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STARTER MOTOR NO LOAD CURRENT

684 Views 4 Replies 2 Participants Last post by  alan c, 
A
Not really an electric car question, more electric boat actually, but I thought people here would have the knowledge.

I obtained an old starter motor from the local mechanic with a view to using it for small boat propulsion knowing that most people would say that they are unsuitable. I removed the solenoid and mechanical parts and had a look inside finding good brushes, shiny commutator and no burning or visible damage.

On testing with a power supply current limited to 40 Amps - that is what it took to turn! At least 10v required to start, and current never dropping below 40 Amps with no load. Is this the best I can expect? On reflection I suppose a starter motor might take 400 Amps starting a cold motor, which would make the measured no load current acceptable.
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E
Yes, a no-load current draw for a starter motor of 40 Amps is about right. See this thread about using one to test the SAFT NiCad batteries in a Berlingo Electrique electric van:

A modern permanent-magnet starter motor may draw less no-load current than the traditional wound-field type. You could also experiment with disconnecting the series field from the armature and supplying it separately.
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A
Thanks for that very useful reply, it confirms that a starter motor is not much use to me! This particular motor has 6 permanent magnets, 4 brushes and a built in epicyclic gearbox by the way.
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alan c said:
This particular motor has 6 permanent magnets, 4 brushes and a built in epicyclic gearbox by the way.
Click to expand...
Sounds like a very useful motor, for something....!
E.g. it would make a good winch or a hoist.
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To wrap up this thread: I tried disabling two of the four brushes and got better results, starts easily on 5v and takes about 30A no load at 10v and 35A at 15v max from the power supply. However, I've decided that it's still no use to me. Thanks for help, electric car people!
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