Time to upgrade the 94 Medalist. Suggestions?

[frank43]

Hey all,

Been a while since i posted. Have a 36v 1994 Medalist, that has 6 good batteries. That said, it is as slow as molasses.

I want to upgrade the cart in a 'phased' approach, eventually moving to 48v.

I have read in the past that you can upgrade the controller, solenoid, wires and F/R switch first, and then upgrade to the 48v battery setup, once the current batteries die.

Question is what parts do you recommend, and how much of an improvement will we see at each 'phase'?

Lastly, I am pretty mechanical; how hard is it to do the upgrades? Seems pretty DIY, but any input would be appreciated.
Thanks!
Frank

[orangeman6]

https://www.cartsunlimited.net/

Check our the site above. Great stuff, good prices and excellent service. It’s a great place to learn a lot too.

You can upgrade your controller, solenoid, cables and f/r. Be sure to order your cables for 8v batteries, so they’ll work when you go to 48v. The 8v cables are longer. When you do go to 48v , you can still run the stock motor.

I think the experts will tell you that torque is where you’ll realistically see an improvement with the upgrades above. The controller just passes the amperage from the batteries. It is voltage that gets you speed. Bigger tires will give more speed too, but at the sake of torque.

A good plan would start with what you ultimately want the cart to be able to do.
Desired speed
Number of passengers
Terrain and elevation
Budget
Tire size

Post that info, red the website, and you’ll get the info you need.

[frank43]

Thanks Orangeman. I think speed is the main desire. The cart is very slow, especially up neighborhood hills (normal sized). Usually have 2-4 people on the cart, half adults/half kids.

Anything I can add on to get some more speed? I am running stock-tires, and everything else
Frank

[JohnnieB]

A completely stock 94 Medalist in good health should have a top speed on level pavement of 12 MPH. If your cart isn't getting up to the speed, or equivalent RPM with tires taller than 18" in diameter, then there might be some speed improvement prior to upping the battery pack to 48V. Otherwise, the improvements will be in low end torque and acceleration.

Upping the battery pack voltage from, 36V to 48V ups both speed and torque by 33.3%, so the top speed will be about 16MPH with 18" tires and 12.44:1 gears.

The tallest tire that can be used without lifting cart frame and body off axles (which raises the cart's center of gravity and reduces stability) is 20" and that ups the speed to about 18 MPH. A faster top speed can be obtained by installing a high-speed motor.

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Neither the stock 36V controller nor the stock 36V solenoid will work at 48V, but there are aftermarket controllers and solenoids that will work at 36V now and 48V later. Alltrax SR48400 (or larger) controller and a MZJ400A solenoid is a good choice.

Of course, the battery charger has to match the battery pack voltage, so it will have to be changed at the same time as the battery pack goes to 48V.

I'd do the cables first. All 13 of them should be upgraded to a minimum of 4Ga and if there is the possibility of tires taller than, or a controller that passes 500A or more, get 2Ga.

Next is the F/R. Either a super-duty one or a reversing contactor. (The mechanical F/R is the weak spot in a series drive and a reversing contactor more or less solves those issues.)

Next is controller and solenoid.

Then up the pack and charger to 48V.

Then figure out the tire height you want to run.
Then figure out what motor is needed.

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The trick is figuring out what you want to end up with and build towards that goal.

[JohnnieB]

Originally Posted by frank43

Thanks Orangeman. I think speed is the main desire. The cart is very slow, especially up neighborhood hills (normal sized). Usually have 2-4 people on the cart, half adults/half kids.

Anything I can add on to get some more speed? I am running stock-tires, and everything else
Frank

What is the cart's top speed on level pavement with a fully charged (38.2V) battery pack?
What does it slow to on the hills you typically climb?
Are of the high current cables hot after climbing hills?

