teenkertoy x2. [Thanks! Dare I say you make me feel
Serene? (Blame GI
Jayne)]
The amplifier's required fuse being placed at the battery end (instead of at the amp end, and another battery-end fuse to protect the cable) is what I was trying to say in my last paragraph.
Though sometimes not understood, that also reduces path resistance and increases reliability (one less fuse etc).
Though I am uncertain, it could be that your Honda splits the alternator's output. One is fused to the battery, the other (maybe also fused but usually not) to the fusebox.
I suspect it has a 3-flink (fuse-link) box at the +ve battery post similar to what I am using, and an ND alternator.
If it's the newer ECU type Civic, it might have the ECU interactive alternator (the ECU/EMS can cut out the alternator for better acceleration and (IMO!) probably worse fuel economy.)
If it is a split alternator cable, then the battery fuse should not require increasing as the battery is likely to limit that current, and that is not changing. (Again, that flink is only there to protect the cable - not the alternator.)
Note that supply voltage (and the battery) determine the battery's charge current. Assuming the existing alternator has adequate charging capacity, increasing its size will have no effect. (Only increasing its voltage will.)
And chances are that your alternator to main fusebox bussbar is unfused. (It instead relies on
physical security instead if inline fusing protection, and the battery-alternator fink will blow if it's the battery that supplies any
fault current to the main fusebox via that alternator path.)
By
main fusebox I mean the fusebox that usually has the major circuit fuses - which may include relays as well.
I assumed you also did
The Big 3 (or 4) in conjunction with this. Heavier grounding between engine-body-battery(-ve) will be required for the added Amps else to reduce their voltage drop. Same for the battery to amp and alternator to amp +12V paths (that's the extra #4th in the Big 3 if I recall correctly..!).
Otherwise ensure adequate grounding. Burning out ground straps can be disastrous for vehicle electrics - especially if sensing the battery voltage as most Hondas do - ie, those with the older 3-wire SIL type alternators. (System voltages can go way above 15V or 16V, though ND and similar "S" type Jap alternators are often limited to around 15.5V max output in case the Sensing S connection goes faulty - or for whatever lucky reason they are limited to under 16V - the common upper design limit for 12V loads.)
And inadequate grounds when cranking can cause fusing of other engine-ground paths - like throttle cables, low current harness grounds, springs - and spot welding or plating of prop-shafts, bearings etc.
As to where you connect your ">1kW" amp cable, that's up to you. You want minimal resistance - but from your battery (for 1kW with engine off), or the alternator (1kW engine charging)?
I'd prefer maybe the main fusebox if convenient with a "1kW" fuse to the amp (ie, 100A, 150A whatever), and similar cable from the battery and from the alternator
added (capacity wise) to the existing alt to fusebox & battery to fusebox wiring... But many take it from the battery +12V, but I'm unsure how they then modify their alt-battery and fusebox-battery cabling and fusing. (IMO such heavy battery termination is for adjacent loading - ie, boot/trunk batteries for amps; winching batteries; starter motors, etc.)
Simple isn't it?
(NOT!!!)
(But that's why I have
my methods... But even they vary with design desire.)