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



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Old 05-05-2019, 07:14 PM   #1
Shepjs
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Default Rxv Brake only getting 12v to connection

Recently acquired a 2009 ezgo rxv. The issue I知 having is the cart will sometimes have a motor brake failure during start up. Then if if the cart passes and able to go forward or backwards is slow moving like the brake is still engaged. I致e already replaced the motor brake and the speed sensor. When I check the voltage to the brake when in forward I知 only getting 12v. But when I put it in tow mode I知 getting 48v. I知 stuck on what to look for next.
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Old 05-05-2019, 08:25 PM   #2
BobBoyce
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Default Re: Rxv Brake only getting 12v to connection

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Originally Posted by Shepjs View Post
Recently acquired a 2009 ezgo rxv. The issue I知 having is the cart will sometimes have a motor brake failure during start up. Then if if the cart passes and able to go forward or backwards is slow moving like the brake is still engaged. I致e already replaced the motor brake and the speed sensor. When I check the voltage to the brake when in forward I知 only getting 12v. But when I put it in tow mode I知 getting 48v. I知 stuck on what to look for next.
Operate mode is current regulated, to provide enough current to keep the motor brake engaged. Tow mode and bypass mode is unregulated on purpose, because the controller is likely not working if you need to tow it. So the voltage applied is due to how the pack energy is applied to the motor brake.

That being said, the voltage being that low does indicate that the motor brake you installed is likely a Heavy Duty motor brake instead of the OEM motor brake that MUST be used on your RXV. With an OEM motor brake, current regulation should resuult in 24 to 36V across the motor brake coil. HD motor brakes draw too much current (due to lower coil impedance) and will result in unreliable operation and eventual failure of the controller!
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Old 05-06-2019, 04:31 AM   #3
Shepjs
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Default Re: Rxv Brake only getting 12v to connection

When I tested the voltage for the brakes it was without the brake being connected. So no current is being applied to the brake wires just voltage. Also I installed a standard brake in the cart not a HD.
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Old 05-06-2019, 08:27 AM   #4
cgtech
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Default Re: Rxv Brake only getting 12v to connection

PWM usually tricks a digital volt meter when zero load is applied to the circuit, I bet a different meter would give a different reading on that same test. I suggest that test while the brake is plugged in, you might get suprised with a higher reading.
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Old 05-06-2019, 01:08 PM   #5
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Default Re: Rxv Brake only getting 12v to connection

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Originally Posted by Shepjs View Post
When I tested the voltage for the brakes it was without the brake being connected. So no current is being applied to the brake wires just voltage. Also I installed a standard brake in the cart not a HD.
Testing voltage without the motor brake connected is totally useless! The controller detects that the motor brake coil is missing and shuts down with a POST fail. The controller will not activate the motor brake FET until after the controller detects the voltage coming through the motor brake coil to the motor brake pin on the controller. As I mentioned before, each pin is an input and an output. When the output goes active, it pulls the pin negative (-). Since it is a PWM, it will not pull it to full negative. Under load with the motor brake coil, it will float above negative at the voltage required to pass the regulated current through the coil.

If you keep messing with I/O pins like this, you are going to hit something critical (like the reverse buzzer), which will kill the controller if disconnected from its I/O pin! The RXV is unlike most other carts before it. The harness wires are not connected to pins that are single state, either an input or an output. Controllers in older carts were like that. Not anymore.

The TXT48 from 2010 to current date also uses a controller with multistate pins. Not as fragile as the RXV controllers, but still easier to damage than older controllers.

With the RXV, all I/O pins are multistate, and when they are in output mode, they monitor their own output while outputting. Applying potential from a multimeter can confuse an input, or even damage it!
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Old 05-07-2019, 01:20 AM   #6
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Default Re: Rxv Brake only getting 12v to connection

Ouch, I guess I said it all wrong. But, a basic voltage reading on a PWM circuit is basically useless, and reckless on any Rxv circuits. Should be avoided. I was not on point on that one.
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Old 05-07-2019, 03:40 AM   #7
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Default Re: Rxv Brake only getting 12v to connection

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Originally Posted by cgtech View Post
Ouch, I guess I said it all wrong. But, a basic voltage reading on a PWM circuit is basically useless, and reckless on any Rxv circuits. Should be avoided. I was not on point on that one.
You were on track. I just wanted to explain why, in detail. This is so others reading this can learn and not make the same mistakes, or those that have killed their RXV controllers can understand why...
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