25/02/2026
We all like to run accessories on our bikes, eg sat navs, CarPlay screens, mobile phone chargers, video cameras etc etc etc and the list goes on. However, when installing whatever device it is give some thought to whatever else may be in the same circuit. There is not an infinite supply of power generated by your bike’s stator, it is very much finite. It’s also very much finite as to how many amps you can pass down a particular gauge cable without it causing problems.
In this instance a customer had installed a Quadlock phone charger. They’d also bought an adapter so they could simply plug it into the bike’s diagnostic port and pick up power from there. The phone charger came with a built in 15A fuse - fantastic. However, on this particular model the diagnostic port was on a circuit which was protected by a 7.5A fuse AND which was shared with the cooling fans. Now the radiator fans draw about 30W each, there’s 2 of them. The Quadlock charger was drawing 40W. A 7.5A fuse will blow when the devices on the circuit it’s protecting need in excess of 90W.
Everything’s fine and dandy, you’re riding along, the phone’s charging away, all is good. You hit stationary traffic. The engine temp rises, the temperature hits 103c, the ECU tells the fans to come on, click, the fuse blows. You probably wouldn’t even know unless you look at your screen and see the engine temperature continuing to rise and rise and rise, until it starts flashing HI, HI, HI and, if you don’t even notice that because you’re so busy listening to the music streaming from your phone which is no longer charging, well, it’s highly likely to end in a cracked cylinder head. So, don’t just connect things any old how, get hold of the wiring diagram and make sure it’s safe to use the circuit you want to use.
Edit: just to add, many bikes come with usb ports or DIN sockets already fitted to run accessories off. Great. It doesn’t mean you can plug in a fecking toaster or the kettle, the fuse will blow. Read your manual and check what the accessories circuit can handle. It will tell you what fuse is in its circuit, then check how many watts your device(s) need, and for those that have forgotten Watts = Amps x Voltage.