93 EZGO Project Cart - Help Needed

[GABulldawg]

Ok, so I posted last week that I was selling/trading my CC Gas Cart and a part of the deal was an old 93 ezgo marathon project cart. The cart had been sitting in my buddies race shop without batteries for a few years.

Picked it up Friday and went directly to Battery Source to have them go over it and put in new batteries. We dropped in fresh batteries, the downloaded the wiring guide, and we wired it all up. Pressed the go pedal and forward it lept. Hopped on, and it did great, forward, reverse, shocks/springs good, brakes were great. Mechanic told me that it appeared the cart had once been a "coil cart" and had been upgraded to a controller. Not sure, but it did have a controller in the middle of the battery compartment with a plastic cover.

We tested the charger I got with the cart, and didn't work. Fuse was good, replaced the "mother board" and that didn't do it. So I opted to but a new 36v DPI charger. We tested it and it worked fine.

Brought it home, unloaded, tested pack voltage and it was a 90% so decided I would run it around to draw it down a little more before I put it on for first full charge. Ran it around and did great, speed wasn't bad, flew down hills, crept up a good grade in front of the house, did well on short hills, good torque.

Washed off the years of dust and grime, pulled it into the garage, and hooked up the charger. Charger worked perfect and started doing it's thing. That was about 8 PM. The next morning at 7:30 it was charged, green light was on and it was in float mode, needle cycling up and down. I noticed there was a slight smell in the garage but I just figured it was the smell of brand new batteries charging

I had to leave so I just left it alone to do its thing. When I got home around 4 PM I unplugged it, jumped on, key on (key may have been left on) and pressed the go peddle. Excited to see how it would do with a full charge....

Nothing. No go. Forward or reverse. I could here the clicking, but nothing.

Raised the seat and tested the pack voltage...38.8. Again, that is fresh off the charger. Then I noticed that plastic cover over the controller I mentioned earlier, It was a little concave in one spot. A little melted. I pulled the cover, the controller was HOT. I mean, really really hot.

So...I am assuming the controller burnt up? Sound right? And if so...why?!

I was planning to get with ScottyB soon to upgrade, but now I am worried that even with an upgrade it still might burn up. Any thoughts? Ideas? Suggetions?

Was the charger not set up right? I know it has the little black cover that you can remove to set it up based on type of batteries. I just left it stock setting as the store manager/tech at Battery Source didn't say anything about adjusting it. Figured it was set for their batteries. We put in their branded deep cycle batteries.

Even off the charger, an hour later the controller was still hot, so I disconnected the main positive.

Sorry for the long post, but wanted to try and include the whole story best I could. For those who made it all the way through, thanks!

[JohnnieB]

All new cart batteries ought to receive an initial full charge prior to first use and never taken below 75% SoC for the first dozen or two charge cycles. After being broken in, they should never be taken below 50% SoC. (It won't kill them to take them lower, they simple will have to be replaced sooner.)

The ammeter on the DPI charger cycling up and down is troubling. That indicates the load is changing and it shouldn't be.

Try disconnecting everything from the battery pack except for the wires from the charge receptacle and the five high current cables that connect the six batteries in series for 36V. If the charger's ammeter still fluctuates while in float mode, either one or more of the batteries is bad, or the charger is. (Call DPI, they'll probably have you do some tests.)

As for the charger being set to the correct charge profile for your batteries, we have to know who made the batteries. The vendor you got then from ought to be able to tell you who makes their store branded batteries.

DPI chargers usually come from the factor set for Trojan batteries (Mode-2), which is the mildest of the four charge profiles. However, none of the charge profiles will cause the controller to overheat, so that is a separate issue.

Since the cart may have been a resistor drive that was upgrade to a controller drive, it may have been wire so the controller is powered up when the key is on (Most series carts don't power up the controller until the pedal is pushed), but being powered up while on charge should not have overheated controller.

