Schematic for 12v/24v System Switching

bomber315

Member
Ok, I have been pondering this more than I should be considering the amount of work I have stacked up but I love trying to figure things like this out.

So a little back story: I am trying to come up with the best solution for a self-driven 1 man stand. I plan to use a mobility scooter for the self-driving part and a typical harbor freight winch for the lifting part. The issue arises when you realized that mobility scooters are 24v (2 12v batteries in series) and most winches are 12v.

As previously discussed in this thread: https://tinyurl.com/56sw7tb3

• Both circuits require HIGH amperage so this eliminates most easy solutions. ie a simple 24-12v transformer

• It is best to not drive the winch off of just one 12v battery because of uneven drain and re-charging concerns.

• Another concern I have (with the trolling motor selector switch solution) is accidentally powering the winch with 24volts or the scooter with only 12v.

Therefore, I have come up with the circuit below using 4 typical lawnmower solenoids like this: https://tinyurl.com/vfthrh3d and a 3-position DPST (double pole, single throw) switch like this: https://tinyurl.com/54kveys4


Now if all of my fellow, amateur (or professional) mechanical/ electrical enginenerds would kindly tell me why this circuit won't work or what my next obstacle is that would be great.

I know of at least one concern, let's see if you guys can find it and more. ;)

Thanks
 

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bomber315

Member
ps figuring out how to physically make all of this happen will be quite the challenge. I will have to cross that bridge when I get all of the parts needed. (including the scooter itself)

re-charging the batteries also is up in the air until I see how it is physically done on the scooter. It is possible that each battery will get charged separately, and independently of this circuit, with its own trickle charger.

Also here is an animated version of the schematics. hope it works: https://tinyurl.com/haa76few

I CANNOT WAIT TO SEE WHAT YOU GUYS SAY!
 
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bomber315

Member
Personally I think you drank too much kool aid lets reinvent the wheel too much junk to deal with at the track later Chuck
The off season is just starting, I have lots of time to tinker with stuff instead of prepping tires. From what can find on the internet this wheel has hardly been invented in the first place. My 2 man kart stand is heavy enough to drag uphill back to my trailer. Once I build a heavier 1 man stand, I want a self powered one.
 

95 shaw

Site Supporter
ps figuring out how to physically make all of this happen will be quite the challenge. I will have to cross that bridge when I get all of the parts needed. (including the scooter itself)

re-charging the batteries also is up in the air until I see how it is physically done on the scooter. It is possible that each battery will get charged separately, and independently of this circuit, with its own trickle charger.

Also here is an animated version of the schematics. hope it works: https://tinyurl.com/haa76few

I CANNOT WAIT TO SEE WHAT YOU GUYS SAY!

First problem I see with the circuit as drawn,
Winch cannot attach directly to ground. You will reverse plus and minus leads to reverse winch. Drive motor the same.

The military trucks use a double master switch to lock out system.
12 volt systems must also be isolated from main ground so you can switch between them, if you want.

Otherwise, use common positive, and get 12 volts negative from battery series crosspoint. Or use common ground and get 12 volt positive from the same crossover.
24 volts can be connected always. Motor control and winch direction control omitted in the schematic.
Can be simplified to only 2 solenoids for 12 volt battery switching. Or use 1 battery for raising, one for lowering.

Attach charger to each battery individually.
Solenoids will need to be rated for continuous operation for use as described in drawings.

Intermittent will work for winch, but not last long on primary drive.

Make sure solenoid operation circuit voltage matches requirements for solenoids.


Fun to think about.
 
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bomber315

Member
95shaw, lots of good stuff to think about. And good catch on both motors not being able to be attached directly to ground. That's the kind of stuff I was looking for. You also caught the one concern I was thinking of. It's likely the cheapest solenoids on Amazon won't be able to handle the continuous usage. Also if they are designed for 12v, the contacts may not like 24v for very long.

I will read and reread the rest of what you have said once the children go to bed.

Bob, those won't work. You can tell just by the sizes of the wires that they can't handle the amps needed to run a winch.
 

