Hey chaps

Just a quick question...I'm powering a starter motor off a 12v car battery, but I need a way to switch it on and off

Could I use one of these relays?

http://www.12voltplanet.co.uk/split-charge-relay-12v-200a.html?gclid=COmaiYCmursCFfHMtAodSWkAiw

Could I, say, use pins 30 & 87 to break the connection between motor & battery and switch with seperate 12v/1.5a applied to 85 & 86?

Cheers

 

Probably not. The starting current for a big V8 is up to 1000A. For a small engine, 200A might be enough, except that the battery charging relay doesn't have the strong spring which pulls the contacts apart when you quit cranking.

I would get and use a real starter relay. Looks like this

 

That looks like a standard aftermarket auto starter switch, my V8 in the winter, -20°c, takes just over 100 amps.
Also is this in a standard auto application or some other useage?
BTW, a starter motor is a Series wound motor so it operates in a runaway condition off load.
Max.

 

It's worth noting that the way this is normally done is by using a starter solenoid. The relay can power the solenoid coil, which in turn switches the large starter current.

 

The motor is under hardly any load, so the 200a max isn't an issue.

The output shaft of the motor is directly connected to a modified straight-6 cam shaft mounted on two pillow-blocks. When the shaft turns, the protruding cams 'knock' against an aluminium casting block to vibrate a viscous epoxy resin - which spreads the mixture ready for curing

Basically I'm trying to find out the switching power required to make this link...or another method which would allow me to cut power to the motor

Thanks

 

Re runaway.
In order to have accurate control, it might be better to convert to a shunt connected motor, if possible?
Or have some way of adjusting the voltage to the motor in the application you intend?
I would think that the anticipated current will be alot less that 200amp in this application?
You could always power it direct and see what the current/rpm actually is.
Max.

 

I realise that the motor output will be unpredictable given that it is under no load, so I was hoping to control the speed by putting a pwm across a relay switch. The amount of vibration would have to be variable as I am experimenting with different materials, which will require different levels of vibration.

The pmw thingy is no problem, I just need a switch to apply it to

 

Do you really anticipate needing that large (HP) of a motor for what you are doing?
Seems a bit of overkill? Unless there is a load I am missing?
Max.

 

bit tricky to explain but there will be a load...as each rotating cam strikes the mould it will also need to push the cam axle away somewhat to complete its rotation