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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV.



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Unread 03-28-2016, 07:33 PM   #11
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Default Re: Checking my RPM

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Originally Posted by kgsc View Post
And is anything getting warm?
I didnt feel anything that I would call hot but the lower cables form the forward reverse switch were slightly warm after my ride.
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Unread 03-29-2016, 01:15 PM   #12
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Default Re: Checking my RPM

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Originally Posted by timmyjane View Post
1. Well I guess the cart is doing what it is supposed to do. I GPSd today and was hitting 18 on slight downhill maybe about level, 15 on slight uphill. 21 down a long maybe 8-10 degree downhill. Tires are 19.75 inches tall.

2. Not sure if this is normal but voltage hung out around 47.2-5. A few times it dropped to 44,x when I punched it but mostly around 46 when I hit the throttle. It would climb to 48.2-5 when going on slight declines. After I got back home and parked it went to 50.1 in a few seconds after I parked.

3. Does all that seem normal?
1. The published speed of a stock 36V TXT series drive is 13 to 14 MPH on 18" tall tires, so I'll use 13.5MPH, which is 3136 RPM at the motor.

Upping the pack from 36V to 48V is a 33.3% increase, which increases the theoretical max motor RPM by 33.3% also, or 4180RPM, which is 18.0MPH on 18" tires, but the drag increases as speed increases, so it won't quite reach 18.0MPH.

Upping the tire height from 18" to 19.75" is a 9.7% increase in speed, or 19.7 MPH, but is also a 8.9% loss in torque, so the cart will not reach the max theoretical speed.

My guesstimate is that the cart ought to do about 18.8 to 19.5 MPH on a level hard surface. Sounds like you are in the ballpark, but a bit on the low side.

2. In and of themselves, the batteries in a typical 48V battery pack will drop 1.5V per 100A of current draw. The combined resistance of the high current cables, connections and contacts, plus the voltage drop of the controller can easily double that amount.

However, your dashboard voltmeter only looks at the 6 batteries and 5 interconnecting cables, plus their connections, so my guess is the expected voltage drop on the dash voltmeter ought to be around 2V per 100A, if the cables and connections are in good condition.

During normal operation, you want to avoid dropping the under-load voltage below 42V and never drop it below 36V. At 1.5VPC (Volts per Cell) and below, irreversible physical damage to the battery's plates occurs, which is 36V with a 48V battery pack.

3. No red flags waving, but there may be room for improvement.
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Unread 03-29-2016, 01:34 PM   #13
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Default Re: Checking my RPM

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Originally Posted by timmyjane View Post
I didnt feel anything that I would call hot but the lower cables form the forward reverse switch were slightly warm after my ride.
Any and all cable and contact heat, is power that ought to be converted to motion by the motor, but is being lost in the form of heat.

I advocate the high current cables not getting more than 10F above the ambient air temperature.

Also, all cables and their connections ought to be very close to the same temperature, so if you have some getting warmer than the others, they need to be fixed.
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Unread 03-29-2016, 08:22 PM   #14
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Default Re: Checking my RPM

JohnieB-How does one improve on efficiency? How about speed? Anyway to squeeze more out of a series motor. My wife makes fun of me because her stock PDs at work is much faster and strogner, according to her. I believe it. Since all appears to be as it should, mostly, I'm a little disappointed for $1k in "upgrades".
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Unread 03-30-2016, 08:40 AM   #15
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Default Re: Checking my RPM

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Originally Posted by timmyjane View Post
1. JohnieB-How does one improve on efficiency?
2. How about speed?
3. Anyway to squeeze more out of a series motor.
4. My wife makes fun of me because her stock PDs at work is much faster and strogner, according to her.
5. I believe it.
6. Since all appears to be as it should, mostly, I'm a little disappointed for $1k in "upgrades".
1. Identify and address things that are wasting electrical energy and/or produce mechanical drag.
a. 4Ga or thicker high current cables with soldered and crimped ring terminals.
b. Heavy duty F/R switch or reversing contactor.
c. 400A solenoid.
d. Clean connections, properly tightened.
e. Inflate tires to max recommended inflation pressure. (What is max inflation pressure embossed on the sidewalls of you Tires?)
f. Check for bad wheel bearings.
g. Change oil in differential.
h. Dragging brake shoes.
To name a few.

2. Reducing the cart's electrical and mechanical inefficiencies will increase speed.

3. Yes. If your are running a 10 year old stock series motor, a thorough cleaning and new brushes as well as a new shaft bearing might do wonders for it, but replacing the stock motor with a more robust one would be better.

4. A stock PDS shouldn't be faster or stronger than series drive running at 48V on 19.75" tires. They night run pretty close to neck and neck at top speed, but the series drive at 48V with a 500A controller ought to have more pulling power.

5. Very wise move.

6. I'm not sure all is as it should be. Speed might be roughly in the ballpark, but the thing about a stock PDS being "stronger" leads me to believe your motor may need some TLC.
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Unread 03-30-2016, 08:01 PM   #16
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Default Re: Checking my RPM

Nice reply. Thank you.

I already have 2AWG cables on all but the wires form the F&R switch to the motor.. Looking a doing some 1/0. I can get it cheaper than 2AWG.

I have an extra motor for a project cart. Ill look at refurbing that one and then make the swap. Never have taken apart a golf cart motor before so this should be fun.
Sure wish I knew what the motor souping up guys actually do and if we could do that at the home shop.
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