Re the wiring diagram you linked earlier...
It shows the battery goes thru a 30A fuse to the rest of the bike EXCEPT the startermotor heavy cable which is direct to the battery +12V when cranking
. (See the starter motor
on the top right corner.)
BTW - diagram orientation assumes 'right way up' - ie, landscape mode.
From that startermotor relay 30A fuse it goes (down) to the alternator's voltage regulator; or (left) to the IGN switch.
IGN then switches 30A +121V to Fuse #1 (10A) & direct down to the fan motor
whose fan switch
connects it to GND;
and to fuses 2, 3, & 4 for +12V to all other circuits(10A, 15A, 10A).
In short, every OEM electric load in that diagram requires the IGN to be on except PERHAPS the fan motor especially if IGN switch does more than simple on-off (eg, off-acc-IGN, Park-off-IGN).
And of course the starter motor heavy +12V terminal which is connected direct to the batt's +12V terminal.
IMO you do want it switched thru IGN hence either power from one of those switched fused circuits 2, 3, or 4 (see below) else similarly switch a 4 or 5 pin aka SPST or SDPT relay coil to connect its Common 30 - the Dual Socket Power
and NO Normally Open 87 via your added 7.5A fuse with maybe a 10A or 30A distribution rating.
Ideally you'd know the max else typical load on any fuse and decide which has the best spare capacity. (If total fuse amperage is exceeded, it could take seconds or hours to blow.)
Otherwise take a chance and move if necessary,
Or if the fuse holder etc and all the wiring off the 10A fuses is suitable for - and hopefully the same as existing - 15A circuit wiring. If so, it should be acceptable to tap into that +12V feed anywhere and upgrade from a 10A to 15A fuse (and hence have a known
5A available). But it should not be a critical circuit - eg, headlights, brake lights.
A relay solves all the above in that you can guarantee all the raw current you need up - ignoring battery limits, life & safety aspects - to the limit of YOUR added fused-cable's rating direct to the unfused battery +12V terminals yet IGN off should guarantee all loads are off...
Unless like me you also want a manual bypass so you can charge your accessories
with the IGN off, either diodes between IGN & the manual switch and the relay;
or grounding control - eg, insert a fuse to bypass the IGN key.
As I've been meaning to do to my HU's power relay, but the IGN-on requirement to turn & then stay on independent of the IGN key IMO isn't too bad - unless I'm camping... And electric windows, but they are already on +12V (I learned from my previous mistake!) but that ain't good security...
So, a few considerations or solutions...
I would ignore the claimed "25 amps".
How can it be if those sockets are specified to only 15A - and many IMO have failed to meet that - what additional protection is there for sub-25A rated loads many of which will not be fused if rated to carry 15A?
IMHO that's dangerous!
Hence reduce the single-socket capability to 15A unless it can only handle less. Or try a reasonably safe size (eg 1A or 2A, usually 5A, but above 10A must be checked) and see whilst checking for hotspots (warm wiring or switches or GND connections) a few times and thereafter reasonable intervals.
And oh boy, I don't think my day is one involving good expression...