Running a motor from a cigarette lighter

[johngiowa]

Hi,

I'm trying to devise a solution to a problem. Basically I'm looking to mount a chain driven system to the side of a car to move an item up/down and away from/towards the car. I was trying to do it hydraulically, but that's starting to look too hard.

I'm trying to find out what the largest electric motor I could run off a cigarette lighter is and if it would be strong enough to lift approx. 5kg of weight. I don't want to blow fuses or drain the battery. The car (turbo diesel) would be running whilst in use.

And just to make things more complicated ideally it would be waterproof.

Is someone able to point me in the right direction? Even if its too the funny farm - just trying to see if this is realistic.

Thanks

John

 

[Marvo]

Is this some kind of lift for disabled purposes? At only 5 Kg weight I'm guessing it's for something else.

What size fuse did you cigarette lighter come with as standard? A lot of the answer to your question depends on the gearing of the motor, it's possible to run a motor from a cigarette lighter socket that can lift several tonnes but only very slowly.


If you want higher speed of lift the gearing reduces and so does the weight capability. Maybe some more details of what you're trying to do would get you better replies.

 

[Besoeker]

Hi,

I'm trying to devise a solution to a problem. Basically I'm looking to mount a chain driven system to the side of a car to move an item up/down and away from/towards the car. I was trying to do it hydraulically, but that's starting to look too hard.

I'm trying to find out what the largest electric motor I could run off a cigarette lighter is and if it would be strong enough to lift approx. 5kg of weight. I don't want to blow fuses or drain the battery. The car (turbo diesel) would be running whilst in use.

And just to make things more complicated ideally it would be waterproof.

Is someone able to point me in the right direction? Even if its too the funny farm - just trying to see if this is realistic.

Thanks

John

I don't think it's a realistic option.
You wouldn't be able to operate anything bigger than say, a sewing machine motor.
Yes, in theory that could lift 5kg - a matter of gearing.

 

[johngiowa]

Thanks for the replies.

From what I can see its a 15 amp fuse.

I'm trying to lift 2 of these.

Power Fit Rotary Brush with Soap Dispenser for Pressure Washers - Walmart.com

I cant find a weight but I would imagine they are heavier when the bristles are wet.

Ideally I'd like to be able to use it across 3 or 4 different vehicles - hence the cigarette lighter question

 

[davesparks]

Get a proper fused supply fitted in the vehicles with an Anderson connector on it so that you can plug it in on each vehicle as required.

Andersons come in 50, 175 and 300A versions, or else they do smaller stuff in their powerpole range.

 

[johngiowa]

So if I had an Anderson connector I could run it straight off the battery from the car? I imagine that would allow me to run a fairly sizeable motor?

 

[davesparks]

You could take a fused supply direct from the battery to the Anderson connector, obviously sizing the cable for current and voltage drop (which is a big issue at 12V)

If this device draws much current though you will probably want the engine running to avoid flattening the battery.
You could easily interlock it so that the socket only becomes live when the engine is running.

 

[johngiowa]

Thanks

It would only be used when the engine was running.

Any idea how I would determine what sized motor I could use? It would be mounted at the base of a water sprayer so water proofing would be fairly important.

Thanks

 

[davesparks]

The biggest motor you can use will be determined by the capacity of the battery and output of the alternator

 

[johngiowa]

I've found waterproof stepper motors - is that the kind of thing that I should be looking for? Looks like their power is measured in g/cm?

 

[davesparks]

If you need a stepper motor then yes, but do you need a stepper motor ?

 

[johngiowa]

If you need a stepper motor then yes, but do you need a stepper motor ?

I'm not sure - jut came up in a google search. I just need one that winds so I can wind a chain to move it up/down, and another chain to move it in/out.

Here is some info on the battery:

Cold cranking amps	850
Amp hours	95
Reserve capacity	175 min

As for the alternator, I'm told the output is about 13.4V

 

[Lucien Nunes]

What you haven't told us is how fast the motor has to lift the load, which governs what power of motor you need. Also how long it needs to run for, which governs how much charge you would take from the battery if the alternator isn't running or does not keep up.

Mechanical power in watts = Lift speed in metres/second X weight in kg X 9.8
Double or treble it (to allow for typical motor / gearbox efficiency) and divide by 12 and you have the current needed in amps to operate the motor. Starting current will be a bit higher.

Typical cigar lighter circuits are 10-20A but the connectors are usually fairly hopeless, there are few that will carry 10A for very long without melting / falling out / being irritating.

You do not want a stepper motor, they are used e.g. in printers to move the printhead to accurate positions under computer control, not for general driving of things. A normal permanent magnet DC gearmotor is what you should be looking for.

BTW g.cm is a unit of torque, not power. Also the figure of interest for the alternator is the current rating in amps, not the voltage. I'm not sure where you got 13.4V from but no alternator is that low, it wouldn't charge the battery. Most are around 14.2V, from 50-120A on passenger vehicles. I would think all but the smallest alternators on old vehicles (1970s cars can have units as low as 28A) will keep up with your motor.

 

[Besoeker]

I've found waterproof stepper motors - is that the kind of thing that I should be looking for? Looks like their power is measured in g/cm?

That's torque, not power. In any case, it probably isn't really the kind of motor that you need.
For your application a series would DC motor, like a starter motor, might be best provided you can ensure that it will never run off load.

 

[UKMeterman]

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