12 MPH is the EZGO spec for a 94-96 Medalist. If you aren't getting at least that speed, something is holding the cart back and whatever it is needs to be identified. The most likely suspects are bad or too small cables, bad bearings (wheels and differential) or dragging brakes. (Or batteries dropping under load)

Once a series drive cart is performing at stock specs, there are only three ways to up the speed significantly.
1. Higher voltage battery pack. Increases both speed and torque (throughout RPM spectrum).
2. Faster final drive ratio. (Taller tires or numerically lower gears in the differential) Note: Speed increases are offset by torque losses.
3. Faster motor. Typically a higher speed motor has lower torque, but there are aftermarket motors that do have more speed as well as more torque.

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How fast do you want the cart to be?

[frank43]

Hi Johnnie,

On a flat road, the cart will get up to 10MPH, but slows to a crawl on any type of hill. That is with a fully charge.

My meter however will drop to 34-35 under load, especially up hill. The brakes are not dragging, but I am unsure of the diff/bearings. I dont think that is the problem as I dont hear any noise or grinding. Runs smooth.

Lastly, the cables are not getting too hot.

I think that the normal 'spec' would be good to me, so I think I am going to start the process like you mentioned above, spaced in intervals based on performance
1. Change cables to 2Ga
2. Get an HD F/R Swtich
3. Controller and Solenoid (48V)
4. Upgrade to 48V

I guess the motor would be last, as I am always looking for speed. But just getting to stock spec should suffice until the batteries die.

Thoughts? Am I missing anything?
Frank

[JohnnieB]

Series drive carts slow more on hills than other type drive, just the nature of the beast, but shouldn't slow to a crawl unless the incline is greater than 25% (14°). I'm not sure how much slowing is normal, but I'm pretty sure it ought to stay above 6 to 8 MPH.

Try putting 20 PSI (or whatever the max inflation pressure stamped on sidewalls is) in the tires. That might up the speed a little. I lose about 2MPh off my top end when I reduce the air in the tires for a more comfortable ride.

In a nutshell, the faster the armature spins, the fewer amps the motor can draw and the fewer amps, the less torque is produced. At a specified voltage. a series motor's RPM will increase until the amps it is capable of drawing produces a torque equal to the mechanical load on the motor. When the mechanical load increases, as it does when you transition from level ground to climbing a hill, the motor's RPM decreases until the amps it is capable of drawing once again produces a torque equal to the new mechanical load.

The insidious part is that the moire amps that are drawn from a lead acid battery, the lower its voltage drops to, which also slows the motor. Basically, you get a double whammy in the speed loss department.

The same thing happens to sepex and AC drive, but the effect is less.

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Your battery's voltage isn't dropping abnormally, but could be better. Good cables and F/R will probable help the cart's speed on the inclines. There is power loss in the cables, contacts and connections no matter how good they are and the thicker the cable and the better the connections, the less the loss.

The solenoid is also a bottle neck. The stock one is only rated at 85A, so its contacts are probably a bit chew up from years of passing up to peaks of 275A, which is the max the stock controller will pass.

Looks like a good plan.

[frank43]

Thanks for your input.
Quick question on moving to Six 8V batteries from Six 6V batteries-
Will they bigger batteries fit in the place of the 6 volts? Are their any adjustments that are needed to fit the new units once purchased?

[JohnnieB]

Originally Posted by frank43

Thanks for your input.
Quick question on moving to Six 8V batteries from Six 6V batteries-
Will they bigger batteries fit in the place of the 6 volts? Are their any adjustments that are needed to fit the new units once purchased?

Six 8V batteries will fit in the six 6V battery rack. 10 3/8" X 7 1/8" is more or less the industry standard Length and Width for 6V and 8V cart batteries. Here is a spec list for Trojan batteries.

The terminals on 8V batteries are both on the same side, so longer cables are needed to connect them together.

A 48V battery pack made up of 170AH 8V batteries has roughly the same driving range as the standard 6V - 225AH 36V pack. If you want to go further on a single charge, go to a higher AH 8V battery.

[Chbyfngr]

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