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Alternator limitations at 12 VDC are limited by the DC conversion at the rectifier because the alternator is an AC machine producing 3 types of power. Only the true power is concerned, with the apparent power the most abundant and the reactive power the reason for field excitement workings are not considered.
So at 40 or 50 Amps you must ask yourself is this peak or constant flow. If its peak then the alternator is not capable of delivering this power at all times but if it is constant maximum flow the machine is capable of delivering this power. But remember the alternator is AC and the rating given is DC, so the components attached for the conversion are rated in DC. At say 50 A DC and at 15 not 12 V nominal the actual alternator is more robust, but power is not free or cheap.
The alternator can be made more efficient but at a cost, the AC is of variable frequency so it could have a higher frequency for greater power but the DC diodes, SCR and any conversion equipment has to handle the higher cycles, thus price goes up.
The alternator as it is, is very robust and since it is a rotary machine, fairly stable. The amount of engine HP to deliver 50 A at 15 VDC is fairly large at 50x 15 or 750 W. The alternator itself is rated in VA and Volt Amps are not the same as watts. Machines using magnetic flux are rated in VA and the alternator could have a much larger rating in VA because of the 3 actual types of power this AC machine produces. And the actual bike HP is higher than the 750 W that the alternator delivers, usually 2:1, so at a minimum over 2 HP SAE Brake have to come from the IC engine, if the alternator is belt driven then the belt losses are added up.
Power factor, 3 phase windings, internal copper losses, bearing losses are not considered on the bike’s power electric horse, but they are considered when the driven alternator is driven mechanically by the prime mover, the engine.
A lot of guys want more electrical power; what about hooking a battery separately to the ground connection and every time the main battery is fully charged the discharged ground goes to the 2[sup]nd[/sup] battery and fills it up, wiring relays and dumping monitoring is needed.
But because a lot of us ride older units taking care of the OE, through maintenance is a cheap and fairly cost effective way to keep the down side of the charging system at a minimum. Do not use excessive loads and with this in mind the lack of care causes excessive loads in all connectors on the bike, indiscriminate use of water, greases dielectric grease or plain neglect will cause the bike’s electrics to age just as the mechanical aspect of the bike gets older.
Just like people some bikes are old before their time. Happy trails!
