Low power after while

[TheOldMan]

1994 Marathon 3 wheeler. Had previous problem, turned out to be bad potentiometer in pot box throttle assy. With bad pot, it would jerk your head when it took off, and spin the wheels. After replacement, it seemed to be pretty docile, but fast enough for what we do. Using this for gardening. Built a bed on the back to haul a 25 gallon spray rig. In use, this requires almost constant stop and go in soft dirt. The cart does great at this for about 15 minutes, then loses power where it will not push through the soft dirt. Reverse a few feet, and it will power forward 2 or three times, then lose power again.
The spray rig has a 12v pump, and rather than tie across 2 batteries, I installed a solid state voltage reducer, and an analog battery condition meter.
After batteries being fully charged (charger indicates 0 amps) that meter indicates up in the white area, which is charging indication. Not satisfied with that, I installed a digital volt meter. I also installed a waterproof cigarette lighter socket to supply 12 v to pump. The 2 meters and the lighter socket are controlled by an automotive relay, whose coil is switched on by a separate toggle switch from 12v. The toggle applies 12 volts to the relay, which in turn applies 36v to the voltage reducer. The batteries are new. With the dvm installed, the cart reads 37.2v static, apply throttle, drops to 36v. On charger right now, will check again when fully charged. Sorry this has turned into a book, but wanted to cover all bases.

[radioman]

Feel around the controller heat fins. It may be getting too hot going into thermal shutdown. If so you might install a fan to circulate air around the heat fins on the controller might help. Soft sand and stop and go is hard on carts.

[radioman]

How big of a garden do you have? Why don't you make a dry run between the rows as fast as the cart will go and make some ruts to make a path and pack the ground? Then when you get to the end of the row, turn around and backtrack fast as the cart can go and widen the rut a little. This might help solve your problem. Do this a couple of times and go back to the charger. Just a thought. I use that method when I disc my woodlands fire breaks so when I have to monitor the fire my golf cart will hold up when the PDS drive system gets overheated and wants to quit.

[TheOldMan]

Radioman, that works! I had done that, but it didn't dawn on me that I was creating a "roadbed" so to speak. I think I'll look into upgrading the cables to #4, and using the nolox like they use on primary electrical connections like in the meter disconnect box.
Would it be beneficial to dis-assemble the f/r switch and burnish the contacts? Is this difficult? how tight should it be when put back together?

[radioman]

Originally Posted by TheOldMan

Radioman, that works! I had done that, but it didn't dawn on me that I was creating a "roadbed" so to speak. I think I'll look into upgrading the cables to #4, and using the nolox like they use on primary electrical connections like in the meter disconnect box.
Would it be beneficial to dis-assemble the f/r switch and burnish the contacts? Is this difficult? how tight should it be when put back together?

The less you work on what is not the trouble the better off you will be. Check for hot connections when it stalls. Let is sit an hour or so and see if it picks back up. It sounds to me the controller may be overheating. I have not had to deal with F/R switch yet but burnishing the contacts is not going to help if they are not getting hot. The contacts may be worn and not making good contact and burnishing them might make them worse. I have looked at F/R switches on my old cart and I would recommend you tend to your garden.

You can replace the individual contacts but it looks like you got to take the whole assembly out to work on it.

[JohnnieB]

What is the pack voltage when you start out in the morning? (37.2V is only 72% charged)

What charger are you using?

A fully charged 36V battery pack ought to read at least 38.2V about 12 hours after the charger shuts off automatically.

[TheOldMan]

After putting the charger on around 3pm yesterday, at 9 this AM it read 38.7.I/m using the EZ go charger I got when I bought it.

[JohnnieB]

Originally Posted by TheOldMan

After putting the charger on around 3pm yesterday, at 9 this AM it read 38.7.I/m using the EZ go charger I got when I bought it.

That sounds about right.

You use the 12V sprayer while the cart is stopped, so what has the pack voltage dropped to when you get back on the cart and it won't take off?

(I'm trying to eliminate the battery pack as the problem source, or as one of the several problem sources)


Definitely want to upgrade all the high current cables (all 13) to 4Ga or heavier.

The motor will get hot, the controller may get very warm and solenoid will get warm, but everything else should stay fairly cool. None of the cables, connections or other components should get more than warm.

[radioman]

You might also try filling sprayer half full or less to lighten the load. 25 gallons of water is about 200 lb..

[TheOldMan]

I don't get off the cart to spray. I travel down along the rows of veggies stop, and spray what I can reach with the stream out of the wand, and move forward and repeat. I can't believe that 200# of spray material, and me alone in the cart are as heavy as 2 old golfers and their bags full of clubs. Today I was riding in the soft sand, looking at things in the garden, and when pulling through the sand, the voltage dropped to 33.7. It was at about 37.6 running on the hard surface. Battereies are new.