Slowing down a 12v motor speed plus running on 24v ?

[CompoSimmonite]

Without using a speed controller, or just tapping into one battery, is there a simple (ie cheap) way of making a 12v brushed motor run slower even when power is 24v ? This is a fixed speed and not variable. I suppose 6-9v might be what's needed but seeing motor is 200 watts then most common voltage reducers can't provide the amperage.
Any ideas ?

 

[bletchmonster]

A lot of vehicle heater motors use a big wire wound resistor to get a slower speed,

 

[MattH]

Just grab a cheap and simple PWM controller. They'll be peanuts on ebay.

 

[MoreWellie]

vehicle heater motor resistors often rely on air flow to keep from melting

Look for an element from an electric fan heater, I found one that had multiple attachment points as it was switched 1kw, 2kw, 3kw

I used mine as a dummy load for testing high power amplifiers up to 500w or more

not sure what dropping the voltage on the motor would do for the torque though

 

[CompoSimmonite]

Just grab a cheap and simple PWM controller. They'll be peanuts on ebay.

Brilliant. Just had a look and as you say dirt cheap

 

[eSCHEn]

Brilliant. Just had a look and as you say dirt cheap

Don't quote them on their duty though, just overspec and you'll be fine.

 

[rikrobson]

I'm not sure the motor is going to like 24v applies to it even if its via a PWM. It probably will work, but at 16A or so its going to need to be driven by some power transistors.

Why are you using 24V to drive a 12V motor?

 

[CompoSimmonite]

I'm not sure the motor is going to like 24v applies to it even if its via a PWM. It probably will work, but at 16A or so its going to need to be driven by some power transistors.

Why are you using 24V to drive a 12V motor?

I have a decent, geared, 12v motor I want to use as a winch to raise and lower the operators (me) seat for ease of access on a custom off road mobility scooter I'm designing that runs on 24v.
I do have other ideas for the raising so no problem if this one is "shot down in flames"

 

[Wendelspanswick]

I have a decent, geared, 12v motor I want to use as a winch to raise and lower the operators (me) seat for ease of access on a custom off road mobility scooter I'm designing that runs on 24v.
I do have other ideas for the raising so no problem if this one is "shot down in flames"

If your using 2 x 12v batteries in series for your 24V why not just run a seperate circuit for this motor using the 2 batteries in parallel?

 

[MattH]

If your using 2 x 12v batteries in series for your 24V why not just run a seperate circuit for this motor using the 2 batteries in parallel?

I'd be interested in how you connect two batteries in Series and in parallel at the same time without creating a dead short???

 

[the snooper]

I'd be interested in how you connect two batteries in Series and in parallel at the same time without creating a dead short???

You could probably do it with some diodes capable of the amperage needed for the motor

 

[rikrobson]

I'd just run a tap fron the middle of the two batteries then find some way of regulating them.

 

[CompoSimmonite]

I suppose I could use a 24v to 14v reducer to keep a small 12v battery topped up that would also be used for lighting etc that could power the winch as it'd only be used for short periods

 

[MattH]

You could probably do it with some diodes capable of the amperage needed for the motor

Yeah, but 200W at 12v is around 16A is a 12W loss through a Diode. That's a lot on a EV, I suppose you could switch it out. But I'm with rikrobson, just centre tap the batteries and then run the PWM control for full speed control.

 

[MattH]

You could probably do it with some diodes capable of the amperage needed for the motor

Just sketching it out on a peice of paper in front of me. To my mind you can't do it even with Diodes because your requiring two of the 4 battery terminals to have both 12v and 24v on them at the same time. Can't happen.

 

[Justme]

I'd just run a tap fron the middle of the two batteries then find some way of regulating them.

Dont do this.

It results in the batteries getting out of sync re the state of charge. Then one either gets over or under charged all the time & will fail sooner.

 

[the snooper]

Just sketching it out on a peice of paper in front of me. To my mind you can't do it even with Diodes because your requiring two of the 4 battery terminals to have both 12v and 24v on them at the same time. Can't happen.

yeah ive just sketched it now im home and you are right, cant be done

 

[rikrobson]

It results in the batteries getting out of sync re the state of charge. Then one either gets over or under charged all the time & will fail sooner.

If they are charged together this may happen.

The real problem is using a 12v unit on a 24v circuit, and a beefy unit at that. Without using Big resitors or voltage regulators, which will waster power, it really not feasable.

A big 12V Zenner may work

 

[the snooper]

now i have read the thread properly i see you want 12 volt to raise and lower yourself, you could use relays that will join both batteries in parallel whilst at the same time disconnecting the 24v circuit so its one or the other, not both

 

[Johnseat]

I'd be interested in how you connect two batteries in Series and in parallel at the same time without creating a dead short???

Mitsubishi Canter vans are 12v with 2 x 12v batteries wired in series and parallel for 24v body builder equipment.
They do install a split charge regulator ecu on the side of the battery box.