Bob Evans

Administrator
95shaw, lots of good stuff to think about. And good catch on both motors not being able to be attached directly to ground. That's the kind of stuff I was looking for. You also caught the one concern I was thinking of. It's likely the cheapest solenoids on Amazon won't be able to handle the continuous usage. Also if they are designed for 12v, the contacts may not like 24v for very long.

I will read and reread the rest of what you have said once the children go to bed.

Bob, those won't work. You can tell just by the sizes of the wires that they can't handle the amps needed to run a winch.
You don't need a winch that will pull a Jeep out of a ditch to lift a kart. You only need to lift a couple hundred lbs. max.
And you're not going to get but ~60 amps max from a scooter battery.
 

95 shaw

Site Supporter
For simplicity, use of 1 battery for up, 1 for down with 2 solenoids.

Connect one wire from crossover between batteries directly to one post of winch. Connect 1 wire thru individual solenoids to each battery post not part of crossover, to the remaining winch motor post. Activate individual solenoids for up or down operation.






When we start racing electric karts, we all will need to know some of this.
Lol
 
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95 shaw

Site Supporter
You don't need a winch that will pull a Jeep out of a ditch to lift a kart. You only need to lift a couple hundred lbs. max.
And you're not going to get but ~60 amps max from a scooter battery.
But I like to over engineer everything!

Knowing you can make it work if something fails......Priceless!
 

bomber315

Member
Yeah the whole reversing of the motors has me a bit deflated. I was planning on getting the smallest cheapest winch harbor fraud had to offer.

I left the control circuity out of my schematic for simplicity btw. It would just get inserted right before the motors basically.

THIS is the stuff that keeps me up at night! Argh.

I'm not too fond of having 4 solenoids anyways. Hell at this point I might just run a 3rd battery for the winch alone.

Like I said, I'll sit down at the computer with pencil and paper once I can concentrate. Aka kids are sleeping. I just can't quit checking in now. Haha

Back to the drawing board.
 

Bob Evans

Administrator
Just run it on 24v ..think how fast it will lift 🤪
Back in the '70's I was messing with VW Baja Bugs, and after we put a couple of Holley Bug Sprays on them, planed the heads, and got a cam in them- I used 6v starters on them with 12v systems. They sure started good, and they lasted longer than you would think. :)
 

Bob Evans

Administrator
On the scooter/kart lift, I have to admit that I'm not clear on what you're trying to do, Bomber 315.
Winch up an incline? Electric lift?
 

bomber315

Member
I want to have the typical one-man kart stand that lots of people have. Only I want mine to also be self-powered so I don't have to pull or push it to and from the grid, because the damn thing is probably going to be heavy, and I like building things.
 
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bomber315

Member
First problem I see with the circuit as drawn,
Winch cannot attach directly to ground. You will reverse plus and minus leads to reverse winch. Drive motor the same.
ok so looking at this picture taken from the harbor freight winch manual, I believe the wired remote will do the + / - flip flop for forward and reverse.

I assume the scooter circuitry would do the same, its not like you have to unhook the battery cables and flip them to go in reverse.

Mind you, my schematic is still incorrect by having each motor grounded to the chassis.
 

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Chipg56

Member
#1 I didn't look over your schematic but I have an idea about an off the shelf piece. Some diesel-powered trucks have starters that run off 24volt, to accomplish this they use a "series/parallel" switch. Check it out maybe it will help.

#2 I had a small HF winch on the shelf for 10 years or so... finally made use of it to pull stuff on to the back of my truck. Burnt out on second use. You may not want their smallest.
 

bomber315

Member
95shaw,

I believe this fulfills the reversing requirements. I'm still trying to figure out what you mean by being able to always keep the 24V circuit live. When I originally sketched it (without solenoids) I had a battery shorted out. You can't have 2 batteries in series and parallel at the same time without one being shorted out. I don't want to pull my 12v from just one battery alone because it will discharge faster than the other and lead.

I could probably make 1 battery the up and 1 battery the down if I threw the stock winch controller in the trash, but I would rather not do that. Also, I don't think raising and lowering would have an equal drain on the batteries anyways.
 
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