The Time has come for nearly all Racers which purely ride on track....except endurance Racing.
It looks like you can remove the Alternator totally.
Hi End Battery Cells are on Market, which ( at still way less weight than the OEM Battery ) allow you to ride from 25 - to 90 Minutes, depending on the Amperes of the Battery Pack. We have tested the Cells/Packs 2007 a whole year on track ( without Alternator ) and found no downside.
Consider that high-end Racing Alternators cost a
fortune.....but you do not need them no longer.
How it works ?
The Lithium Ferrum Polymer Cell has only 35% of the weight of a comparable usual Led Bike Battery , so if you decide to let build a LiFePo Cellpack with the same weight as your OEM Battery, you'd have 3 Times the Amperes of what your OEM Battery has ( lets say 27Ah you'd have then , because usually 9Amps Batterys are used in Motorcycles).
But 27 Amps is a bit too much, its more than you'd ever need on track ( considered you are not able to ride more than 60 Minutes fast ).
Usual trackdays have 20 Minutes Sessions and 40 Minutes for recovery.
Usual Riders are not able to ride fast for more than 30 Minutes.
Usual Riders need at least 30 Minutes for Recovery.
Usual Time to charge these Battery-Pack : 15 Minutes maximum, if the Battery is totally empty, normally 6-10 Minutes.
The Charger you need to charge these Batterys has to have at least 4 Times the Amperage of what the Battery-Pack has, so I.E your Battery Pack has 11 Amps then the charger should have 44 Amps.
I've got 60 Amps chargers on stock.
A Bike with Injection has a Fuelpump, which needs most of the Electrical Power .
This Fuelpump has a Power-Consumption of ~ 5 Amps, then you need to drive 2-8 Injectors, which leads into a total Power Consumption of 7-12 Amps, depending on how many Injectors you have, and at which RPM's you usually stay ( Injector Duty's ).
....and if you decide to keep your Alternator, then these new Battery's save you still 3-6 lbs !!
But the Alternator is directly on the crank, is turning the same revs per Minute as the crank, and has a HUGE rotational Inertia.
I have focused myself at my new Ducati 1098 that I will run no Alternator anymore.
It's simple, a new Generation of Battery's is born, so the Time for Alternators for Trackbikes is gone.
.....as said, except endurance Racing.