Starter Current

[Crispin]

Any guess at what a starter would use when cranking? So far, google seems to think up to around 300A. Guessing cranking an 80's engine on a cold morning would be a lot different to mine on a cold morning.

Pretty certain it would be less than 500A?

 

[Ian Rubie]

I would say 225 amps on your engine. I think yours has a 2.7kw starter. 12 volts, 2700 watts = 225 amps.

Ian

 

[Rob]

But is that mechanical power or electrical power? From my experience motors are rated by mechanical power. So at a say 60% efficiency, you will be drawing 4500w which equates to 375 amps at 12v.

 

[Jon Wildsmith]

is the 120 a 12v or 24v starter? makes a difference

 

[Crispin]

I had not thought of looking at the parts catalogue.

The 120 is a 12V starter.

I want to get a shunt resister to put inline with the batteries so need a rough figure. I'll see for a 300-400A one.


Hmmm, just thought about the winch. That would be much higher at load, very high when stalled.... Maybe a bad idea...

 

[Jon Wildsmith]

you don't need to measure it, just assume it's lots

 

[Crispin]

not really for the starter, it's for the whole lot. I would have liked to measure everything but think it would be better to split the two off. A 120A shunt would be offer better accuracy anyway.

 

[Graham]

is the 120 a 12v or 24v starter? makes a difference

The 120 is a 12 volt starter.

I expect the 12 volts starting, vehicle will draw twice the current ( amps ) as a 24 volt starter.

I would thing the peak starting amps, for the first second or so, until the starter motor gets the inertia of the engine turning, could well be as much as 1000 amps.
Then would drop back to around 300 amps.

Graham