Need help with Golf Cart E-Z-GO 12v battery conversion

[BrokeFarmerJohn]

This story starts with a golf cart following me home, not first time using a cart but first time owning or working on one.



Got it home. The issue with the cart was the batteries are shot and I gave $200 for the cart. But I had some 12v batteries laying around I wanted to try.



Pulled out the old batteries and found the rails where the batteries sit to be just roached and crumbling so I made me a few out of sheet metal and S-Lock.



I got the pans mounted and STUFFED the batteries in lol, they are 120lbs each and not easy to maneuver.



I got it all wired up using 4g wire from a set of jumper cables (was cheaper than automotive wire and relatively the same stuff). Existing was mainly 6g with some 4g.



So the cart runs, forward and reverse works, has a good bit of torq, enough to spin the tires when I was backing into my garage lol. BUT, I smelled a hot electrical smell, opened up the seat and found the controller in between the two big batteries to be really hot and smoking a little, i unhooked one of the batteries just to be safe and called it quits for tonight.

So my question is why is the controller so hot, is that normal? How do I test it?

The big batteries are both 1400cca rated at 200 amp per hour at 20 hours, the small one is a Napa gold 850cca battery but last time it was tested it only tested at 820cca. All 3 together are 36v (should be). So what do you all think?

 

[aczlan]

Having different size batteries length like that is a big problem as the small battery will discharge faster and the two big ones will try to recharge it as you drive.

Aaron Z

 

[RNeumann]

If it’s hot it is either a short somewhere or the voltage is low (this causes a high amp draw). I’d pull a battery cable to the controller and test the amp draw with nothing on to see if it has a short. I’d also verify it isn’t a 48v cart.

 

[BrokeFarmerJohn]

Having different size batteries length like that is a big problem as the small battery will discharge faster and the two big ones will try to recharge it as you drive.

Aaron Z

I figured it wouldn’t be the best but I only needed it for the 36v, the two bigger ones should be more than enough to carry the cart a long time. The little one is in the middle of the series, idk if that will change anything.

 

[BrokeFarmerJohn]

If it’s hot it is either a short somewhere or the voltage is low (this causes a high amp draw). I’d pull a battery cable to the controller and test the amp draw with nothing on to see if it has a short. I’d also verify it isn’t a 48v cart.

I plan on going threw the rest of the wiring later, replacing all the connections and replace the existing wiring with the 4g wire I have left.

I will test the voltage and make sure I don’t have a short, the motor wasn’t warm, just the controller.

 

[zzvyb6]

My electric cart taps into one of the batteries for running a relay and the speed controller. Although mine is 48v (6 8V batteries), yours would have been 6 6V batteries and the controller may be looking for 6V excitement, not 12V.

 

[BrokeFarmerJohn]

I ran a test, jacked up the rear end and ran for 5 mins, didn’t heat up, nothing heated up, I plugged the charger in and will watch it.

I took pics of the inside of the controller (I think), it’s the box I saw smoke coming out of the rear, these pics are from that same end.



That’s the best pics I could get. Maybe the smoke I saw was just stuff in the box around the coil idk.

 

[BrokeFarmerJohn]

I found a little more out, this cart was from 1987 and has a resistor coil system, the pics above are the resistor coils.

If you press the gas peddle, the lighter you press the pedal the more resistance the coil gives, if you pressed wide open then little resistance. The same power is used if the peddle is full throttle or slightly pressed, if lightly pressed the resistor coil eats up the power before it gets to the motor.

So the resistor coil getting hot was normal.

 

[KYErik]

This website a great resource for troubleshooting golf cart issues: Electric EZ GO RXV, Marathon, Medalist and TXT I had a 2 cycle ezgo for a few years and found the people there to be very helpful- they have different forums for gas, electric as well as other brands.

 

[George2615]

Just an FYI. In your first post one pic shows 6V batteries. Make sure you connect your 12V batteries correctly or you will damage all the wiring. You may have to do some reading up on the controller wiring. Not sure what voltage tap point the controller should be connected to.