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Author Topic: anyone really know how the Low Power B+ circuit fuse works? I need help  (Read 838 times)

TEV

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Re: anyone really know how the Low Power B+ circuit fuse works? I need help
« Reply #15 on: February 05, 2022, 06:58:13 PM »


The other battery (100 volt) input to the MBB is via the key and the lower power B+ fuse.

A 2013 model only have the traction (96V nominal) battery, that year model doesn't have a 12V battery.

I never said anything about another battery. I said "other battery (100 volt) input." I was referring to the fact that there are two connections between the battery pack and the MBB. One is always on (no relay or contactor) but as far as I can tell is used only to pass battery power to the key-on input of the Sevcon. The other input to the MBB passes through the low power B+ fuse and ignition switch and provides power to the MBB for its processing needs before the DC-DC converter is activated.

Sorry, my bad, but you did said "other battery..." input, not "other input from the battery"
It seems weird that they will connect something to the battery without any fuse.
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Gains

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Re: anyone really know how the Low Power B+ circuit fuse works? I need help
« Reply #16 on: February 08, 2022, 01:36:47 AM »

When the contactor is open (key is switched off) and the low power fuse removed, there schould not be any power on the bike ,the battery is then completely isolated from the rest of the bike. On the 2013 models there where two fuses on the original batteries, but on most bikes the original battery has been replaced by a 2015 one ( with only one fuse)
The MBB and the dc-dc converter are hot wired via this fuse, and it protects the bms in the event of a short in the hot wired parts and cables.
If you still have voltage with contact off and low power fuse removed, you have to find out where it comes from. Make sure the contactor is open (could be welded) Check if the high voltage pins on the dc-dc also receive 110v. You could unplug the battery (very hard to reach, especially on a 2013 )
I wouln d install a new MBB before you know where this voltage comes from and this is corrected.
Good luck

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