Most modern motorcycles have...
Most modern motorcycles have a stator/alternator charging system. The key components are the battery, stator, rotor and the regulator/rectifier.
Busting the myths and digging up the truth about sportbike folklore. We're here to get to the bottom of it all so you know where you stand and don't follow any bad advice.
Although some might consider it outlandish, a large number of people believe their bikes make less power with the high beam headlight(s) on. We've heard all sorts of explanations why this occurs (though never from an electrical engineer), with the most common being: "The headlights suck too much juice and I don't get as strong of a spark as if I had my lights off."
To keep things simple and consistent at the dyno, all runs were made within five minutes of each other on the same bike-a stock 2011 Yamaha R1. We took the theory one step further and ran three different tests; low beams, high beams and no headlights at all.
With the headlights in the low position, peak power was 143.2 HP. The second set of pulls in the high beam position netted us 143.1. Finally, we removed the headlight fuse and spun the drum another three times to the tune of 143.3.
The dyno discrepancy between...
The dyno discrepancy between low beam, high beam and no headlights was roughly .2 HP on a 143 HP spread. The minimal differences between the pulls can be attributed to dyno error, not increases or decreases in horsepower from the headlights.
A look at the three graphs shows small discrepancies that boil down to dyno error. To put it into perspective, we're talking about changes of less than a tenth (.1) of a horsepower on a 143 horsepower spread, which is well within the dyno's margin of error.
This shows that running high, low or without headlights has no effect on horsepower if the bike has a properly functioning charging system. The reason for this is easily explained: OEMs build the charging systems large enough to handle all of the onboard electronics and still have a healthy reserve in case a rider was to add aftermarket doodads like a fueling computer, alarm or LED lights.
Most modern motorcycles use a stator/alternator charging system to keep the battery charged. This system uses a metal rotor connected to the crankshaft that spins around a stator (a stator is essentially coiled copper wire wrapped around metal heads). When the rotor spins around the coiled copper wire (the stator) it creates electricity. The faster you spin it (by way of engine RPM) the more electricity it produces.
The electricity from the stator/rotor then travels as AC current to the regulator/rectifier where it rectifies the electricity from AC to DC-the type of current your battery needs. Along with rectifying the electricity, it also regulates it so that the battery isn't over or under charged. When the battery needs more juice the regulator/rectifier dumps the current into the battery, and when the battery is full it dumps the current into the ground(s).
The charging system is designed to support all of the components that require electricity, and the headlights are a drop in the bucket compared to other systems. If you want to talk about sucking juice (amps and volts), the starter motor and the fuel injection are the real doozies.
MYTH: [CONFIRMED] [PLAUSIBLE] [BUSTED]
Modern sportbikes with properly functioning charging systems can run headlights without fear of losing power.