Built my hunting Buggy - Need some Help

[Daleco]

Thanks Dave

[JohnnieB]

Originally Posted by Daleco

I have an DPI Accusense charger. Brand new.

I thought about the brakes and bearing thing. I loosened my brakes up so there was no contact. Same results. The cart does appear to roll better in reverse than forward on flat ground. Which I can't explain why. It's not the brakes. Scotty b and I had talked about that. I was trying to blame my rear end at one point.

Just tested voltage. 11 mph forward 48.1 volts at full speed flat ground.
47.4 volts in reverse at 14 mph same test. It's drawing more power in reverse?? DVM said 52.1 volts at static for pack.

22" tires.

Cart has never gone over 14 mph with these tires. So now I'm thinking its weight, batteries, and something that is causing resistance going forward. Any ideas on the resistance?

The DPI goes into float charge at the end of the regular charge cycle, so you need to take a quick spin around the yard (3 to 5 minute drive) to get rid of the slight surface charge, and then let the batteries rest for about 15 minutes to get an accurate SoC reading.

With 22" tires, you should get close to 15MPH with a 36V battery pack. I don't know what it should be for 48V, but it would be over 15.

3 MPH and 0.7V difference between F and R. I don't know if 0.7 would make that much difference in speed or if the pack is being drawn down 0.7V more in one direction due to increased mechanical load.

What does the battery pack itself read under load (max speed) in F and R?
If the pack voltage is different between F and R, there is a difference in mechanical loading between F and R.
If the pack voltage stays close to the same between F and R while it is different between M- and B+, there is an electrical issue.

FWIW: With a series cart, pack voltage and voltage between M- and B+ should be nearly the same at wide open throttle on level ground.
Unless you are losing voltage in undersized or bad cables and/or dirty contacts, you'll get a voltage drop in the 0.3V to 0.5V range per 100A of current flow through the controller.

Not on carts, but I have seen some shafts with worn out bearings that turn easier in one direction than the other.
It would be pretty easy to check the front wheels, but checking the rear one might be a bit of a challenge.

Since you have a 19 year old cart, it might be time to replace the wheel bearings.

[Daleco]

Yes the voltage on the dVM on the whole system matches the voltage at b+ and m- Lower voltage in reverse than forward. Which would represent more force being exerted in reverse, which should mean more resistance. But reverse is more powerful. Why is forward slower and less powerful and using less voltage? That's a hard one to answer. If the rear end was causing more resistant to make forward slower, it would be drawing more volts. Essentially working harder. But it's not. It's using less volts than reverse. I'm a mechanical engineer and can't figure this out. All I can come up with is factory motor and D&D motor spin better in reverse.

I tested at the motor itself. And those voltages matched m- and b+ as well.

[JohnnieB]

Originally Posted by Daleco

Yes the voltage on the dVM on the whole system matches the voltage at b+ and m- Lower voltage in reverse than forward. Which would represent more force being exerted in reverse, which should mean more resistance. But reverse is more powerful. Why is forward slower and less powerful and using less voltage? That's a hard one to answer. If the rear end was causing more resistant to make forward slower, it would be drawing more volts. Essentially working harder. But it's not. It's using less volts than reverse. I'm a mechanical engineer and can't figure this out. All I can come up with is factory motor and D&D motor spin better in reverse.

I tested at the motor itself. And those voltages matched m- and b+ as well.

Lower pack voltage in reverse means more Amps are being drawn and with a series wound motor, Amps equate to Torque while Volts equate to speed.
(Having more torque will overcome more drag, which will result in more speed)

There is some asymmetrical drag in there someplace. And there may be more than one problem.

The F/R switch can be eliminated by bolting the cables together.
A to D and B to C for one direction. (Black arrows on attached schematic)
A to B and C to D for the other. (White arrows)

If the cart still goes fast in one direction than the other, the entire electrical system, except for the motor, has been eliminated.

[Daleco]

Well I have gone full circle on this. Wiring is fine. FnR is fine. I'm going with Scotty B's first call. Time to replace my new batteries with better new batteries. I think it's a weight vs power issue. I'm going with 6-8volts and dropping the 12 volt accessory battery. That's roughly 150lbs weight reduction. Right now it's the only option I can see. I have a cart that runs 8 mph with two people in it. Rear seat is pointless. If that doesn't work I am reversing the rear axle so reverse is forward. Tie end went out tonight while working on it. Stuck in progress until those come in this week.

[ab46501]

I really doubt weight is the issue. I only run 36v but have a D&D motor and have plenty of power in both directions. My car is an older metal body Marathon and is no light weight for sure with a line-x top, front basket and rear box that is loaded most of the time.

If all of your wiring and the FNR is checking out OK it must be you have some resistance in forward that you do not have in reverse. If the cart will run 14mph in reverse it should do it in forward. Changing direction would not add weight. Did you try the suggestion of reversing the wiring on the FNR just to make sure there is no problem with the switch or with the motor?

It could be possible that the brakes are dragging in forward for some reason. I would check the drum brakes. Pull the drum off and make sure the springs are good and that the pads are seated correctly. Make sure your axle and springs are tight and not shifting. It could be that something is causing tension on your brake cables when in forward and a shifting axle might do it.

[Daleco]

I have reversed the wires on FnR multiple times.

I actually took the leaf springs off and reinstalled checking every thing out.

When you say plenty of power, I am curious your levels. If you have two people in the cart how fast will it run on flat ground? How quickly will it get up there?

In Forward I have about a 1 second delay and then it takes off, real powerful until about 5 mph then it just loses acceleration and climbs up slowly.

In reverse, as soon as you hit the gas peddle it spins the tires and pavement, and climbs to top speed without hesitation.

[ab46501]

I can spin the tires even on pavment from a dead stop in forward and reverse. My cart tops out at about 14-16mph depending on terrain but it gets there pretty quick. It does not seem to be any different if there is 1 or 2 people and sometimes I have had a third person hop on the back with little noticable difference even climbing hills.

I run 36v with a 650 amp Alltrax, 2 gauge cables, 22 inch tires and D&D 170-002-0001motor.

I went from from a stock motor to an upgraded EMP motor. There was inprovement but not enough for me. Eventually I went with the D&D which was a big torque difference even over the upgraded EMP. I am not sure what model motor you went with but you should be noticing a difference in power with the D&D.

If you have eliminated all the electrical issues I really think the only thing it could be is something causing drag in forward. Even if the batteries are weak it should be the same power in both directions. Can you push the cart by hand and if so is it harder in forward than reverse?

[Daleco]

thats interesting. As soon as I get the tie rod end fixed, I am going to take the brakes off and run it free spirited. I've got enough land to test it out. It is a little harder to push forward, but not enough that it would slow me down that much. Hopefully my tie rod end's will be in by the end of the week.

The thing I can't still understand is why in forward its at a higher voltage reading that in reverse. Seems like if there were more drag, it would be a lower voltage.

[Daleco]

I have the D&D motor Model #ES-5E