Understanding solenoids

[JohnnieB]

So the problem isn't the cart not having the wherewithal to climb the hill, instead the problem is not having enough energy left in the battery pack by the time you get to the hill on the seventeenth hole.

Replacing the motor probably won't solve the problem. In fact, it might make it worse since a high torque motor will draw more amps and the battery packs inability to provide the needed amps by the time you reach the seventeenth hole is the root cause of the problem.

It could be the batteries nearing the end of their useful life, or there might be one or more weak cells, or they may have been too small from the get-go. Or there might be excessive resistance in the high current cables, or bad contacts in the F/R switch, stealing power that should be going to the motor. Or it could be that the batteries are not being fully charged.

What is the AH rating of the 8V batteries being used?
How old are they?
What charger is being used?
What size cables? (4Ga would be minimum with a 400A controller)
What size tires? (18" tall is stock)

[cyclebender]

Thanks JonnieB, appreaciate your input. The batteries are Crown 185, only a year old. Cables are new 4 ga fine strand 100 copper, Charger is a 48 volt Power Wise, batteries read 50.2 volts after full charge. Heavy Duty f/r switch in also new, as is the throttle sensor, solenoid and the controller. Motor was just rebuilt. Wheels are 12" alloy with low profile tires, about 19" in dia. I really liked your idea of using SPDT contactors, but I looked into SPDT contactors, and they are too expensive for the task at hand. I think I'll take Radioman's advice and just have the old man next to me walk up the hill, but I'll carry his clubs for him.

[JohnnieB]

Originally Posted by cyclebender

Thanks JonnieB, appreaciate your input. The batteries are Crown 185, only a year old. Cables are new 4 ga fine strand 100 copper, Charger is a 48 volt Power Wise, batteries read 50.2 volts after full charge. Heavy Duty f/r switch in also new, as is the throttle sensor, solenoid and the controller. Motor was just rebuilt. Wheels are 12" alloy with low profile tires, about 19" in dia. I really liked your idea of using SPDT contactors, but I looked into SPDT contactors, and they are too expensive for the task at hand. I think I'll take Radioman's advice and just have the old man next to me walk up the hill, but I'll carry his clubs for him.

Two things are amiss here.

A Crown CR-185 is a 12V battery. Are you running a 4 X 12V battery pack?
If so, your pack only has about 73% of the kWh of a standard 36V pack.

Perhaps they are CR-165 (8V - 165AH) batteries. If so, you have about 98% of the standard 36V pack kWh capacity.

Also, 50.2V is only about an 85% SoC. A full charge is 50.9V when measured about 12 hours after charger shuts off automatically.

The 19" tire height only drops the torque by about 5% - 8%, so that probably isn't a major contributing factor.

-------
Being an old guy myself, I suggest you walk up the hill and let him drive the cart.

[Bilito]

Back to the original question, I think.
Is 12V enough juice to trip a 36 or 48 Volt Solenoid??
I am tbhinking about getting a heavy duty Golf Cart solenoid for my RV since the ones available from Auto Zone etc. start to stick closed after a few starts and I have to bang on it with a hammer or heavy screw driver handle to make it open and turn off the starter motor.

[Sergio]

No, a 36v or 48v solenoid would not work at 12v, specially for this application.

Solenoids used to open and close under DC loads should be (or typically are) "intermittent duty" (not continuous duty) and should not have a "flyback" diode installed across the coil.

There are several reasons for that, the intermittent duty Solenoids have a higher power coil than the continuous duty which means they generate a much stronger magnetic field.

That is important since you want the plunger to close the contacts as fast as possible and have enough strength to keep them from bouncing.

The stronger coil allows for a stronger return spring to be used which is also important in order to minimize the contact damage caused by the arc that gets created as the contacts start to separate.

That is also the reason why a flyback diode should not be used for this application as it has the side effect of creating a slower decay rate of the magnetic strength that is holding the contacts together.

You want that magnetic field to end quickly so the return spring can separate the contacts quickly.

Unless You keep buying the cheapest economic solenoids, You may have an issue with your RV.