[GABulldawg]

Pack was at 85% when I put it on charge. No where near 75%. I have all the SOC % tables and info regarding battery breakin printed and studied closely. I have gleamed so much great info from the site and trying to put that into action. As everyone here knows, you drop a grand on batteries and a charger you want to take good care of it all.

Needle only pulsed, down and up once it showed full charge. Didnt know what it should do once in float/maintain mode.

Headed to garage to just hookup pack and charge port cables. Will take ignition and other cable out of play.

Stay tuned...

[GABulldawg]

Ok, I just isolated the full pack to just the charging port cables.

Pack is reading at 38.8, where it was yesterday when I pulled it off charge.

Plugged charger in, went through the pre-qual test, went into constant current (bulk) charge, and dc amperes first went to 15, after just a minute or so dropped back to 12 where it is now. Still only a few minutes after plugging in.

Will try to keep am eye on it and timing of change.

[GABulldawg]

4 more minutes into charge, about 6 total, amperes needle down to 10

[GABulldawg]

15 minutes on charge down to approx 5.5. (In between 5 and 6)

(Sorry for the play by play posts, serving as , uch as a journal for diagnosing , or eliminating an issue with charger or batteries.

[JohnnieB]

The thing to remember about the 75% SoC in the breaking in process is that it is a limit rather than a goal. In other words, it is okay to recharge the battery pack before it is discharged to 75% SoC, just strive not to discharge it more than 75% SoC while breaking the batteries in.

The normal reading on the ammeter is about 5A while in the Yellow LED is blinking, then it climbs to upwards of 20A when Yellow LED comes on steady.

The ammeter will stay pretty close to 20A until the On-Charge pack voltage reaches about 42.3V (Mode-2 selected) and then the charger switches from Bulk-Charge mode (constant current) to Absorption-Charge mode (constant voltage) and the amps slowly decrease down to about 7A.

When the Yellow and Green LEDS are both on steady, the pack is 80% to 90% charged and the charger goes into a dV/dT mode (change in Voltage over change in Time) and stays there until the rate the pack voltage is increasing at meets a predetermined rate and the the regular charge is terminated and the charger goes into Float-Charge mode. (Green LED only on steady)

In Float-Charge the battery pack is held a a constant 39.4V (approximately) and the ammeter will show what the battery pack's self-discharge rate is, plus any parasitic current flows.

The self discharge rate for a typical 225AH 36V battery pack is about 1% per day, or 2.25AH per day, so the current flow is about 0.10A, which doesn't move the ammeter needle far enough off Zero to be seen.

If the needle is much above zero, there is a parasitic load of some sort.

[JohnnieB]

The charger and batteries appear to be behaving normally so far.

[GABulldawg]

Originally Posted by JohnnieB

The charger and batteries appear to be behaving normally so far.

So after exactly 1 hr on the charger the green light is on solid and the needle is sitting (perfectly still) at zero. So, battery and charger do appear in great shape.

So, I am now pretty much thinking of, instead of chasing a problem, basically going this route:

- upgraded controller / solenoid
- full 4g wire set
- heavy duty reversing contactor
- and probably a new key switch

JohnnieB, does that sound like a good plan? With best outcome? Or would you chase the problem?

With how dang hot that controller was, I feel like it has to be fried.

If it all sounds like a plan, I will just need to get with ScottyB and determine the right 400amp controller for a 93 ezgo marathon and build a custom package around that.

[JohnnieB]

Your plan sounds good.

If you do replace the keyswitch, get one that is uniquely keyed. Makes cart harder to steal.

I'd check the motor for wanted and unwanted continuity. (Motors often take out controllers when they go bad - don't ask how I know. )

With cables disconnected, you should have about 1Ω to 3Ω between the A studs and about the same between the S studs. Very little continuity (greater than 100kΩ) between the A and S studs and same between either A or S studs and motor case. (The continuity on the last two places is caused by carbon dust from the brushes and a motor as old as yours is, probably needs new brushes and a good cleaning)

If the motor passes the above continuity tests, you can check to see if it runs right using the attached diagram.