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Old 21-01-2013, 18:30   #1
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Starter motor amps query

Hi,
I have a Yanmar 2qm15 marine diesel engine in my boat and I am trying to determine the amps draw so I can buy the correct starter cable size. The 2qm15 specification chart reads as follows -

" Starting - Electrical Starting Device - 1.2Kw Starter Motor, 35A-A.C. generator and regulator"

As I am a bit thick and don't quite understand it could someone explain this for me please? does it give me the current draw?

Thanks,
bony.
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Old 21-01-2013, 18:41   #2
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Re: Starter motor amps query

1.2 KW / 12 volts = 100 amps. What is the length of the cable run?
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Old 21-01-2013, 18:50   #3
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Re: Starter motor amps query

Hi deckofficer

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1.2 KW / 12 volts = 100 amps. What is the length of the cable run?
Length about 4.0 Metres (a little over 13 feet)

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Old 21-01-2013, 19:15   #4
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Re: Starter motor amps query

bony,

At 13' if you want to stay below 3% voltage drop, 2/0 awg. I used 125 amps for your load. 1/0 would be 3%, and 1 awg would see almost 4% voltage drop which is acceptable.
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Old 21-01-2013, 19:42   #5
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Re: Starter motor amps query

2QM 15

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Old 21-01-2013, 19:46   #6
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Re: Starter motor amps query

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bony,

At 13' if you want to stay below 3% voltage drop, 2/0 awg. I used 125 amps for your load. 1/0 would be 3%, and 1 awg would see almost 4% voltage drop which is acceptable.
Ok, d/o, thanks for working out the sizes for me, you've been a great help.

Cheers,
bony
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Old 21-01-2013, 19:49   #7
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Re: Starter motor amps query

Well that sure helped, 315 amps, thanks again Maine Sail. So now with real amps during start, your looking at 10.7% voltage drop with the 1 awg, so skip that. 8.5% with the 1/0, and 6.7% with the 2/0.
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Old 21-01-2013, 20:10   #8
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Re: Starter motor amps query

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Hi M/S,

I watched the video but not sure what it all means. Seems like an awful lot of amps, but reading the comment below it is a spike of very short duration,

".....The inrush happens, in this case, only for around 0.5 msec...."

(Great Howto's by the way. I bookmarked the page to have a look at later.)

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Old 21-01-2013, 20:19   #9
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Re: Starter motor amps query

Was that 4 m one way or return? When sizing cables you need to take into consideration the length from the batteries to the load and back.
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Old 21-01-2013, 20:28   #10
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Re: Starter motor amps query

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Was that 4 m one way or return? When sizing cables you need to take into consideration the length from the batteries to the load and back.
One way.
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Old 21-01-2013, 20:55   #11
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Re: Starter motor amps query

Circuit Wizard

This will help you. Notice if you put the mouse pointer on any of the required inputs it will give you the details on the right.
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Old 22-01-2013, 00:56   #12
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Re: Starter motor amps query

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Circuit Wizard

This will help you. Notice if you put the mouse pointer on any of the required inputs it will give you the details on the right.

Great Calculator, thanks.
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Old 22-01-2013, 05:19   #13
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Re: Starter motor amps query

Sorry forgot to add that average CA will be about half of in-rush...
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