First make sure the solenoid is getting the full battery voltage at the coil while cranking, a bad connection on the solenoid activation circuit could prevent the solenoid from developing its full magnetic strength, that is specially possible if you use the metal can of the solenoid as the negative or have its negative bolted to a poor frame connection.

You could also have a bad starter that is acting almost like a short when the solenoid closes, have you measured the battery voltage drop while cranking?

If You have a clamp style amp meter you can also measure how much current your starter is consuming in case the starter is bad or you are under rating your solenoids.

[Bilito]

Right now I cannot get it to crank. I have a remote start switch and the solenoid is not clicking. power is there because I can see small sparks when I clip onto the ignition (I) post on the solenoid and my multi meter shows 12.6 volts there, I don't want to use a screwdriver to jump across the big posts, too much spark arcing for my taste. I am thinking the solenoid is possibly dead. When you go to an auto parts store and ask an (expert) there for a heavy duty truck solenoid you get the deer in the head lights look and they ask the same questions, make, model, year, engine size, auto tranny or not and type in the computer and come up with something, it is always the same thing. I want to get something stronger then china junk. MY RV has an old Ford big block engine, that takes a bit of power to crank over.
I know this is a golf cart site but I am getting desperate.
What is the best way to check the solenoid while in the car?

[JohnnieB]

Originally Posted by Bilito

Right now I cannot get it to crank. I have a remote start switch and the solenoid is not clicking. power is there because I can see small sparks when I clip onto the ignition (I) post on the solenoid and my multi meter shows 12.6 volts there, I don't want to use a screwdriver to jump across the big posts, too much spark arcing for my taste. I am thinking the solenoid is possibly dead. When you go to an auto parts store and ask an (expert) there for a heavy duty truck solenoid you get the deer in the head lights look and they ask the same questions, make, model, year, engine size, auto tranny or not and type in the computer and come up with something, it is always the same thing. I want to get something stronger then china junk. MY RV has an old Ford big block engine, that takes a bit of power to crank over.
I know this is a golf cart site but I am getting desperate.
What is the best way to check the solenoid while in the car?

Does the solenoid mount on the starter? If so, it may engage the Bendix gear into the flywheel teeth as well as connecting the high amps to the starter motor.

If so, you might be able to let the stock solenoid do the mechanical stuff and add a 500A or 100A solenoid with a 12V coil to do the electrical stuff.

[HeatWave]

Originally Posted by Bilito

Right now I cannot get it to crank. I have a remote start switch and the solenoid is not clicking. power is there because I can see small sparks when I clip onto the ignition (I) post on the solenoid and my multi meter shows 12.6 volts there, I don't want to use a screwdriver to jump across the big posts, too much spark arcing for my taste. I am thinking the solenoid is possibly dead. When you go to an auto parts store and ask an (expert) there for a heavy duty truck solenoid you get the deer in the head lights look and they ask the same questions, make, model, year, engine size, auto tranny or not and type in the computer and come up with something, it is always the same thing. I want to get something stronger then china junk. MY RV has an old Ford big block engine, that takes a bit of power to crank over.
I know this is a golf cart site but I am getting desperate.
What is the best way to check the solenoid while in the car?

Back in the late '80s, I had a '78 Lincoln Town Coupe w/a 460, had chronic starting problems, the real fix was to use a GM style Starter (Solenoid mounted on the Starter). No more starting issues.

IIRC the GM style (Ford) Starter was used on the Ambulances of the day, probably not something to be found at Autozone.

Some of the old Fords had Heat Shields for the Starters (sometimes we would make our own)

Good Luck!

[Bilito]

The solenoid is mounted on a bracket behind the grill and in front of the radiator (not on the starter)

JohnnieB said,"If so, you might be able to let the stock solenoid do the mechanical stuff and add a 500A or 100A solenoid with a 12V coil to do the electrical stuff."

Where do I find such a solenoid? in the photo I have removed the wire to the starter motor. BTW I really want to thank you guys for this off golf cart help.

[Mooncarter]

Have you tried going to a Ford dealer and getting a good one?