1992 EZ GO Marathon

[72volt_ezgo]

System voltage drops to 2VDC??? As in battery voltage accross the pack?
That would be a bad battery (or more!). What happened to 35.5V?
Barna

[mike71]

System voltage drops 2vdc. Sorry about that. I edited it in previous post.

I just tested the ind. batteries while pressing on and off the pedal and they were all consitently dropping 0.3vdc

The Curtis controller model # 1204 027

[JohnnieB]

Originally Posted by mike71

Ok here is the results from the tests that I have performed this morning

The system voltage is 38.10vdc and with pedal pressed it drops about 2vdc.

Voltage from B+ to M- +6.8(vdc)

Continuity of wires(disconnected) between M- and B+(to motor)= Rings
Continuity of wires(disconnected) between M- and B+(to solenoid)= Rings

Ohm test: M- to B+(to motor) = 0.7 What unit of measurement? Ohm, Kilohms, Megohms
M- to B+(to sol.) = OL Something amiss here. You get continuity above and an open here.

With M- disconnected at controller, I checked between it and and B+(while still attached to the controller) and got 38.10vdc with pedal pressed(which matched the system voltage) and 0 vdc without pedal pressed.
Let me make sure I'm reading this right. You have one DVM lead attached to controller terminal labeled "B+ and the other attached to controller terminal labeled M- and the heavy gauge wire is disconnected. You get fully battery voltage with pedal depressed and Zero when it is not.

If that is correct, let's try it again, starting with the pedal slightly depressed and slowly pressing it until it is fully depressed while watching DVM.
The reason it is Zero when pedal is up is because solenoid isn't energized and B+ is not being sent to B+ terminal on controller.
With the pedal slighty depressed, the HPD microswitch closes and solenoid energizes.
If the controller is good, the voltage should start low with the pedal slightly depress and climb to near full battery pack voltage as the pedal is depressed.
I will go check the model number of the controller and check the ind. batt. voltages with pedal pressed and reply back shortly.

Also, On smooth level ground, kneel or sit in the cart, place one hand on the ground and push the cart forwards or backward. If you can't do it, there is a mechanical bind someplace keeping the motor from turning.

[72volt_ezgo]

Originally Posted by mike71

System voltage drops 2vdc. Sorry about that. I edited it in previous post.

I just tested the ind. batteries while pressing on and off the pedal and they were all consitently dropping 0.3vdc

The Curtis controller model # 1204 027

Ok thanks for the correction!

I still fail to see how 35+V at the solenoid or controller during takeoff attempt could cause the cart not to move due to one or more weak batteries but that's just my opinion

Barna

[JohnnieB]

Originally Posted by mike71

System voltage drops 2vdc. Sorry about that. I edited it in previous post.

I just tested the ind. batteries while pressing on and off the pedal and they were all consitently dropping 0.3vdc

The Curtis controller model # 1204 027

You posted while I was composing.

Batteries are probably okay, so something is drawing enough current to drop the pack voltage by 2V.
Could be a stalled motor or a bad controller. See if the motor will turn (cart moves when pushed) before looking at the electrical system any further.

Here is a manual for the 1204 and 1205 series controllers. Be careful reading it since not everything applies to your specific application, but it explains how a controller works and the troubleshooting steps towards the end are pretty good.

Figure-9 on Pg-13 is a pretty good generic diagram of the high current circuit in your cart.

[72volt_ezgo]

Good point to see whether the cart can be pushed or not! I assumed it did (never assume!)!

However I'm willing to bet, if there was a mechanical lockup and he tries to take off,the battery voltage will sag way below 35.5 at full pedal accompanied by some kind of torquing action/sizzling/heat/smoke etc from somewhere under the seat.

I'm also a fan of LOAD testing electronics and not to rely on what a volt meter says without a load across the circuit. Even if it is 3 automotive incandesent bulbs in series to simulate a 36V load.(headlight or at least turn signal/brake light bulbs).
Because if there is high resistance internally in the controller,you will read perfect voltage until you put a load across there and I'm not going to lie,I learned that the hard way : ) )
Barna

[JohnnieB]

Originally Posted by 72volt_ezgo

Good point to see whether the cart can be pushed or not! I assumed it did (never assume!)!

However I'm willing to bet, if there was a mechanical lockup and he tries to take off,the battery voltage will sag way below 35.5 at full pedal accompanied by some kind of torquing action/sizzling/heat/smoke etc from somewhere under the seat.

I'm also a fan of LOAD testing electronics and not to rely on what a volt meter says without a load across the circuit. Even if it is 3 automotive incandesent bulbs in series to simulate a 36V load.(headlight or at least turn signal/brake light bulbs).
Because if there is high resistance internally in the controller,you will read perfect voltage until you put a load across there and I'm not going to lie,I learned that the hard way : ) )
Barna

Yeah, if the motor was stalled, there would probably be smoke and fire coming out from under the seat by now.

I also prefer measuring circuits under load. And I prefer to use the right tools and test equipment for the job, but sometime one has to make do with what is available.

I'm sure if either of us had mike's cart sitting in front of us, we would have had the problem nailed in 5 minutes or less, but trying to do it by remote control takes longer.

I also learned some things the hard way. For example, I learned how DOMs read pulsed DC after replacing a $10,000 photomultiplier tube. (Bad filter cap on a full wave bridge that feed an adjustable regulated power supply feeding a 10V to 10KV DC-DC converter. When DOM read 10V the regulated PS was actually putting out clipped sine waves that peaked at 14.4V so the tube was getting hit with 14.4KV 120 times per second and didn't like it too much)

Hopefully mike71 will be able to figure out what is wrong with his cart despite being pulled/pushed in different directions.

[mike71]

Ok. Here we go again.

With M- disconnected at Controller and B+ still attached I tested from Controller(where M- would normally be if I hadn't detached it) to B+ and received 39vdc shortly after pedal was pressed and the solenoid clicked but the voltage did not build up gradually to this point nor did it increase any farther than 39vdc.

Retested M- to B+(which leads to motor and not the one that goes to the solenoid) with them both removed from the contactor(just testing the wires themselves) and I got 0.5(Ohms).

The DVM that I am using is a Fluke 177 True RMS

I haven't tested the cart by sitting in it and pushing with my hand yet but the wheels seem to spin easily with the cart up on the jack stands.

Any more ideas?

[simple man]

Have someone hold one wheel while you try and spin the other one. If it still turns ( although stiff ) nothing is frozen up. If you don't hold one wheel, it just turns the differential.

[mike71]

Makes sense. Thanks