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23 Cyber Gray Limited AWD
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Discussion Starter · #1 · (Edited)
In a thread Dead 12V battery and some lessons learned the poster noted a fuse labeled B+ and asked what that means. The tech types know that B+ is the 12V bus that lives just below the main battery fuses. B+ probably dates back to WWII or earlier for battery plus voltage, all the way back to the first battery powered vacuum tube portable radios.

I am starting to go through the schematics, so will post some here that might be helpful to those interested. I think I'm off the main strip in this sub forum so hopefully will not bother those less interested. Drawing may vary by year and AWD or RWD, these schematics were found under 2022 AWD.

[Anyone can sign up for maintenance, service information. (BTW, sign up as public, not independent repair facility if you are a DIY EVGearhead owner like myself, it is less expensive.) Free to owners would be ideal, but short that of that $60 for a month seems okay, at least we get access.]

There are at least 5 fuses labeled B+ which distribute the 12V bus to various subsystems and sub panels, some with fuses.

In the maintenance manuals online, there are power distribution schematics at different levels. Each level references the level below. Here are two examples.

In this first drawing, SD110-1, the battery center feeds the 12V B+ bus on either side of center. To the left are systems from A/C to the power outlets. To the right are systems from AMS to E-Shifter1, then off to other schematics beginning with SD110-2, which continue the thick black line of the 12V B+ bus.
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Here is the second page. Note that upper left comes from the first page, and upper right continues the 12V B+ bus to the third page:
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Here is the third page. I will make another post that shows the path to the often discussed charge port door motor (noted as a common source of phantom drain) Fuses in the charge port door path. Leading into that post, note the bottom right B+4 fuse which powers the ICU junction block and goes off to schematic SD110-6, a level below these B+ diagrams.
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