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



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Old 09-12-2021, 01:19 PM   #11
JRaf
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Default Re: Batteries, charger, a long confessionary tale...

Thanks JohnnieB, I've seen everything you attached (been following a while.) I've done that Lester test. I don't remember the exact results but they were within the recommended numbers with either cap.
I have submitted some questions to Centennial (regarding the source of their design, recommended charge voltages, chargers, etc.). That's something that I clearly should have done BEFORE I purchased batteries. I'll report back.
The USBattery site is very informative (until it gets over my head), most importantly they recommend a charger that uses dV/dT technology rather than a ferroresonant design.
Empirically, the cart wouldn't go up the hill this morning. That could be because the batteries are undercharged or haven't been broken in. I'll order an appropriate charger and the old TCIII will gather dust in the barn. Yet another lesson learned. Thanks again.
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Old 09-12-2021, 01:31 PM   #12
Mooncarter
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Default Re: Batteries, charger, a long confessionary tale...

Been following this, and JB is the man to lead you through this.

Just curious. How steep is this hill you are talking about?
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Old 09-12-2021, 01:48 PM   #13
JohnnieB
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Default Re: Batteries, charger, a long confessionary tale...

I went back to your first post in this thread. You said the cart made it up your "Long, hilly driveway" a few times on the 12V marine batteries. Well, your 6V 200AH batteries are more than equal to them and should not fail to make it up the hill, nor should the cart have stopped climbing it after a day or two with the 12V batteries.

Something went wrong with the cart's drive system and at most, the batteries are only a secondary factor.

Need to do some troubleshooting on the drive system!

You have more than one voltmeter, so connect one between the battery pack's main B- and main B+ terminals to monitor pack voltage.

Connect another one between the controller's M- and B+ terminals to measure the voltage being applied to the motor.

At full throttle going up the hill, both meters ought to read the same voltage, or withing 0.1V or so.

IF not, either the controller or the throttle is misbehaving.

------------
BTW here's a grade chart.
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File Type: jpg Grade conversion chart.jpg (167.3 KB, 0 views)
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Old 09-12-2021, 03:43 PM   #14
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Default Re: Batteries, charger, a long confessionary tale...

I'll run that test. I'll go back through the posts for the others as well.
I've re-read my posts and I think my experience with both sets of batteries were told accurately.
I'd estimate the grade as between ten and 20 percent. With good momentum you can just make the climb on a single speed beach cruiser (no batteries). Without any momentum you won't get far.
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Old 09-12-2021, 04:33 PM   #15
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Default Re: Batteries, charger, a long confessionary tale...

The max recommended incline for a stock EZGO cart is 14° (25% grade), or at least it is for the Medalist, TXT, RXV and TXT48 most other body styles, but I cannot find the max incline spec for a Marathon, however if it made it up once, it ought to be able to do it again.

The bottom line is the batteries don't seem to be dying more than expected and nothing is smoking (getting hot), so that more or less leaves the motor not being allowed to draw the amps needed to climb the hill.
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Old 09-12-2021, 11:16 PM   #16
JRaf
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Default Re: Batteries, charger, a long confessionary tale...

