1988 36v marathon HOT battery

[Cmartin2001]

Thank you for adding me to the group. im a first time cart owner trying to get my feet wet but im running into problems.

I picked up this 1988 ezgo marathon 36v resistor coil perpindicular driven cart that came from disney world. it appears to be in great shape. when i got it all of the wiring was taken out so i have searched forums and google for schematics to get this thing back in working order. im by no means an electrician or a cart mechanic but i do have a background in industrial maintenance so ive been known to fabricate and troubleshoot from time to time. i did install a 4 inch lift and some 20 inch tires unfortunately i did that before i decided to try my hand at wiring it up.

the first thing i did was test each battery( 8 ) 6v duracell. the previous owner had 6 in the stock location and 2 more under the rear seat. out of the eight batteries 4 were bad at first glance testing at just 2v. i purchased 2 new 6v to get me back up to 36v.

i attempted to charge them all day but i noticed the charger would take off at around 15 amps and after 30 minutes it would drop to 10 amps. and then about 2 hours in the charger would drop out all together. 37v. i could unplug the charger and plug it back in and the process would start over. after 4 or 5 cycles i was charged to just over 38v.

first test drive lasted about 3 minutes. i backed it out of the garage and down the driveway and while i didnt expect 36v to be a speed demon it felt slow. when i turned into my yard(flat grass) it really slowed down so much that i didnt think it was going to make it back to the driveway. and i started to smell something get hot.

the first battery coming from the f/r switch was getting hot. both terminals and the cables. all others were still cool. all of the connections were clean and tight but the cable looked like it had taken some heat before so i removed it and made a new cable out of an old weld lead. this did not help the situation. the new cable got hot as well so i put my meter on each battery while i pushed the pedal and i found the first battery was dropping to 0v while the rest would only drop to about 5 under load.

i removed the battery and wanted to test again but all i had at my disposal was a 12v lawn mower battery. i knew it wouldnt last as long and i was going over the 36v but if the previous owner was running 48 i figured 42 wasnt going to be a problem. i just wanted to get 15-20 minutes of testing done before i continued to throw money into it.

this time the cart felt like it was taking off like a rocket but if i put the pedal to the floor the cart would lose all power. i noticed A1 terminal on the series motor was very lose. and barely holding onto the case of the motor.

against my better judgement i took the back of the motor off and found the brushes were no longer connected to the post. and the other post had the brush wiring wrapped around it.

i had no luck finding a set of brushes locally so i took the brush wiring and crimped a ring lug to it and connected it to the bottom side of the stud. i used a rubber block with a hole drilled in it as my insulator along with 2 rubber washers. i pulled the armature from the rear axle and fit it inside the brushes and then reassembled everything.

during this round of testing the cables and battery terminals got hot again. and a fully charged 12v lawn mower battery lasted less than 60 seconds of flat surface driving.

im positive ive errored in my testing methods and my temporary 12v battery theory but im trying to save project money until i find out if its a major issue.

im just looking for some advice from this experienced crew

[Cmartin2001]

ill post some pictures if i can get them to upload

[DubK]

Sounds like there's a lot going wrong on this cart. Resistor carts were not meant for 48 volts..so I'd get it back to 36 volts using your best, strongest batteries out of all of them. Hot posts and cables come from loose connections. I've had a battery where I tightened the nut all the way down and the cable was still loose so I had to add some washers underneath. First things first, I'd change out all those old cables to a new bigger 4 gauge or 2 gauge set on the entire cart. Then, if you want to keep this as a resistor coil cart, you can buy a set of new coils. I have a 79 3 wheeler resistor cart that was running bad.. I put a new higher amp solenoid, new 2 gauge cables, new coils, and a heavy duty forward reverse switch on the cart and it ran great after that and felt a couple mph faster but that could have been just in my head, but sure ran great. I then broke a terminal off of the motor like yours is from not using 2 wrenches while working on it, tried to repair it but it kept arcing. I'm not sure an aftermarket motor would fit that perpendicular rear end. But I ended up putting a newer style parallel motor rear end on it from a parts Marathon with a controller set up that I got for $200. Motor was sent off to Plum Quick for a rebuild, and I'm currently in the process of swapping over some parts to make it a solid state cart with a new 500 amp controller and when it's time for batteries I will go with 48 volts. Highly suggest doing a solid state conversion on your marathon. It was make it so much more efficient and opens up a world of upgrades. You can do it the cheaper route like me by using a parts cart (90-94 marathons were solid state controller carts), or Scottyb from cartsunlimited.net sells a solid state conversion for these carts. Game changer!

[Cmartin2001]

thank you for your response. unfortunately a major conversion isnt in the budget for this dinosaur. im sure by the end of this journey ill wish i would have. as of right now im hoping to throw a couple hundred at it each week till i can make it functional. my goals are set pretty low i think. id like to be able to take a family of 4 on flat grass or roads at around 15 mph and get 4-5 hours of actual drive time. trying to find another 6v battery to complete my set and finding a complete wiring kit are next on my list. im wondering if maybe an upgraded fnr switch would help. but i havent looked into it to see if all fnr switches are created equal.

