed & torque increases as long as motor can handle it. I think most motors can handle up to a 40% increase from their stock voltage, but you need to check this out with your existing motor manufacturer once you get the model/serial numbers from existing motor. I am guessing you would benefit from a plumquick motor rebuild for torque and speed. Just let plumquick know your 'cart's desires' along with tire size, main use of cart, weight of cart, etc. and they can fix you up! You're going to enjoy your upgrades I have done what you are doing to my 42 volt cart and it is a noticeable improvement over stock. Remember to go to 2 gauge throughout the entire system, not just the batteries.

scottyb

It looks like you have done the research properly. The series stock TXT motor can handle 500a access on 48v. You will see a 33% increase in speed and torque minus any unique drag like brake drag, under inflated tires, excessive load, etc. Generally speaking the speed goes from 14 to 18-19 mph on stock tires.

JohnnieB

Need to know the tire height to estimate the theoretical speed. (Also, the max inflation pressure.)
The numbers stamped on the sidewall can be off by an inch or more in either direction, so measure the height of the rear tires.

A level and a yardstick is typically close enough, but if you want a highly accurate diameter, measure the distance traveled per tire revolution while the cart is loaded with its normal load and divide by Pi.

FWIW: I measured the distance traveled in four tire revolutions, so I know within 0.01", or so, what my tire height actually was at the time, but temperature, inflation pressure and load carried changes the dynamic height slightly.

The taller tires you have on your cart will increase speed and reduce the torque available where rubber meets road. If the are 22", the mathematical speed increase is 22% and the torque loss is 18% and if they are 23" the mathematical speed increase is 28% while the torque loss is 22%. There are other factors in addition to height change, so the mathematical speed may not be reached, and the torque loss may be greater.


Going from 36V pack to a 48V pack will increase both speed and torque by about 33%.

A higher ampacity controller will increase low end torque and acceleration off the line. Top speed will remain the same, however the cart might not slow quite as much on hills, but it will still slow down.

Other than running cooler, there won't be much performance difference with 2Ga cables and HD F/R switch, unless the items being replaced are in bad shape. If the existing cables and F/R switch are getting more than lukewarm after a hard run, they are either underrated or in bad condition.

The solenoid should match the controller. HD (200A continuous) for 400A and below controllers and Super-Duty (400A continuous) for 500A and above controllers.

Sounds like you want to do it right, so you might want to consider a HD reversing contactor rather than a HD F/R switch.

As for the motor, it depends on what you use the cart for and what your expectations are. In general terms, you have a choice between more speed or more torque (or something in the middle that give a bit more of both) and there are two speed motors available that changes the motor from High torque to high speed at the flick of a switch. (As well as two speed differentials that allows you to shift between 20:1 and 10:1 gear ratios instead of the stock 12.44:1 ratio).

A stock series motor will tolerate 400A @ 48V okay and up the stock speed of ~14 MPH on stock height (18") tires to about 18.5 MPH. If you go with a 500A controller, turn it down to about 400A while running a stock motor.

JohnnieB

I stand corrected.

I'm a SepEx guy rather than Series.

Shaunb914

The cart is mainly used around my 50 acre property. It is fairly hilly and the main issue I have right now is crawling going uphill. If I could get around 18 mph without a significant drop in speed going uphill that is what I'm shooting for. Do you think the upgrade to 48 volt alone will be sufficient or should I go ahead and upgrade the controller also? In other words, will an upgrade to a 400 amp controller give me a significant enough boost in performance to justify the cost?

Shaunb914

Also, thanks for the taking the time to answer my questions. I really appreciate the help.

rbuggies48IN

Plumquick motor rebuild will give you noticeable speed and torque improvements, but 300 amp controller is a problem for what I think you want to accomplish. Have you looked into getting your controller rebuilt? This would lower your costs a little.

JohnnieB

You cannot upgrade to 48V alone. The stock 36V controller and 36V solenoid will not work at 48V, so they will have to be replaced, as well as the battery charger, which is also voltage specific.

The stock motor will work at 48V.

The cables and F/R switch will work at just about any voltage, but are limited by the amp handling capacity. They have to be compatible with the rest of the amp delivery system.

If your tires are taller than stock (18"), you are already behind the curve for how much it slows down going up hills, so you have to upgrade the drive system somewhat, just to break even with a stock cart.

Series drive systems slow down more than SepEx drive systems and AC drive systems, but all carts slow down going up hill. It is simply the laws of physics. Basically, the maximum RPM a motor can reach is when the torque being generated is equal to the mechanical load being applied to it. The amount of torque generated is determined by how many amps are flowing through the motor windings and the faster the motor is spinning, the fewer amps it can draw. The mechanical load increases when a cart goes uphill, so the motor slows in RPM until it is electrically capable of drawing the amps needed to generate the torque needed to match the drag (mechanical load).

A higher applied voltage will force more amps through the same impedance (dynamic resistance of the motor), so a 48V cart will be faster going uphill than the same cart at 36V, but the percent of RPM loss will be similar since the percent of drag increase on the same hill will be roughly the same. Therefore, the taller the tires, the greater the difference between the max speed on level ground and the max speed going up a hill.

An aftermarket motor whose Torque vs RPM curve is better suited for climbing hills with tall tires might be needed in addition to the other upgrades.

Shaunb914

I don't mind investing the money in a new controller and motor rebuild if it will give me the speed and torque I'm looking for. What size controller would you recommend?