2002.5 Club Car DS 48V controller upgrade questons

[CP241]

The part you’re missing, is that your pack voltage is staying pretty constant. If the motor were allowed to pull as much current as it wants (needs) it creates a significantly larger draw and pack voltage will drop quickly. The reason it stays high is because the controller limits the current.

This will also explain part of the benefit of lithium technology vs. lead acid. Lithium batteries have significantly less “voltage sag” than lead acid. So with higher current demand and less voltage drop, acceleration and performance are dramatically increased.

Take a stock series cart limited to 250 amps. Hit a hill and it will drop from 13mph to 8mph real fast. Voltage will not drop below 48v on a good charged pack. Add just a controller. It will go a little faster and hold speed much better, but you’ll see pack voltage drop (but you won’t have a drop in pack voltage vs. available voltage at the motor like you have been measuring). Add an aftermarket motor onto it. Under a heavy load with a healthy pack it wouldn’t be unheard of for it to drop down to 42-43v during that heavy loaded period. But once it stabilizes (top of the hill) the total pack voltage recovers quite quickly. But still pack voltage vs. available voltage at the motor will be about the same.

Here’s where lithium comes in nicely. Upgraded motor, controller, etc. that voltage drop/sag under load is substantially less than a FLA battery pack. They’re much more stable under load.

So what you’re measuring with the voltage drop at pack vs motor is a good thing to know, but it doesn’t tell a whole lot. The only reason you’d have a substantial voltage drop between pack voltage and available V+ at the motor would be either a motor issue, or bad connection/cable. But you’re seeing pack voltage available at the motor, so no connection issues. The total pack voltage is what the variable is here, with a larger demand/load the overall pack voltage drops much more if the controller allows 500 amps va 250 amps. But pack voltage available at the motor will still be pretty consistent comparatively if all you’re looking at is voltage drop.

I’m not trying to be rude here, I am just trying to explain the basic electrical theory that plays here. There are other influences that can affect both voltage and current, but generally what I’ve outlined is what you can expect in real world application.


If I’m wrong on anything here, I’m sure Sergio, Johnnieb, or a plethora of other knowledgeable folks on here will thrash me. And I welcome the thrashing. We’re all here to learn and nobody knows everything

[DaveMJ]

CP241 - I agree with some of your statements, others I struggle with. I would truly welcome Sergio or JonnieB's input into this discussion.

Just to be clear the conversation we are having relates Series motors only.

Originally Posted by CP241

If the motor were allowed to pull as much current as it wants (needs) it creates a significantly larger draw and pack voltage will drop quickly. The reason it stays high is because the controller limits the current.

A controller cannot apply full pack voltage to a motor and simultaneously limit the current drawn by the motor. Ohm's Law says otherwise.

A couple of quotes from Alltrax Technical Note 003.

"It varies “power” by modulating voltage." It referring to the controller. They are saying the controller controls power (voltage squared/impedance) to the motor by limiting the applied voltage. Not by applying full voltage and limiting the current as you suggested - it can't be done.

"Changing the controller on a series motor will not increase the speed of the vehicle."

JonnieB commented on a thread "What to expect with 500 amp controller and Stock Motor":

Originally Posted by JohnnieB

4. There are basically three ways to increase the speed of a cart with a series wound motor.
A. Increase the battery pack voltage.
B. Change the final drive ratio. (Tire height and differential gear ratio)
C. Motor that is wound for high end torque (High-speed motor).

He did not suggest an upgraded controller as an option to increase speed.

I maintain that if the motor is seeing full available pack voltage under load you are getting all the speed and or torque that motor is capable of delivering.

Now if the controller was not capable of providing full pack voltage to the motor under heavy load conditions; I agree an upgraded controller will help.

But in my case I observed full pack voltage to the motor under acceleration and at top speed. So the motor was maxed out. In my test the cart had a single occupant and the roads are flat, other conditions may have yielded a different result.

[CP241]

As I said in the first post; voltage equals speed. Current equals torque. You are only stating what I already said.

OP wants torque to go up hills.

Thanks for agreeing

[DaveMJ]

CP241 - I'm not sure how you interpret my response as agreeing with you.

OP said he wanted more speed in addition to more torque for hills.

Originally Posted by hrk

Like to pick up some MPH top end, .......

All I'm saying is that if the controller isn't the limiting factor in the system for speed or torque an upgraded controller is not going to yield any benefits.

We obviously have fundamental differences of opinion on this that we are not going to resolve with more posts. So I am not going to debate further.

hrk - I suggest you contact Scotty.B at Carts Unlimited or Dave at Revolution Golf Cars. Explain what you want and they will provide some guidance.

[hrk]

Appreciate the discussion, interesting about the two sides of the equation.

I'll contact them and see what they think, I'm not looking to set land speed records
just to find a bit more power for going up hills (which are not big in FL) and handling the extra weight of the cart with more suspension, bigger wheels/tires and a back seat.

Right now it's stock height, stock wheels etc. My concern is will it slow it down with all the extra parts

Most likely I"ll do the work leaving the stock configuration, leave it be and see...

or

1) Bump the Controller, or

2) Bump the controller and motor

I'd rather not replace the motor if bumping up the control module
will give me an increase in power/tq, conversely if the controller isn't
going to gain me anything keeping the motor stock then it's not worth
the investment...

[CP241]

If the tires are larger, it will go faster. This changes the overall gear ratio of the cart so top speed will improve.

Larger tires, back seat, etc adds weight and it won’t hurt the top speed, but it will take longer to get there.

Upgraded controller will help that. Along with the supporting parts... correct solenoid, good wires to handle the extra current demand, etc.

Adding just the controller and supporting parts will probably put you where you want to be. And leave you plenty of headroom for when you decide you do want more performance and upgrade the motor too. The 500 amp controller will handle just about any motor you want to put in there

[Swan]

I ran my stock motor and solenoid for many years after I added a 700 amp controller and 2 ga cable. 4 yrs later I replaced just the motor and still ran stock solenoid. 5 years went by before I replaced the solenoid and two yrs after that I went with reverse contactors . A series cart is the workhorse of DS . mine will hit 30 mph on the flat and climb a flight on stairs .