Starter motor current

[elecLear78]

When we are trying to start the engine, what is the maximum current drawn and how long it will be? Is there anything like peak current and steady current? Is a fuse required? If I continuously try to start the engine if the engine does not start will the starter motor get damaged?

 

[Nigel Goodwin]

No point in a fuse, currents well over 100 amps aren't at all unusual, and the motor won't be damaged as the battery will go flat MUCH sooner than any potential damage.

 

[ronsimpson]

Many cars have 200, 250, or 300A fuses in line. (fuse link)
There are many types of starters.
I think 100 to 150A when the starter is turning good.
I think 200 to 300 when the starter is turning slow. (at first)
Those are DC readings on a meter.
Years ago I put an oscilloscope and a current probe on a starter. The peaks are very high (don't remember 600A) and the lowest points are near zero. As you compress air in the engine it is hard to turn. Then when the engine brakes over it actually pushes back into the starter.

A new high compression engine is hard to turn over.

 

[MikeMl]

The cranking current is high enough to cause the nominal 12.6V lead-acid battery voltage to sag to as low as 8V. Note the Cold Cranking Current rating of automotive batteries of ~800A to 1000A!

 

[Geoff-AU]

If I continuously try to start the engine if the engine does not start will the starter motor get damaged?

Yes you can damage it with continuous cranking, although it's not a certain thing. Besides which, if you have been cranking for 10 seconds and it hasn't started it's probably not going to so there is no point abusing the starter motor and battery. Wait 30-60 seconds and then try again. After 10 seconds of cranking you will have either flooded it (and this needs time to clear) or the ECU will just stop injecting fuel after X cranking cycles so cranking it more than that is a waste of time.

 

[MaxHeadRoom78]

Starter motors until quite recently were series wound motors due to their extremely high torque capability, the current at switch on is at the extremely low resistance of combined rotor/stator, and does not reduce that much but relies on the generated voltage which can be low due to never reaching very high rpm.
Being series motor they can run up to uncontrolled rpm when operated off load, on a bench etc.
Max.

 

[audioguru]

Are there snow covered mountains in India where people start their cold cars? I don't think so.
Do cars in India have a huge V8 to V12 engine? I don't think so.

When my first car ran out of gasoline I used its starter motor to drive it to a gas station. The starter motor survived and was never replaced. But the car and its engine were small.

 

[ronsimpson]

My first "go-cart" (child's home made car) used a starter for power and a car battery for fuel. Normally people use a lawn mower motor.
I could only go around the block twice before needing recharging.

 

[audioguru]

Today I saw a parked Maserati sports car (2015 one is $124,000 American or $164,000 Canadian) but it might have been a 2016 one. Then an Oriental young couple got in it and it started making a lot of noise (V8 engine). It started in less than one second like most new cars. It also made a lot of noise when it drove along.
I have seen other Maserati cars parked there so maybe the girl or guy works for Maserati.