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Offline v8guy

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Starter motor current draw
on: December 04, 2018, 11:01:17 PM
Does anyone have any idea how much current the starter draws when cranking the engine? I'm looking into fitting a battery isolator switch, so need to know before I can buy the switch and cabling. Research into the topic suggests that it shouldn't exceed 100A, but if anyone has ever measured it some more accurate info would be much appreciated.

Would it be reasonable to assume that if there's a starter motor fuse, that the rating of the fuse would be the maximum possible current? The owner's manual does not list the fuses so I'm not sure if there's one dedicated to the starter.. anyone have an idea?

Many thanks!
Last Edit: December 04, 2018, 11:09:14 PM by v8guy
Current: BMW R1200RS, 2003 Yamaha TDM900
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Offline Throbber

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Re: Starter motor current draw
Reply #1 on: December 05, 2018, 10:54:20 AM
Hi,  The 2015 owner's manual gives the main fuse rating as 30A.  Therefore the starter motor must draw less than that as the 30A must allow for starter, fuel pump, headlamps etc all drawing power together - plus a little safety margin on top.

Online voodoo

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Re: Starter motor current draw
Reply #2 on: December 05, 2018, 03:22:11 PM
I think there is a direct wire from battery to startermotor, so the main fuse is no indication of the amps running trough it.
Stop making sense

Offline v8guy

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Re: Starter motor current draw
Reply #3 on: December 06, 2018, 08:49:53 AM
The logic may be sound, but 30A does seem very low... some research indicates that even a little scooter engine draws over 60A when starting up. I'm tempted to err on the side of caution and find something rated for a lot more. Some marine isolator switches are rated for 100A and 500A burst, so if I can find a way to mount one I'll likely opt for something like that.

Ta for replies!
Current: BMW R1200RS, 2003 Yamaha TDM900
Past: Honda CLR125, Honda CB500, Triumph Sprint Sport, Honda VFR750FS, Suzuki DRZ400SM, 2001 Triumph Speed Triple 955i, 2015 Honda VFR800X

"Being shot out of a cannon will always be better than being squeezed out of a tube" - HST

Offline Throbber

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Re: Starter motor current draw
Reply #4 on: December 06, 2018, 09:56:28 AM
I checked the wiring diagram for the 800F and Voodoo is correct - the connection to the starter motor does not go through the main fuse - or any other fuse. I had previously assumed (incorrectly) that everything was protected by the main fuse. 
 

Online Skids

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Re: Starter motor current draw
Reply #5 on: December 06, 2018, 10:20:26 AM
*Originally Posted by v8guy [+]
Does anyone have any idea how much current the starter draws when cranking the engine? I'm looking into fitting a battery isolator switch, so need to know before I can buy the switch and cabling. Research into the topic suggests that it shouldn't exceed 100A, but if anyone has ever measured it some more accurate info would be much appreciated.

Would it be reasonable to assume that if there's a starter motor fuse, that the rating of the fuse would be the maximum possible current? The owner's manual does not list the fuses so I'm not sure if there's one dedicated to the starter.. anyone have an idea?

Many thanks!

Have you tried asking over on VFRD? They have a lot of very knowledgeable members over there who may be able to help you (remember, we have the same engine as the 800F so owners may be able to assist as well).
98 VFR800 - 130,000 miles (sold)
08 VFR800 - 76,000 miles (sold)
14 VFR1200 - 20,000 miles
15 VFR800X - 44,000 miles (sold)
18 VFR800X - 9,000 miles

Offline v8guy

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Re: Starter motor current draw
Reply #6 on: December 06, 2018, 08:55:31 PM
*Originally Posted by Throbber [+]
I checked the wiring diagram for the 800F and Voodoo is correct - the connection to the starter motor does not go through the main fuse - or any other fuse. I had previously assumed (incorrectly) that everything was protected by the main fuse.
Good to know, ta!  :028:
Current: BMW R1200RS, 2003 Yamaha TDM900
Past: Honda CLR125, Honda CB500, Triumph Sprint Sport, Honda VFR750FS, Suzuki DRZ400SM, 2001 Triumph Speed Triple 955i, 2015 Honda VFR800X

"Being shot out of a cannon will always be better than being squeezed out of a tube" - HST

Offline v8guy

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Re: Starter motor current draw
Reply #7 on: December 06, 2018, 08:59:20 PM
*Originally Posted by Skids [+]
Have you tried asking over on VFRD? They have a lot of very knowledgeable members over there who may be able to help you (remember, we have the same engine as the 800F so owners may be able to assist as well).
Not yet... thought I'd see if I could save myself yet another forum membership first...! But yeah, good idea.. I'll have a browse.
Current: BMW R1200RS, 2003 Yamaha TDM900
Past: Honda CLR125, Honda CB500, Triumph Sprint Sport, Honda VFR750FS, Suzuki DRZ400SM, 2001 Triumph Speed Triple 955i, 2015 Honda VFR800X

"Being shot out of a cannon will always be better than being squeezed out of a tube" - HST

 



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