Mmmm... I don't think the hill is a big deal. I suspect it's more 10 degrees than 20. I've played a certain amount of golf in my time and really, this is nothing, even in 1993 when this cart was new.
Okay, on to my latest test. I couldn't hook up two meters for a variety of bad reasons but I thought I'd make two runs and see if the readings got similar results.
The results from monitoring pack voltage running up the hill with a headstart are similar to yesterday. I hook up to the terminals marked as BL+ and BL- on the wiring diagram, attached. Pack sits at about 38.6, then as I accelerate on flat ground, drops a hair, then, as I start up the hill flashes down to around 33.5, but then rises as the cart slows, gets up to beyond 36, up to 36.5 and then the cart dies-- only today it doesn't die! The cart slows considerably then keeps going up the hill. All the way to the top. And I don't dangle out a boot and kick it up either. So that's good right?
But I've charged the cart three times today, and two times before this run, I've stalled out and failed to make it to the top. But... this feels something like progress.
So now I go back down the hill and move my meter to B+ and B- on the controller. (If you look at the schematic B- is connected directly to the pack negative with a smaller wire connected to one of the small posts on the solenoid. B+ is connected to the A post of the F/R switch and there's a big wire that leads to A1 on the motor (and I double check that its A1). There's also a small resistor or maybe a varistor between the B+ and B- terminals.
But with the key on and brake on I only see 27.5 volts. Oh, what's this? Then I push on the pedal, the parking brake disengages, the solenoid clicks, and the meter shows pack voltage. Right where we're supposed to be. And my journey up the hill is exactly like the last one, down as low as 33.5 at roughly the same signposts, then revival, working up to 36 volts, and I just make it up the hill. Twice in a row!!
(Not a big deal but I know I'm Heisenberging this test a bit. I know where the little flat spots are, if I turn at this rise and that crack I get a little momentum, I can get a little Venturi-like effect by spinning around deep into the turn instead of taking a more direct path. I have learned to climb this driveway, even when the vehicle is clearly underpowered.)
Anyway, I THINK the test has proven that... well I don't know what it's proven but those two readings are essentially the same.
Finally I pull the white and blue wires off the spade lugs on the controller. Pedal down, I get around 6000 ohms, maybe 6250. Pedal up, I'm very close to zero. So the throttle passes that test.
I put the cart back on the charger. It runs for an hour and shuts off.
After dinner, after dark, I realized I forgot to run the trash can down the hill. ****. A moron's work is never done. I haul the bin into the back bed and take off down the hill. I love this part, no windshield, freewheeling, the cart rolls briskly, 20mph? I drop the container, head back and then die on the hill. And no conniving advances us. I perform the now standard gymnastics and push the cart up the hill.
I hook up the charger again, why not? It clicks and hums, the needle gauge shoots straight up. 18 volts. I know the machine's not laughing at me and this isn't the end of the world but... I still don't get it.
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Old 09-12-2021, 11:19 PM   #17
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Default Re: Batteries, charger, a long confessionary tale...

Forgot to post the schematic in case anyone was following along. I suspect JohnnieB originally uploaded it, not sure.
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File Type: jpg Marathon - Controller Schematic.jpg (119.6 KB, 0 views)
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Old 09-13-2021, 10:05 AM   #18
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Default Re: Batteries, charger, a long confessionary tale...

That's the first time I recall seeing quantum mechanics (Heisenberg's uncertainty principle) being associated with golf cart performance.

There is about a Farad of capacitance between the controller's B- and B+ terminals to filter out the electrical noise produced by chopping DC at about 15kHz and the 250Ω resistor between the solenoid's large terminals keeps the filter capacitors charged to near battery pack voltage to reduce the amount of arcing as the solenoid's contacts bounce to a close, prolonging their usable lifespan. Seeing a voltage a bit less than pack voltage before the solenoid clicks is normal, typically about 3V to 5V less.

The controller appears to be opening up all the way so both the controller and throttle are good. Looks like everything except the motor has passed the tests, or at least nothing has completely failed.

The motor is running, so the only thing that comes to mind is the carbon dust (from the brushes) build up is so thick it is providing an alternate current path through the motor and a significant number of amps are effectively bypassing the windings.

The measuring the ohms between studs on the motor and the motor case.
Ought to be 5Megohms or more.
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Old 09-13-2021, 10:49 AM   #19
JRaf
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Default Re: Batteries, charger, a long confessionary tale...

I will disengage the motor cables and measure resistance to the case... but I did that before, looking for parasitic drain... which I thought might be the cause of my problem (it wasn't or isn't, that was ghost voltage). But I will try again.
I disconnected the board relay earlier today and I'm letting the cart sit on the charger. It's up to 45.87 volts which is almost a full volt higher than I got letting the charger decide when to shut down. I don't think anything harmful will happen because the amperage is down below 2. BTW, why, when using my clamp meter is there a difference between the number I get on the positive cable (from the charger) and the negative? Is that just resistance in the system?
I'm intentionally confusing the Heisenberg principle with the observer effect. It just sounds cooler.
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Old 09-13-2021, 12:13 PM   #20
JohnnieB
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Default Re: Batteries, charger, a long confessionary tale...

Here are a couple US Battery publications for your reading enjoyment.

PDF-1 is the 2021 version of their User manual which does not recommend using a single stage charger (IE: Ferroresonant transformer type).

PDF-2 is an older set of charging instructions that includes single stage charging.

Image-1 is the power board of a Curtis 1206SX controller (DCS drive), showing a dozen 1,000µF filter capacitors.

--------------
Don't know why the amps on the pos and neg wires don't read the same. Maybe the sensor is direction sensitive. Try flipping it over on one of them so electron flow is same direction through the clamp on both.
Attached Images
File Type: jpg curtis 1206SX.jpg (174.0 KB, 0 views)
Attached Files
File Type: pdf USB_DC_UserManual_821.8.pdf (13.20 MB, 0 views)
File Type: pdf usb-charging-recommendations.pdf (2.33 MB, 0 views)
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