[bronsonj]

Originally Posted by Cmartin2001

out of the eight batteries 4 were bad at first glance testing at just 2v. i purchased 2 new 6v to get me back up to 36v.

...

i found the first battery was dropping to 0v while the rest would only drop to about 5 under load.

That's your huckleberry. So you have eight 6v batteries. 4 were good-ish, giving you four 6v (24v) and four others that aren't worth a second thought. The first time you hit the gas those other four will drop to 0V each and good luck getting the cart to move... Removing two and adding two new 6V batts just adds confusion. The four "good" batteries are probably shot just not as shot as the other four. Plus it sounds like you're charging a 48V pack with a 36v charger? That's no bueno.

To me your options are a 36v pack and keep your current charger or a 42V or 48V pack and get a different charger. You really can't test well until you have the batteries sorted. Bad batteries will make the rest of your testing error prone.

[Cmartin2001]

Originally Posted by bronsonj

That's your huckleberry. So you have eight 6v batteries. 4 were good-ish, giving you four 6v (24v) and four others that aren't worth a second thought. The first time you hit the gas those other four will drop to 0V each and good luck getting the cart to move... Removing two and adding two new 6V batts just adds confusion. The four "good" batteries are probably shot just not as shot as the other four. Plus it sounds like you're charging a 48V pack with a 36v charger? That's no bueno.

To me your options are a 36v pack and keep your current charger or a 42V or 48V pack and get a different charger. You really can't test well until you have the batteries sorted. Bad batteries will make the rest of your testing error prone.

sorry i guess that sounded confusing. i have not ran it on 48. there were 8 batteries and i removed 4 from the system. (first go around) and added 2 new batteries that brought me back up to 36v. i then found the one battery that was dropping out under load so that left me with 5. all i had laying around was a fully charged lawn mower battery that was charged separate with a 12v charger. which should have brought me up to 42. i do have a 48v charger and a 36v charger that i can use when i get a complete set . i dont want to try to charge any of them with a lawn mower battery in the system.

[bronsonj]

That lawnmower battery is not helping. It's so out of it's league in terms on sustained high current draw. A large car battery can give 400 or more amps for 5 or 10 seconds, while you start your car. But it cannot do 100 amps continuous drain for very long. A lawnmower battery is just not a complication to add to that pack really.

You need another 6v battery. The issue is if you have five 6v batteries that have 60% life left and one with 100% then when you charge them as a group the other 5 will be undercharged and the new one will be overcharged. In very short time you'll end up with six batteries that are all at 55% life left because of that.

The correct solution is to get a new set of batteries. You can get 6V or 8V golf cart batteries. The cheapest place I've found for new batteries is Sams Club. Not all Golf Cart batteries are the same but if you're looking for the cheapest way Sams Club is it. The batteries sometimes are on sale. You need to bring in cores but Sams doesn't care if the core is out of a car or emergency exit sign... At least mine didn't care. As long as it says Lead Acid somewhere on the battery they'll take it. Heck, I turned in a Power Wheels battery as a core! Otherwise it's $20 or $25 more if I remember correctly. The Sams near me has 6v golf cart batteries right now for $108, not on sale. I think the once a year sale is like $20 off each battery.

There are a few 12v golf cart batteries. Those really aren't very good and will generally need replaced sooner and give you less range and less useful life compared to 6v or 8v batteries. But still you could buy four 12V golf cart batteries likely cheaper than six 8v or 6v batteries. I have not priced 12v golf cart batteries.

Whatever you do, don't buy Marine "Deep Cycle" batteries or regular car starting batteries. It's not designed for the abuse golf cart batteries are made for and they will die a short painful death.

[scottyb]

Welcome to the electric vehicle world. The learning curve can be strict schoolmaster. There are a few rules that will apply to battery health, performance, and maintenance that will apply to the cart and your wallet.

1. When mixing batteries be sure they are all of the voltage, amperage size, and condition.
2. If new batteries are added to old batteries expect the new batteries to degrade to match the old batteries in a months not years.
3. Golf cart batteries (wet cell) require a bulk charge rate of 10% of their capacity. For 6v this is about 20-25 amps. Use of a smaller charger will allow rapid sulfation as the heavy elements will be left separated and stranded near the bottom of the battery where they will permanently attach themselves to the plates never to be used again

[Cmartin2001]

Just an update, this thing is testing my patience. I have purchased a new 6v battery, replaced cables with 4g. Replaced brushes. Now I hear a slight drag or hissing sound from the motor. I'm not sure if it just the new brushes or if I messed something up. It lasted about 45 seconds before it was crawling. I checked voltage and 1 battery is 4.4 and the rest are 6.3-6.5. And the jump wire from battery 1 to 2 is warm. And battery smells like rotten eggs. Battery 2 is also the 4.4 battery

[kah00na]

You could try swapping your battery 2 location with a different battery and see if the voltage still drops on that same battery. Hopefully battery 2 is not the new on you just purchased.

Can you post a picture of the batteries and their wiring? Maybe there is something someone will see.

Also, you could connect your voltmeter with some alligator clips and monitor the voltage while you're driving it. The voltage should sit around 35v while it is moving and go back up to 37-ish volts when the accelerator pedal is released. If it gets down to 32v while driving, that is about the time it needs to go home for a charge.